i

THE RESPONSE OF BASIL (OCIMUM BASILICUM L.) TO CHICKEN MANURE,

COMPOST AND UREA APPLICATIONS

A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

IN

HORTICULTURE

AUGUST 2000

By Theodore J. Radovich

Thesis Committee:

Hector Valenzuela, Chairperson Bernard Kratky

Catherine Cavaletto Nguyen Hue

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We certify that we have read this thesis and that, in our opinion, it is

satisfactory in scope and quality as a thesis for the degree of

Master of Science in Horticulture.

THESIS COMMITTEE

______________________

Chairperson

____________________

____________________

____________________

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ACKNOWLEDGEMENTS I would like to acknowledge my committee members for their help and guidance

over the course of this project.

Thanks also to the many other people who have helped: Mr Ted Goo, Ms.

Christine Crosby, Mr. Roger Corrales and the staff at the Waimanalo experiment

station, for their help in field preparation, maintenance and harvesting; Mr. Ray

Uchida, Ms. M.C. Ho, Mr. Desmond Ogata, Ms. Julana Jang and the ADSC Staff

for their help with sample analysis; Mr. Randy Hamasaki for sharing his

knowledge of basil; Dr. James Silva for help with data analysis; Ms. Natalie

Nagai and the members of both sensory panel committees for their help with the

sensory analysis; Mr. Ivan Kawamoto and staff for technical assistance in the

field; MOA Hawaii for their technical assistance and financial contribution to this

project.

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ABSTRACT

Once essential components of agriculture, organic amendments are regaining

importance in the management of agricultural soil fertility. Three experiments

were conducted at the University of Hawaii Waimanalo Experiment Station to

determine the effect chicken manure, compost and urea applications have on the

yield, nutrient status and sensory quality of basil. Yield of basil plants receiving

applications of either chicken manure at 5 t ha-1 or compost applications at

23 t ha-1 were comparable or greater than plants to which recommended rates of

synthetic fertilizer (urea) had been applied. Although higher rates of compost

(90 t ha-1 ) generally increased yield over the lower rates, N use efficiency was

determined to be greatest at the lower rates of compost application. Tissue N

and sap nitrate-N levels were increased with organic amendment applications.

Tissue N levels of 4.5-4.8 were associated with highest yields. Sap nitrate-N was

well correlated with tissue N levels at 65 days after transplanting. Sap nitrate-N

levels varied with cultivar, while tissue N did not. Nitrate-N levels were not

affected by compost applications, but were increased with applications of urea.

Compost applications increased soil organic matter over the control and urea

treatments, while soil pH was lowest in the urea plots. Although low in all

treatments after 5 years of annual fertilizer applications, soil salinity was slightly

higher in the treatment receiving high rates (90 t ha-1) of a manure-based

compost. In one experiment, fresh basil aroma intensity increased with fertilizer

applications.

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Compost was therefore determined to be a very valuable resource for Hawaii

vegetable growers.

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TABLE OF CONTENTS

Acknowledgements…………………………………………………………………….iii Abstract.................................................................................................................iv List of Tables…………………………………………………………………………….v List of Figures…………………………………………………………………………...ix Chapter 1: Introduction…………………………………………………………………1 Chapter 2: Literature Review…………………………………………………………..4 Introduction………………………………………………………………………4 Compost Applications Effects on Vegetable Yield…………………………..4 Poultry Manure Effects on Vegetable Yield…………………………………11 Basil……………………………………………………………………………..15 Plant Nutrient Status…………………………………………………………..18 Nematode Control with Compost and Chicken Manure Applications……21 Fusarium wilt Control with Compost Applications………………………….24 Sensory Quality of Fresh Basil……………………………………………….28 Literature Cited…………………………………………………………………33 Chapter 3: Basil Yield and Tissue Levels in Response to Poultry Manure and Urea Applications…………………………………………………………………...…47 Abstract…………………………………………………………………………47 Introduction…………………………………………………………………….48 Materials and Methods………………………………………………………..49 Results………………………………………………………………………….52 Discussion and Conclusions………………………………………………….52 Literature Cited…...……………………………………………………………55 Chapter 4: Effects of Compost Applications on Basil Yield, Tissue Nitrogen Concentration and Sap NO3

- -N Levels……………………………………………...66 Abstract…………………………………………………………………………66 Introduction……………………………………………………………………..67 Materials and Methods………………………………………………………..69 Results and Discussion……………………………………………………….73 References Cited………………………………………………………………78 Chapter 5: Basil Yield and Soil Quality As Affected By Compost and Urea Applications…………………………………………………………………………….99 Abstract…………………………………………………………………………99 Introduction……………………………………………………………………100 Materials and Methods………………………………………………………102 Results and Discussion……………………………………………………...106 Conclusions…………………………………………………………………...110 Literature Cited……………………………………………………………….111 Chapter 6: Effects of Compost and Synthetic Fertilizer Applications On the Aroma and Flavor Intensity of Basil………………………………………………..126 Abstract………………………………………………………………………..126 Introduction……………………………………………………………………127 Materials and Methods………………………………………………………128 Results………………………………………………………………………...131

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Discussion…………………………………………………………………….132 Conclusions…………………………………………………………………...134 Literature Cited……………………………………………………………….135 Chapter 7: General Discussion……………………………………………………..143 Introduction……………………………………………………………………143 Yield……………………………………………………………………………145 Nematodes……………………………………………………………………148 Fusarium………………………………………………………………………149 Soil Quality……………………………………………………………………150 Plant Tissue Nitrogen and Sap NO3

--N Concentrations………………….151 Sensory Quality………………………………………………………………152 Concluding Statement……………………………………………………….153 Literature Cited……………………………………………………………….155

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LIST OF TABLES Table Page 3.1 Selected Soil Chemical Properties ......................................................60 3.2 Mean Nutrient Concentration of Most Recently

Mature Basil Leaves ('UH')......................................................................61 3.3 Estimated Yield Increase Due to Chicken Manure

and Urea Applications.............................................................................62 3.4 Effect of Poultry Manure and Synthetic Fertilizer Treatment on Nitrogen

Use of Basil.........………………………………………………...................63 4.1 Selected Chemical Properties of the Compost Used In This Experiment.........................................................................81 4.2 Mean Sap Nitrate and Tissue Nitrogen Concentrations and Mean Standard Error By Cultivar and Treatment.............................87 4.3 Relative Yield Increase of Fertilizer Treatments Over Control..................88 4.4 Treatment Effect on Nitrogen Use of Basil Cultivar ‘Sweet Italian’...........89 4.5 Treatment Effect on Nitrogen Use of Basil Cultivar ‘UH’...........................90 4.6 Treatment Effect on Nitrogen Use of Basil Cultivar ‘Thai’.........................91 5.1 Selected Chemical Properties of the Compost Used In This Experiment.......................................................................115 5.2 Selected Chemical Properties of Treatment Soil Prior To Compost Application...............................................................115 5.3 Relative Cumulative Yield Increase of Fertilizer Treatments Over Control........................................................123 5.4 Effect of Fertilizer Treatments On Nitrogen Use of Basil Cultivar ‘UH’..........................................................................................124 5.5 Root Gall and Root Health Index Scores

By Treatment and Cultivar....................................................................125

5.6 Selected Chemical Properties of Treatment Soil………………………....126

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6.1 Analysis of Variance For Aroma and Flavor Intensity of Fresh Basil Leaves, Fall 1998……………………………………….....137 6.2 Effect of Fertilizer Treatments on Sensory Scores of First Panel...........137 6.3 Descriptors Used Independently By Panelists To Qualify Fresh Basil Aroma, Panel 1.................................................138 6.4 Terms Used Independently By Panelists To Qualify Fresh Basil Flavor, Panel 1..................................................139 6.5 Analysis of Variance For Aroma and Flavor Intensity of Fresh Basil Leaves, Spring 1999......................................................140 6.6 Effect of Fertilizer Treatments on First Panel Sensory Scores...............140 7.1 Treatment Effect on N use Efficiency of cv. Sweet.................................159 7.2 Fertilizer Treatment Effect on selected Chemical Properties of Treatment Soil................................................................169 7.3 Fertilizer Effect on Tissue Nutrient analysis (cv. UH)..............................170 7.4 Fertilizer Effect on Tissue Nutrient Analysis (cv. Sweet).........................171

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LIST OF FIGURES Figure Page 3.1 Effect of Chicken Manure and Urea Application

on Mean Cumulative Yield of Basil.........................................................57

3.2 Effect of Poultry Manure and Synthetic Fertilizer on Final Plant Weight.............................………………………………………..................58

3.3 Effect of Poultry Manure and Synthetic Fertilizer Treatment on Mean

Tissue NitrogenConcentration...................................................................59 3.4 Tissue Nitrogen Relative to Basil Yield…..................................................64 3.5 Effect of Poultry Manure Application on

Soil Organic Carbon Content..................................................................65 4.1 Effect of Compost Rates and Urea Applications

on Mean Cumulative Yield By Treatment................................................82 4.2 Mean Cumulative Yield of Cultivars By Treatment...................................83 4.3 Effect of Fertilizer Treatments on Soil Organic Carbon Content....... .......84 4.4 Effect of Treatment on Root Gall Index Scores of Cultivars.....................85 4.5 Effect of Treatment on Root Health Index Scores

Basil Cultivar ‘UH'...................................................................................86 4.6 Total Nitrogen Concentration of Basil Leaves

Relative To Stem Sap Nitrate-N.............................................................92 4.7 Total Nitrogen Concentration of UH Basil Leaves Relative to Stem Sap Nitrate-N...............................................................93 4.8 Total Nitrogen Concentration of SWEET Basil Leaves Relative to Stem Sap Nitrate-N...............................................................94 4.9 Total Nitrogen Concentration of THAI Basil Leaves Relative to Stem Sap Nitrate-N...............................................................95 4.10 Yield of Cultivar SWEET Relative to

Stem Sap Nitrate-N Concentration.........................................................96

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4.11 Yield of Cultivar UH Relative to Stem Sap Nitrate-N Concentration...................................................................97 4.12 Yield of Cultivar UH Relative to Tissue N

Concentration..........................................................................................98 5.1 Effect of Several Compost and Synthetic Fertilizer

Treatments on Yield………………………………………………………..116 5.2 Effect of Several Compost and Synthetic Fertilizer Treatments on Yield Response of Cultivars to Treatment……………..117 5.3 Effect of Treatment on Stem Sap Nitrate-N of Basil................................118 5.4 Effect of Several Compost and Synthetic Fertilizer Treatments on Total Nitrogen Content of Basil Leaves........................119 5.5 Mean Plant Health Index of Cultivar UH As Affected By Treatment.....................................................................120 5.6 Percent of the Total Number of ‘Thai’ Plants exhibiting Symptoms of Fusarium Wilt Relative to the NH4+-N:NO3- N Ratio In the Soil......121 5.7 Mean Soil NH4+ N and NO3- N Levels of Treatments Over Time.............................................................................................122 6.1 Score Sheet Used By Panelists In the First Sensory Evaluation of Basil, Fall 1998..........................................141 6.2 Score Sheet Used By Panelists In the Second Sensory Evaluation of Basil, Spring 1999...............................142 7.1 Effect of Treatments on Cumulative Yield of ‘Sweet’..............................160 7.2 Effect of Treatments on Cumulative Yield of ‘Thai’.................................161 7.3 Effect of Treatments on Cumulative Yield of ‘UH’..................................162 7.4 Yield Trend of ‘UH’ Over Time, Fall 1998...............................................163 7.5 Yield Trend of ‘UH’ Over Time, Fall 1998 and Spring 1999....................164 7.6 Mean Plant Parasitic Nematode Levels By Treatment............................165 7.7 Root Gall Index by Treatment for Two Experiments...............................166

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7.8 Mean Gall and Root Health Index Scores of 'UH'...................................167 7.9 Effect of Fertilizer Application on Soil Organic Carbon Content..............168

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CHAPTER 1

INTRODUCTION

Prior to the nineteenth century, fresh and composted manure were among

the primary tools employed to maintain agricultural soil fertility (Martin and

Gershuny, 1992). In the mid 1800’s, Justus von Liebig and others proposed that

mineral salts replace organic amendments as the source of essential plant

nutrients needed for agricultural production (Brock, 1997). This new emphasis on

chemistry, and the industrialization of agriculture in America and Europe through

the first half of the 20th century, brought with it a reduced emphasis on the use of

manure and organic matter to sustain soil fertility (Howard, 1943).

Application of organic amendments such as compost and chicken manure

have been demonstrated to be effective tools to manage soil fertility in vegetable

production (Roe, 1998; Verma, 1995). These amendments not only supply

essential plant nutrients to a crop, but by virtue of their organic fraction can

improve the nutrient holding capacity of soils, nutrient availability, beneficial soil

micro organism activity, soil structure, and plant growth in acid soils (Marchensini

et al.,1988; Woomer et al. 1994; Marcus et al., 1995; Hue and Sobieszczyk,

1999). In addition to these effects on crop production, utilization of chicken

manure and compost in vegetable systems in Hawaii provides an opportunity to

reduce the amount of inputs (i.e. fertilizers) needed to be brought into the State.

Maximum use of locally available resources is an integral part of sustainable

vegetable production in the tropics (Valenzuela, 2000), and composting provides

an opportunity to recycle materials that would otherwise add to the amount of

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waste needing disposal. In fact, recycling is one of the primary reasons cited by

growers for substituting organic fertilizers for their synthetic counterparts

(Wallace, 1994)

Basil is an important crop in Hawaii (HASS 1999) that has shown positive

yield response to applications of locally produced compost (Valenzuela et al.

1999). However, rate recommendations are not available for organic fertilization

of basil in the tropics. Chicken manure and compost have been used to

effectively control root-knot nematodes and disease caused by Fusarium

oxysporum (Coosemans, 1982; Chindo and Kahn, 1990, Raj and Kapoor, 1997),

both of which are major constraints to basil production in Hawaii. No detailed

information is available on the response of these pests to compost and other

fertilizer applications in a basil production system under Hawaii conditions. Also,

no information is available on the effects of fertilization on the nutrient status of

basil, nor have critical N levels been determined specifically for this crop. There

is evidence that fertilization may affect the sensory quality of fresh-market basil

(Alder et al. 1989), but no studies have yet been conducted to evaluate the

impact that changes in nutritional regime may have on the taste or aroma of this

herb.

Thus, the objectives of this project were:

1. To evaluate the effects of available organic and synthetic fertilizers on the

yield of basil produced under field conditions in Hawaii.

2. To evaluate the effects of organic and synthetic fertilizers on important soil

qualities.

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3. To determine the potential of sap nitrate analysis using a portable nitrate ion

selective electrode to diagnose the nitrogen status of basil.

4. To evaluate the potential of organic fertilizer use as a pest control measure in

basil produced under field conditions.

5. To evaluate the sensory quality of fresh sweet basil as affected by organic

and synthetic fertilizer applications

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CHAPTER 2

LITERATURE REVIEW

Introduction

Much work has been conducted on the use of compost and chicken manure as a

soil amendment in vegetable production. The literature pertaining to basil as an

important agricultural crop, the potential for fertilization practices to influence the

sensory quality of fresh produce, and the use of rapid sap nitrate analysis to

manage the fertilization of vegetable crops is similarly extensive. This review of

the literature focuses on the following topics:

1. The effects of compost applications on vegetable yield

2. The effects of chicken manure applications on vegetable yield

3. Basil as an important agricultural crop

4. Rapid analysis of petiole sap NO3- to determine crop nutrient status

5. Nematode control with compost and chicken manure applications

6. Fusarium wilt control with compost applications

7. The potential of fertilization to affect the sensory quality of fresh basil

Compost Application Effects on Vegetable Yield

Compost Quality and nutrient value

A major obstacle to the development of universal recommendations for the use of

compost in vegetable production is the considerable variation in quality of

commercially available composts (Hue et al, 1995; Ozores-Hampton, 1998; Roe,

1998). The concepts of maturity and stability are frequently associated with

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compost quality, and used interchangeably (Hue, 1997). Standards in Canada

designate compost of adequate maturity for vegetable production if it has a C:N

ratio ≤ 25:1, it does not inhibit the germination of radish or cress seed, and if the

microbial activity within the compost is low (Composting Council of Canada,

1998). Ozores-Hampton et al. (1998) define a mature compost as one which is

not phytotoxic, and which does not immobilize soil N. Use of an immature

municipal solid waste compost negatively affected cucumber seed germination

and seedling development (Sainz et al, 1998); further composting eliminated

phytotoxicity of the product. Adverse effects of immature compost on vegetable

production were also observed by Kostewicz (1993), who reported a negative

linear correlation between pole bean yield and application rates (0, 25, 50, 100 t

ha-1 ) of an immature, unscreened, wood based compost, most likely due to

nitrogen immobilization.

Nitrogen content and availability are often the most important criteria

vegetable growers are interested in when the primary goal of compost

applications is increased crop yield. Most of the nitrogen will be in organic form

and therefore subject to release over time by microbial degradation. High soil

moisture, high temperatures, and aerobic conditions facilitate rapid conversion of

organic N to plant available mineral form by soil microorganisms (Tisdale et al.

1993). As a result, N release rates may be expected to be higher in the tropics

than in temperate regions (Woomer, et al., 1994).

Compost stability refers to the potential for a compost to release, or mineralize,

its organic N and is frequently measured by the ratio of total organic carbon to

6

organic nitrogen (C:N) (Hue and Liu, 1995; Ozores-Hampton et al., 1998). A C:N

ratio <25:1 is usually necessary for any mineralization of N, with a C:N ratio <15

indicating high N availability (Bezdicek and Fauci, 1997). For example, first year

N mineralization of a compost with a high N concentration and low C:N ratio may

be as high as 50% (Buchanan and Gliessman, 1991). General N mineralization

estimates developed for the continental U.S. are 10% the first year, 5% the

second year, and 2-3% the third year (Compost Council, 1996), and those for the

tropics are 15, 5, 3 and 3% for the 1st, 2nd, 3rd, and 4th year after application,

respectively (Hue, 1997). Erbertseder et al. (1996) found the ratio of organic

carbon to total nitrogen C:N (total) of the compost solid phase to accurately predict

the N release rate of a compost as measured by N uptake in oat seedlings. N

availability increased with decreasing C:N ratio. However, these workers found

that using C:N (total) to compare nitrogen availability between composts was only

useful when composts originated from similar feedstocks. This may explain the

findings of Hue et al. (1995), who observed the C:N(total) ratio of the solid phase to

be a poor indicator of compost stability when applied to a group of composts

varying in parent material.

Application of compost to meet crop N needs results in the addition of

considerable amounts of other nutrients. Estimates of compost P availability from

Washington State University is 5-15%, while almost all compost K is plant

available (Bezdicek and Fauci, 1997). Additions of 11 t ha-1 of a chicken manure

based compost significantly increased soil P and K, and shoot P concentrations

in peppers with respect to those grown in synthetic fertilizer plots that received

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149, 0, 93 kg ha-1 of N,P,K, respectively (Douds et al., 1997). A review of several

long-term studies on the effect of compost applications on rice yield

demonstrated that the positive yield response observed was primarily due to

nitrogen effects, although continued applications increased plant available soil P

and K levels by 35 and 113% respectively (Kumazawa,1984). Sainz et al. (1998)

also found compost applications to increase soil and plant tissue concentrations

of P, K, and micronutrients. In another study, tissue N, P, Mn and Cu levels of

bean increased with increasing compost applications (Browaldh, 1992).

Compost effects on soil quality

Compost applications may affect soil properties important in vegetable

production, such as pH, organic matter content, CEC and salinity. For example,

applications of ammonium sulfate were found to significantly increase soil acidity,

while low rates of compost applied with synthetic N appeared to buffer soil pH

(Buchanan and Gliessman, 1991). The same study showed compost

applications of 30 t ha-1 to significantly raise soil pH with respect to plots

receiving either synthetic fertilizer or no amendment. Sainz et al. (1998)

observed that application of compost to a slightly acid soil raised the pH from 6.5

to 7.2. In Hawaii, soil salinity as well as pH increased with increasing rates of

chicken manure-and-wood-chip-based compost applications (Silva et al., 1995.).

Bevacqua and Mellano (1994) reported a decrease in soil pH from 7.7 to 7.4

with applications of compost, while soil organic matter, nutrient concentration,

and salinity increased compared to the control. In Thailand, soil CEC increased

8

after 9 years of compost applications in flooded rice production, but soil pH and

organic carbon content was little affected (Songmuang et al., 1984).

Compost applications affect microbial activity

Compost applications affect plant growth by influencing soil

microorganism populations. For example, applications of chicken litter-based

compost increased mycorrhizal colonization, and compost additions increased

the number of mycorrhiza spores over levels in soil receiving synthetic fertilizer or

raw dairy manure (Douds et al., 1997). Applications of composted stable manure

(0.3% P) to pepper reduced mycorrhiza root colonization with increased rates up

to the maximum applied 300 dry t ha1 (Brechelt 1989). In another study, compost

applications increased extractable P and decreased root colonization by

mycorrhiza (Sainz et al., 1998). In Australia, Sivapalan et al. (1993) found soil

fungi, total bacteria, and actinomycete populations to be significantly higher in

plots receiving 120 t ha1 than those receiving 80 t ha1 of compost. They also

found that microbial populations, particularly those of Trichoderma and

Penicillium, were higher in soil receiving a chicken manure based compost as the

sole source of crop nutrients than those in synthetic fertilizer plots. In a pot trial

with tomatoes, additions of manure based composts did not stimulate total soil

microorganism populations in the rhizosphere with respect to a control receiving

no amendment. However, the compost treatments did increase the percentage of

phytopathogen antagonists (de Brito Alvarez et al., 1995). In other work, compost

applications to contaminated soil improved plant growth, enhanced microbial

9

activity, and resulted in degradation of persistent soil pesticides with respect to

unamended soil (Liu and Cole, 1996).

Compost application rates associated with increased crop yields

Compost Application rates of 10-60 t ha-1, on a dry weight basis, are

generally recommended for vegetable production, although applications as low

as 7 t ha-1 have shown positive effects on vegetable yields (Compost Council,

1996; Roe, 1998).

In Hawaii, a chicken manure and wood-chips compost treatment

increased corn biomass production up to a rate of 50 t ha-1, with yield decreasing

at higher rates (Silva et al., 1995). Other workers reported that applications of 11

t ha-1 dry weight compost increased azuki bean yields over 112 kg ha-1 synthetic

N and control treatments (Robinson 1983). Lettuce and onion yields were

increased with compost applications of 37 and 74 t ha-1 over a control treatment

(Bevacqua and Mellano, 1994). Lettuce yields in this experiment were higher

with the highest compost application rate, while onion yields were not different

between the two compost application rates. The same study found stand

establishment of lettuce and onion to increase with sewage sludge compost

applications of when compared to controls, with no significant difference between

rates. Also with lettuce, Stopes et al. (1989) reported a yield increase in response

to application of composted farm yard manure (.9% N), with highest lettuce yields

obtained at the highest rate of application of 18 dry t ha-1. Yield at this rate was

not different than that obtained with 160 kg ha-1 synthetic N. Other studies have

10

shown similar results. For example, when a manure based compost was applied

to cabbage and carrot to provide 300 and 170 kg ha-1 N respectively, crop yields

and tissue N levels were the same as those obtained in synthetically fertilized

plots receiving the same N rate (Warman and Havard 1997). This ability of

compost to meet all plant nutrient needs previously met with synthetic fertilizers

was also reported in rice (Inoko, 1984). However, crops may differ in their

response to fertilizer type. Chu and Wong (1987) investigated the yield response

of carrot, tomato and Chinese cabbage to compost applications between 0-150 t

ha-1, and an application of a 15-9-15 fertilizer at 2 t ha-1. Optimum carrot yields

were obtained with 50 t ha-1 compost, while the highest tomato and Chinese

cabbage yields were observed in the synthetic fertilizer treatment. In this

experiment, cabbage leaf yield was not increased with compost applications,

while tomato plant biomass increased at a much higher rate than did fruit yield in

the compost treatments. Yields of bitter eggplant (Solanum aethiopicum) plants

receiving 20 t ha-1 of composted wood chips were 750% higher than those

receiving no amendment (Seck and Lo, 1998).

In addition to the application rate, the method of application may also

effect plant response to compost applications. Plant response to compost

applications may be greater, for example, when the compost is incorporated into

the soil than with surface application of compost. Compost incorporation to a

depth of 15 cm is recommended by the Compost Council (1996) . McSorley and

Gallaher (1995) found that incorporation of compost at 269 t ha-1 was more

11

effective in increasing squash and okra yield than surface applications at the

same rate.

Despite the positive effects compost has on the yield of food crops, the

low nutrient concentration and high cost of composts relative to synthetic

fertilizers makes it impractical to consider compost as a complete replacement

for mineral fertilizers in conventional systems (Buchanan and Gliessman, 1991;

Bittenbender et al., 1998). However, they may be used in conjunction with each

other to increase soil organic matter, and reduce loss of inorganic N from the

agroecosystem.

Buchanan and Gliessman (1991) observed that applying 3 t ha-1 compost plus 75

kg ha-1 synthetic N improved N use efficiency of broccoli, probably due to the

compost serving as both a sink and a subsequent source for inorganic N. It was

also observed that when 15-21 t ha-1 of compost was applied with synthetic N at

rates greater than 170 kg ha-1, there was an increase in rice yield that could not

be obtained with synthetic N alone (Kumazawa, 1984). Again, the likely

explanation for this apprently synergistc effect is the immobilization and

subsequent mineralization by compost microbial activity of excess synthetic N

that would otherwise be lost to the crop.

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Poultry manure effects on vegetable yield

Introduction

With over 500,000 layers in the state, poultry manure represents a

significant potential source of plant nutrients to Hawaii vegetable growers (HASS,

2000). As with other organic fertilizers, no crop specific recommendations are

available to Hawaii vegetable growers who want to incorporate poultry manure

into their fertility program. Currently, the University of Hawaii recommends

thoroughly composting animal manure to ensure destruction of any human

pathogens it may contain (LeaMaster et al., 1998).

Poultry manure as a source of plant nutrients

Poultry manure generally has a higher total N concentration and lower C:N

ratio than composts resulting in a relatively quick release of plant available N

(Parnes, 1990). A portion of the total N in poultry manure is organic, and release

rates are therefore generally slower than with synthetic fertilizers (Goh and

Vityakon, 1983). Approximately 30-50% of total N in poultry manure becomes

available over to a crop following application (Castellano and Pratt, 1981; Hue,

1997). Vegetable yield increases in response to poultry manure applications are

frequently attributed to N effects (Hochmuth et al. 1993; Hue and Sobiezczyk,

1999). However, poultry manure contains a wide range of plant nutrients, and is

also considered a good source of Mg and Ca (Mengbo et al. 1997). In fact, P

levels in both soils and plant tissues have been shown to significantly increase

13

with poultry manure applications, and may actually lead to excessive P levels in

soils not deficient in that nutrient (Cheung and Wong, 1983; Browaldh, 1992; Hue

and Sobiezczyk, 1999).

Poultry manure affects soil quality

Poultry manure applications can affect soil properties. Poultry litter

applications of 4.8, 9.5 and 19.0 t ha-1 increased soil pH over a control and

synthetic fertilizer treatment, but showed no significant difference in this effect

between manure application rates (Brown et al., 1993). In another study, poultry

manure applied at rates above 10 t ha-1 raised soil pH (Opara and Asiegbu,

1996). Similarly, Cheung and Wong (1983) observed poultry manure increased

cabbage yield, and raised soil pH and OC content. Surface application of poultry

manure also effectively increased soil pH and decreased plant available

aluminum (Hue and Licudine, 1999). Mian and Rodriguez-Kabana (1982) found a

positive linear relationship between application rates of poultry manure, and

increasing soil pH. Soil quality may also be negatively affected by applications of

chicken manure. Increased soil salinity was speculated to be the cause of

significantly more tipburn of cabbage observed in plots receiving poultry manure

than in those receiving synthetic fertilizer (Hochmuth et al, 1993). However, in an

earlier study Goh and Vityakon (1983) reported that manure applications did not

alter soil salinity or pH levels, while ammonium sulfate and urea increased

salinity and lowered pH.

14

Effects on soil microbial activity

Soil microorganism activity may also be affected by poultry manure

applications. Doran et al. (1988) found no effect of synthetic fertilizers on soil

microbial populations, but found that incorporation of organic amendments

including manure enhanced soil microorganism levels. Chicken manure

applications at three rates (1x, 2x and 3x) increased common bean biomass and

rhizobial infection (Browaldh, 1992). Bean biomass in this experiment was

similar for all three manure treatments and root nodule dry weight significantly

higher in the 3x treatment than in the lower rates.

Application rates associated with increased vegetable yield

General poultry manure application rate recommendations of 7-23 t ha-1

have been made in the past for Hawaii home-gardeners (McCall, 1974). Oikeh

and Asiegbu (1992) observed an increase in tomato yield with applications of 10 t

ha-1 dry weight chicken manure over plants receiving no amendment or synthetic

fertilizer at 150 kg ha-1 N, with yield decreasing at manure rates of 20 and 30 t

ha-1. In northern Florida, highest marketable yields in cabbage were obtained

with 19 t ha-1 chicken manure, and were statistically similar to yields obtained

with 130 kg ha-1 synthetic N (Hochmuth et al. 1993). Kogbe (1980) found no

increase in yield of Celosia sp. (a West African leafy vegetable) with chicken

manure applications lower than 20 t ha-1, with highest yields obtained at 20 or 40

t ha-1. This response to manure applications was found to be cultivar dependant.

15

Warman (1990) found no yield response in tomato, cabbage, or cauliflower to

applications of chicken manure at 10 t ha-1. Opara and Asiegbu (1996) reported a

linear increase in West African eggplant (Solanum sp.) yield with increased rate

of poultry manure application of 0-20 t ha-1. Yield of strawberries increased with

increased rate of chicken manure application between 0-12 t ha-1, while lettuce

yield was not significantly affected by additions of manure or synthetic fertilizer

(Rubeiz et al.,1998). Yield response of vegetables to poultry manure

applications varies with crop and location; it is therefore important to conduct

yield response trials on a crop by crop basis in the region in the region the

commodity is to produced.

Basil

Ocimum basilicum is one of the best known of ∼160 Ocimum species, all

of which are commonly referred to as basil (Sobti and Pushpangadan,1977). O.

basilicum is an important crop world wide grown for its fresh and dry herb, and

the essential oil which is used as a food additive and in cosmetics (Prakesh,

1990). There are literally dozens of forms of O. basilicum which are classified

based on plant morphology, pigmentation, and/or chemical composition of the

essential oil (Simon et al., 1990; Prakesh, 1990; Small, 1997). Rindels (1997)

classifies several distinct types of O. basilicum as subspecies; types having

distinct scents of cinnamon, lemon, or licorice are given the designation O.

basilicum odoratum, and dwarf varieties are O. basilicum minimum.

16

Reproduction

O. basilicum (basil) is a tetraploid (2n=48) (Sobti and

Pushpangadan,1977; Ryding, 1994). Forms within the species are interfertile,

although differences in flower morphology may prevent natural outcrossing

(Darrah, 1974; Sobti and Pushpangadan,1977; Nation et al., 1992).

Basil is open-pollinated (OP) with honey bees being the most common pollinators

(Darrah, 1974; Nation et al., 1992). Darrah (1974) found reduced seed set in

manually selfed plants compared to OP plants, but no differences in germination

rate, percentage, seedling growth or other indications of inbreeding depression

were observed.

Importance in Hawaii

Sweet and Asian basil are the commercially important varieties in Hawaii.

850 tons of basil were produced in the state in 1998 for a total farm-gate value of

$2.7 million, making it by far the most important herb crop grown in the state

(HASS, 1999). Sweet basil accounted for 70% of the total locally produced basil,

and had a higher farm-gate value that the Asian type.

Cultural requirements

Basil is either direct seeded or transplanted, and may be propagated by

cuttings. Most varieties germinate in 4-6 days and initiate flowering 14 weeks

after germination (Darrah, 1974).

17

Spacing is dependent on cultural practices. Multiple row beds are commonly

used with 60-90 cm row spacing and plants within a row 15-60 cm apart; spacing

for single-harvest operations is generally less dense than that for a planting

harvested over an extended period of time (Hamasaki et al., 1994). Fertilizer

recommendations for basil production in Hawaii are 135 kg ha-1 each N, P205,

K20 as a preplant application when plants are grown in soils deficient in these

nutrients, plus a sidedress of N at 22-34 kg ha-1 following the first harvest

(Hamasaki et al., 1994). These recommendations are similar to those made for

the temperate U.S. (Davis, 1997). Recommendations for India are similar in total

amount of nutrients applied, but differ in that the preplant application is reduced

by one third, and the balance is applied as several split applications over the crop

lifecycle (Gulat and Duhan, 1972). A complete fertilizer applied at 120-100-100

kg ha-1 N-P205-K20 was found to be optimum for basil production on a nutrient

poor sandy soil (Wahab and Hornol, 1982). Tesi et al. (1995) found basil to be

sensitive to high rates of fertilizer, with plant growth reduced with increasing rate

of soluble fertilizer between 1-5 g/l applied to plants growing in a peat potting

mix. Excess N fertilizer will reportedly reduce the postharvest quality of basil

(Hamasaki et al., 1994; Davis, 1997). No difference in yield response was

observed between ammonium and nitrate N sources by Tesi et al. (1995), and

they reported better plant response with a 1-1-2 than a 1-1-1 fertilizer ratio. Tesi

(1997) observed that plant growth and leaf nitrate content increased with

increased N applied at rates of 0-80 kg ha-1. Gupta and Shah (1989) found B,

18

Cu and Mn foliar sprays to increase yield of field-grown basil. Levels of these

nutrients in the soil and other soil information were not reported.

There are no rate recommendations for organic fertilization of basil. In

Hawaii, Valenzuela et al. (1999) recorded commercially acceptable basil yields

with applications of 25 t ha-1 of compost, with yields from compost plots not

being significantly different from those receiving 110 kg ha –1 of synthetic N.

When using an organic source of nutrients for basil fertilization, the reduced rate

of nutrient release from organic materials must be taken into account. For

example, Aflatuni (1993) found 34% greater yields in basil fertilized with synthetic

fertilizer than plants given compost to supply an equivalent amount of total N.

Zidan and Al-Zahrani (1994) report basil to be moderately tolerant to salinity. A

pH range of 4.3-8.2 is reported to be acceptable for basil (Simon et al. 1984),

while the optimum range is 6.0-7.5 (Hamasaki et al., 1994). In Hawaii, harvested

shoots are 10-15 cm long and consist of 2-4 pairs of true leaves (Hamasaki et al.

1994).

Plant Nutrient Status

Determination of nutrient concentrations in plant tissues is an important tool to

manage a crop fertility program (IFA, 1992). Tissue nutrient concentrations may

be used to diagnose the nutrient status of a plant at the time of sampling,

estimate the potential for a crop to reach optimum yield, and to time fertilizer

applications (Coltman, 1988; Smith and Lonegran, 1997). Plant age, genotype,

19

type of tissues sampled, and environmental conditions affect tissue nutrient

concentrations in vegetables, and need to be considered when determining or

using critical ranges to determine the nutrient status of vegetables (Mills and

Jones, 1996; Huett et al. 1997). Scaife (1988) maintains that directly relating

tissue nutrient levels to yield is inherently flawed because the relationship

between the two parameters is not necessarily one of cause and effect.

Nitrogen is the plant nutrient required in largest quantities, and N deficiency is

often a limiting factor in vegetable production (Marschner, 1995). Much work has

been done to establish sufficiency ranges for total N, and more recently sap

nitrate-N evaluations have been conducted for various vegetable crops

(Hochmuth, 1994; Smith and Lonegran, 1997). Sap nitrate-N as measured by a

quick test method such as merkoquat (Merk) test strips or a hand-held nitrate ion

selective electrode can be an effective way for a grower to determine the nutrient

status of a crop in the field (Hochmuth, 1999; Huett and White, 1992). Not only

are results obtained more quickly, but sap nitrate-N levels may be a better

indicator than total tissue N of plant nutrient availability in the soil. For example,

petiole sap nitrate-N concentrations as measured with Merck test strips were

more sensitive, but more variable (higher CV), than total tissue N to nitrogen

fertilizer applications (Huett and Rose, 1989). Olsen and Lyons (1994) similarly

reported that sap nitrate-N in pepper showed greater change than tissue N

concentrations in response to fertilizer applications. Sap nitrate-N concentrations

were found to be better correlated than total tissue N with nitrogen application

20

rates (Prasad and Spiers, 1985). Warnke (1996) found petiole sap nitrate-N to

increase with increased rate of N fertilizer in carrot.

Results from rapid analysis of sap nitrate-N which can be conducted in the

field have been shown be reliable when compared with laboratory results. Work

done with cabbages and tomatoes showed that sap nitrate-N concentrations

measured with a Merck test strip were significantly correlated with laboratory

results (Prasad and Spiers, 1984; Huett and Rose, 1989). In Hawaii, the

monitoring of petiole sap nitrate-N levels using Merck strips was used to

effectively manage N fertilization of greenhouse tomatoes, but required frequent

sampling (Coltman, 1988).

Use of a nitrate ion selective electrode is another method for rapid sap nitrate-N

analysis. Results between test strips and nitrate selective electrodes have been

found to be similar (Scaife and Stevens 1983). Kubota et al. (1996) found

broccoli petiole nitrate-N measurements taken with a portable Cardy nitrate ion

meter to correlate well with previously developed critical ranges for sap nitrate-N.

Hartz et al. (1994) also found determinations of sap nitrate-N using a portable

nitrate meter to be highly correlated with measurements made with conventional

lab techniques in a wide variety of vegetables.

Rapid sap nitrate-N analysis has been proposed to be a potentially

valuable tool for growers to use in managing the nutrient status of their crop. In

fact, critical ranges of petiole sap nitrate-N concentrations have been determined

for a number of vegetables including broccoli, carrots, lettuce, collard, cucumber,

melons, squash, pepper, potato, tomato, and eggplant (Hochmuth, 1994;

21

Warnke, 1996; Huett et al., 1997). However, some studies with sap analysis for

nutrient calibrations have also shown inconsistent reports. For example, Beverly

(1994) found tomato petiole sap nitrate-N as measured with a portable meter to

be highly variable and not correlated with either nitrogen applications or plant dry

weight.

Some studies have shown that sap nitrate-N measures can be more

variable than other techniques to determine crop N status (Beverly, 1994; Huett

and Rose, 1989). No differences were found between sap measurements taken

immediately after sampling and those taken up to 16 h after sampling if petioles

without leaves were stored on ice in sealed plastic bags (Hochmuth 1994).

Internal crop factors may also contribute to the observed variability in sap nitrate

concentrations. For instance, Scaife and Stevens (1983) found significant

differences in concentrations between individual cabbage plants of the same

cultivar, and between tissue location within a plant, but there was no effect of

time of day on sap nitrate-N concentrations. Therefore, while it has been shown

to be a potentially useful tool to determine plant nutrient status, the wide

variability of results obtained with rapid sap nitrate-N analysis demonstrates the

importance of conducting research under field conditions before making

recommendations to growers.

22

Nematode control with compost and chicken manure applications

Introduction

Root-knot nematodes (Meloidogyne spp.) are serious pests of vegetable

crops world-wide (Johnson, 1998). In Hawaii, nematodes are a major limiting

factor in basil production, with M. incognita and M. javanica being the primary

pests (Hamasaki et al., 1994). In addition to directly affecting a crop’s ability to

develop normally, nematodes can interact with other phytopathogenic organisms

to create a disease complex that may have more devastating effects than either

pathogen individually (Webster, 1985). Effects of organic amendments on

nematode populations varies with nematode species and type of amendment,

and organic amendments play a relatively minor role in an integrated nematode

management program (Miller, 1977; Duncan and Noling, 1998). Application of

organic amendments may affect nematode populations and their virulence

towards a host crop by improving plant vigor and thereby increasing resistance to

attack, by promoting soil microorganism populations which may compete with or

be antagonistic towards parasitic nematodes, or by containing nematicidal

compounds (Coosemans, 1982).

23

Nematode suppression with chicken manure

Several reports have documented nematode suppression with poultry

manure applications. For example, M. incognita levels and root galls on tomato

were reduced with the application of chicken manure at 2 t ha-1, and continued to

decline with increased application rates (Chindo and Kahn, 1990). This effect

was attributed to nematicidal properties in the manure; researchers found that a

solution of 4% manure in water inhibited hatching in over 99% of exposed eggs,

and killed all juveniles after 12 h exposure. Babatola (1989) found chicken

manure rates as low as 1 t ha-1 to decrease Meloidogyne and Helicotylencus

populations and to reduce root galling of tomato. Mian and Rodriguez-Kabana

(1982) found chicken manure incorporated into potting soil at 1% by volume to

reduce root galling of squash caused by M. arenaria and observed the decline in

galling to be associated with a corresponding increase in soil microbial levels as

determined by urease activity.

Nematode suppression with compost

Work done with compost has shown it to effectively suppress some plant

parasitic nematodes. In one study, leaf mold composts applied at 20 t ha-1

reduced Pratylenchus penetrans populations with respect to a control receiving

no compost or nematicide, while nematicide applications gave the highest and

most consistent level of control (Miller 1977). Coosemans (1982) observed that

compost mixed with soil at 10% by volume resulted in the lowest levels of root

galling in lettuce by M. hapla and the highest levels of soil microbial activity. Both

24

higher and lower rates of compost incorporation (0, 5, 15, 20%) resulted in higher

galling incidence and lower microorganism activity. This study indicates that

there may be a relatively narrow range of compost application rate within which

nematode levels are effectively suppressed, with rates outside this range

ineffective in supressing nematodes. Application of 18 t ha-1 compost caused no

significant yield improvement in nematode infested citrus (Tarjan, 1977). Also,

McSorley and Gallaher (1995) found M. incognita densities in okra and squash to

be unaffected by very high compost application rates (269 t ha-1).

Fusarium wilt control with compost applications

The various formae specialis of Fusarium oxysporum cause significant

losses in vegetable production globally, particularly in the tropics (Roberts and

Boothroyd, 1972). F. oxysporum f. sp. basilici causes a disease in basil that

seriously limits production around the world (Wick and Haviland, 1992, Gamliel et

al.,1996). In Hawaii, F. oxysporum is a major pest of basil which effects almost

all commercial production areas in the state, and for which there is no chemical

control registered for use on the crop (Hamasaki et al., 1994; Uchida et al.,

1996).

A number of different cultural practices are available as useful tools in an

integrated Fusarium management program for basil. These include heat

treatment to sterilize seed (Davis, 1997), use of tolerant varieties (CTAHR, 1996;

Ruveni et al., 1998; Hamasaki unpubl. data), manipulation of microorganisms

25

antagonistic to the fungus (Minuto et al., 1995), and application of composts to

suppress the disease (Raviv et al., 1998).

The potential of compost to suppress plant diseases has received much

attention. While the use of compost in controlling Fusarium wilt of field grown

basil is promising, extensive work has not yet been conducted. Raviv et al.

(1998) showed that composts suppressed the disease in greenhouse produced

transplants. Severity of visual symptoms of basil seedlings grown in 100%

compost was lower than those grown in peat. The suppressive effect was found

to be biological as determined by a loss of suppressiveness when the compost

was autoclaved.

Compost applications have been shown to effectively reduce disease

severity caused by numerous other plant pathogens, and this suppressive effect

is generally associated with soil microbial activity (Huber et al, 1966; Cheung and

Hoitink, 1990; Hardy and Sivasithamparam, 1991; Hoitink and Grebus, 1996; Kim

et al., 1997). Serra-Wittling et al. (1996) showed that the addition of compost

increased a soil’s suppressiveness to Fusarium wilt, and the investigators

determined that this was caused by competition for nutrients by the total

microflora population with the pathogen (general suppression). They also

showed soil microflora to be more suppressive of Fusarium than the compost

microflora, and suggested that suppressiveness of compost is due to its acting

as a nutrient rich substrate for colonization by soil borne, antagonistic organisms.

In another study, the severity of Fusarium wilt of tomato was reduced with

compost application, and corresponded with an increase in total soil microflora

26

population (Raj and Kapoor, 1997). Amir et al (1993) found soils high in organic

matter to be significantly more suppressive to F. oxysporum than those with low

organic matter, despite the fact that the soil with higher organic matter also had a

larger population of the pathogen. These workers proposed that the beneficial

nature of a soil high in organic matter to the general microflora resulted in more

intense competition for nutrients resulting in survival of the pathogen innoculum,

but inhibiting germination of the propagules. Suppression of Fusarium may also

be associated with specific organisms. For example, Alvarez (1995) reported

that compost application affected species composition of the soil microflora

populations, favoring antagonists to Fusarium (Psuedomonas sp.), but did not

stimulate an increase in the total microbial population. Also demonstrating

specific antagonism of bacteria to Fusarium, Tsuge et al (1995) isolated the

bacteria B. subtilis from Bark compost and found it to produce substances

suppressive to Fusarium oxysporum. Bacteria are not the only biological control

agents with potential to suppress Fusarium. Minuto et al (1993) found that seed

treatment of basil with isolates of two antagonistic fungi significantly reduced the

number of infected plants. The biological antagonism afforded by compost may

be environmentally dependent, however. For example, Pera et al (1987) found

that fully composted poplar bark containing Bacillus pseudomonas antagonistic

to Fusarium increased resistance to Fusarium wilt in carnations in green house

experiments, but had no effect in field trials.

27

In addition to the biological soil fraction, soil chemical properties,

particularly pH, play a role in determining the severity of Fusarium. For example,

Scher et al (1980) eliminated the effectiveness of a soil suppressive to F.

oxysporum by reducing the pH from 8 to 6. In Italy, Melloni et al. (1995) reported

cucumber seeds planted in Fusarium infested soil, amended with compost, had a

higher germination rate than seeds planted in the same soil without compost; the

beneficial effect was associated with higher pH in compost amended soil.

Disease suppressiveness is dependent on compost quality. High salt

content, and rapid N release (i.e. high N, low C:N ratio) in compost can negate

suppressiveness (Hoitink and Grebus, 1994). The severity of Fusarium root rot

on bean was observed to increase with increasing soil inorganic N (Lewis and

Papavizas, 1977). Schmidt (1972) found F. solani pathogenecity in pea to

increase as the C:N ratio of incorporated plant residues decreased. Chef et al.

(1983) found fully composted tree bark to suppress Fusarium wilt in

chrysanthemum and Flax, with hardwood bark being more suppressive than pine

bark and immature compost less suppressive than mature compost. The authors

concluded that the higher carbon content in the hardwood compost provided

better nutrition for microorganisms and resulted in the highest level of

suppression.

The rate of nitrification of soil ammonium also plays a role in disease

suppression and is affected by the type of organic amendment applied as

demonstrated by Kirpichenko (1975) who found that the pathogenicity of F.

28

oxysporum was greater on media with ammonium than with nitrate .

Amendments which stimulate nitrification of soil ammonium are likely to suppress

soil pathogens, while amendments inhibiting or slowing nitrification may increase

disease severity (Watson and Huber, 1970). Use of nitrate rather than

ammonium fertilizers is recommend for control of Fusarium (Agrios, 1993). For

example, F. oxysporum in tomato was less severe when plants were supplied

with nitrate-N compared to ammonium-N (Woltz and Jones, 1973).

Therefore, the usefulness of compost to suppress Fusarium wilt of crops

varies, and is dependant in part on the chemical and biological quality of compost

to be used.

Sensory Quality of Fresh Basil

Introduction

Sensory quality of fresh produce is an important factor for consumers in

making purchasing decisions (Misra and Huang, 1991), and any cultural practice

which alters the sensory quality of produce may affect its marketability.

Little attention has been given to the sensory attributes of fresh basil, although

much work has been done on the composition of basil essential oil due to its

importance as an additive in food, toiletries and cosmetics (Parry, 1921; Charles

and Simon, 1990; Prakesh, 1990). It is from this oil that the fresh herb gets its

characteristic odor and flavor (Simon et al., 1990; Sheen et al, 1991).

29

Potential for fertilization to affect basil quality

Environmental effects on basil essential oil content and composition have

been well documented (Simon and Reiss-Bubenhiem, 1987). Ichimura et al.

(1995) found essential oil concentrations in basil to be higher in summer than

spring. Nitrogen fertilizer was found to affect essential oil content in sweet basil

increasing with increased N to an optimum level, then decreasing with higher N

rates (Youssef et al., 1998); these workers observed that the treatments

producing the highest herb yield also produced the highest concentration of

essential oil. Nitrogen and potassium fertilizers decreased the levels of eugenol

in tomato (Wright and Harris, 1985); eugenol is a major constituent of basil

essential oil (Sheen, 1991; Prakesh, 1990). Alder et al. (1989) found the form of

N applied to affect both the content and composition of basil oil.

Cultural methods which cause changes in basil essential oil content and

composition thus have the potential to also affect the aroma and taste of the

fresh product. However, analysis of chemical composition has limitations as a

tool in predicting sensory quality of fresh produce (Johnson et al. 1998;

Meilgaard et al. 1987). Direct panel evaluation of possible fertilizer effects on the

aroma and taste of fresh basil leaves is therefore necessary to evaluate the

potential of fertilization to affect fresh basil quality.

30

Evaluation of taste and aroma of fresh basil

Qualifying taste and aroma of basil is difficult because the sensory quality

attributes of fresh basil have not been thoroughly described, nor have specific

procedures been developed for evaluating the aroma and taste of fresh basil.

Lacking specific guidelines, objective measurements can only be made on the

intensity of aroma and taste. Paakokonen et al. (1990) evaluated taste and

aroma intensity of both dried and fresh basil with 12 trained sensory panelists

who scored samples 'weak' to 'strong' on a linear scale, and found both taste and

aroma intensity of dried basil to be stronger than that of fresh samples. The basil

samples were blended into a medium of mash potato.

Fertilization affects quality of other vegetables

Fertilization rate can affect the taste and aroma of agricultural products,

possibly as a result of changes in the chemical composition of the commodity.

Spinach fertilized with organic N sources were observed to have no differences

in flavor to spinach receiving similar rates of mineral nitrogen (Magna et al.,

1976). The same study did report a difference in flavor between leaves from

plants receiving low and high rates of nitrogen, and found these differences to

correspond with increased concentration of volatile compounds in the leaves with

the higher N rate. This suggests that some differences in taste and other qualities

between organic and conventional produce may be detected due to variability in

the amount of nutrients available to the crop between different fertilizer regimes.

31

Organic fertilizers such as manures and compost generally have lower nutrient

concentrations than mineral fertilizers (Roe, 1995). Plant availability of nutrients

in organic fertilizers varies; generally, lower levels of soluble nutrients are

immediately available to a crop when using organic fertilizers when compared

with mineral fertilizers (Brinton, 1985). In kiwifruit, taste panelists could

distinguish between fruit from fertilized and unfertilized trees, with scores for

sourness correlating well with titratable acidity (Gorini, 1990). Haglund et al.

(1997) found tomatoes from plants grown in a "nutrient rich" substrate containing

25% compost by volume to have lower sugar content and pH, and higher scores

for acidity than those grown in a "nutrient-poor" substrate containing no compost.

Also in tomato, nitrogen and potassium fertilization increased both short chain

carbonyls and unacceptable flavor (Wright and Harris, 1985). The authors

suggest that the higher scores for unacceptability may be due to nitrogen

fertilization increasing short-chain carbonyl production to a level high enough to

mask compounds contributing to desirable flavor in tomato. When Jia et al.

(1999) doubled the rate of fertilizer in peaches, fruits from trees receiving the

higher rates were less sweet and had lower aroma scores than fruit from trees

receiving lower fertilizer rates. These sensory scores corresponded with lower

sugar, and decreased concentration of the main volatile constituents of peach

aroma in fruit from highly fertilized trees. In corn, Wong et al. (1995) found

nitrogen fertilization to increase levels of S-methylmethionine, the precursor to

dimethyl sulfide, a compound responsible for sweet corn aroma.

32

The change in sensory quality of vegetables affected by fertilization are usually

attributed to an N effect. For example, in kohlrabi N had the leading role in

altering chemical components most affecting taste and aroma (Fischer, 1992). In

another study, Wong et al. (1995) found nitrogen to be more important than sulfur

for the production of dimethyl sulfide, which contains no nitrogen.

However, changes in chemical composition does not necessarily equate to a

change in sensory quality. Applications of potassium sulfate decreased the pH of

pear fruits, but had no effect on scores for flavor or firmness (Johnson et al.,

1998). Also, Vieira et al. (1998) found nitrogen applications to have no effect on

leaf taste or texture. Although N applications did increase leaf nitrate levels, leaf

volatiles were not reported in this study.

Although it is possible that fertilization may alter the chemical composition

of basil, and therefore the sensory quality of the fresh herb, direct panel

evaluation would be necessary to determine any changes fertilization affected in

the taste and aroma intensity of fresh basil.

33

Literature Cited

Aflatuni, A. 1993. The effect of manure composted with drum composter on aromatic plants pp. 63-68. In: International symposium on medicinal and aromatic plants, Tiberius on the Sea of Galilee, Israel, 22-25 March 1993. Acta Horticulturae no.344. Agrios, G.N. 1988. Plant Pathology. 3rd Ed. Academic Press, INC. San Diego, Ca. Alder, P.R., J.E. Simon, and G.E. Wilcox. 1989. Nitrogen form alters sweet basil growth and essential oil content and composition. HortScience 24:789-790. Alvarez, M.A., S. Gagne, H. Antoum. 1995. Effect of compost on the rhizosphere microflora of the tomato and on the incidence of plant growth promoting rhizobacteria. Applied and Environmental Microbiology. 61;1 pp 194-199. Amir,H.;Alabouvette,C. 1993. Involvement of soil abiotic factors in the mechanism of soil suppressiveness to Fusarium wilts. Soil Biology and Biochemistry 25:2157-2164. Babatola, J.O. 1989. Effects of some organic manures on nematodes in tomato cultivation. Pak. J. Nematol. 7:39-46. Bezdicek D. and M. Fauci. 1997. Nutrient aspects of compost. Compost Connection Newsletter no. 3. Bevacqua, R.F. and V.J. Mellano. 1994. Cumulative effects of sludge compost on crop yields and soil properties. Commun.Soil Sci. Plant Anal. 25:395-406. Beverly, R.B. 1994. Stem sap testing as a real-time guide to tomato seedling nitrogen and potassium fertilization. Commun.Soil Sci. Plant Anal. 25:1045-1056. Brechelt, A. 1989. Effect of different organic manures on the efficiency of VA mycorrhiza. Agriculture, Ecosystems and Environment 29: 55-58. Brinton, W.F., Jr. 1985. Nitrogen response of maize to fresh and composted manure. Biological Agriculture and Horticulture 3:55-64. Brock, W.H. 1997. Justus von Liebig, the chemical gatekeeper. Cambridge University Press, England. Browaldh, M. 1992. Influence of organic and inorganic fertilizers on common bean (Phaseolus vulgaris L.) grown in a P-fixing mollic andosol. Biological Agriculture and Horticulture 9:87-104.

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CHAPTER 3

BASIL YIELD AND TISSUE N LEVELS IN RESPONSE TO

POULTRY MANURE AND UREA APPLICATIONS

Abstract

An experiment was conducted at the University of Hawaii Waimanalo

Experiment station organic farming plots to determine the yield response of basil

cv. UH to applications of chicken manure, and to evaluate possible residual N

effects from urea applied to previous crops in the same location. The experiment

was arranged in a randomized complete block (RCB) design. The four

treatments, replicated four times, were: poultry manure applied at 5 t ha-1 wet

weight in plots which had previously received urea plus compost applications;

poultry manure applied at 5 t ha-1 wet weight in plots having received compost

+no synthetic fertilizer; 100 kg ha-1 N applied as urea ; and an unamended

control with no previous history of amendment applications. The chicken manure

was applied 7 days after basil transplanting (DAT) and incorporated to a depth of

3 cm. The urea was applied in two equal split applications at 12 and 43 DAT. Six

weekly harvests were taken beginning 28 DAT. Leaf tissue was analyzed for

total N concentration at 35 and 55 DAT. Soil organic carbon (OC) content and

nematode levels were determined at 75 DAT. All fertilizer treatments

significantly increased basil yield over the control and there was no significant

difference between yield in the organic and synthetic fertilizer treatments. Poultry

manure applications increased tissue N concentrations over those in the control,

and leaf N concentration was positively correlated with yield at both sampling

48

dates. Greater plant weights and tissue N concentrations in the CM5(urea)

treatment indicated a likely residual N effect from previous urea applications.

Fertilizer treatments had no significant effect on soil organic carbon content or

nematode levels.

Introduction

Poultry manure is an organic fertilizer which has proven effective in

enhancing the yield of vegetable crops. In regions of the world where high costs

and unavailability makes the widespread use of synthetic fertilizers impractical,

poultry manure is a valuable alternative source of crop nutrients (Kogbe, 1980).

In Hawaii, agricultural use of waste products such as poultry manure recycles a

material which would otherwise need disposal, and reduces the reliance of local

farmers on expensive, imported fertilizers. Numerous vegetables have shown a

positive yield response to poultry manure applications (Cheung and Wong, 1983;

Mbagwu, 1985; Rubiez et al., 1998). The positive yield response from chicken

manure treatments is attributed to increased nitrogen nutrition as indicated by

increased N concentration in plant tissues (Hochmuth et al, 1993; Opara and

Asiegbu, 1996). In addition to its value as an organic N source, poultry manure

has also been shown to increase soil organic matter content and to effectively

reduce root knot nematode populations and root galling in vegetables (Cheung

and Wong, 1983; Babatola, 1989; Chindo and Khan, 1990).

Synthetic fertilization of basil has been investigated to a very limited extent.

Fertilizer recommendations for basil production in Hawaii are 135 kg ha-1 each

49

N, P205, K20 as a preplant application when plants are grown in soils deficient in

these nutrients, plus sidedress applications of N at 22-34 kg ha-1 following the

first harvest (Hamasaki et al., 1994). These recommendations are similar to

those made for the temperate U.S. (Davis, 1997). However, as with other

organic fertilizers, no crop specific recommendations are available to Hawaii

vegetable growers who want to incorporate poultry manure into their fertility

program. In the past, general poultry manure application rate recommendations

of 7-23 t ha-1 have been made for Hawaii home-gardeners (McCall, 1974).

This experiment was thus conducted to determine the response of basil to

moderate rates of poultry manure and urea applications under tropical conditions,

and was part of a long-term organic farming project established in 1993 to

evaluate the effect of organic and synthetic fertilizers on long term soil quality,

crop yields and other production factors.

.

Materials and Methods

Site Description

The experiment was conducted at the University of Hawaii’s Waimanalo

Experiment Station on Oahu. Soil at the station is a silt clay (Mollisol, Waialua

series). Mean monthly temperature range at the station is 22-27 C, and mean

annual rainfall range is 500-800 mm.

50

Experimental Design

Four treatments replicated four times were arranged in a randomized

complete block design. Each treatment consisted of a 1 m by 12 m bed. The

field was blocked according to a slope and fertility gradient.

The treatments were:

1. Control: No amendment.

2. CM5(urea): Locally obtained, aged chicken manure applied at 5 t ha-1 fresh

weight in beds with a 5 year history of both compost and urea annual

applications (25 t ha-1 + 100 kg ha-1 respectively)

3. CM5: Locally obtained, aged chicken manure applied at 5 t ha-1 fresh weight in

beds with a history of compost applications (25 t ha-1) annually

4. Urea: 100 kg ha-1 nitrogen applied as urea in beds with a 5 year history of

synthetic N applications

The chicken manure was applied between rows 7 days after transplanting

(DAT) and incorporated with a hand rake to a depth of 3 cm. The urea was

sidedressed in two equal split applications at 12 and 43 DAT. The crop was drip

irrigated and hand weeded as needed. No pesticides were applied to the crop.

Planting and Harvest

Seeds of a Fusarium tolerant sweet basil variety developed by the

University of Hawaii were planted in Speedling trays in early April, 1998. Seven

week-old seedlings were transplanted in double rows spaced 30 cm apart on 28

51

May,1998. Six weekly harvests were taken beginning 28 DAT. Harvested

materials consisted of 10-15 cm long shoots with 3-4 nodes per shoot. Weight of

harvested materials for an entire plot were recorded, and grams per plant values

calculated based on the number of plants in each plot. Final plant weights were

determined following the final harvest at 75 DAT.

Tissue Sampling

The most recently fully expanded leaf pair from 10 shoots in each

replication were taken 35 and 55 DAT. Samples were analyzed for N (total), P,

K, Ca, Mg, Na, Mn, Fe, Cu, Zn and B by the UH Agricultural Diagnostic Service

Center.

Analysis of Chicken Manure and Soil

Prior to application, the chicken manure was analyzed for pH, organic

carbon, P, K, Ca, and Mg. The pH was determined using a saturated paste.

Organic carbon content was measured by a modified Wakely-Black method. The

modified Truog procedure was used to determine available P. Exchangeable Ca,

Mg and K were determined with a NH4Oac, pH 7 extract, and an atomic

absorption spectrophotometer.

Soil organic matter was determined from samples taken at a depth of 15

cm immediately after the last harvest (75 DAT). Nematode counts were taken at

the same time from rhizosphere soil samples at a depth of 15 cm.

52

Statistical Analysis

The data was analyzed with the GLM procedure (SAS® version 6.1).

Duncan’s New Multiple Range Test was conducted with the corresponding error

term for each variable.

Results

Yields in the fertilizer treatments were similar to each other and higher

than the control (Fig. 3.1). Final plant weights were greatest in the urea and CM5

(urea) plots and lowest in the control (Fig. 3.2). Mean tissue N levels across

dates were greater in the CM5(urea) treatment compared to the control (Fig. 3.3).

There was no significant treatment by date interaction. Tissue N levels were

positively correlated with crop yields obtained at both sampling dates (Fig. 3.4).

A trend was observed toward greater organic matter levels in the chicken manure

plots compared to the control and urea plots, but the differences were not

statistically significant (Fig. 3.5). Nematode populations were not significantly

affected by treatment, with very low counts in all plots (see the General

Discussion section, Chapter 7).

Discussion and Conclusions

Application of 5 t ha-1 of poultry manure increased cumulative basil yield

by ~39% with respect to the control, and produced yields similar to those

53

obtained with 100 kg ha-1 synthetic N. This follows the findings of Ospara and

Asiegbu (1996), Cheung et al. (1983) and Browaldh (1992) who observed poultry

manure applications to increase yield of Solanum sp., Chinese cabbage and

bean biomass, respectively. This increase in yield is due to a nitrogen effect.

Addition of both the organic and synthetic fertilizers increased tissue N levels,

which were positively correlated with yield (Fig. 3.4). Lowest yields were

associated with tissue N concentrations below 4.5%.

Higher cumulative yield (11%) and higher total tissue N levels were observed in

the CM5(urea) plots than in the CM5 plots (Figs. 3.1 & 3.3), despite identical

fertilizer applications to the two treatments in this experiment. This would

indicate a residual N effect from previous urea applications in the CM5(urea)

plots. The estimated amount of N removed from each treatment is listed in Table

3.4. During the crop cycle plants in the CM5 and CM5(urea) removed 17 and 26

kg ha-1 more N, respectively, than the control plants from the system. This

difference of 9 kg ha-1 between the two chicken manure treatments may be the

amount of residual N contributed from previous urea applications. Residual plant

available N remaining from previous compost applications may also be estimated

from data listed in Table 3.4. Over the course of the crop cycle, plants in plots

with chicken manure estimated to supply 25 kg ha-1 plant available N removed

the same amount of N as plants supplied with 89 kg ha-1 of synthetic N.

Therefore, the residual plant available N remaining from previous compost

applications may be as great as 64 kg ha-1. However, N equivalent from the

control must also be taken into account. Early in the crop cycle, this amounts to

54

25 kg ha-1 compared with 33 kg ha-1 from the chicken manure plots, with an

estimated 8 kg ha-1 supplied by previous compost applications. This number

decreases over the crop cycle as the N equivalent of the control increases over

time indicating a source of N available to the control plants. The high rate of N

removal from plots receiving 0 N compared those receiving 100 kg ha-1 may be

due to greater microbial activity in the control plots; it is possible that microbial

activity may be inhibited by acidic and/or high soil nutrient conditions resulting

from the application of both synthetic and organic fertilizers. Vigorous basil

plants producing good yields removed between 62-72 kg ha-1 N from the system

over a 75 day cycle (Table 3.4).

The poultry manure (11% OC) did not significantly increase soil organic

matter content when applied at 5 t ha-1 on a wet weight basis. Assuming a

moisture content of 30-50%, the amount of organic carbon added to the soil with

this application of chicken manure is 275-385 kg ha-1.

Poultry manure applications did not significantly affect final nematode

counts in this experiment, although Babatola (1989), and Chindo and Khan

(1990) have reported poultry manure to reduce nematode levels in vegetable

production systems at rates of 1 and 2 t ha-1, respectively.

55

Literature Cited

Babatola, J.O. 1989. Effects of some organic manures on nematodes in tomato cultivation. Pak. J. Nematol. 7:39-46. Browaldh, M. 1992. Influence of organic and inorganic fertilizers on common bean (Phaseolus vulgaris L.) grown in a P-fixing Mollic Andosol. Biological Agriculture and Horticulture 9:87-104. Cheung, Y.H. and M.H. Wong. 1983. Utilization of animal manures and sewage sludges for growing vegetables. Agricultural wastes 5:63-81. Chindo, P.S. and F.A. Khan. 1990. Control of root-knot nematodes, Meloidogyne spp., on tomato, Lycopersicon esculentum Mill., with poultry manure. Tropical Pest Management 36:332-335. Hue, N.V., R.Uchida, M.C. Ho. 1997. Sampling and analysis of soils and plant tissues, Section G. In: Hawaii soil fertility manual. CTAHR, University of Hawaii. Koge, J.O.S. 1980. Effects of poultry manure on yield components of Celosia Argentea L. Vegetables for the Hot Humid Tropics 5: 54-60. Mbagwu, J.S.C. 1985. Subsoil productivity of an ultisol in Nigeria as affected by organic wastes and inorganic fertilizer amendments. Soil Science 140:436-441. Opara, C.N. and J.E. Asiegbu. 1996. Nutrient content of poultry manures and the optimum rate for eggplant fruit yield in a weathered tropical ultisol. Biological agriculture and Horticulture 13: 341-350. Rubeiz, I.G., Farran, M.T., R.Y. Khoury and I.A. Al-Assir. 1992. Comparative evaluation of broiler and layer poultry manure for greenhouse lettuce production. Commun.Soil Sci. Plant Anal. 23: 725-731.

57

Figure 3.1. Effect of chicken manure and urea applications on the mean cumulative yield of basil. Values are means of four replications. Means designated by the same letter are not significantly different at P<0.05 as determined by Duncan’s New Multiple Range test. CM5= chicken manure applied at 5 t ha-1 in plots with a history of 10 t ha annual compost applications. CM5(urea)= chicken manure applied at 5 t ha-1 in plots with a history of 10 t ha annual compost applications plus urea. Urea= 100 kg N ha-1 applied as urea in plots with of a history of annual urea applications of 100-300 kg N ha-1 . Control= no amendment.

4000

5000

6000

7000

80009000

10000

11000

12000

13000

control CM5(urea) CM5 ureaTreatment

Yiel

d (k

g ha

-1)

aa

a

b

58

Figure 3.2. Effect of poultry manure and synthetic fertilizer treatments on final plant weight. Weight of above ground plant parts were determined after final harvest, 75 days after transplanting. Values are means of all plants in four replications . Means designated by the same letter are not significantly different at P<0.05 as determined by Duncan’s New Multiple Range test.

200

250

300

350

400

450

500

550

control cm 5(urea) cm 5 ureaTreatment

Fin

al p

lan

t wei

gh

t (g

)

aab b

c

59

Figure 3.3. Effect of poultry manure and synthetic fertilizer treatments on mean tissue nitrogen concentration of most recently matured leaves. Values are means of four replications and two sample dates (35 and 55 days after transplanting). Means designated by the same letter are not significantly different at P<0.05 as determined by Duncan’s New Multiple Range test.

4.3

4.4

4.5

4.6

4.7

4.8

4.9

5.0

control cm 5(urea) cm 5 urea

Treatment

Mea

n tis

sue

N c

once

ntra

tion(

%)

a

abab

b

60

Table 3.1. Selected Soil Chemical Properties at 1/15/98, four months prior to basil transplanting, and of chicken manure applied in this experiment. Soil samples were composites of four replications.

Treatment

OCy

(%)

pH

ECz

(dS m-1)

P

-----------

K

----------

Ca

--(mg kg-1)-

Mg

---------

Control 2.3 7.0 0.1 319 420 4700 1100

Comp 2.3 6.7 0.1 91 460 4525 1100

MOA 2.3 7.4 0.2 240 460 4700 1200

Urea 2.4 6.8 0.1 395 540 4600 1100

Chicken Manure 11.5 8.1 ---- 3498 24420 6330 2258

YOrganic carbon

ZElectrical conductivity

----Not determined

61

Table 3.2. Effect of poultry manure and synthetic fertilizer treatments on mean nutrient concentration of most

recently matured basil leave (UH) grown in four treatments at 55 DAT. Values obtained from a composite sample

of four replications.

Treatment

P

------------

K

---------

Ca

----%---

Mg

---------

Na

----------

Mn

-----------

Fe

----------

Cu

mg kg-1

Zn

--------

B

-----------

Control 0.53 2.34 2.42 0.71 0.07 57 229 18 43 22

CM5(urea) 0.48 2.88 2.57 0.72 0.02 84 353 18 50 25

CM5 0.54 2.48 2.36 0.66 0 67 252 17 41 24

Urea 0.47 2.69 2.2 0.67 0.01 67 268 19 41 22

62

Table 3.3. Estimated yield increase (kg ha-1) due to chicken manure and urea applications

Treatment

Cumulative Yield (kg ha-1 )

Yield as % over control

N applied (kg ha-1)

Control 8361 0 CM5 10935 31 50y CM5(urea) 12007 44 50 Urea 12434 49 100

yTotal N supplied by 5 t ha-1 of chicken manure based on an assumed moisture and total N content of 50% and 2%, respectively.

63

Table 3.4. Effect of poultry manure and synthetic fertilizer treatments on N use of basil at 35, 55 and 75 days after transplanting (DAT). Values are means of four replications. CM5= chicken manure applied at 5 t ha-1 in plots with a history of 25 t ha annual compost applications. CM5(urea)= chicken manure applied at 5 t ha-1 in plots with a history of 25 t ha annual compost applications plus urea. Urea= 100 kg N ha-1 applied as urea in plots with of a history of annual urea applications of 100-300 kg N ha-1 . Control= no amendment.

Date

Treatment

Cumulative yield

(kg ha-1)v

Biomass

N removed (kg ha-1) w

N equivalent x

N applied (kg ha-1)

35 DAT control 549 55 3 25 0 CM5 1166 117 7 58 25 y CM5(urea) 1578 158 9 75 25 urea 1098 110 6 50 50

55 DAT control 4254 425 23 61 0 CM5 6037 604 34 89 25 CM5(urea) 6449 645 38 100 25 urea 6449 645 38 100 100

75 DAT control 8361 836 45 64 0 CM5 10935 1094 62 89 25 CM5(urea) 12007 1201 71 100 25 urea 12434 1243 70 100 100

vCumulative yield at sampling date. wN removed from the fertilized crop (kg ha-1) calculated by multiplying biomass by mean tissue content of each treatment. xN equivalent is the N removed from the treatment divided by the N removed by urea plots then multiplied by the amount of N applied as urea at sample date. Assumes 100% plant availability of synthetic N. yPlant available N from manure estimated at 50% total N supplied by 5 t ha-1 of chicken manure based on an assumed moisture and total N content of 50% and 2%, respectively. zTissue levels are means of those from 35 and 55 DAT sampling dates

64

Figure 3.4. Tissue N concentration relative to basil yield at 35 and 55 days after transplanting.

y = 76.54x - 302.53

R2 = 0.20

020406080

100120140

4 4.2 4.4 4.6 4.8 5 5.2 5.4

Tissue N (%)

Yie

ld (

gr

pla

nt)

65

Figure 3.5. Effect of poultry manure applications on soil organic carbon content (%). Soil samples were taken immediately following the last basil harvest, 75 days after transplanting. Values are means of four replications. Means designated by the same letter are not significantly different at P<0.05 using Duncan’s New Multiple Range test. CM5= chicken manure applied at 5 t ha-1 in plots with a history of 10 t ha annual compost applications. CM5(urea)= chicken manure applied at 5 t ha-1 in plots with a history of 10 t ha annual compost applications plus urea. Urea= 100 kg N ha-1 applied as urea in plots with of a history of annual urea applications of 100-300 kg N ha-1 . Control= no amendment.

1.5

1.6

1.7

1.8

1.9

2

2.1

control cm 5(urea) cm 5 urea

Treatment

So

il o

rgan

ic c

arb

on

(%

)

a

aa

a

66

CHAPTER 4

EFFECTS OF COMPOST APPLICATIONS ON BASIL YIELD, TISSUE N

CONCENTRATION AND SAP NO3- LEVELS

Abstract

A field trial was conducted at the University of Hawaii Waimanalo

Experiment Station to determine the effects of compost (0.3% N) and urea

applications on basil production and nutrient status. The experiment was

arranged as a split split plot with fertilizer treatments as the main plots, cultivars

as sub plots, and harvest dates as sub sub plots. The three cultivars were

‘Sweet Italian’, ‘UH’ and ‘Thai Siam Queen’. The four treatments replicated four

times were: 110 kg ha-1 synthetic N, compost applied at 45 t ha-1, compost

applied at 180 t ha-1, and a control receiving no amendments. The compost was

applied 7 days prior transplanting and incorporated with a roto-tiller to a depth of

15 cm. Graviota 16-16-16 fertilizer supplying 30 kg ha-1 N was applied at

transplanting. The remaining 80 kg ha-1 N was applied as urea in two equal split

applications 35 and 73 DAT. Eight weekly harvests were taken beginning 30

DAT. The most recently matured leaves of 10 marketable shoots per replication

were sent to the University of Hawaii Agricultural Diagnostic Service Center

(ADSC) for analysis of total N at 37, 65 and 100 DAT. Sap nitrate concentration

was determined at the same sampling dates from marketable shoots with a

nitrate ion selective electrode. Application of 45 t ha-1 of a low nutrient compost

increased basil yield in all varieties by an average of 38% over the control.

67

Highest yields were obtained with ‘Sweet’, the only variety to remain relatively

pest-free during the crop cycle. ‘UH’ was determined to be more susceptible to

root-knot nematode attack and associated root rot than the other two cultivars,

while ‘Thai’ was more susceptible to Fusarium wilt. Sap nitrate levels were more

sensitive to fertilizer treatment and were a slightly better indicator of plant nutrient

status than total tissue N levels. Mean sap nitrate levels varied with cultivar,

emphasizing the need for critical range determinations to be done at the cultivar

level. Urea applications increased plant nitrate levels with respect to the control

while compost applications did not.

Introduction

The positive yield response observed in vegetable crops in response to

compost applications is often attributed to factors other than the direct

contribution of essential nutrients provided by composts. Applications of chicken

litter-based compost increased mycorrhizal colonization of corn roots, and

additions of compost increased the number of mycorrhizal spores over levels in

soil receiving synthetic fertilizer or raw dairy manure alone (Douds et al., 1997).

Sivapalan et al. (1993) found that microbial populations, particularly those of

Trichoderma and Penicillium, were higher in soil receiving a chicken manure

based compost as the sole source of crop nutrients than those in synthetic

fertilizer plots. Also, application of organic amendments may suppress nematode

populations and their virulence towards a host crop by improving crop vigor,

68

promoting antagonistic soil microbes, or by containing nematicidal compounds

(Coosemans, 1982). Similarly, compost applications have been shown to

effectively reduce disease severity caused by numerous other plant pathogens,

and this suppressive effect is generally associated with microbial activity (Huber

et al, 1966; Cheung and Hoitink, 1990; Hardy and Sivasithamparam, 1991;

Hoitink and Grebus, 1996; Kim et al., 1997). For example, Serra-Wittling (1996)

showed that the addition of compost increased a soil’s suppressiveness to

Fusarium wilt in flax.

An organic source of plant nutrients, compost may also be used to

increase the level of plant available nutrients in the soil, and to increase the

concentrations of essential elements in crop tissues (Browaldh, 1992; Hue et al.,

1994; Douds et al., 1997; Sainz et al., 1998). Analysis of nutrient concentrations

in crop tissues is an important tool for fertility management in vegetable systems,

but little crop specific information is available for growers in the tropics (Fox and

Valenzuela, 1992). Work has been conducted to establish sufficiency ranges for

total N, and more recently sap nitrate-N for various vegetable crops in the sub-

tropics (Hochmuth, 1994). Critical nutrient ranges have not been established for

basil (Mills and Jones, 1996; Huett et al., 1997). Sap nitrate-N as measured by a

quick test method such a hand-held nitrate ion selective electrode can be an

effective way for a grower to determine the nutrient status of a crop in the field

(Huett and White, 1992; Hochmuth, 1999). Not only are results obtained quickly,

but sap nitrate-N levels may be a better indicator than total tissue N of nitrogen

69

availability. Petiole sap nitrate-N concentrations as measured with Merck test

strips were more sensitive but more variable (higher CV) than total tissue N to

nitrogen fertilizer applications (Huett and Rose, 1989). Olsen and Lyons (1994)

reported that sap nitrate-N in pepper was more closely related than tissue N

concentrations to fertilizer applications. Sap nitrate-N concentrations were found

to be better correlated than total tissue N with nitrogen application rates (Prasad

and Spiers, 1985). Warnke (1996) found petiole sap nitrate-N to increase with

increased rate of N fertilizer in carrot.

This experiment was conducted as part of a long-term organic farming project

initiated in 1993. This replicated trial was established to evaluate the effect of

organic and synthetic fertilizers on long term soil quality, crop yields and other

production factors. Specific objectives of this experiment were to:

1. Determine the effect of various application rates of a low nutrient compost on

yield, N status, and plant health of three basil varieties.

2. Determine the effect of compost applications on soil organic matter.

3. Determine the feasibility of using a portable, hand-held nitrate selective

electrode to diagnose the nitrogen status of different basil cultivars.

Materials and Methods

Experimental Design

The experiment was arranged as a split split-plot with treatments as the

main plot cultivars as the sub plot and harvest dates as the sub sub plots. Work

70

was conducted in the same location as described in chapter 3, without any

changes in bed arrangement.

The treatments were:

1. Control: No amendments were applied to these plots.

2. C45: On-farm produced compost applied at 45 t ha-1 fresh weight in beds with

a history of annual compost and urea applications (25 t ha-1+ 100 kg ha-1

respectively)

3. CM180: On-farm produced compost applied at 180 t ha-1 fresh weight in beds

with a history of annual compost applications (25 t ha-1).

4. Urea: 110 kg ha-1 nitrogen applied as urea and 16-16-16 as Graviota fertilizer.

The relatively high rates of compost were selected based on the low nutrient and

organic carbon content of the compost (Table 1.). The compost was applied 7

days prior transplanting and incorporated with a roto-tiller to a depth of 15 cm.

30 kg ha-1 N was applied as Graviota 16-16-16 complete fertilizer at

transplanting. The remaining 80 kg ha-1 N was applied as urea in two equal split

applications 35 and 73 DAT.

The varieties used in this experiment were:

'Sweet Italian' Italian type commercially grown in Hawaii. Obtained from

Fukuda Seed Store (Honolulu, HI 96817).

'UH' Italian type, Fusarium resistant variety developed by the

University of Hawaii. Obtained from the UH seed program.

'Thai Siam Queen' Commercial Asian variety. Obtained from Fukuda Seed.

71

Planting and Harvest

Seeds of the three basil cultivars were planted in Speedling trays in early

June, 1998. Seven week-old seedlings were transplanted at a 30 x 43 cm

spacing in double rows on 10 August, 1998. Eight weekly harvests were taken

beginning 9 September, 30 DAT. Harvested materials consisted of 10-15 cm

long shoots with 3-4 nodes. Weight of harvested materials for an entire plot were

recorded, and grams per plant values calculated based on the number of plants

in each plot.

The crop was drip irrigated and hand weeded as needed, and no pesticides or

other inputs were used in the plots.

Tissue Sampling and Sap Nitrate Analysis

The most recently fully expanded leaf pair from 10 shoots per replication

were collected at 37, 65 and 100 DAT for total N analysis. Sap nitrate-N content

was measured using a Cardy sap nitrate meter (Horiba Instruments Inc., Irvine,

CA), also at 37, 65 and 100 DAT. Stems were harvested between 9-11 am at all

dates from the same side of the row. Samples were stored in sealed plastic bags

in a cooler with ice until analysis in the lab. Stem portions between the first and

third node from the apex were obtained from 10 marketable shoots in each

replication and leaves removed. Stems were macerated with a mortar and pestle

and sap extracted with a garlic press.

72

Analysis of Compost and Soil

The sample of the compost used was sent to the ADSC for analysis (as

soil) of pH, organic carbon, P, K, Ca, and Mg. The pH was determined using a

saturated paste. Organic carbon content was measured using a modified

Walkley-Black method. The Olsen method was used to measure available P.

Exchangeable Ca, Mg and K levels were extracted with NH4OAc, pH 7 and

measured with an atomic absorption spectrophotometer.

Soil organic matter was determined from samples taken at a depth of 15

cm. immediately after plant removal (120 DAT). Nematode counts were taken at

the same time from rhizosphere soil samples at a depth of 15 cm.

Plant Root Indexes

Roots of all plants in each replication were rated visually for severity of

galling caused by root-knot nematode infestation, and overall root health 120

DAT using the following index:

Galling Root Health

1= 0-20% of roots galled 1= very poor (81-100% rot)

2= 21-40% of roots galled 2= poor (61-80% rot)

3= 41-60% of roots galled 3= fair (41-60% rot)

4= 61-80% of roots galled 4= good (21-40% rot)

5= 81-100% of roots galled 5=excellent (0-20% rot)

73

Statistical Analysis

The data was analyzed with a proc GLM procedure (SAS version 6.1).

Duncan’s New Multiple Range Test was conducted with the corresponding error

term for each variable.

Results and Discussion

The fertilizer treatments had a significant effect on yield at P<0.07.

Differences between yield of cultivars were highly significant (P<0.01). There

was no significant cultivar by treatment interaction (P=0.56) as tested by the error

b (Little and Small, 1978). Figure 4.1 shows the mean cumulative yield of the

treatments across cultivars, with yield from the lower rate of compost 40% and

15% greater than those from the control and urea plots respectively. A trend for

higher yields with increased rate of compost application was observed in cvs.

Sweet and Thai, but not in UH (Fig. 4.2, Table 4.3). The trend for lower yields in

the urea treatment compared to the compost treatments was more apparent in

'Thai' (Fig. 4.2, Table 4.3). Soil organic carbon levels were higher in the compost

plots than in the control, but were not affected by the rate of compost application

(Fig. 4.3). Root galling as a result of nematode attack was highest in c180 for all

cultivars (Fig. 4.4). Decline associated with heavy nematode infestation

(Hamasaki et al. 1994) was observed only in ‘UH’ , and associated with moderate

to severe levels of root rot in this treatment (Fig. 4.5). Root knot nematodes

(Meloidogyne sp) were the predominant plant parasitic nematode species in the

74

rhizosphere (80%). Spiral and Reniform nematodes were also identified in

rhizosphere soil. Although not significantly affected by fertilizer treatments,

nematode levels in the root zone of ‘UH’ in c180 (487 per L of soil) were over

twice those in the other treatments. This implies an environment favoring

nematode populations with the higher applications of compost, probably due to

an initial stimulation of root growth in that treatment. Of the three cultivars, only

‘UH’ had a significant difference in root health between treatments (fig. 4.5). This

implies that ‘UH’ is more susceptible than ‘Thai’ or ‘Sweet’ to reduced yields

resulting from root knot nematode infestation. Increased root rot as a result of

nematode attack has been observed previously with applications of municipal

waste compost in tomato (Duncan and Noling, 1998).

Fertilizer treatments affected sap nitrate-N levels at P<0.1, and differences

between cultivars were highly significant. Cultivar differences in tissue nitrate

levels in response to fertilizer treatments were also observed in pumpkin and

endive (Swaider et al, 1991; Reinik et al., 1994). The effect of genotype on sap

nitrate-N levels must therefore be considered when determining critical ranges of

a crop. Although tissue N levels were increased with fertilizer applications, there

was no difference between cultivars in mean tissue N concentrations (Table 4.2).

Urea applications significantly increased sap nitrate levels with respect to the

control, while compost applications did not (Table 4.2). This increase in sap

nitrate-N over the compost treatments observed in the urea plots did not

correspond with an increase in yield. This observation agrees with the findings of

others. For example, Smith and Hadley (1989) have shown inorganic fertilizer to

75

increase nitrate levels in lettuce leaves, while applications of compost contributed

very little or no nitrate to tissues. In another study, Dominguez et al (1984) found

lettuce grown with compost to contain 10% less nitrates than that grown with

inorganic fertilizers. Excessive nitrate in the diet is known to increase the risk of

such health problems as cancer and inhibited oxygen transport by blood, and it

has been estimated that nitrates from vegetable can contribute to more that 80%

of total dietary nitrates (Lyons et al, 1994; Huarte-Mendicoa, et al 1996).

There was no significant treatment by cultivar interaction for sap nitrate-N as

tested with the error b, nor were there interactions between sample date and

treatment or cultivar. Sap nitrate levels were more sensitive than total tissue N

concentration to fertilizer application. This is in agreement with similar

observations made by Huett and Rose (1989). Measurements obtained with the

Cardy meter were positively correlated with results from total tissue N analysis at

65 DAT across all cultivars, although correlation is improved when considered by

cultivar, as would be expected by the genotypic differences observed in sap

nitrate levels (Fig 4.6-9). Sap nitrate levels of ‘Sweet’ and both sap nitrate and

tissue N concentrations of ‘UH’ were correlated with yield at 65 DAT (Fig. 4.10-

12). Yields decreased to below 857 kg ha-1 at sampling date with increasing sap

nitrate-N levels above 800 mg L-1 in both cultivars. As in Chapter 3, lowest yields

(643 kg ha-1 at sampling date) of 'UH' were associated with tissue N levels lower

than 4.5%. Neither total tissue N or sap nitrate concentrations in ‘Thai’ were

significantly correlated with yield at any sample date.

76

N removal data is listed in Tables 4.4-6. N removed by crops producing

the highest yields was 67-71 kg ha-1 over 120 days. This is similar to previous

estimations of 62-70 kg ha-1 N removed by basil over a 75 day crop cycle

(Chapter 3). Disease incidence affected N uptake in ‘UH’. This cultivar removed

26 kg ha-1 N from the control compared to 48, 42 and kg ha-1 removed by ‘Sweet’

and ‘Thai’, respectively. The fact that this was due to the root rot observed in

‘UH’ in this experiment is indicated by the removal of 45 kg ha-1 N by healthy

‘UH’ plants in the previous experiment (Chapter 3). Estimation of residual plant

available N from previous compost applications is discussed relative to the other

experiments in Chapter 7. It is unlikely that the yield response of basil to fertilizer

applications in this experiment is simply an N effect. Increased soil organic

matter in the soil, plant nutrients other than N contained in the compost, and an

interaction between fertilizer treatments and pest incidence may also have

contributed to the additional crop yield observed in the compost plots.

Conclusions

Application of 45 t ha-1 of a low nutrient compost increased basil yield with

respect to the control in all three cultivars. Very high rates of compost applied to

compensate for the low nutrient content did not result in the expected yield

increase over the yield obtained from the lower rate of compost. This may have

been due to phytotoxicity resulting from excess N and/or a higher incidence of

root galling in the c180 treatment. Relative nitrogen use efficiency was greatest

in plots receiving 45 t ha-1 compost (See General Discussion Chapter). Low

77

rates of compost combined with moderate applications of synthetic fertilizer is

likely to be the most efficient fertilization regime for basil, as observed previously

by Valenzuela et al. (1999) with basil in the same location. Highest yields were

obtained with ‘Sweet’, the only variety to remain relatively pest-free during the

crop cycle. N removed by crops producing the highest yields was 67-71 kg ha-1

over 120 days. ‘UH’ was determined to be more susceptible to root-knot

nematode attack and associated root rot than the other two cultivars, while ‘Thai’

was more susceptible to Fusarium wilt. It was therefore determined possible to

grow disease tolerant basil cultivars organically.

Values obtained with rapid analysis of stem sap nitrate levels using a

portable hand-held nitrate ion selective electrode were positively correlated with

total tissue N values obtained from a professional plant diagnostic service

provider. Sap nitrate levels were more sensitive to fertilizer treatment and were

a slightly better indicator of plant nutrient status than total tissue N levels. This

indicates the potential of sap nitrate-N analysis as a useful tool in management of

crop nutrition. However, mean sap nitrate levels varied with cultivar,

emphasizing the need for critical range determinations to be done at the cultivar

level. Urea applications increased plant nitrate levels with respect to the control

while compost applications did not, indicating that compost may be used as a

fertilizer to lower nitrate levels in vegetables.

78

Literature Cited:

Browaldh, M. 1992. Influence of organic and inorganic fertilizers on common bean (Phaseolus vulgaris L.) grown in a P-fixing mollic andosol. Biological Agriculture and Horticulture 9:87-104. Cheung, Y.H. and M.H. Wong. 1983. Utilization of animal manures and sewage sludges for growing vegetables. Agricultural wastes 5 63-81. Coosemans, J. 1982. Influence of organic material on the population dynamics of Meloidogyne hapla Chitwood. Agricultural Wastes 4:193-201. Douds, Jr., D.D., L. Galvez, M. Franke-Snyder, C. Reider, L.E. Drinkwater. 1997. Effect of compost addition and crop rotation point upon VAM fungi. Agriculture Ecosystems and Environment 65:257-266. Dominguez,G.P. 1994. Accumulation of nitrates in lettuces grown using organic fertilizer. Alimentaria. 31:251. Duncan, L.W. and J.W. Noling. 1998. Agricultural sustainability and nematode integrated pest management, p 251-288. In: Barker, K.R., G.A. Pederson, and G.L. Windham (eds.). Plant nematode interactions. ASA 36. Fox, R.L. and H.R. Valenzuela. 1992. Vegetables grown under tropical/subtropical conditions, p. 293-337. In: World fertilizer use manual. International Fertilizer Industry Association, Paris. Hochmuth, G. 1999. Plant petiole sap testing. Citrus and Vegetable magazine. June:30-33. Hochmuth, G.J. 1994. Efficiency ranges for nitrate-nitrogen and potassium for vegetable petiole sap quick tests. HortTechnology 4:218-222. Huarte-Mendicoa,J.C., I. Astiasaran and J. Bello. 1996. Nitrate and nitrite levels in fresh and frozen broccoli. Effect of freezing and cooking. Food Chemistry 58:39-42. Hue, N.V., H. Ikawa, and J.A. Silva. 1994. Increasing plant available phosphorus in an ultisol with a yard waste compost. Commun. Soil Sci. Plant Anal. 25:3291-3303. Hue, N.V., R.Uchida, M.C. Ho. 1997. Sampling and analysis of soils and plant tissues, Section G. In: Hawaii soil fertility manual. CTAHR, University of Hawaii.

79

Huett, D.O., N.A. Mair, L.A. Sparrow and T.J. Piggott. 1997. Vegetables. Chapter 8 in: Rueter, D.J. and J.B. Robinson (eds.). Plant analysis: an interpretation manual. CSIRO Publishing, Australia. Huett, D.O. and G. Rose. 1989. Diagnostic nitrogen concentrations for cabbages grown in sand culture. Australian Journal of Experimental Agriculture 29: 883-892. Huett, D.O. and E. White. 1992. Determination of critical nitrogen concentrations of lettuce (Lactuca sativa L. Cv. Montello) in sand culture. Australian Journal of Experimental Agriculture 32: 759-764. Kim, K.D., S. Nemec and G. Munsson. 1997. Effects of composts and soil amendments on soil microfora and Phytophthora root and crown rot of bell pepper. Crop Protection 16: 165-172. Little, T.M. and F.J. Small. 1978. Agricultural experimentation. John Wiley and Sons, New York, NY. Lyons,D.J.; G.E.Rayment; P.E. Nobbs and L.E. McCallum. 1994. Nitrate and nitrite in fresh vegetables from queensland. J. Sci. Food Agriculture. 64:279-281. Mills, H.A. and J.B. Jones. Plant analysis handbook II. Micromacro Publishing, Athens, Georgia USA. 1996. Olsen, J.K. and D.J. Lyons. 1994. Petiole sap is better than total nitrogen in dried leaf for indicating nitrogen staus and yield responsiveness of capsicum in subtropical Australia. Australian Journal of Experimental Agriculture 34:835-43. Prasad, M. And T.M. Spiers. 1984. Evaluation of a rapid method for plant sap nitrate analysis. Commun. Soil Sci. Plant Anal. 15:673-679. Reinink, K., M. Van Nes and R. Groenwold. 1994. Genetic variation for nitrate content between cultivars of endive (Cichorium endivae L.). Euphytica 75: 41-48. Sainz, M.J., M.T. Taboada-Castro, and A. Vilarino. 1998. Growth, mineral nutrition and mycorrhizl colonization of red clover and cucumber plants grown in a soil amended with composted urban wastes. Plant and Soil 205: 85-92. Serra-Wittling, C., S. Houot and A. Alabovette. 1996. Increased soil suppressiveness to Fusarium wilt of flax after addition of municipal solid waste compost. Soil Biol. Biochem. 9: 1207-1214.

80

Sivapalan, A., W.C. Morgan and P.R. Franz. 1993. Monitoring populations of soil microorganisms during a coversion from a convetional to an organic system of vegetable growing. Biological Agriculture and Horticulture 10: 9-27. Smith, F.W. and J.F. Loneragan. 1997. Interpretation of plant analysis: concepts and principles. 3-26 in: Rueter, D.J. and J.B. Robinson (eds.). Plant analysis: an interpretation manual. CSIRO Publishing, Australia. Smith, S.R. and P.Hadley. 1989. A comparison of organic and inorganic nitrogen fertilizers: Their nitrate-N and ammonium-N release characteristics and effects on the growth response of lettuce. Plant and Soil 115:135-144. Swaider, J.M., Y. Chayan and W.E. Splittstoesser. 1991. Genotypic differences in nitrogen uptake, dry matter production, and nitrogen distribution in pumpkins (Curbita mochata Poir.). Journal of Plant Nutrition 14: 511-524. Uchida, R. 1997. Recommended crop tissue nutrient levels: vegetables, fruits, ornamental plants, ornamental flowering plants, section J. In: Hawaii Soil Fertility Manual. CTAHR, University of Hawaii. Valenzuela, H, R. Hamasaki and T. Radovich. 1999. Nature Farming Experiments in Waimanalo, 1993-1998. Proceedings SARE Organic Farming Workshop. 12 February 1999, University of Hawaii, Honolulu. Warneke, D.D. 1996. Soil and plant tissue testing for nitrogen management in carrots. Commun.Soil Sci. Plant Anal. 27:597-605.

81

Table 4.1. Selected chemical properties of the compost applied.

OC pH P K Mg Ca Compost 4% 7.2 141 ppm 1316 ppm 1166 ppm 8174 ppm

82

Figure 4.1. The effect of compost rates and urea applications on the mean cumulative yield of basil by treatment.

Values are means of four replications and three cultivars. Means designated by the same letter are not

significantly different at P<0.05 as determined by Duncan’s New Multiple Range test. C45= compost applied at 45

t ha-1 in plots with a history of compost applications. C180= compost applied at 180 t ha-1 in plots with a history

of compost applications plus urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea

applications of 100-300 kg ha-1 N. Control= no amendment.

6000

8000

10000

12000

control C45 C180 urea

Treatment

Yie

ld (

kg h

a-1) a

aab

b

83

Figure 4.2. The effect of compost rates and urea applications on the mean cumulative yield of cultivars by

treatment. Values are means of four replications. C45= compost applied at 45 t ha-1 in plots with a history of

compost applications. C180= compost applied at 180 t ha-1 in plots with a history of compost applications plus

urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea applications of 100-300 kg ha-1 N.

Control= no amendment.

400050006000700080009000

1000011000120001300014000

Sweet UH ThaiCultivar

Yiel

d (k

g ha

-1)

controlc45c180mineral

84

Figure 4.3. Effect of fertilizer treatments on soil organic carbon content, 120 days after transplanting. Values are

means of four replications. Mean values designated by the same letter are not significantly different at P<0.05 as

determined by Duncan's New Multiple Range Test.

11.21.4

1.61.8

2

control c45 c180 urea

Treatment

Org

anic

Car

bon

(%)

aa

abb

85

Figure 4.4. Effect of treatment on root gall index scores of cultivars, 120 DAT. Values are means of four

replications. Root Gall Index: 1= 0-20% of roots galled, 2= 21-40% of roots galled, 3= 41-60% of roots galled, 4=

61-80% of roots galled, 5= 81-100% of roots galled.

0.0

1.0

2.0

3.0

4.0

5.0

Sweet Thai UH

Cultivar

Gall I

nd

ex control

C45C180Urea+

a abb

c

ab

c c

aa

b

c

86

Figure 4.5. Effect of treatment on root health index scores of basil cv. UH, 120 DAT. Values are means of four

replications. Root health index: 1= very poor (81-100% rot), 2= poor (61-80% rot), 3= fair (41-60% rot), 4= good

(21-40% rot).

012

34

control c45 c180 Urea

Treatment

Ro

ot

Healt

h I

nd

ex

abc b

87

Table 4.2. Mean sap nitrate and tissue N concentrations and mean standard error by cultivar and treatment.

Sap Nitrate-N (mg L-1) Treatment Sweet Thai UH Mean (treatment) Control 748 ± 110 470 ± 82 820 ± 125 679 ± 67 C45 764 ± 105 540 ± 102 946 ± 101 750 ± 66 C180 691 ± 127 549 ± 95 858 ± 126 699 ± 70 Urea 981 ± 87 701 ± 103 1098 ± 117 927 ± 67 Mean (cultivar) 795 ± 55 565 ± 48 930 ± 59

Tissue N (%) Treatment Sweet Thai UH Mean (treatment) Control 4.36 ± 0.09 4.40 ± 0.07 4.30 ± 0.09 4.36 ± 0.05 C45 4.59 ± 0.10 4.48 ± 0.07 4.47 ± 0.10 4.51 ± 0.05 C180 4.46 ± 0.09 4.43 ± 0.09 4.42 ± 0.12 4.43 ± 0.06 Urea 4.60 ± 0.04 4.68 ± 0.10 4.49 ± 0.10 4.59 ± 0.05 Mean (cultivar) 4.50 ± 0.04 4.50 ± 0.04 4.42 ± 0.05

88

Table 4.3. Effect of compost and synthetic N on relative yield increase of fertilizer treatments over control.

Treatment

Cumulative Yield (kg ha-1)

Sweet

Yield increase over control

(kg ha-1)

Yield increase over control (%)

Control 8785 C45 12080 3295 38 C180 13178 4393 50 Urea 12080 3295 38

Treatment UH Control 5491 C45 8785 3294 60 C180 7412 1921 35 Urea 6863 1372 25

Treatment Thai Control 8236 C45 10158 1922 23 C180 12080 3844 47 Urea 8511 275 3

89

Table 4.4. Effect of compost and synthetic fertilizer treatment on N use of basil cv. Sweet Italian, at 37, 65 and 100 days after transplanting (DAT). Values are means of four replications. C45= compost applied at 45 t ha-1 in plots with a history of compost applications. C180= compost applied at 180 t ha-1 in plots with a history of compost applications plus urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea applications of 100-300 kg ha-1 N. Control= no amendment. Date Treatment Cumulative yield

(kg ha-1)w Biomass (kg ha-1)

N removed (kg ha-1)x

N equivalenty N applied (kg ha-1)

37 DAT Control 1647 165 7 16 0 C45 2538 254 14 33 24z C180 2950 295 16 37 95 Urea 2401 240 13 30 30

65 DAT Control 6175 617 32 49 0 C45 8439 844 46 70 24 C180 9262 926 49 75 95 Urea 8233 823 45 70 70

100 DAT Control 8782 878 48 80 0 C45 12075 1207 67 110 24 C180 13172 1317 71 117 95 Urea 12075 1207 67 110 110

wCumulative yield at sampling date. xN removed from the fertilized crop (kg ha-1) calculated by multiplying biomass by mean tissue content of each treatment. yN equivalent is the N removed from the treatment divided by the N removed by urea plots then multiplied by the amount of N applied as urea at sample date. Assumes 100% plant availability of synthetic N. zPlant available N from compost estimated at 25% total N supplied by compost based on an assumed moisture and total N content of 30% and 0.3%, respectively.

90

Table 4.5. Effect of compost and synthetic fertilizer treatment on N use of basil cv. UH, at 37, 65 and 100 days after transplanting (DAT). Values are means of four replications. C45= compost applied at 45 t ha-1 in plots with a history of compost applications. C180= compost applied at 180 t ha-1 in plots with a history of compost applications plus urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea applications of 100-300 kg ha-1 N. Control= no amendment. Date

Treatment

Cumulative yield

(kg ha-1)

Biomass (kg ha-1)

N removed

(kg ha-1)

N equivalent

N applied (kg ha-1)

37 DAT Control 823 82 4 21 0 C45 1784 178 10 46 24 C180 1921 192 11 52 95 Urea 1166 117 6 30 30

65 DAT Control 3911 391 21 55 0 C45 6175 617 35 91 24 C180 5763 576 32 83 95 Urea 4940 494 27 70 70

100 DAT Control 5491 549 26 84 0 C45 8785 879 44 141 24 C180 7412 741 35 110 95 Urea 6863 686 35 110 110

wCumulative yield at sampling date. xN removed from the fertilized crop (kg ha-1) calculated by multiplying biomass by mean tissue content of each treatment. yN equivalent is the N removed from the treatment divided by the N removed by urea plots then multiplied by the amount of N applied as urea at sample date. Assumes 100% plant availability of synthetic N. zPlant available N from manure estimated at 25% total N supplied by compost based on an assumed moisture and total N content of 30% and 0.3%, respectively.

91

Table 4.6. Effect of compost and synthetic fertilizer treatment on N use of basil cv. Thai, at 37, 65 and 100 days after transplanting (DAT). Values are means of four replications. C45= compost applied at 45 t ha-1 in plots with a history of compost applications. C180= compost applied at 180 t ha-1 in plots with a history of compost applications plus urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea applications of 100-300 kg ha-1 N. Control= no amendment.

Date Treatment Cumulative yield

(kg ha-1) w

Biomass (kg ha-1)

N removed (kg ha-1) x

N equivalent

N applied (kg ha-1) y

37 DAT Control 1578 158 8 22 0 C45 2813 281 15 40 24z C180 2813 281 14 39 95 Urea 2058 206 11 30 30

65 DAT Control 5969 597 32 59 0 C45 8027 803 44 81 24 C180 9056 906 50 91 95 Urea 6380 638 38 70 70

100 DAT Control 8236 824 42 97 0 C45 10158 1016 55 126 24 C180 12080 1208 64 146 95 Urea 8511 851 48 110 110

wCumulative yield at sampling date. xN removed from the fertilized crop (kg ha-1) calculated by multiplying biomass by mean tissue content of each treatment. yN equivalent is the N removed from the treatment divided by the N removed by urea plots then multiplied by the amount of N applied as urea at sample date. Assumes 100% plant availability of synthetic N. zPlant available N from manure estimated at 25% total N supplied by compost based on an assumed moisture and total N content of 30% and 0.3%, respectively.

92

Figure 4.6. Total nitrogen concentration of most recently matured basil leaves relative to stem sap nitrate-N, 65

days after transplanting. Each value represents the mean of 20 leaves for tissue N analysis and 10 stem portions

for sap nitrate-N determination from each cultivar in a single replication.

3.5

4

4.5

5

5.5

0 500 1000 1500

Sap Nitrate-N (mg L-1)

Tis

su

e N

(%

)

y = 0.00090 x - 0.00000035 x2+ 4.35r2 = 0.19 P<0.01

93

Figure 4.7. Total nitrogen concentration of most recently matured UH basil leaves relative to stem sap nitrate-N,

65 days after transplanting. Each sample consisted of 20 leaves for total N analysis, and 10 stem portions for sap

nitrate-N determination.

3.5

4

4.5

5

5.5

0 500 1000 1500

Sap Nitrate-N (mg L-1)

Tis

su

e N

(%

)

y = 0.0018x - 0.00000084x2 + 3.81

r2 = 0.53 P<0.01

94

Figure 4.8. Total nitrogen concentration of most recently matured SWEET basil leaves relative to sap nitrate-N, 65

days after transplanting. Each sample consisted of 20 leaves for total N analysis, and 10 stem portions for sap

nitrate-N determination.

3.53.73.94.14.34.54.74.9

0 500 1000 1500

Sap Nitrate-N (mg L-1)

Tis

su

e N

(%

)

y = 0.0017x - 0.00000070x2 + 3.73

r2 = 0.39 P<0.05

95

Figure 4.9. Total nitrogen concentration of most recently matured THAI basil leaves relative to stem sap nitrate-

N, 65 days after transplanting. Each sample consisted of 20 leaves for total N analysis, and 10 stem portions for

sap nitrate-N determination.

44.24.44.64.8

55.25.4

0 200 400 600 800

Sap Nitrate-N (mg L-1)

Tis

su

e N

(%

)

r2 = 0.41y = 0.0010 x + 4.33

P<0.01

96

Figure 4.10. Yield of cv. SWEET relative to stem sap nitrate-N concentration, 65 days after transplanting. Each

value represents a sample from a single replication consisting of 10 stem portions.

0100200300400500600700800900

1000

0 200

400

600

800

10

00

12

00

14

00

Sap Nitrate-N (mg L-1)

Yie

ld (

g)

y = - 0.30x + 763.76

r2 = 0.25 P<0.05

97

Figure 4.11. Yield of cv. UH relative to stem sap nitrate-N concentration, 65 days after transplanting. Each value

represents a sample from a single replication consisting of 10 stem portions.

0

100

200300

400500

600700

0 100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

Sap Nitrate-N (mg L-1)

Yie

ld (g

)

y = 1.28 x - 0.00083 x2 - 10.5

r2 = 0.42 P<0.05

98

Figure 4.12. Yield of cv. UH relative to total nitrogen concentration of the most recently matured leaves, 65 days

after transplanting. Each value represents a sample from each replication consisting of 20 most recently

matured leaves.

0100200300400500600700

4.0 4.2 4.4 4.6 4.8 5.0 5.2

Tissue N (%)

Yie

ld (

g)

y = 7159x -775x2 - 16072

r2 = 0.49 P<0.01

99

CHAPTER 5

BASIL YIELD AND SOIL QUALITY AS AFFECTED BY

COMPOST AND UREA APPLICATIONS

Abstract

A field trial was conducted at the University of Hawaii Waimanalo

experiment station to determine the effects of compost and urea applications on

the marketable yield of three basil cultivars, ‘Sweet Italian’, ‘UH’, and ‘Siam

Queen’. The experiment was arranged in a split split-plot design with fertilizer

treatments as the main plots, cultivars as the sub-plots, and harvest dates as the

sub sub-plots. The four treatments, replicated four times, were 230 kg ha-1 N

applied as urea, compost applied at 23 t ha-1, compost applied at 90 t ha-1, and a

control receiving no amendment. The chicken manure/woodchip-based compost

contained 1.2% N on a dry weight basis and 30% moisture. Compost was

incorporated to a depth of 15 cm one week prior to transplanting basil seedlings.

Urea was applied in six split applications. Twelve weekly harvests were taken

beginning 45 days after transplanting. Soil pH, organic carbon (OC), electrical

conductivity (EC), and nematode levels were determined at the end of the

harvest period. Fertilizer treatment, cultivar, and harvest date had significant

effects on yield. The cultivar by fertilizer treatment interaction was not significant

with respect to yield. Highest yields were obtained with 90 t ha-1 compost.

Cumulative yields from the 23 t ha-1 compost treatment were comparable to that

from the urea plots. Lowest yield for ‘Siam Queen’ was recorded in the urea

treatment and corresponded with a high incidence of wilt disease caused by

100

Fusarium oxysporum. Compost applications significantly increased OC content

and EC compared to the other treatments, while soil pH was significantly lower in

the urea plots. There was no significant treatment effect on rhizosphere

nematode levels , with populations high in all treatments. Relatively low yields in

the urea plots were attributed to high disease incidence and associated with high

levels of soil N late in the crop cycle, and a reduction in soil pH.

Introduction

Compost use as the primary means to provide essential nutrients to

vegetable crops is an effective way to sustain and build soil fertility as well as a

valuable waste management strategy. Chicken manure contains many plant

nutrients and has proven to be an effective fertilizer for vegetables, with the

added potential of improving soil physical and chemical characteristics (Cheung

and Wong, 1983; Hue and Licudine, 1999). However, there are some health

risks associated with untreated manure, which are minimized or eliminated by

composting (Strauch, 1996; LeaMaster et al., 1998). Composting as described

throughout this paper refers to the controlled microbial degradation of organic

residues to produce temperatures (40-55°C) high enough to kill pathogens and

weed seeds (Zibilske, 1999) . Other wastes, such as woodchips, may be

combined with manure to produce a valuable organic amendment. A chicken

manure and wood-chips based compost increased corn biomass production up

to a rate of 50 t ha-1, with yield decreasing at higher rates (Silva et al., 1995).

Stopes et al. (1989) reported increased lettuce yields in response to composted

FYM (0.9% N) applications, with highest yields obtained at the highest

101

application rate of 18 dry t ha-1. Yield at this rate was not different from that

obtained with 160 kg ha-1 synthetic N. When a manure based compost was

applied to cabbages and carrots to provide 300 and 170 kg ha-1 N respectively,

crop yields and tissue N levels were the same as those obtained in synthetically

fertilized plots receiving the equivalent N rates (Warman and Havard 1997). In

addition to yield benefits compost applications may also improve or maintain soil

quality, contributing directly and indirectly to improved crop growth (Bevaqua and

Mellano, 1994). Compost has also effectively suppressed numerous plant

pathogens, with the suppressive effect generally associated with microbial

activity (Huber et al, 1966; Hoitink, 1980 ; Cheung and Hoitink, 1990; Hardy and

Sivasithamparam, 1991).

Due to relatively low nutrient content and increased labor involved with

application, composts are generally more expensive than synthetic nutrient

sources. Its use in large quantities can be justified, however, when applied to

high value crops, when additional objectives of the grower are to recycle on-farm

wastes, build soil organic matter and control plant disease, or in cropping

situations where the use of synthetic fertilizers are not an option (i.e. certified

organic systems) (Buchanan and Gliessman, 1993; Serra-Wittling, 1996).

Basil is an important crop in Hawaii with a 1998 total farm-gate value of $2.7

million, but there are currently no fertilizer recommendations available to growers

wishing to grow this crop organically in the state (Hamasaki et al, 1994; HASS,

1999). In Hawaii, compost applied at 25 t ha-1 increased basil yield with respect

to unfertilized plants, and produce yields similar to those obtained with

102

100 kg ha-1 synthetic N (Valenzuela et al., 1999). However, information on the

response of basil to higher rates of compost is not available.

This experiment was thus conducted to determine the yield response of

three basil cultivars to compost and urea applications, and the effect of fertilizer

type and rate on soil quality and pest incidence.

Materials and Methods

Experimental Design

The experiment was arranged as a split split-plot with fertilizer treatments

as the main plot, cultivars as the sub-plot and harvest date as the sub sub-plot.

This was the third of three consecutive experiments conducted in the same field

plots to determine the response of basil to organic fertilization in the tropics. The

first experiment was conducted in the Spring, 1998, with basil in the field for 75

days. The second basil planting was in the field for 120 days. Work was

conducted as described in Chapter 4, without any changes in bed arrangement

or varieties used. However, the location of cultivars within the beds was re-

randomized.

The treatments were:

1. Control: No amendment

2. C23: Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1

compost.

3. C90: Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1.

103

4. Urea: 230 kg ha-1 N applied as urea

The compost was applied 7 days prior to transplanting and incorporated with a

roto-tiller to a depth of 15 cm.

34 kg ha-1 N was applied as urea at 13 DAT. The remaining urea was applied in

5 split applications 2 weeks apart beginning at the time of first harvest, 45 DAT

Planting and Harvest

Seeds of the three basil cultivars were planted at the University of Hawaii

Magoon Greenhouse in 200 cell Speedling trays 25 January, 1999. Seven

week-old seedlings were transplanted in double row beds at a distance of 45 cm

between plants in the row, and 60 cm between rows on 3 March, 1999. Twelve

weekly harvests were taken beginning 45 DAT. Harvested materials consisted of

10-15 cm long shoots with 3-4 nodes. Weight of harvested materials for an

entire plot were recorded, and grams per plant values determined based on the

number of plants in each plot.

The crop was drip irrigated as needed, and no pesticides or other inputs were

used in the plots.

Tissue N and Sap Nitrate-N Analysis

The most recently fully expanded leaf pair from 10 shoots per replication

were collected at 70, 113 and 135 DAT for total N analysis. Sap nitrate-N

content was measured using a Cardy sap nitrate meter (Horiba Instruments Inc.,

104

Irvine, CA) at 70 DAT. Stems were harvested between 9-11 am at all dates from

the same side of the row. Samples were stored in a cooler with ice until analysis

in the lab. Stem portions between the first and third node from the apex were

obtained from 10 marketable shoots in each replication and leaves removed.

Stems were macerated with a mortar and pestle and sap extracted with a garlic

press.

Analysis of Compost

Locally obtained aged chicken manure and wood chips (2 : 3 by volume)

were composted in piles for ten weeks. Piles were turned weekly, and moisture

content maintained at approximately 50%. A sample of the compost was

analyzed at the University of Hawaii Agricultural Diagnostic Service Center prior

to application. Electrical conductivity was determined on a slurry of 50 g compost

and 50 ml of water.

Organic carbon content and pH were determined as previously described for soil

in Chapter 4. Results of the analyses are given in Table 1.

Soil Analysis

Soil samples of two replications were taken to a depth of 15 cm and

analyzed for NO3--N and NH44

+-N prior to compost application, then again at 22,

74, 96, and 103 days after compost application. Organic carbon content,

electrical conductivity and pH of each replication was conducted on samples

obtained at 15 cm at 175 DAT. Composite samples of four replications were

105

analyzed for extractable nutrients (Table 2). The nutrient analysis was

conducted as described previously in Chapter 4.

Pest and Disease Levels

The number of plants exhibiting symptoms of disease caused by

Fusarium oxysporum were counted 52 DAT.

Plants of ‘UH’ were visually rated for severity of decline 150 DAT on a scale of 1-

5, where:1=dead; 2=severe decline; 3=moderate decline; 4=little decline;

5=healthy

Roots of all varieties were rated for severity of galling, and overall root health

using the following indexes:

Galling, where: 1= 0-20% of roots galled, 2= 21-40% of roots galled, 3= 41-60%

of roots galled, 4= 61-80% of roots galled, 5= 81-100% of roots galled.

Root Health, where: 1= very poor (81-100% rot), 2= poor (61-80% rot), 3= fair

(41-60% rot), 4= good (21-40% rot), 5=excellent (0-20% rot)

Nematode counts were taken made from rhizosphere soil samples collected at a

depth of 15 cm 175 DAT.

Statistical Analysis

The data was analyzed with a proc GLM procedure (SAS version 6.1).

Means separation was done using Duncan’s New Multiple Range test.

106

Results and Discussion

Fertilizer treatment and genotype both significantly affected mean yields

(P<0.01), but there was no significant cultivar by treatment interaction. Mean

cumulative yields for each fertilizer treatment are shown in Figure 5.1. Individual

cultivar respose is shown in Figure 2. Compost applications increased yield with

respect to the control, and applications of 90 t ha-1 resulted in the highest yields;

at 30% moisture, 90 t ha-1 corresponds to the highest reccommended compost

application rate for vegetable production of 60 dry t ha-1 (Compost Council,

1996). Tables 5.1 and 5.2 list the results of the compost and soil nutrient

analysis.

Yields from c90 treatment were 30 and 80% higher than c23 and control

plots respectively across cultivars. Yield response of the cultivars differed slightly

with respect to treatment (Figure. 5.2). Statistical analysis had shown no

significant treatment by cultivar interaction, and may have not been sensitive

enough to pick up slight differences. The effect of the high compost application

rate on cumulative yield was most pronounced in ‘Sweet’. Yield response of

each cultivar with respect to the control is given in Table 5.3. Only in ‘Sweet’ did

the magnitude of increase in compost rate (4x) matched that of increased yield

over the control. Table 5.3. lists the cumulative yield of cultivars by treatment and

the yield difference between fertilizer treatments and the control. Tissue levels

were taken only from cv ‘UH’.

107

Tissue N and sap nitrate-N levels were highest in the C90 treatment. The

estimated N removed from each treatment is listed in Table 5.4. A total of 78 kg

ha-1 N was removed by the highest yielding treatment in this experiment. As in

the previous experiment, disease levels affected the N uptake of ‘UH’ . The lack

of difference between in N equivalents of the two compost rates at later sample

dates corresponded to high amounts of root rot (i.e. low root health) and plant

decline in the C90 treatment. The high N equivalents in control and compost

treatments relative to the urea treatment corresponds with the highest levels of

rot and plant decline observed in the urea plots over the compost and control

treatments (Figure 5.5, Table 5.5). Estimation of residual plant available N from

previous compost applications is discussed relative to the other experiments in

Chapter 7.

All plants of cultivar ‘UH’ exhibited mild to severe symptoms of decline

attributed to root-knot nematode infestation. Symptom severity was significantly

affected by treatment, being greatest in the urea treatments, followed by c90

(Figure 5.5). Root galling was most severe in the urea and c90 treatments as

well, as was the severity of root rot indicated by the low root health index scores

(Table 5.5). Root gall index scores were highest and root health index scores

lowest for ‘UH’. This cultivar is apparently more susceptible to nematode attack

than either ‘Thai’ or ‘Sweet’. While no fungal pathogen was isolated from the

vascular system of ‘UH’ plants exhibiting servere symptoms of decline, it is

possible that resistance to fusarium broke down as a result of nematode

108

infestation, or that some other nematode by pathogen interaction had adverse

effects on plant growth.

Fusarium wilt was observed in ‘Thai’ and ‘Sweet’ but not in ‘UH’, with 42%,

21%, and 0% of plants exhibiting symptoms of infection, respectively. Although

symptomatic plants were observed in all treatments of ‘Sweet’, the effect on yield

of this cultivar was observed to be minimal. No symptoms of the disease were

observed in the resistant cultivar, ‘UH’. Lowest cumulative yields for ‘Thai’ (2942

kg ha-1) were obtained in the urea treatment and corresponded with high levels of

disease incidence (58% of plants infected by 52 DAT) compared with the other

treatments (<35% of total plants infected by 52 DAT). The severity of symptoms

caused by F. oxysporum was not rated. Soil analysis of two replications showed

that NH4+ was the predominat form of mineral N in the urea treatment, while NO3

-

predominated in the soil of the other three treatments (data not shown). N

supplied as NH4+ has been shown to increase the pathogenicity of Fusarium spp

with respect to NO3- - N applications (Woltz and Jones, 1973; Kirpichenko, 1975).

This effect is associated with a decrease in soil pH resulting from the release of

H+ from plant roots when absorbing NH4+ (Agrios, 1988; Marschner, 1995). The

percentage of plants exhibiting symptoms of Fusarium wilt was positively

correlated with the ratio of ammonium to nitrate-N in the soil (Fig. 5.6), with

ammonium to nitrate-N ratios highest in the urea treatment. Soil pH levels were

significantly lower in the urea treatment with respect to the compost treatments

and control (Table 7). Scher et al. (1980) eliminated the effectiveness of a soil

suppressive to Fusarium wilt by decreasing the soil pH from 8.0 to 6.0.

109

The high NH4+ : NO3

- ratio observed in the urea treatments may also be

responsible for the relatively low yields of all varieties in this treatment, despite

the addition of 230 kg ha-1 N. Alder et al. (1995) found basil stem and petiole

yields to be lower when supplied with ammonium nitrogen than when given

nitrate-N. Another reason for the poor yield response to split urea applications

may be reduced synchrony of N availability with plant requirements. Most N in

the urea plots was available late in the crop cycle (Fig. 5.7). High soil nitrate

levels early in the development of broccoli corresponded to higher final yields

(Buchanan and Gliessman, 1991), and was attributed to the ability of the crp to

store N in its tissues to be translocated as needed.

Compost (pH 6.5) applications did not significantly affect soil pH. While

compost may increase the pH of acid soils (Buchanan and Gleissman, 1991;

Silva et al., 1995; Sainz et al., 1998), effects are usually negligible on neutral or

basic soils (Compost Council, 1996). Bevaqua and Mellano (1994) reported a

reduction in pH of a basic soil (7.7) with applications of a slightly acid compost.

Soil salinity levels in all treatments were extremely low, although EC in c90 was

significantly higher than the other treatments (Table 5.6). This was the fifith year

of compost and urea applications. The compost used in this experiment had a

relatively high salt content (EC = 23 dS-1); repeated applications of compost with

similar levels may increase soil salinity to concentrations negatively affecting

110

plant growth. Silva et al. (1995) and Bevaqua and Mellano (1994) also observed

increased soil salinity with compost applications.

Compost applications of 23 and 90 t ha-1 increased soil organic carbon

content 15 and 35% over the control and urea plots, respectively. Increased soil

organic matter benefits plant growth by improving soil structure and nutrient

holding capacity, and by buffering the soil pH (Buchanan and Gleissman, 1991;

Woomer et al, 1994). Although four times as much compost, and therefore

organic carbon, was applied in c90 than c23, the resulting increase in soil OC

with the higher rate of application was little more than twice that of the lower rate

over the control. This disproportionate increase in soil OC may indicate an

increase in microbial activity resulting in increased OC mineralization at the

higher rate of compost application. Research has shown compost applications to

enhance microbial activity (Siviplan et al., 1993; Liu and Cole, 1996; Raj and

Kapoor, 1997). Since soil organic matter is decomposed by microbial activity in

the soil (Tisdale et al., 1993), the higher rate of compost application possibly

stimulated soil microbial populations, thereby increasing the rate of OC

decomposition.

Conclusions

Results from this experiment indicates that composts may be used as the

sole external source of essential nutrients to grow basil. Applications of a

chicken manure and wood chips based compost increased basil yield, sap nitrate

111

levels, mineral N in the soil, and soil organic matter over the control. Yields

obtained were significantly higher with 90 t ha-1 than those receiving either 23 t

ha-1 compost or 230 kg ha-1 synthetic N. This effect was likely due to a

combinaton of improved plant nutrition and an increase in soil organic matter.

Relatively low yields in the urea plots were associated with high disease

incidence, high levels of soil N late in the crop cycle (Fig. 5.7), and a reduction in

soil pH. Final nematode levels were not affected by treatments; however, plant

damage as a result of nematode attack was highest in the plots recieving urea

and compost at 90 t ha-1. The data indicates that cultivar UH is highly

susceptible to nematode attack. Fusarium incidence in cv. Thai was positively

correlated with the ratio of ammonium to nitrate in the soil, and associated with a

decrease in the soil pH.

Selection of disease tolerant and potentially high yielding basil cultivars

such as ‘Sweet Italian’ is important to help ensure maximum yield response to

compost applications.

112

Literature Cited

Agrios, G.N. 1988. Plant Pathology. 3rd Ed. academic Press, INC. San Diego, Ca. Alder, P.R., J.E. Simon, and G.E. Wilcox. 1989. Nitrogen form alters sweet basil growth and essential oil content and composition. HortScience 24:789-790. Bevacqua, R.F. and V.J. Mellano. 1994. Cumulative effects of sludge compost on crop yields and soil properties. Commun.Soil Sci. Plant Anal. 25:395-406. Buchanan, M. and S. Gliessman. 1991. How compost fertilization affects soil nitrogen and crop yields. Biocycle December: 72-77. Chung, Y.R. and H.A.J. Hoitink. 1990. Interactions between thermophilic fungi and trichoderma hamatum in suppression of rhizoctonia damping-off in a bark compost-amended container medium. Phytopathology 80: 73-77. Cheung, Y.H. and M.H. Wong. 1983. Utilization of animal manures and sewage sludges for growing vegetables. Agricultural wastes 5 63-81. Hamasaki, R.T., H.R. Valenzuela, D.M. Tsuda, and J.Y. Uchida. 1994. Fresh basil production guidelines for Hawaii. CTAHR, University of Hawaii. Research Extension Series 154, Coop. Ext. Service. Hardy, G. E. St. J. and K. Sivasithamparam. 1991. Suppression of Phytophthora Root Rot by a Composted Eucalyptus Bark Mix. Aust. J. Bot. 39: 153-159. Hawaii Agricultural Statistics Service. 1999. Hawaii herbs. http://www.nass.usda.gov/hi/vegetable/herb.htm . Downloaded February, 2000. Hoitink, H.A.J. 1980. Composted bark, a lightweight growth medium with fungicidal properties. Plant Disease 64:142-147. Huber, D.M., A.L Anderson, and A.M. Finley. 1966. Mechanisms of biological control in a bean root rot soil. Phytopathology 56: 953-954. Hue, N.V. and D.L. Licudine. 1999. Amelioration of subsoil acidity through surface application of organic manures. J. Environ. Quality 28:623-632. Hue, N.V., R. Uchida, M.C. Ho. 1997. Samplig and analysis of soils and plant tissues, Section G. In: Hawaii soil fertility manual. CTAHR, University of Hawaii. Coop. Ext. Service.

113

Kirpichenko, L. 1975. Effect of different sources of nitrogen on the growth and pathogenicity of Fusarium oxysporum. Sestematika, Ekologiya i Fiziologia Pochvennykh Gribov 152-154. LeaMaster, B., J.R. Hollyer and J.L Sullivan. 1998. Composted animal manures: precautions and processing. CTAHR, University of Hawaii. UWM-1, Coop. Ext. Service. Little, T.M. and F.J. Small. 1978. Agricultural experimentation. John Wiley and Sons, New York, NY. Liu, X., and M.A. Cole. 1996. Minimum effective compost addition for remideation of pesticide contaminated soil, p 903-912. In: de Bertoldi,M., P. Sequi, B. Lemmes and T. Papi (eds.). The science of composting. Blackie Academic and Professional. Marschner, H. 1995. Mineral Nutrition of higher plants, 2nd ed. Academic Press, INC, San Diego, Ca. Raj, H. and I.J. Kapoor. 1997. Possible management of Fusarium wilt of tomato by soil amendments with composts. Indian Phytopath. 50:387-395. SAS Institute Inc. 1990 SAS user’s guide, version 6, Fourth ed. SAS Institute Inc., Cary, NC. Serra-Wittling, C., S. Houot and A. Alabovette. 1996. Increased soil suppressiveness to Fusarium wilt of flax after addition of munincipal solid waste compost. Soil Biol. Biochem. 9: 1207-1214. Scher, F.M. and R. Baker. 1980. Mechanism of biological control in a Fusarium suppressive soil. Phytopathology 70:412-417. Silva, J.A., E.L. Woods, W.C. Coleman, J.R. Carpenter and E. Ross. 1995. The use of composted chicken manure as a fertilizer. Hawaii Agriculture: Positioning for Growth. Conf. Proc. April 5-6, 1995. Sivapalan, A., W.C. Morgan and P.R. Franz. 1993. Monitoring populations of soil microorganisms during a coversion from a convetional to an organic system of vegetable growing. Biological Agriculture and Horticulture 10: 9-27. Staruch, D. 1996. Occurrence of micro organisms pathonegenic for man and animals in source seperated biowaste and compost- inportance, control, limits, epidemiology, p. 224-232. In: M. de Bertoldi, P. Sequi, B. Lemmes and T. Papi (eds.). The science of composting. Blackie Academic and Professional, Glasgow.

114

Tisdale, S.L., W.L. Nelson, J.D.Beaton, and J.L. Havlin. 1993. 5th ed. Soil fertility and Fertilizers. Macmillan Publishing Company, New York, NY. Warman, P.R. and K.A. Havard. 1997. Yeild, vitamin and mineral contents of organically and conventionally grown carrots and cabbage. Agriculture, Ecosystems and Environment 61: 155-162. Woltz, S.S. and J.P. Jones. 1973. Interactions in source of nitrogen fertilizer and liming procedure in the control of Fusarium wilt of tomato. HortScience 137-138. Woomer, P.L., A. Martin, A. Albrecht, D.V.S. Resk and H.W. Scharpenseel. 1994. The importance and management of soil organic matter in the tropics, p 47-80. In: Woomer, P.L. and M.J. Smith (ed.) The biological management of tropical soil fertility. John Wiley and Sons, West Sussex, UK. Zibilske, L.M.. 1999. Composting of organic wastes, pp 482-497. In: Sylvia, M.S., J.J. Fuhrmann, P.G. Hartel, D.A. Zuberer (eds.) Principles and applications of soil microbiology. Prentice Hall, Upper Saddle River, NJ

115

Table 5.1. Selected chemical properties of the compost used in this experiment.

C:N

pH

EC (mmhos cm)

N (%)

P (%)

K (%)

Ca (%)

Mg (%)

Na (%)

Mn (ppm)

Fe (ppm)

Cu (ppm)

Zn (ppm)

B (ppm)

Compost 13:1 6.5 23 1.2 1.3 1.3 6.9 0.7 0.3 1586 11240 72 241 111

Table 5.2. Selected chemical properties of treatment soil prior to compost application (Feb. 1999), and 182 days after application (Aug. 1999) of compost. Treatment OC (%) pH EC (dS m-1) P (mg L-1) K (mg L-1) Ca (mg L-1) Mg (mg L-1)

Feb. 1999 Control 1.4 7.2 0.28 72 492 4950 1340 C23 1.7 7.2 2.2 128 570 5168 1306 C90 1.8 7.2 0.38 105 560 4900 1486 Urea 1.3 6 0.36 288 288 5092 1370

Aug 1999 Control 2 7.2 0.27 296 344 5040 1468 C23 2.3 7.4 0.29 120 500 5564 1422 C90 2.7 7.5 0.33 152 830 5736 1466 Urea 2 6.4 0.19 177 192 4380 1346

116

Figure 5.1. Effect of several compost and synthetic fertilizer treatments on mean cumulative basil yield. Values are means of four replications and three cultivars. Means designated with the same letter are not significantly different at p<0.05 according to Duncan’s New Multiple Range Test. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds previously receiving 45 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1, Urea=230 kg t ha-1 N applied as urea.

0

5000

10000

15000

20000

25000

control c23 c90 urea

Treatment

Yie

ld (

kg

ha

-1)

a

b

c bc

117

Figure 5.2. Effect of several compost and synthetic fertilizer treatments on mean cumulative yield reponse of cultivars to treatment. Values are means of four replications, and means within cultivars designated with the same letter are not significantly different at P<0.05 according to Duncans’ New Multiple Range Test. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1, Urea=230 kg t ha-1 N applied as urea.

0

5000

10000

15000

20000

25000

30000

Sweet UH Thai

Variety

Yie

ld (

kg h

a-1)

controlc23c90urea

a

ab

ab

b

a

bbb

a

b

ab

ab

118

Figure 5.3. Effect of several compost and synthetc fertilizer treatment on stem sap nitrate-N of basil, 50 days after transplanting. Values are means of samples consisting of 10 stem portions from three cultivars and four replications. Means designated with the same letter are not significantly different at P<.05 as determined using Duncan's New Multiple Range Test. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1, Urea=230 kg t ha-1 N applied as urea.

0

100

200

300

400

500

600

control c23 c90 urea

Treatment

Sap

NO

3- -N (m

g L-1

) a

ab bb

119

Figure 5.4. Effect of several compost and synthetic fertilizer treatments on total nitrogen content of most recently matured basil leaves, 50 days after transplanting. Values are means of samples consisting of 20 most recently matured leaves from three cultivars and four replications. Means designated with the same letter are not significantly different at P<.05 as determined using Duncan's New Multiple Range Test. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1, Urea=230 kg t ha-1 N applied as urea.

2.8

2.9

3.0

3.1

3.2

3.3

3.4

control c23 c90 urea

Treatment

Tis

sue

N (

%)

ab ab

a

b

120

Figure 5.5. Mean plant health index of cv. UH as affected by treatment at 150 DAT. 1=Dead 2=Severe decline 3=Moderate decline 4=Mild decline 5=No decline. Mean values designated by the same letter are not significantly different at P<0.05 as determined using Duncan's New Multiple Range Test. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1, Urea=230 kg t ha-1 N applied as urea.

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Control C10 C40 Urea

Treatment

He

alt

h In

de

x a a

b

c

121

Figure 5.6. Percent of the total number of ‘Thai’ plants exhibiting symptoms of Fusarium wilt relative to the NH4+-

N : NO3--N ratio in the soil. Each value represents the mean of two replications.

y = -24.66x2 + 98.74x + 7.00r2 = 0.77 P<0.05

020406080

100120

0 0.5 1 1.5 2 2.5 3 3.5

NH4+-N : NO3

--N

Infe

cte

d p

lan

ts(%

of

tota

l)

122

Figure 5.7. Mean soil NH4+ N and NO3- N levels of treatments over time (days after compost application, DAC).

Urea applications were made 0, 29, 80, 92 and 106 DAC. Values are means of two replications.

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120

Days After Compost Application

So

il N

H4+

-N +

NO

3- -N

(m

g k

g-1

)

controlc23c90urea

123

Table 5.3. Effect of compost and synthetic fertilizer treatment on relative cumulative yield increase of fertilizer

treatments over control.

Treatment Cumulative Yield

(kg ha-1) Yield as % over

control N applied (kg ha-1)

Sweet

Control 14825 0 c23 17711 19 193 c90 25147 70 756 Urea 16727 13 230

UH

control 10338 0 c23 15932 54 193 c90 19210 86 756 Urea 12396 20 230

Thai

control 5274 0 c23 9967 89 193 c90 12688 141 756 Urea 2942 - 56 230

124

Table 5.4. Effect of fertilizer treatments on N use of basil cv. UH at 70, 113 and 145 days after transplanting

(DAT). Values are means of four replications. Control= No amendment, C23= Compost applied at 23 t ha-1 in beds

previously receiving 90 t ha-1 compost, C90= Compost applied at 90 t ha-1 in beds previously receiving 180 t ha-1,

Urea=230 kg t ha-1 N applied as urea.

Date Treatment Cumulative yield

(kg ha-1) w Biomass (kg ha-1)

N removed (kg ha-1) x N equivalenty

N applied (kg ha-1)

70 DAT control 347 35 1 107 0 C23 669 67 2 199 48 C90 1533 153 6 502 193 Urea 394 39 1 110 110 113 DAT control 5283 528 19 143 0 C23 9230 923 34 258 48 C90 13417 1342 50 375 193 Urea 7969 797 31 230 230 145 DAT control 10330 1033 45 209 0 C23 15919 1592 69 322 48 C90 19197 1920 78 367 193 urea 12405 1240 49 230 230 wCumulative yield at sampling date. xN removed from the fertilized crop (kg ha-1) calculated by multiplying biomass by mean tissue content of each treatment. yN equivalent is the N removed from the treatment divided by the N removed by urea plots then multiplied by the amount of N applied as urea at sample date. Assumes 100% plant availability of synthetic N. zPlant available N from manure estimated at 25% total N supplied by compost based on an assumed moisture and total N content of 30% and 1.2%, respectively.

125

Table 5.5. Root Gall and Root Health Index scores by treatment and cultivar. Root Gall Index: 1= 0-20% of roots

galled, 2= 21-40% of roots galled, 3= 41-60% of roots galled, 4= 61-80% of roots galled, 5= 81-100% of roots

galled. Root Health Index: 1= very poor (81-100% rot), 2= poor (61-80% rot), 3= fair (41-60% rot), 4= good (21-40%

rot).

Gall Index Treatment Sweet Thai UH Mean (treatment)

control 3.3±0.2 2.3±0.4 3.7±0.2 3.3±0.2 c23 3.9±0.2 3.7±0.3 3.7±0.2 3.8±0.1 c90 4.1±0.2 4.2±02 4.9±0.3 4.5±0.1 urea 4.8±0.1 5.0±0.0 4.7±0.1 4.7±0.1

Mean (cultivar) 4.0±0.1 3.5±0.2 4.3±0.1

Root Health Index Treatment Sweet Thai UH Mean (treatment)

control 3.7±0.2 4.1±0.3 2.9±0.2 3.4±0.1 c23 3.5±0.2 3.2±0.2 2.9±0.2 3.2±0.1 c90 3.2±0.2 2.5±0.2 1.6±0.1 2.4±0.1 urea 3.4±0.2 3.0±0.0 1.8±0.1 2.3±0.1

Mean (cultivar) 3.5±0.1 3.2±0.1 2.3±0.1

126

CHAPTER 6

EFFECTS OF COMPOST AND SYNTHETIC FERTILIZER APPLICATIONS ON

THE AROMA AND FLAVOR INTENSITY OF BASIL

Abstract

The sensory quality of fresh basil was evaluated in two experiments to

determine if compost or synthetic fertilizer applications affected flavor and aroma

intensity. The four treatments in the first experiment, arranged in a randomized

complete block design with four replications, were: compost applied at 45 t ha-1 ;

compost applied at 180 t ha-1 ; synthetic N applied at 110 kg ha-1; and a control

receiving no amendment. In the second experiment, the compost applications

were reduced by half and the synthetic fertilizer rate was doubled. Different basil

cultivars were used for each experiment. Other methodology remained the same

for both experiments. Leaves from the first four nodes of young shoots were

used in the evaluations. Twelve trained panel members scored samples of three

leaves from each treatment for aroma and flavor intensity using a linear scale,

converted to a scale of 0-10 where 0 = much less intense than a reference

sample (control), and 10 = much more intense than the reference. Significant

differences between treatments in aroma intensity were found in the first

experiment. Aroma scores were highest in samples from the compost and

synthetic fertilizer treatments, and lowest in those from the control. Scores for

aroma from the compost and synthetic fertilizer treatments were similar to each

127

other. Aroma intensity increased with increased rate of compost application.

The increase in aroma intensity was possibly due to enhanced essential oil

production in fertilized plants. No significant correlation was found between

aroma intensity and plant tissue N content, sap NO3- levels, or yield. No

significant difference between treatments was found in flavor intensity in the first

experiment, nor was there any significant treatment effect on flavor or aroma

intensity in the second experiment. Fertilization may alter the post harvest quality

of fresh basil and possible effects on product quality should be taken into account

when making nutrient management decisions.

Introduction

Sensory quality of fresh produce is an important factor for consumers in

making purchasing decisions (Misra and Huang, 1991). Sweet basil is a high

value crop which is grown for the fresh market in Hawaii (Hamasaki et al., 1994),

and any change in cultural practice which affects the quality of fresh basil may

also affect its marketability. Basil is an herb frequently grown in Hawaii without

the use of chemical fertilizers. Popular claims that organic fertilization improves

the quality of fresh produce with respect to synthetic sources of plant nutrients

are largely unfounded (Rader et al. 1985; Jeong et al., 1996; Woese et al., 1997).

No studies have been conducted to determine the effect of fertilizer type and rate

on the flavor or aroma of sweet basil. However, previous work has shown both

type and rate of fertilizer to affect the content and composition of basil essential

oil, the source of the herb's characteristic aroma and flavor (Alder et al, 1989;

Simon et al, 1990; Youssef et al, 1998).

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Thus, the objectives of this study on the sensory quality of fresh basil were to:

1) Generate information to qualify attributes of fresh basil flavor and aroma;

2) Determine if fertilization can affect the flavor and aroma intensity of fresh

basil leaves;

3) Determine if a difference in aroma and flavor intensity can be detected

between plants fertilized with compost compared to synthetic fertilizer.

Materials and Methods

Panel 1

Basil cv. Sweet Italian plants were grown in the Fall of 1998 under the

conditions described in chapter 4 of this text. The treatments were: a control

receiving no amendment; compost at 45 t ha-1; compost at 180 t ha-1; and

synthetic N at 110 t ha-1. Seedlings were transplanted 10 August, 1999. The

first application of synthetic fertilizer was as Gaviota 16-16-16 containing one

third of nitrogen and all the P and K to be received. The remaining N was

applied in two additional split applications of urea. The last application occurred

2 weeks prior to the taste panel evaluation. All the compost was applied one

week prior to transplanting, 13 weeks before the panel evaluation. Plants were

harvested nine times over a period of twelve weeks. Sensory evaluation was

conducted 12 weeks after transplanting.

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Shoots with 3-4 nodes were removed approximately six inches from the

apex. These were placed in plastic bags and stored at approximately 20 C.

Samples were removed from field blocks one and two for preparation and testing

less than 24 and 48 hours respectively. Immediately following panel testing of

block two, blocks three and four were harvested in the same manner.

Twelve panel members were trained for an hour on methods of evaluation.

A modified difference from a reference test was used. Scoresheets were pre-

labeled with panelist identification numbers and divided into two sections (Fig. 1).

The top section was used to score aroma, the bottom to score taste. Each

section contained four lines with anchor marks 10 cm apart; in the center of each

line, 5 cm from either anchor, was a mark indicating the pre-determined score of

the reference sample. Each line was preceded by a randomly selected 3-digit

number corresponding with a labeled sample. Tests were conducted over four

consecutive days, treatments within a single block being evaluated each day.

Each panelist was given a reference sample, and a sample from each treatment.

Presentation order was randomized. The reference sample was from the control

treatment. Samples consisted of three leaves removed from their stems and

rinsed with deionized water. Leaves within a sample were from the same

treatment and block, but not necessarily from the same plant.

When evaluating for aroma intensity, panelists first macerated all the leaves in

the reference, inhaling at close proximity to determine aroma intensity. The

same was done for each of the four other samples, referring as needed to the

reference sample. For taste intensity, all three leaves in a sample were chewed

130

at their proximal ends; water and unsalted crackers were provided between

samples. Samples were scored for perceived aroma or taste intensity as

compared to that of the reference. If intensity was identical to the reference, a

mark was made at the center tick of the score line. If intensity was perceived to

be less than the reference, a mark was made at an appropriate distance from the

center tick; increasing distance from this center tick corresponded to a decrease

in intensity. If intensity was perceived to be greater than the reference, a mark

was made at an appropriate distance from the center tick; increasing distance

from this center tick corresponded to an increase in intensity.

Using a ruler, sample scores were converted to a numerical value based on their

distance from the left anchor mark; for example, a mark 3.4 cm from the left

anchor was given a score of 3.4. An increase in the numerical score indicates an

increase in intensity. Data was analyzed using the GLM procedure in SAS.

Panel 2

The plants were grown in the field as described in Chapter 5. Seven week-

old seedlings were transplanted on 3 March , 1999. The variety used was ‘UH’

due to the leaf shape uniformity compared with that of ‘Sweet Italian’. This

morphological uniformity was considered beneficial to minimize perceived

variation by panelists due to leaf size and shape, and possible genetic variation

as indicated by the variable morphology. The treatments were : a control

receiving no amendment; compost at 23 t ha-1; compost at 90 t ha-1; and

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synthetic N at 230 kg ha-1. Synthetic fertilizer treatment was applied as urea at

230 kg ha-1 in split applications. The last application was received 2 weeks

before sensory evaluation.

Plants were harvested 12 times over twelve weeks. The sensory

evaluation was conducted 20 weeks after transplanting.

This second sensory panel was analyzed in the same way as the first.

Results

The fertilizer treatments significantly affected fresh basil aroma intensity,

but not flavor intensity (Table 6.1). Aroma intensity was 20% higher in the

treatments receiving compost and synthetic fertilizer than in the control (Table

6.2). Table 6.2 also shows a similar trend in flavor for increased intensity (7%)

with fertilization compared to the control. This corresponded to a 7% increase in

tissue N levels with fertilization; no significant correlation between flavor intensity

and tissue N levels were found, however. Aroma intensity increased by 6% with

the higher rate of compost application as compared to the lower rate. There was

no difference in aroma intensity scores between the highest rate of compost

application and the synthetic fertilizer treatment. Highest aroma scores were

observed in the same treatments where higher tissue N and yield were recorded.

However, no significant correlation was found between aroma score and tissue N

concentration, sap nitrate levels, or yield in the compost and synthetic fertilizer

treatments. Panelists noted variations in leaf size, shape, and color. Descriptive

terms used by panelists are listed in tables 6.4 and 6.5. Aroma descriptors were

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more negative in the C180 and urea plots than in the control and c45 plots (Table

6.3), while flavor descriptors were most positive in the c45 treatment (Table 6.4).

Analysis of variance and data from panel two is shown in Tables 6.5 &

6.6. No significant difference was found in taste or aroma intensity between any

of the treatments. However, there was a trend for decreased flavor with

increased fertilization, which was accompanied by a corresponding decrease in

tissue N levels (Table 6.6). Scores for flavor were not significantly correlated

with tissue N levels. Plants that samples were taken from were seriously

affected by a decline related to nematode infestation and resulting root rot. As a

result, some samples were small and/or chlorotic. Panelists noted variations in

leaf size.

Discussion

Results from panel 1 indicate that fertilization may affect the sensory

quality of basil. The increase of intensity with increasing amounts of compost,

and the lack of intensity difference between the compost and synthetic fertilizer

treatments indicate that nutrient availability plays a role in determining aroma

intensity. The aromatic compounds found in basil are primarily terpenes and

other hydrocarbons (Prakesh, 1992; Bettelheim and March, 1998; C. S. Tang,

personal communication). Fertilization may increase the concentration of

volatiles in basil due to increased enzyme activity in the fertilized plant (Youssef

1998). Some descriptors (sweet, minty, grassy, green, fresh) used

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independently by panelists to qualify aroma follow those used by Sheen et al.

(1991) to describe the aroma of individual basil oil constituents. This supports

the suggestion that aroma changes resulting from fertilization may be due to

changes in the essential oil content and composition. Aroma intensity scores

from the c180 and urea treatments were the same. However, the marked

difference between the number, type and frequency of terms used to describe

the aroma of samples from the c180 and urea plots (Table 6.3) may indicate a

quality difference between the two treatments not best measured by intensity.

Panelists generally associated an increase in intensity with a decrease in

desirability (Tables 6.3 and 6.4, personal communication). Positive, negative and

neutral values assigned to the descriptors indicate that the aroma of samples

from the urea plots may have been less desirable than that of samples from

c180, while aroma from the c45 treatment was most desirable of all the fertilizer

plots (Table 6.3). Data listed in Table 6.4 also indicates that the lower rate of

fertilizer produced basil with the most desirable flavor. Therefore, lower rates of N

fertilizer may increase fresh basil quality. Similarly, basil fertilized with compost

may be of higher quality than that fertilized with urea. Cumulative yields obtained

from the c45 plots were similar to that obtained with the higher rate of compost

and synthetic fertilizer (Table 6.2). Therefore, 45 t ha-1 of compost may be the

best of the fertilizer treatments, producing good yields of high quality fresh basil.

The lack of significance between flavor scores may be due to the

inadequacy of measuring flavor intensity to account for the complexity of this

quality. As shown in table 6.5, terms used to describe the flavor of basil involve a

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mix of aromatic (e.g. anise, clove), gustatory ( e.g. bitter, sour), and chemical

(e.g. astringent) sensations (Meilgaard et al., 1989). Evaluations of fresh basil

flavor may therefore be better conducted by focusing on specific qualities, such

as bitterness.

Results from panel 2 cannot be directly compared to those from panel 1,

as the experimental conditions were different (i.e. different compost quality an

rate, and different cultivars). Failure to find a significant difference between

treatments may indicate that there was no treatment effect on sensory quality in

this experiment. However, severe root rot and the resulting plant decline

observed in the variety ’UH’ (data not shown) in the second experiment is likely

to have confounded any possible treatment effects.

Conclusions

Results from one of the two experiments indicate that fertilization can

affect the sensory quality of fresh basil leaves. Aroma intensity increased with the

rate of fertilization in the first experiment. Changes in aroma intensity were the

same for the compost and synthetic fertilizer treatments, although some aroma

quality characteristics possibly affected by nutrient source may not be best

measured by overall aroma intensity. Intensity may not be an adequate measure

of fresh basil flavor; evaluating a specific taste quality (e.g. bitterness) is likely to

be more appropriate. Results from two separate experiments varied, and may

reflect the influence of environmental and genotypic factors. Growers should be

135

aware that cultural practices may affect the postharvest quality of basil.

Increased fertilization of basil may result in increased aroma intensity of the fresh

product, which was a characteristic considered undesirable by some evaluators.

Literature Cited Adler,P.R., J.E. Simon and G.E. Wilcox. 1989. Nitrogen form alters sweet basil growth and essential oil content and composition. HortScience 24:789-790. Bettelheim, F. H., and J. March. 1998. p 355. In: Introduction to general, organic and biochemistry. 5th ed. Harcourt Brace College Publishers, Orlando, Florida. Eggert, F.P. and C.L. Kahrmann. Response of three vegetable crops to organic and inorganic nutrient sources. pp 97-109. Chapter 8 in Organic Farming: Current Technology and its Role in a Sustainable Agriculture. ASA, Madison Wisconsin 1984. Evers, A. M. 1989 Effects of different fertilization practices on the glucose, fructose, sucrose, taste and texture of carrot. Journal of Agricultural Science (Finland). 61:113-122. Fischer, J. 1992. The influence of different nitrogen and potassium fertilisation on the chemical flavor composition of kohlrabi (Brassica oleracea var gongylodes L.). J. Sci. Food Agric. 60: 465-470. Haglund, A., L. Johansson, L. Garedal, and J. Dlouhy. 1997. Sensory Quality of tomatoes cultivated with ecological fertilizing systems. Swedish J. Agric. Res. 27:135-145. Hamasaki,R.T., H.R. Valenzuela, D.M. Tsuda, J.Y. Uchida. 1994. Fresh Basil Production Guidelines for Hawaii. Research Extension series 154. CTAHR, University of Hawaii. Jeong, E-K., Y-B Shin, Y-B. Oh, I-H. Choi, and Y-S. Shin. 1996. Effects of organic matter application on rice growth and grain quality. RDA. J. Agri. Sci. 38:17-26. Meilgaard, M., G. V. Civille, and B. T. Carr. 1987. Sensory evaluation techniques. CRC Press, Boca Raton, Florida.

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Misra, S., and C. L. Huang. 1991. Georgia consumers’ preference for organically grown fresh produce. Journal of Agribusiness. 9:53-65. Prakesh, V. 1990. Basil. P. 3-11 In: Leafy spices. CRC Press, Boca Raton, Florida. Rader, J. S., R. H. Walser, C. F. Williams, and T. D. Davis. 1985. Organic and conventional peach production and economics. Biological Agriculture and Horticulture. 2:215-222. Sheen, L-Y., Y-H. T. Ou, and S-J. Tsai. 1991. Flavour characteristic compounds found in the essential oil of Ocimum basilicum L. with sensory evaluation and statistical analysis. J. Agric. Food Chem. 39:939-943. Simon, J.E., J. Quinn, and R.G. Murray. 1990. Basil: a source of essential oils. P. 484-489. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber press, Portland, OR. Woese, K., D. Lange, C. Boess, K. W. Bogl. 1997. A comparison of organically and conventionally grown foods- results of a review of the relevant literature. J. Sci. Food Agric. 74:281-293. Youssef, A. A., I. M. Talaat, and E. A. Omer. 1998. Physiological response of basil green ruffles (Ocimum basilicum L.) to nitrogen fertilization in different soil types. Egypt. J. Hort. 25:253-269.

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Table 6.1. Analysis of variance for aroma and flavor intensity of fresh basil leaves in Fall, 1998

Source df Aroma Intensity Taste Intensity Treatment 3 * ns block (field) 3 ns ns Judge 11 ** ** Treatment*block 9 ns ns Treatment*judge 33 ns ns Error 124 ns, *, **Nonsignificant or significant at P<0.05, 0.01, respectively Table 6.2. Effect of fertilizer treatments on sensory scores of 1st panel. Corresponding tissue nutrient levels and

yield are also listed. Values within a column having the same letter are not significantly different from each other

at P<0.05 as determined by Duncan’s New Multiple Range Test.

Treatment

Flavor score

Aroma score

Mean Tissue Nitrogen(%)

Mean Sap Nitrate-N (mg L-1)

Yield (kg ha-1) at Sample

Date

Total Yield (kg ha-1)

Control 5.4a 4.4b 4.3c 715b 1647a 8785b C45 5.8a 5.0ab 4.6a 735b 2265a 12080a C180 5.8a 5.3a 4.5b 671b 2162a 13178a Synthetic 5.7a 5.3a 4.6a 954a 2368a 12080a

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Table 6.3. Descriptors used independently by panelists to qualify fresh basil aroma, panel 1. Frequency of usage

for each treatment in parentheses.

Control C45 C180 Urea

light/fresh (2) + wintergreen (1) 0 sweet (2) + sweet (4) +

green (1) - grassy (1) 0 licorice (2) 0 clove (3) 0 clove (1) 0 best (1) +2 green (1) - anise (1) 0

light/pleasant (1) + minty (1) 0 leafy (1) - green (1) - medicinal (1) - worst (1) -2

+2a

+2

0

-1

-, -2, +, +2, 0 Assumed to be negative, strongly negative, positive, strongly positive, and neutral qualities, respectively. a The sum of the above quality designations within the treatment.

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Table 6.4. Terms used independently by panelists to qualify fresh basil flavor, panel 1. Frequency of usage for

each treatment in parentheses

Control C45 C180 Urea bitter (2) - bitter (1) - bitter (3) - bitter (2) - sweet (2) + acid (1) - minty (2) 0 sour (2) - grassy (1) - sweet (1) - sour (1) - clove (1) 0

medicinal/wintergreen (1) 0 licorice (1) 0 green (1) - astringent (1) - licorice (1) 0 better (1) + anise (1) 0 anise (1) 0 minty (1) 0 best (1) +2 medicinal (1) - leafy/organic (1) -

strong/unpleasant (1) -2 strong/worst (1) -2 pleasant (1) +

- 3a

0

- 6

- 6

-, -2, +, +2, 0 Assumed to be negative, strongly negative, positive, strongly positive, and neutral qualities, respectively. a The sum of the above quality designations within the treatment.

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Table 6.5. Analysis of variance for aroma and flavor intensity of fresh basil leaves in Spring, 1999.

Source df Aroma Intensity Taste Intensity Treatment 3 ns ns block (field) 3 * ns Judge 11 ** ** Treatment*block 9 ns ns Treatment*judge 33 ns ns Error 124 ns, *, **Nonsignificant of significant at P<0.05, 0.01, respectively Table 6.6. Effect of fertilizer treatments on 1st panel sensory scores. Corresponding tissue nutrient levels and

yield are also listed. Values within a column having the same letter are not significantly different from each other

at P=0.05 as determined by Duncan’s multiple range test.

Treatment

Flavor score

Aroma score

Mean Tissue Nitrogen(%)

Mean Sap Nitrate-N

(ppm)

Yield (kg ha)

at Sample Date

Total Yield

(kg ha) Control 4.9a 4.6a 3.6a 443a 1600 10338b C-25 4.9a 4.9a 3.6a 553a 2100 15932ab C-100 4.8a 4.6a 3.4a 350a 1300 19210a Synthetic 4.6a 4.9a 3.3a 418a 1400 12396ab

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Figure 6.1. Scoresheet used by panelists in the first sensory sensory

evalution of basil, Fall 1998.

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Figure 6.2. Scoresheet used by panelists in the second sensory evaluation

of basil, Summer 1999.

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CHAPTER 7

GENERAL DISCUSSION

Introduction

Three experiments were conducted at the The University of Hawaii

Waimanalo experiment station between April, 1998 and December, 1999 to

evaluate the response of basil to applications of locally available organic and

synthetic fertilizers.

The first experiment (Chapter 3) was conducted in the Spring of 1998.

The treatments were: a control receiving no amendment; locally obtained, aged

chicken manure applied at 5 t ha-1 fresh weight in beds with a five year history of

both annual compost and urea applications (25 t ha-1 +100 kg ha-1 respectively);

locally obtained, aged chicken manure applied at 5 t ha-1 fresh weight in beds

with a history of annual compost applications (25 t ha-1); 100 kg ha-1 nitrogen

applied as urea in plots with a five year history of annual urea applications. Data

collected in this experiment included marketable yield and tissue N levels.

The second experiment (Chapter 4) was conducted in the same location and

immediately following the first. The treatments for this experiment were: a

control receiving no amendment; on-farm produced compost applied at 45 t ha-1

fresh weight in beds with a history of both compost and urea applications (25 t

ha-1+ 100 kg ha-1 respectively) annually; the same compost applied at 180 t ha-1

fresh weight in beds with a history of annual compost applications (25 t ha-1); 110

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kg ha-1 nitrogen applied as urea. Data collected included marketable yield, tissue

N and sap nitrate-N levels, nematode counts and organic carbon levels in the

soil, galling and health indexes of plant roots, and sensory panel scores for fresh

leaf taste and aroma intensity. Immediately following this experiment, sunnhemp

(Crotolaria juncea) cv. Tropic Sun was planted at a rate of 60 kg ha-1 in an effort

to reduce nematode pressure on the next basil crop.

The third experiment (Chapter 5) was conducted in the same location in

the Spring, 1999. Treatments for the third experiment were: a control receiving

no amendment; on-farm produced compost applied at 23 t ha-1 fresh weight ; the

same compost applied at 90 t ha-1 fresh weight; 230 kg ha-1 nitrogen applied as

urea. Data collected during this experiment included marketable yield, tissue N

and sap nitrate-N levels, soil nematode counts, soil organic carbon, salinity and

pH levels, galling and health indexes of plant roots, and sensory panel scores for

fresh leaf taste and aroma intensity.

The three experiments have previously been discussed individually in this

thesis; the purpose of this chapter is to discuss the results of the individual trials

as the relate to each other. This general discussion will focus on data from all

three experiments pertaining to yield, pest (nematodes and Fusarium wilt)

incidence, soil quality, plant nutrient status, and fresh basil sensory quality.

Future research needs are also discussed.

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Yield

Yield of all basil cultivars was increased with compost and chicken manure

applications with respect to the control. These results agree with other studies

which have shown chicken manure and compost to be effective tools to manage

soil fertility in vegetable production (Roe, 1998; Verma, 1995). The magnitude of

yield increase varied with cultivar and amendment. This variation was due

primarily to a differential response of cultivars to pest pressure.

The N removed by the highest yielding plants in all experiments was 69-78

kg ha-1. This indicates that general fertilizer recommendations of 130 kg ha-1 N

for basil are adequate for good yields. Differences in N uptake between pest-free

cultivars was small; highest yielding plants of 'UH' removed 70 kg ha-1 N over 75

days, while cv. Sweet removed 71 kg ha-1 N in 100 days. However, N uptake

was affected by disease incidence; plants of 'UH' exhibiting symptoms of root rot

removed 45 kg ha-1 N over 100 days. Residual N from previous organic

amendment applications was likely available to the crop, and may have been as

much as 86 kg ha-1 N (Chapter 4). However, control plants receiving no

amendment removed as much N as plants receiving 64-80 kg ha-1 synthetic N

(Chapters 3-5). This indicates a source of N unaccounted for (i.e. improved

mycorrhizal associations in the control plots, mineralization of soil organic matter,

movement of mineral N03- from fertilizer plots, etc). It is difficult to estimate the

contribution this unaccounted for N source made to the N removed from the

fertilizer plots.

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In the first experiment, plants were supplied with 25 kg ha-1 plant available

N in the CM5 and CM5(urea) treatments and removed248% and 280%,

respectively of that N, while Urea removed 70% of the N supplied as urea. The

estimated residual N in the CM5 and CM5(urea) plots remaining from previous

compost applications were 37 and 46 kg ha-1 respectively. In the second

experiment, plants were supplied with 24 and 95 kg ha-1 in the C45 and C180

plots, respectively. 279% of the N supplied was removed by the C45 treatment,

with residual N estimated at 43 kg ha-1. 75% of the N supplied was removed by

the c180 treatment, indicating lower N use efficiency for this treatment. Plants in

this treatment were disease free. Utilization of supplied compost was higher in

both compost treatments than in the urea treatments (61%). Results from the

third experiment were similar, with plants receiving the lower rate of compost (23

kg ha-1) removing a greater percentage of N applied than plants receiving 90 kg

ha-1 compost or 230 kg ha-1 synthetic N (144%, 40% and 21%, respectively).

Again, the plants receiving the lower compost rate were most efficient in utilizing

N supplied, while plants receiving urea were least efficient. 21 kg ha-1 was the

estimated amount of residual N available to the plants in the lower rate compost

plots. Results from all three experiments indicate that n use efficiency is greatest

in plants receiving moderate rates of organic fertilizers. Residual N available to

basil plants in the first, second and third experiment were estimated to be 37, 23,

and 21 kg ha-1, respectively.

Highest yields were obtained in the cultivar ‘Sweet Italian’. The higher

rate of compost applications increased yields of this cultivar above those

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obtained with both the lower compost rate and synthetic fertilizer (fig. 7.1).

However, the higher yield per unit of N applied observed in the lower compost

rate treatments (Table 7.1) indicates that plants made most efficient use of the N

applied in the lower rate of compost. The yield difference between compost rates

was greater when compost 2 (1.2% N, 13.3% C) was used than with application

of compost 1 (0.3%, 4% C), and is probably due to differences in compost

quality, particularly with respect to the N and organic matter content. These two

qualities often determine the effectiveness of compost as a fertilizer (Eberseder,

1996; Ozores-Hampton et al., 1998). ‘Sweet’ exhibited no serious pest problems

in the field. Yield obtained with synthetic fertilizer applications were similar to

those obtained with lower rates of compost applications.

As with the previous cultivar, ‘Thai Siam Queen’ responded well to

compost applications (figure 7.2.), with yields being highest at the highest

compost application rate, and the difference between rates greatest when the

higher N and C compost was used. Yield in the synthetic fertilizer treatment was

markedly lower (25-300%) than that from the compost plots (Fig7.2). This

difference in yield was associated with a higher incidence of Fusarium disease

observed in the urea treatments.

The cultivar UH varied greatest among the varieties with respect to yield

response to compost applications (figure 7.3.). This variation was attributed to

this cultivar's apparent sensitivity to root knot nematode infestation. The planting

established in the Spring 1998 was the first basil planting in this location in years,

and the crop was observed to be relatively disease free for the short time (~10

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weeks) it remained in the field. Yields obtained with 5 t ha-1 of chicken manure

were greater than those in the controls, and similar to those obtained with

applications of 100 kg ha-1 of synthetic N as urea. Vigor of UH was markedly

reduced in the second and third experiment, most probably due to increased

nematode attack. Applications of urea and the higher rate of compost 1

decreased yields with respect to the lower compost 1 rate (fig. 7.3). High

applications of compost 2 increased cumulative yield with respect to the other

treatments. This effect was due to high yields obtained during the first few weeks

of harvest, which then rapidly declined (fig. 7.4). This trend for declining yields

with high compost applications was observed with applications of compost 1 as

well (fig. 5). The period of initially high yields in the second compost experiment

was more likely due to reduced nematode populations resulting from planting

Crotolaria juncea ‘Tropic Sun’ between the second and third experiment, than

from differences in compost quality. C. juncea has been shown to be a poor host

to root knot nematodes (Sipes and Arakaki, 1997). This yield decline was

associated with high root galling index scores, and low root health index scores.

Nematodes

Final soil plant parasitic nematode levels were low in the first basil

planting, but increased in subsequent plantings (fig. 7.6). Treatments were not

found to have a significant effect on soil nematodes counts in any experiment.

However, the severity of root galling measured using a root gall index was

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significantly affect by fertilizer applications. Root galling was greater in plants

receiving fertilizer than those from the control plots and the severity of root galling

generally increased with increased compost application rate (fig. 7.7). Increased

nematode attack in plants receiving higher nutrient levels as indicated by high

galling index scores is probably a result of greater initial plant vigor and root

growth. ‘UH’ had higher mean galling index scores than ‘Sweet’ or ‘Thai’ and

was the only cultivar to exhibit severe symptoms of nematode decline as

indicated by low root health associated with high root galling index scores (fig

7.8.). Use of cultivars such as 'Sweet' and 'Thai' which were found to be tolerant

to root knot nematodes, was adequate to avoid serious crop losses due to this

pest.

Fusarium

Disease caused by Fusarium oxysporum was observed to affect yield only

in ‘Thai’. Yield in the urea treatment was 25-300% lower than that from the

compost plots (Fig7.2). Incidence of the disease was greatest in the plots

receiving urea (58% of plants infected) and positively related to an increased

predominance of NH4+ to NO3

- in the soil, and associated with a significantly

lower pH value in the urea plots with respect to the other treatments. This

supports the findings of others who have reported increased pathogenicity of

Fusarium oxysporum in response to the addition of NH4+ or to a reduction in the

soil pH (Woltz and Jones, 1978; Scher et al., 1980). Compost applications

150

probably resulted in indirect suppression of the disease due to a combination of

increased plant vigor and maintenance of soil pH.

Soil quality

Soil properties prior to and at the completion of the experiment are listed

in Table 7.2. The higher rate of compost applications increased soil organic

carbon over the course of the three basil plantings, while OC levels were

maintained with lower rates of compost, and decreased in the control and urea

plots where no organic amendment was added. Removal of organic carbon from

the system without returning organic matter to the soil will result in decreasing

organic matter levels (Bevaqua and Mellano ,1994). Compost is therefore a

fertilizer which can increase soil organic matter relative to synthetic fertilizer

treatments. Another interesting trend observed was a decrease in soil K in the

urea plots, while soil K increased with the higher rate of compost applications.

Although K deficiency was not observed in the urea treatment, it may become

necessary to add K fertilizer to replace that removed by the crop. Conversely,

the increase in soil K with the application of large amounts of compost indicate

the possibility of excess soil nutrient levels when organic amendments are used.

Frequent soil samples are therefore important in order to monitor soil nutrient

levels when frequently applying compost. Soil analysis in the final experiment

demonstrated that soil pH was maintained (i.e. not different from the control) with

compost applications. Soil pH was significantly lower in the urea plots than in the

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plots receiving compost or no fertilizer. This observation is similar to that of

Buchanan and Gleissman (1991) who found applications of ammonium sulfate to

significantly reduce soil pH relative to a control and compost treatments.

Applications of a chicken manure plus woodchips compost increased soil

electrical conductivity (EC), indicating that soil salinity may be a concern with

frequent and repeated applications of a manure based compost. Silva et al.

(1994) also found soil EC to increase with incorporation of a chicken manure and

woodchip based compost.

Plant tissue N and Sap NO3-- N concentrations

Plant tissue N and sap NO3--N were increased with applications of

compost in these experiments, indicating that improved growth in these

treatments was due in part to a N effect. Sap NO3--N concentration of basil

shoots was found to be a slightly more sensitive indicator of plant nutrient status

and more responsive to fertilizer treatment than total N concentration of the most

recently matured leaves. These findings agree with those of Huett and Rose

(1989) and Olsen and Lyons (1994). Sap nitrate levels were higher in plants

receiving urea applications than those grown with compost, without a

corresponding increase in yield, indicating that compost may be an effective

fertilizer for reducing nitrate levels in vegetables. The best correlations between

sap nitrate-N levels, tissue N, and yield occurred 65 days after transplanting.

Only in 'UH' was a correlation between tissue N levels and yield observed, with

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highest yields corresponding with tissue N levels between 4.5-4.8%. This range

is slightly lower than values reported by Youssef et al. (1998), who found

maximum yield of basil cv. Green Ruffles to be associated with tissue N levels

greater than 4.9%. Sap nitrate-N was correlated with yield in 'UH' and 'Sweet'.

Highest yields in 'Sweet' occurred at sap nitrate-N levels below 800 mg L-1.

Highest yields in 'UH' corresponded to sap nitrate-N levels between 600-900 mg

L-1. Sap nitrate-N levels were significantly different between cultivars,

emphasizing the need for critical range development on a cultivar basis. Levels

of other nutrients were found to be adequate for production of leafy vegetables

(Tables 7.3 and 7.4).

Sensory quality

Increased aroma intensity of fresh basil was observed with application of

fertilizers, with no difference in intensity observed between compost and urea

treatments. This effect is likely due at least in part to increased plant vigor and

related production of essential oils as a result of fertilization. Flavor intensity was

not affected by fertilizer treatment, and it was determined that evaluation of

specific qualities such as ‘bitterness’ is probably more appropriate than over-all

intensity as an indicator of flavor of fresh basil as affected by fertilization.

Descriptors used by panelists indicate lower rates of N fertilizer may increase

153

fresh basil quality. Similarly, basil fertilized with compost may be of higher quality

than that fertilized with urea.

Concluding Statement

Basil may be grown organically with compost as the sole fertilizer to produce

yields comparable, or exceeding those obtained with recommended synthetic N

rates. Compost applied at moderate rates (i.e. 25 t ha-1) generally resulted in the

least disease problems, and the most efficient use of fertilizer N. Results from all

three experiments indicate that N use efficiency is greatest in plants receiving

moderate rates of organic fertilizers. Residual N available to basil plants in the

first, second and third experiment were estimated to be 37, 23, and 21 kg ha-1,

respectively.

Cultivar selection for disease resistance and high yields is important for

commercial production of basil. With the appropriate cultivar, compost rates as

high as 90 t ha-1 may be used to maximize yield. N removal data indicates that

the current recommendations of approximately 130 kg ha-1 N is adequate for

basil production in Hawaii.

Very little work has been published on the sap nitrate-N or tissue levels of

basil, and work to develop critical nutrient ranges for basil should continue.

While it would be premature to make grower recommendations based on the

observations recorded here, some conclusions may be made. First, sap nitrate-

N was positively correlated with tissue N indicating its potential usefulness for

154

basil growers in fertility management. Also, sap nitrate levels varied with

genotype; further studies should be done on a cultivar by cultivar basis. Finally,

urea applications increased basil nitrate content compared with the control while

compost applications produced high yields and no increase in plant nitrate levels.

Important soil qualities may be affected by fertilizer use. Applications of

urea significantly reduced pH, while compost did not. In fact, compost showed a

trend to increase soil pH. Although all of the pH values recorded here were

within the optimum range for crop growth, it may be possible to apply compost to

acidic tropical soils to improve plant growth and raise soil pH with reduced use of

additional amendments such as lime. After five years of annual fertilizer

applications, salinity levels in all treatment plots were within acceptable range for

plant growth. However, soil salinity was higher in plots receiving the highest

rates of fertilizer, so regular soil testing is recommended to monitor soil EC levels

when applying high rates of compost. Compost applications increased soil

organic matter, while there was a trend for decreased organic matter in the plots

not receiving compost. The increase in soil organic matter was greatest with the

higher rates of compost application. Therefore, while lower rates of compost

may applied for optimum nutrient use efficiency, initial or occasional application

of higher compost rates may be used to increase soil organic matter. Finally,

lower rates of N fertilizer may increase fresh basil quality. Similarly, basil

fertilized with compost may be of higher quality than that fertilized with urea.

155

Compost use has great potential to improve vegetable production in

Hawaii. This project has highlighted the need for increased research in the

following areas:

1. Extended field trials to determine the response of vegetable crops to multiple

rates (5-6) of compost at various locations in the State.

2. Detailed study of pest population dynamics as affected by fertilizer type and

rate of application under field conditions in Hawaii.

3. The potential of compost as a fertilizer to reduce nitrate levels in other leafy

vegetables relative to synthetic fertilizer applications.

4. Efficient and inexpensive methods of on-farm compost production to reduce

the cost discrepancy between compost and synthetic fertilizers.

5. Continued research to determine the most cost effective and crop use

efficient combination of synthetic plus organic fertilizer.

156

Literature Cited

Bevacqua, R.F. and V.J. Mellano. 1994. Cumulative effects of sludge compost on crop yields and soil properties. Commun.Soil Sci. Plant Anal. 25:395-406. Buchanan, M. And S. Gliessman. 1991. How compost fertilization affects soil nitrogen and crop yields. Biocycle December: 72-77. Erbertseder, T., R. Guster and N. Classen. 1996. Parameters to estimate the nitrogen effect of biogenic waste composts, p. 306-313. In: M. de Bertoldi, P. Sequi, B. Lemmes and T. Papi (eds.). The science of composting. Blackie Academic and Professional, Glasgow. Hamasaki, R.T., H.R. Valenzuela, D.M. Tsuda, and J.Y. Uchida. 1994. Fresh basil production guidelines for Hawaii. Research Extension Series 154. CTAHR, University of Hawaii. Huett, D.O. and G. Rose. 1989. Diagnostic nitrogen concentrations for cabbages grown in sand culture. Australian Journal of Experimental Agriculture 29: 883-892. Olsen, J.K. and D.J. Lyons. 1994. Petiole sap is better than total nitrogen in dried leaf for indicating nitrogen staus and yield responsiveness of capsicum in subtropical Australia. Australian Journal of Experimental Agriculture 34:835-43. Ozores-Hampton, M., B. Scaffer, H.H. Bryan and E.A. Hanlon. 1994. Nutrient concentrations, growth and yield of tomato and squash in municipal solid-waste-amended soil. HortScience 29:785-788. Scher, F.M and R. Baker.1980. Mechanism of biological control in a Fusarium suppressive soil. Phytopathology 70:412-417. Silva, J.A., E.L. Woods, W.C. Coleman, J.R. Carpenter and E. Ross. 1995. The use of composted chicken manure as a fertilizer. Hawaii Agriculture: Positioning for Growth. Conf. Proc. April 5-6, 1995. Sipes, B.S. and A.S. Arakaki. 1997. Root-knot nematode management in dryland taro with tropical cover crops. Nematology 29: 721-724. Verma, L.N. 1995. Conservation and efficient use of organic sources of plant nutrients. pp. 101-143. in: Thampan, P.K. (ed.) Organic Agriculture. Peekay Tree Crops Development Foundation, Cochin, India.

157

Woltz, S.S. and J.P. Jones. 1973. Interactions in source of nitrogen fertilizer and liming procedure in the control of Fusarium wilt of tomato. HortScience 8:137-138. Youssef, A. A., I. M. Talaat, and E. A. Omer. 1998. Physiological response of basil green ruffles (Ocimum basilicum L.) to nitrogen fertilization in different soil types. Egypt. J. Hort. 25:253-269.

159

Table 7.1. Treatment effect on nitrogen use efficiency of basil cv. Sweet in Fall 1998 and Spring 1999. Values are

means of four replications. Control= No amendment, C45= compost applied at 45 t ha-1 in plots with a history of

compost applications. C180= compost applied at 180 t ha-1 in plots with a history of compost applications plus

urea. C23= Compost applied at 23 t ha-1 in beds previously receiving 90 t ha-1 compost, C90= Compost applied at

90 t ha-1 in beds previously receiving 180 t ha-1, Urea=110 and 230 kg t ha-1 N applied as urea for Fall 1998 and

Spring 1999, respectively.

Date Treatment

Cumulative Yield (kg ha-1)

N applied (kg ha-1)

Yield per unit of N (kg ha-1)

Fall 1998 control 8785 0 C45 12080 24 503 C180 13178 95 139 urea 12080 110 110

Spring 1999 control 14825 0 C23 17711 48 369 C90 25147 193 130 urea 16727 230 73

160

Figure 7.1. Effect of treatments on cumulative yield of ‘Sweet’ . Yield for each treatment is represented as

percent of that obtained in the control plots. Compost 1 was applied in Fall 1998 and contained 4% and 0.3%

total organic carbon and N, respectively. Compost 2 was applied in Spring 1999 and contained 14% and 1.2%

total organic C and N, respectively.

100110

120130140150160

170180

Compost 1 Compost 2

Amendment

Yie

ld (

% o

f co

ntr

ol)

Low compostHigh compostUrea

161

Figure 7.2. Effect of treatments on cumulative yield of ‘Thai’ . Yield for each treatment is represented as percent

of that obtained in the control plots. Compost 1 was applied in Fall 1998 and contained 4% and 0.3% total

organic carbon and N, respectively. Compost 2 was applied in Spring 1999 and contained 14% and 1.2% total

organic C and N, respectively.

0

50

100

150

200

250

300

Compost 1 Compost 2

Amendment

Yie

ld (

% o

f co

ntr

ol)

ControlLow compostHigh compostUrea

162

Figure 7.3. Effect of treatments on cumulative yield of ‘Sweet’ . Yield for each treatment is represented as

percent of that obtained in the control plots. Compost 1 was applied in Fall 1998 and contained 4% and 0.3%

total organic carbon and N, respectively. Compost 2 was applied in Spring 1999 and contained 14% and 1.2%

total organic C and N, respectively.

100

120

140

160

180

200

Compost 1 Compost 2

Amendment

Yie

ld (

% o

f co

ntr

ol)

Low compostHigh compostUrea

163

Figure 7.4. Yield trend of ‘UH’ over time in Fall '98. Line equations are: control, y = -8.17x2 + 227.96x - 600.96;

C45, y = -14.71x2 + 340.72x - 658.15; C180, y = -21.04x2 + 362.17x - 508.42; urea+, y = -19.41x2 + 455.31x - 1641.3

0200400600800

1000120014001600

5 7 9 11 13 15Weeks After Transplanting

Yie

ld (

kg

ha

-1)

c180

ureac45

control

164

Figure 7.5. Yield trend of ‘UH’ over time in Fall '98 (top) and Spring '99. Line equations are: control, y = -1.4418x2

+ 119.04x - 352.52; C23, y = -4.73x2 + 183.57x - 95.85; C90, y = -23.91x2 + 530.76x - 880.29; urea, y = -28.06x2 +

745.38x - 3544.20.

0

500

1000

1500

2000

2500

3000

8 10 12 14 16 18 20Weeks After Transplanting

Yie

ld (

kg

ha

-1)

c90

c23

control

urea

165

Figure 7.6. Effect of fertilizer treatment on mean plant parasitic nematode levels at the end of each experiment.

Values are means of four replications.

0

100

200

300

400

500

600

700

800

900

Spring '98 Fall '98 Spring '99

Nem

ato

de (

# p

int)

ControlLow CompostHigh CompostUrea

166

Figure 7.7. Root Gall Index by treatment for two experiments. Values are means of four replications. Root Gall Index: 1= 0-20% of roots galled, 2= 21-40% of roots galled, 3= 41-60% of roots galled, 4= 61-80% of roots galled, 5= 81-100% of roots galled.

0

1

2

3

4

5

sweet thai uh

Cultivar

Gal

l Ind

ex control

C23C90Urea

Spring '99

0

1

2

3

4

5

sweet thai uh

Gal

l Ind

ex

controlC45C180Urea+

Fall '98

167

Figure 7.8. Mean Gall and Root Health Index scoresof ‘UH’. High gall scores correspond with low root health

scores in all treatments of both experiments. Root Gall Index: 1= 0-20% of roots galled, 2= 21-40% of roots galled,

3= 41-60% of roots galled, 4= 61-80% of roots galled, 5= 81-100% of roots galled. Root health index: . 1=Dead

2=Severe decline 3=Moderate decline 4=Mild decline 5=No decline.

0

1

2

3

4

5

1998 1999

Ro

ot

Healt

h I

nd

ex

controlLow compostHigh compostUrea

168

Figure 7.9. Effect of fertilizer applications on soil organic carbon content (%). Values are means of four

replications.

0

0.5

1

1.5

2

2.5

3

Chicken Manure Compost 1 Compost 2

Org

an

ic C

arb

on

Co

nte

nt(

%)

ControlLow compostHigh CompostUrea

169

Table 7.2. Fertilizer treatment effect on selected chemical properties of treatment soil prior first experiment (Feb. 1999), and immediately following the third (Aug. 1999).

Treatment OC (%) pH EC (dS m-1) P (mg L-1) K (mg L-1) Ca (mg L-1) Mg (mg L-1) Jan 1998

Control 2.3 7.0 0.1 319 420 4700 1100 Low compost 2.3 6.7 0.1 91 460 4575 1100 High compost 2.3 7.4 0.1 240 460 4700 1200 Urea 2.4 6.8 0.1 395 540 4600 1100

Aug 1999 Control 2 7.2 0.27 296 344 5040 1468 Low compost 2.3 7.4 0.29 120 500 5564 1422 High compost 2.7 7.5 0.33 152 830 5736 1466 Urea 2 6.4 0.19 177 192 4380 1346

170

Table 7.3. Fertilizer effect on tissue nutrient analysis of most recently matured basil leaves 55 days after

transplanting (cv. UH). Samples were composites of four replications. CM5= chicken manure applied at 5 t ha-1 in

plots with a history of 10 t ha annual compost applications. CM5(urea)= chicken manure applied at 5 t ha-1 in

plots with a history of 10 t ha annual compost applications plus urea. Urea= 100 kg N ha-1 applied as urea in

plots with of a history of annual urea applications of 100-300 kg N ha-1 . Control= no amendment.

Treatment

P ------------

K ---------

Ca ----%---

Mg ---------

Na ----------

Mn -----------

Fe ----------

Cu mg kg-1

Zn --------

B -----------

Control 0.53 2.34 2.42 0.71 0.07 57 229 18 43 22 CM5(urea) 0.48 2.88 2.57 0.72 0.02 84 353 18 50 25 CM5 0.54 2.48 2.36 0.66 0 67 252 17 41 24 Urea 0.47 2.69 2.2 0.67 0.01 67 268 19 41 22

171

Table 7.4. Fertilizer effect on tissue nutrient analysis of most recently matured basil leaves 65 days after

transplanting (cv. Sweet). Samples were composites of four replications. C45= compost applied at 45 t ha-1 in

plots with a history of compost applications. C180= compost applied at 180 t ha-1 in plots with a history of

compost applications plus urea. Urea= 110 kg ha-1 N applied as urea in plots with a history of annual urea

applications of 100-300 kg ha-1 N. Control= no amendment.

Treatment

P ------------

K ---------

Ca ----%---

Mg ---------

Na ----------

Mn -----------

Fe ----------

Cu mg kg-1

Zn --------

B -----------

Control 0.65 3.90 2.67 0.71 0.32 80 650 31 77 27 C45 0.51 3.62 2.78 0.72 0.23 94 938 28 62 27 C180 0.43 2.93 2.71 0.79 0.21 93 775 25 55 28 Urea 0.51 3.37 2.65 0.68 0.28 76 687 27 59 27