optimizing tomato productivity and water use …optimizing tomato productivity and water use...

IRRIGATION AND DRAINAGE

Irrig. and Drain. 63: 640–650 (2014)

Published online 17 September 2014 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ird.1868

OPTIMIZING TOMATO PRODUCTIVITY AND WATER USE EFFICIENCY USINGWATER REGIMES, PLANT DENSITY AND ROW SPACING UNDER ARID LAND

CONDITIONS†

SALEH M. ISMAIL1,2* and MAGDI A. A. MOUSA1,3

1Arid Land Agriculture Department, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia2Soil and Water Department, Faculty of Agriculture, Assiut University, Assiut, Egypt3Horticulture Department, Faculty of Agriculture, Assiut University, Assiut, Egypt

ABSTRACT

A field experiment was conducted to study the effect of water regime (W), row spacing (RS) and plant density (D) on growthand productivity of tomato cv. ’Pito Pride’ at the Agriculture Experimental Station of King Abdulaziz University. Two waterregimes, W1 (70% of water requirement) and W2 (full water requirement) were studied. Under each water regime three rowspacings (RS1, RS2, RS3) and two plant densities D1 (single plant per dripper) and D2 (two plants per dripper) were investi-gated. Results revealed that W1 reduced number of days to flowering and fruit setting, plant height, plant fresh weight and totalyield, while it increased water productivity (WP). Decreasing RS increased water supply and total yield but decreased growthcharacteristics. D2 increased total yield by 122–168% and WP by 131–180% compared to D1. Interaction between the threevariables investigated was significant for all assessed characteristics except fruit yield per plant, total fruit yield and WP. Thesecharacteristics were affected by the interaction between RS and D. The highest total yield and WP were obtained from theRS2-D2 treatment. This treatment increased total yield per ha by 11–331% andWP by 12–300% compared with the maximumand minimum yield of other investigated treatments of both seasons. Copyright © 2014 John Wiley & Sons, Ltd.

key words: water regime; plant density; row spacing; tomato

Received 16 November 2013; Revised 13 April 2014; Accepted 13 April 2014

RÉSUMÉ

Une expérience sur le terrain a été réalisée pour étudier l’effet de régime de l’eau (W), l’écartement des rangs (RS) et la densitéde plantation (D) sur la croissance et la productivité de (CV) de la tomate ’Pito Pride’ à la station expérimentale d’agriculturede l’Université King Abdulaziz. Deux régimes des eaux, W1 (70% des besoins en eau) et W2 (exigence de pleine eau) ont étéétudiés. Sous chaque régime d’eau, trois écartements de rangs (RS1, RS2, RS3) et deux densités de semis D1 (un seulpied/goutteur) et D2 (et deux pieds/goutteur) ont été étudiés. Les résultats ont révélé que W1 a réduit le nombre de jours àla floraison et à la nouaison, la hauteur de la plante, le poids frais de la plante et le rendement total, alors qu’il a augmentéla productivité de l’eau (WP). RS décroissant a augmenté l’approvisionnement en eau et le rendement total mais a diminuéles caractéristiques de croissance. D2 a augmenté le rendement total de 122 à 168% et WP de 131 à 180% par rapport àD1. L’interaction entre les trois variables étudiées était significative pour toutes les caractéristiques évaluées, sauf la productionde fruits / plante, le rendement total du fruit et WP. Ces caractéristiques ont été affectées par l’interaction entre RS et D. Lerendement total le plus élevé et WP a été obtenu par le traitement RS2-D2. Ce traitement a augmenté le rendement total /ha de 11 à 331% et WP de 12 à 300% par comparaison aux valeurs maximales et minimales des autres traitements étudiés pourles deux saisons. Copyright © 2014 John Wiley & Sons, Ltd.

mots clés: régime des eaux; densité des plantes; écartement des rangs; tomate

*Correspondence to: Dr. Saleh M. Ismail, Arid Land Agriculture Department, Faculty of Meteorology, Environment and Arid Land Agriculture, KingAbdulaziz University, 21589 Jeddah, Saudi Arabia. Tel.: +966-596-068-380. E-mail: [email protected]†Optimisation de la productivité de la tomate et de l’utilisation efficace de l’eau en utilisant différents régimes de l’eau, densités de semis et espacement de rangsdans des conditions des terres aride.

Copyright © 2014 John Wiley & Sons, Ltd.

641ON FARM IRRIGATION MANAGEMENT

INTRODUCTION

Nowadays, the demand on water resources in the arid cli-mate of Saudi Arabia is at a critical level because the mainwater resource, groundwater, has been severely exploited.The majority of the groundwater is used for agricultural ac-tivities, which forms the main sector for water consumptionand consumes about 85% of available water. Increasing cropper drop is a good option to conserve irrigation water and toexpand the agricultural area under dry land conditions.However, irrigation water requirement depends upon theweather conditions, irrigation method and cultivar. A dripirrigation system is able to increase irrigation efficiency be-cause a small portion of the soil mass around the plant iskept moist by very frequent or continuous application ofwater. When drip irrigation is used, irrigation efficiencymay reach above 90%. However, under a sprinkler systemirrigation efficiency is expected to be less than a drip systemand ranged from 50 to 80% (Chimonides, 1995; Zalidiset al., 1997). Subsurface drip irrigation might be the bestmethod to improve water productivity since water is becomingscarcer and more valuable especially under dry land conditions(Ismail and Almarshadi, 2013)

The production of tomato fruit is mainly affected by rowspacing and fertilizer application (Abdel-Mawgoud et al.,2007). Proper plant spacing optimizes the utilization oflight, water, land and nutrients to produce good fruit yieldand quality. Narrow spacing produced higher yield withgood quality fruits per plants. However, large spacing ledto increased fruit yield per plant and fruit size (Adaniet al., 1998). Ara et al. (2007) reported that row spacing of50 cm gave higher marketable yield compared to narrowspacing which produced the lowest marketable yield andnumber of fruits per plant. Row spacing of 80 × 30 and60 × 45 cm gave higher total and marketable fruit yield thana row spacing of 100 × 30 cm (Balemi, 2008). Adjusting thespacing of fresh market tomato (Count II cultivar) to be30 cm between plants in a single row significantly increasedtotal yield but decreased yield per plant (Smith et al., 1992).

Incorrect plant spacing is considered the most notable rea-son for reduction of productivity of tomato crop since it affectsmost of the tomato’s characteristics (Lemma et al., 1992;Mehla et al., 2000). On the other hand, proper row spacinghas an important role in improving the availability of mois-ture, nutrients, light and aeration (Nagaz et al., 2012).

Increasing plant density reduces vegetative growth, im-proves earliness and increases tomato yield per unit area (Tanand Dhanvantari, 1985; Frost and Kretchman, 1988; Warneret al., 2002). Increasing economic yield of most crops espe-cially tomato is through cropping at high density (Bodundeet al., 1996; Law-Ogbomo and Egharevba, 2009). Increasingplant density reduced above-ground dry weight per plant atfinal harvest, increased total fruit yield per ha but reducedfruit yield per plant (Agele et al., 1999).


The single effect of the water regime, plant density or rowspacing may increase the total yield. Our hypothesis for thecurrent study being that, the combined effect of water re-gime, plant density and spacing is expected to effect onthe production per unit of water and area particularly underconditions of dry areas. Therefore, the objectives of thisstudy were to optimize tomato production per unit of waterand area and to maximize water productivity.

MATERIALS AND METHODS

Experimental location and design

A field experiment was carried out at the Agriculture Exper-imental Station Research of King Abdulaziz University(KAU) located at Hada Alsham village, north-east of Jeddah,KSA. The soil texture was classified as sandy loam. The climateof the area is arid, with high temperatures during the summerseason. The experiment was designed in split-split plot withthree replications. The main plots contain two water regimes(W), the sub-main plots contain three row spacings (RS) andthe sub-sub main plots comprised two planting densities (D).

Irrigation system installation

The experimental field was levelled then the dripper lineswere installed at three different row spacings, namely: 60,50 and 40 cm apart between two adjacent dripper lines to rep-resent the investigated row spacing treatments. The distancebetween drippers was 60 cm. The downstream end of eachdripper line was connected to a manifold for convenientflushing. Inlet pressure on each tape was about 1.5 bars. Thewater source was from two containers always full of watervia the main irrigation network installed in the location.

Treatments

Two water regime treatments were investigated, 70 and 100%of water requirement (W1 andW2 respectively). The requiredamount of water to be supplied for each water regime wascalculated based on the Penman–Monteith equation and themeteorological data of the local area as described by Allenet al. (1998) as follows:

ETc ¼ Kc�ET0 (1)

where ETc = crop evapotranspiration (mmday�1), ET0 = refer-ence evapotranspiration (mmday�1) and Kc = crop coefficient.

The crop coefficient values listed by Allen et al. (1998)for tomato crops were used. Under each water regime threerow spacings were investigated. The first row spacing (RS1)was 60 × 60 cm between each two adjacent rows and plants.The second row spacing (RS2) was 50 60 cm while the thirdrow spacing (RS3) was 40 × 60 cm. Under each row spacingtwo plant densities were studied. With single line density

Irrig. and Drain. 63: 640–650 (2014)

642 S. M. ISMAIL AND M. A. MOUSSA

(D1), one plant was cultivated under each dripper and withdouble line density (D2), two plants were cultivated undereach dripper (one plant on each side of the dripper line).Based on the distance between row spacing and plant densi-ties, different numbers of plants per ha were obtained. Thenumber of plants per ha were 28 000, 33 000 and 41 000for RS1, RS2 and RS3 respectively under the first plant den-sity (D1), while these numbers doubled under the secondplant density (D2).

Cultivation practices

The tomato cv. ‘Pito Pride’ seedlings were transplanted inJanuary 2011 and December 2011 for the first and secondgrowing seasons respectively. The watering of the seedlingswas automatically control by PSM timer. The timer was pro-grammed to supply irrigation water for a period of 5mintwice a day starting at 7:00 am and 6:00 pm for a period of10 days. Then the watering time was gradually extendedalong the growing season to cover the required amount ofwater for each water regime investigated. The plants werefertigated by the recommended dose of 20 : 20 : 20N-P-Kcombined fertilizer, divided into six equal doses andinjected with irrigation water. The other culture practices re-quired for tomato cultivation were applied as recommended.

Data collection

The following crop characteristics were recorded during andat the end of each growing season:

• weekly and total water supply for each treatment: re-corded by collecting the readings of the installed gaugesevery week;

• water content distribution: measured at certain timesduring the experiment using the WATERMARK datalogger system. Watermark is a resistance-type granularmatrix sensor. The resistance across a pair of electrodesembedded within the granular matrix varies with mois-ture content. This varied resistance is calibrated againstknown values and reported as soil water tension. Inter-nally installed gypsum is used as a buffering agent tocompensate for the effects of varying salinity levelstypically found in the irrigated agricultural environment.The Watermark data logger automatically reads up toeight sensors. The readings can be downloaded to a com-puter for graphical representation, which makes changesin the soil moisture easier to identify;

• water productivity (WP kg mm�1 ha�1): estimated bydividing yield by depth of water applied including rain-fall in mm;

• date to flowering;• date to fruit setting;• fruit yield per plant;


• total yield (t ha�1);• at the end of the growing season the following charac-teristics are measured in five plants for each replicate ineach treatment:

* plant height (cm);* plant fresh weight (g);* plant dry weight (g).

Statistical analysis

The data was statistically analysed as a split-split plot designwith three replicates by the analysis of variance (ANOVA)procedure after application of ANOVA assumptions. Thenthe least significant difference (LSD) at P< 0.05 was usedto compare the treatment means according to the SASprocedure.

RESULTS

Weekly and seasonal water supply

Results of weekly and seasonal water supply for tomato un-der different water regimes, row spacing and plant densityare presented in Figures 1 and 2. The results indicated thatdecreasing row spacing increased water supply. The highestwater supply was obtained from RS3 followed by RS2,while the least was found in RS1 for both water regimes dur-ing both growing seasons. Results also indicated that watersupply during the first growing season was higher than thatof the second. Moreover, water supply of W2 was higherthan that of W1.

Soil water content (SWC) distribution

The results of the SWC distribution measured at the upper15 cm of soil surface are presented in Figure 3. Results indi-cated that SWC measured at W2 was higher than that of W1for both growing seasons. Results also showed that the soilmoisture content was higher during the second growing sea-son than during the first. The differences in measured soilwater content as affected by row spacing and plant densitywere less than 5% between treatments under both water re-gimes during both growing seasons.

Agronomic traits

Days to flowering and fruit setting. Results of the ef-fects of water regimes, row spacing and plant density ondays to flowering and fruit setting are presented in Table I.Results indicated that increasing the water regime as inW2 significantly increased days to flowering and fruit set-ting during both growing seasons compared to W1.

Irrig. and Drain. 63: 640–650 (2014)

Figure 1. Weekly water supply as affected by water regimes and row spacing during both growing seasons. This figure is available in colour online atwileyonlinelibrary.com/journal/ird

Figure 2. Seasonal water supply as affected by water regime and row spac-ing during both growing seasons


Decreasing row spacing significantly reduced days toflowering and fruit setting. The shortest days toflowering and fruitsetting were obtained from RS3, followed by RS2 and RS1during both growing seasons respectively (Table I). Increasingplant density as in D2 significantly shortened days to floweringand fruit setting in both growing seasons compared with D1.

Results of the interaction between water regimes and rowspacing (W * RS) shown in Figure 4 indicated that days toflowering were longer in W2 than that of W1. Under eachwater regime, the longest days to flowering were recordedin RS1 followed by RS2 and RS3 respectively. Results ofthe effect of triple interaction (W * RS * D) on days to fruitsetting are presented in Table III. The results indicated thatthe longest days to fruit setting were obtained from the


treatment with the least plant density of the widest row spac-ing under the high water regime (D1-RS1-W2) and were 45and 39 days for the first and second growing seasons respec-tively, while the shortest days to fruit setting were found inthe treatment of D2-RS3-W1 and were 34 and 30 days forthe first and second growing seasons respectively.

Plant height (cm), plant fresh and dry weights (g).Results of plant height, plant fresh weight and plant dryweight are presented in Table II. Results revealed thatincreasing irrigation the water regime as in W2 increasedplant height and fresh and dry weights compared with W1.However, the increase in plant height and dry weight wasnot significant during the first growing season.

Decreasing row spacing decreased plant height where theleast plant height was measured in RS3. Plant heights of RS1and RS2 were almost the same, but higher than that of RS3in both growing seasons. Row spacing significantly affectedplant fresh weight. The highest plant fresh weight was obtainedfromRS2, followed by RS3 and RS1 during both growing sea-sons respectively (Table II). Different behaviour was found inplant dry weights. Decreasing row spacing increased plant dryweight. The highest plant dry weight was obtained from RS3,followed by RS2 and RS1 for both growing seasons respec-tively. The interaction of water regimes and row spacing signif-icantly affected plant height and fresh dry weight except for theplant height of the second growing season where the interac-tion was not significant (Table II). Results of plant density pre-sented in Table II show that increasing plant density as in D2

Irrig. and Drain. 63: 640–650 (2014)

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Figure 3. Soil water content distribution as affected by water regime, row spacing and plant density during both growing seasons. This figure is available incolour online at wileyonlinelibrary.com/journal/ird

Table I. Days to flowering and fruit setting as affected by water regime, row spacing and plant density during 2011 and 2012 seasons

Treatments

Days to flowering (days) Days to fruit setting (days)

2011 2012 2011 2012

Water regimes (W)W1 31b 27.5b 37.2b 33.4bW2 34a 31.2a 40.8a 36.3aF-test ** ** ** **

Row spacing (RS)RS1 35.1a 31.9a 41.4a 37.0aRS2 32.8b 28.7b 39.1b 34.0bRS3 29.9c 27.4c 36.5c 33.6cF-test ** ** ** **LSD (0.05) 0.76 0.60 0.91 0.27

Interaction (W * RS)F-test * ** * **

Plant density (D)D1 34.3a 29.8a 40.6a 35.1aD2 30.9b 28.8b 37.3b 34.7bF-test ** ** ** **

Interaction (W * D)F-test NS NS * NS

Interaction (RS * D)F-test NS NS * NS

Interaction (W * RS * D)F-test NS NS ** **

- Means with the same letter within each column are not significantly different; NS= not significant.


Copyright © 2014 John Wiley & Sons, Ltd. Irrig. and Drain. 63: 640–650 (2014)

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Figure 4. Effect of the interaction between water regimes and row spacingon days to flowering


significantly increased plant height but reduced plant fresh anddry weights compared with D1 for both growing seasons.

The interaction between water regime and plant density(W * D) did not significantly affect the plant height and freshand dry weights (Table II). Similar behaviour was found in theinteraction between row spacing and plant density (RS * D),except for plant fresh weight during the second growing sea-son where the effect was significant.

Table II. Plant height and plant fresh and dry weights as affected by wateof 2011 and 2012

Treatments

Plant height (cm) Plan

2011 2012 2011

Water regimes (W)W1 61.0 56.4b 612bW2 65.0 65.9a 889aF-test NS ** **

Row spacing (RS)RS1 64.0 63.5a 690bRS2 64.5 61.1ab 840aRS3 61.1 58.7b 721bF-test NS * **LSD (0.05) - 4.2 43

Interaction (W * RS)F-test ** NS **

Plant density (D)D1 57.3b 58.1b 915aD2 69.1a 63.8a 586bF-test ** ** **

Interaction (W * D)F-test NS NS NS

Interaction (RS * D)F-test * NS NS

Interaction (W * RS * D)F-test NS ** **

- Means with the same letter within each column are not significantly different; N


Results of the interaction of W *RS * D on plant heightand plant fresh weight are presented in Table III. The resultsindicated that the highest plant height was obtained from D2of RS3 under W1 and from D2 of RS1 under W2 for bothgrowing seasons. The highest plant fresh weight was obtainedfrom D1 of RS3 under W1 and from D1 of RS2 under W2 forboth growing seasons. Generally, the results of plant heightand plant fresh weight of W2 were higher than that of W1.

Tomato yields and water productivity

Results of yield per plant, total yield per ha and WP are pre-sented in Table IV. The results indicated that W2 signifi-cantly increased yield per plant and total yield per hawhile it decreased WP compared to W1.

Results of yield per plant were not significantly affectedby row spacing during both growing seasons. Decreasingrow spacing significantly increased total tomato fruit yield.The highest yield per ha was obtained from RS3, followedby RS2 and RS1 for both growing seasons respectively.WP was significantly affected by row spacing. The highestWP was obtained from RS3 during the first growing seasonwhere it was 18.0 kgmm�1 ha�1, while the differences

r regime, row spacing and plant density during the growing seasons

t fresh weight (g) Plant dry weight (g)

2012 2011 2012

598b 154 150854a 185 177** NS *

660c 161 153810a 172 166708b 176 172** NS NS46 – –

** NS NS

886a 200a 193a566b 140b 135b** ** **

NS NS NS

** NS NS

* NS NS

S= not significant; (–) = not calculated.

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Table III. Effect of the interaction between water regime, row spacing and plant density on days to fruit setting, plant height and plant freshweight for the growing seasons of 2011 and 2012

Waterregimes

Rowspacing

Plantdensity

Days to fruit setting (days) Plant height (cm) Plant fresh weight (g)

2011 2012 2011 2012 2011 2012

W1 RS1 D1 37.0 36.0 54.0 56.0 820 771D2 41.0 35.0 64.0 60.0 460 446

RS2 D1 38.0 33.0 49.0 52.0 683 676D2 35.0 34.0 65.0 56.5 394 377

RS3 D1 36.0 31.0 64.5 47.1 856 876D2 34.0 30.0 69.5 66.5 460 443

W2 RS1 D1 45.0 39.0 54.5 64.5 860 817D2 41.0 37.0 83.5 74.0 619 604

RS2 D1 42.0 34.0 62.5 65.5 1440 1370D2 40.0 34.0 81.5 70.5 845 8234

RS3 D1 40.0 36.0 59.5 65.5 830 812D2 35.0 36.0 51.5 55.5 740 700

Table IV. Plant yield, total fruit yield and WP as affected by water regime, row spacing and plant density during the growing seasons of 2011and 2012

Treatments

Yield per plant (g) Tomato yield (t ha�1) WP(kgmm�1 ha�1)

2011 2012 2011 2012 2011 2012

Water regimes (W)W1 210b 202 10.8b 10.9b 19.2a 17.7aW2 236a 211 12.3a 11.2a 15.0b 15.5bF-test ** NS * * ** **

Row spacing (RS)RS1 226 209 10.0b 8.6b 16.9b 17.4bRS2 231 217 11.1b 11.9a 16.3b 20.5aRS3 211 194 13.6a 12.7a 18.0a 17.9bF-test NS NS ** ** NS **LSD (0.05) - - 1.36 2.2 - 2.3

Interaction (W * RS)F-test NS NS NS NS NS NS

Plant density (D)D1 208b 173b 7.2b 6.0b 10.3b 9.79bD2 238a 239a 16.0a 16.1a 23.8a 27.5aF-test * ** ** ** ** **

Interaction (W * D)F-test NS NS NS NS NS **

Interaction (RS * D)F-test NS ** NS ** * **

Interaction (W * RS * D)F-test NS NS NS NS NS NS

- Means with the same letter within each column are not significantly different, NS= not significant; (–) = not calculated.


between RS1 and RS2 were insignificant but less than thatof RS3. The highest WP in the second growing seasonwas 20.5 kgmm�1 ha�1, obtained from RS2 (Table IV).


Results of the effect of plant density on plant yield, totaltomato yield and WP presented in Table IV clearly indicatedthat D2 significantly increased yield per plant, total tomato

Irrig. and Drain. 63: 640–650 (2014)


yield per ha and WP compared with D1. The increase ofplant and total yields in D2 was about 15 and 38 and 122and 168% for the first and the second growing seasons, re-spectively, compared with D1. The large increase of totalyield resulted in an incredible increase in WP. D2 increasedWP by about 131 and 180% for the first and second growingseasons respectively compared with D1.

A high significant interaction between row spacing andplant density was found (RS*D). The result of the effect ofthe interaction between RS and D on yield per plant is pre-sented in Figure 5. Results indicated that the highest plantyield was obtained from D2 of RS2 during the second grow-ing season. The increase ranged from 12 to 96% comparedto the maximum and minimum plant yield of the other in-vestigated treatments in both growing seasons.

A similar trend of interaction was also found in total yieldwhere the highest total tomato yield (t ha�1) was obtainedfrom D2 of RS2 during the second growing season (Figure 6).The increase in total yield ranged from 11 to 331% comparedwith the maximum and minimum yield of other investigatedtreatments of both growing seasons. The highest WP as

Figure 6. Effect of the interaction between row spacing and plant density ontotal fruit yield (t ha�1) for both growing seasons

Figure 5. Effect of the interaction between row spacing and plant density onplant yield (g) for both growing seasons


affected by the interaction between row spacing and plantdensity was obtained from D2 of RS2 during the secondgrowing season (Figure 7). This treatment increased WP from12 up to 300% compared with the maximum and minimumWP of other investigated treatments of both growing seasons.

DISCUSSION

The reduction in weekly and seasonal water supply by de-creasing the water regime and/or increasing row spacingcould be attributed to the lower supplied water under W1than that supplied in W2. Increasing row spacing decreasedthe number of dripper lines per ha where the least number ofdripper lines were in RS1 while the maximum dipper lineswere in RS3. Thus, the highest weekly and seasonal watersupply was recorded in RS3 while the least was found inRS1 under both water regimes. The increase in weekly andseasonal water supply for the first season might be due tothe weather conditions and the longer growing period thanthat of the second season. The growing period of the firstseason was characterized by higher temperature and low rel-ative humidity compared with the same period of the secondseason which was characterized by low temperature andhigh relative humidity, as presented in Table V. Many re-searchers found that irrigation water supply might be differ-ent under different weather conditions, irrigation systemsand amount of irrigation water (Waddell et al., 1999; Onderet al., 2005; Ismail and Almarshadi, 2013).

Increasing soil moisture content of W2 compared to W1during both growing seasons could be due to the higher wa-ter supply in W2 than in W1 and ability of the soil to retainwater. When the water supply is lower than field capacity allsupplied water can be retained and increased by increasingthe water supply. The increase in soil moisture content ofthe second growing season compared to the first might beattributed to the low temperature and high relative humidity

Figure 7. Effect of the interaction between row spacing and plant density onWP (kgmm�1 ha�1) for both growing seasons

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Table V. Measured temperature and relative humidity during the growing periods of the experiment

Growing seasons Growing period (month) Average temperature (°C) Average relative humidity (%)

First growing season (2011) January 22 69February 25 59March 25 51April 29 45May 33 34

Second growing season (2012) December 24 63January 23 61February 25 58March 26 66


during the second season compared to the first season(Table V). Low soil temperature and high relative humidityreduce evaporation and evapotranspiration consequentlyincreased soil water content.

The most important finding which can be drawn from thedistribution of soil moisture is that the differences in soil watercontent between treatments as affected by plant density and/orrow spacing during both growing seasons were minimal andless than 5%. These results mean that increasing plant densityto be on both sides of the dripper line instead of t one sidemight increase tomato production and maximize water pro-ductivity in all investigated treatments without any symptomsof water stress or the need for extra irrigation water. These ob-tained results could be attributed to the root distribution pat-tern. When plant density is high root growth is expected tobe condensed and occupied the whole wet area especially inthe surface layer due to the strong competition between plants.As a result, all supplied water was efficiently used by plantswith minimal or no losses and covered their water require-ments. Similar results were reported by Ismail and Ozawa(2007), Singh et al. (2011) and Ismail and Almarshadi(2013) who said that when the water distribution pattern ismet by the root distribution system, water uptake is increased,supplying the plant water requirement, which increased plantgrowth and production.

Longer days to flowering and fruit setting associated withW2 than in W1 might be due to the length of the vegetativegrowth phase as a result of the higher available soil moisturecontent of W2 compared with W1. Similar results werereported by Law-Ogbomo and Egharevba (2009). Theincrease in plant length, plant fresh and, dry weights, yieldper plant and total yield per ha of W2 than in W1 could alsobe attributed to the previous reason, besides nutrient avail-ability. The growth and yield are a great concern withimprove soil condition including greatly affected by waterand nutrient availability. Water deficiency restricts normalcrop growth resulting in enormous yield loss. However,the presence of available SWC encourages extensive rootdevelopment which can occupy a large soil mass and increasewater and nutrient absorption, resulting in enhanced growth


characteristics and higher tomato yield (Warner et al., 2002;Ismail et al., 2007, 2008; Law-Ogbomo and Egharevba,2009; Madani et al., 2012).

Increasing plant population density per unit area decreaseddays to flowering and fruit setting, plant height and yield perplant. This reduction might be due to the competitionbetween plants. Competition is expected to be less in lowplanting density than in high. Competition might be highfor nutrients, physical space and water (Ismail et al., 2008;Law-Ogbomo and Egharevba, 2009).

Of the investigated row spacing and plant density, thetreatment of RS2-D2 of the second growing season pro-duced the highest yield per plant and total yield per ha.The results might be due to light interception by plants.Higher light interception occurred in high plant density thanin low and resulted in higher growth parameters and cropyield. However, if plant density is very high, shade mightbe increased and result in a reduction of light interceptionespecially in the lower parts of plants. As a result, growthparameters and yield might be decreased (Bryan et al.,1997; Law-Ogbomo and Egharevba, 2009). Under the cur-rent study, RS2-D2 might present the best row spacing andplant density, which maximized light interception and con-sequently increased production over all treatments investi-gated. In higher plant density, the performance of plants isreduced, but a higher number of plants per ha made up forlower individual performance and consequently increasedthe total yield.

Increasing WP of W1 compared with W2 could be attrib-uted to the high yield production in relation to water supply.When water supply is decreased or water deficit practised,most crops especially those growing in dry land conditionsuse irrigation water efficiently. Al-Jamal et al. (2001),Lindenmayer et al. (2008) and Ismail and Almarshadi(2013) have published similar results. The high increasesin WP of D2 compared to D1 and in RS2 compared toRS1 and RS3 of the second growing season might be dueto the high yield production per unit of water. Increasingproduction which resulted from increasing plant populationdensity per unit of area and water resulted in the high WP.

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The results of this research clearly revealed that the mostsignificant interaction that optimized days to fruit setting,plant height and plant fresh weight was the triple interactionamong the three investigated variables (W*RS*D), while itwas between row spacing and plant density for yield perplant, total yield (t ha�1) and WP. The best combinationwhich maximized tomato yield and WP under the currentstudy was RS2-D2, especially during the second growingseason. In this combination, the row spacing of 50 × 60 cmalongside a plant density of double side (D2) resulted in aprecise plant arrangement which led to a uniform distributionof plants across the area. This homogeneous distribution pro-vided each plant with an equal chance to intercept more light,and get enough nutrients and water which improved plantgrowth characteristics. As a result, an increase in total tomatoyield and WP was obtained. The results are in conformitywith those published by James and Anderson (1994).

CONCLUSIONS

The findings of this experiment revealed that low waterregime W1 decreased days to flowering and fruit setting,reduced plant height, plant fresh weight, yield per plant,total yield per ha and increased WP. The reduction in totalyield ranged from 3 to 13.2% compared with W2. Decreas-ing row spacing decreased growth characteristics and daysto fruit setting but increased water supply and total yieldper ha. Increasing plant density population per unit area asin D2 increased total tomato yield by about 122–168% com-pared with D1 with minimal effect on soil water content. Asa result, WP was enhanced and the increase ranged from 131to 180%. Results revealed that days to fruit setting, plantheight and plant fresh weight were significantly affectedby the interaction between the three investigated variables(W*RS*D). However, yield per plant, total yield per haand WP were mainly affected by the interaction betweenrow spacing and plant density (RS*D). The highest totalyield and WP were obtained from the RS2-D2 treatment.This treatment increased total yield per ha by about 11–331%and WP by about 12–300% compared with the maximumand minimum yield of the other investigated treatments ofboth growing seasons. In conclusion, using a row spacingof 50 × 60 cm between plants and cultivation in both side ofthe dripper line is recommended for use under dry landconditions.

ACKNOWLEDGEMENTS

This work was funded by the Deanship of Scientific Research(DSR), King Abdulaziz University, Jeddah, under grant No.(155–006–D1433). The authors, therefore, acknowledge withthanks DSR technical and financial support.


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