Indi an Journal of Biotechnology Vol I, July 2002, pp 280-285

Optimal Exploitation of Native Arbuscular and Vesicular-Arbuscular Mycorrhizae for Improving the Yield of Banana through IPNM

N V Phirke, S B Chincholkar and R M Kothari *

School of Life Sciences, North Maharashtra University, P B 80, Jalgaon 425 00 I , India

Received 2 July 2001; accepted 8 March 2002

The R&D banana orchard of the North Maharashtra University harboured diversified species of vesicular­arbuscular mycorrhizal (VAM) fungi belonging t() the genera Glomus , Gigaspora , Sclerocystis and Scutellospora. These fungi infected the roots severely (78.3%) and showed elevated (68.7 g-I soil) spore d(~nsity in the mycorrhizosphere of plants for integrated plant nutrition management (IPNM) system as compared to chemical fertilizers alone (traditional farming; 49.2 % & 39.3 g-I soil). This resulted in retardation of the establishment of nematodes in root zone of IPNM treatment (2.1 g-I soil) as compared to chemical treatment (5.5 g-I soil). VAM fungi enabled proper nourishment and protection of crop in IPNM treatment as compared to traditional way, which was evident from (a) reduced plant mortality (12%) of planted sword suckers, (b) enhanced greenery (foliar chlorophyll 778 ~g g-I), (c) improved nutrient uptake on dry weight basis (3.62% N; 0.31 % P; & 6.45 % K), (d) elevated finger number (137.6 per bunch) size (length 21.6 cm & girth 12.4 cm) and weight (130.8 g), and (e) overall vigour and robustness. Hence, exploitation of V AM through adoption of IPNM system revealed the (i) relatively increased banana productivity (76.5%,72 tonnes ha- I) and recyclable biowaste (36.6 kg), (ii) saving of 50 % chemical fertilizers, and (iii) permitted control over soil fertility in farmer 's favour over traditional cultivation practices. These findings related to native V AM fungi in IPNM, traditional farming and typical soil systems for cultivation of bananas are discussed in detail.

Keywords: improved banana productivity, VAM, IPNM, traditional farming, yield improvement. relative banana productivity

Introduction Bananas, grown on 45 ,000 ha in Jalgaon district of

Maharashtra, produce 2.25 million tonnes annually and serve as a major source of income for inhabitants in Tapati river basin. The last decade witnessed a decline in banana yields as a result of inappropriate cultivation practices, improper nourishment, micro­nutritional deficiencies, and soil-borne diseases. The control of diseases after occurrence was not only expensive and counter productive to soil fertility but also unsatisfactory, because sword suckers used as planting material provided a vector for root parasites. In recent years, there has been an upsurge of interest in V AM since they stimulate plant growth and also provide protection against soil-borne pathogens (Strullu, 1991). This may have substantial impact on present problem, because V AM are known to occur in Indian banana cropping eco-systems (Rohini et ai, 1988). Despite a few YAM inoculation experiments conducted to date, an increase in phosphate uptake

* Author for correspondence: Tel.: 91-257-252193; Fax: 91-257-252183 E-mail: rmkothari@rediffmail.com

and banana plant growth (Kn ight, 1988; Lin & Fox, 1992) and its increased tolerance to nematodes has been reported (Umesch et ai, 1988; Pinochet et ai, 1997). Thus, harbouring conditions for the survival of native YAM in soil will permit the maintenance of a healthy, disease-free and robust banana orchard eco­system.

Therefore, a semi-commercial R&D plantation trial was undertaken from July , 1998 to October, 1999 at University Research Farm, to minimise irrigation, eradicate soil-borne pathogen(s) affecting plant productivity, cu ltivate banana sustainably in societal and environmental favour and to demonstrate integrated plant nutntlOn management (lPNM) practices to farmers. The results of this field trial for the occurrence of native V AM fl ora, its management and exploitation in banana orchard for recurring maximal benefits to soil fertili ty and yield are presented here.

Materials and Methods Plantation of Dwarf Cavendish (AAA) banana

(Musa paradisiaca Linn. var. Shrimanti; family­Musaceae) was undertaken on pre-ploughed medium

PHIRKE e/ at: V AM FOR IMPROVING BANANA YIELD THROUGH IPNM 281

Table I-Analytical profiles of research farm soil prior to banana plantation

No. Soil Characteristics Contents Status

pH 7.9 normal 2 Total soil salinity 0.47 normal

(mmho cm- I) 3 Water holding capacity (%) 52.38 moderate 4 Soil density (g cm-J

) 1.28 normal 5 Organic matter (%) 0.58 low 6 Available N (kg ha- I) 147.3 low 7 Available P20 5 (kg ha- I) 17.0 low 8 Available K20 (kg ha- I) 678 very high 9 Exchangeable Ca 61.6

(meq/lOO g soil) 10 Exchangeable Mg 10.5

(meq/lOO g soil) II Exchangeable Na 50.0

(meq/lOO g soil) 12 Cu (~g g-I) 11.0 enough 13 Mn (~g g-I) 36.6 enough 14 Zn (~g g- I) 2.1 enough 15 Fe (~g g-I) 3.02 enough 16 VAM spore density (g- I) 14.0 low 17 Nematode QOQulation (g-I) 0.8 low

black, sandy soil (Table 1). Besides control, two treatments were given: (i) chemical or traditional i.e. chemical fertilizers alone, N @ 900 kg ha -I, P20 S @

350 kg ha- ' , K20 @ 900 kg ha- ' ; single super phosphate (SSP) and muriate of potash (MOP) were applied as a basal dose, while urea was applied in four splits (0, 1.5, 3.0, 4.5 months after plantation); and (ii) IPNM system i.e. soil conditioner (properly engineered fluffy compost) @ 10 tonnes ha- ' , consortium of biofertilizers (fresh inocula of Azotobacter chroococcum @ 20 I ha- ' and Aspergillus awamorii @ 20 I ha- ' ), fly ash @ 5 tonnes ha- ' (as a boosting source of micro-nutrients) and half dose of chemical fertili sers given above, N @ 450 kg ha- ' , P20 S @ 175 kg ha- ' , K20 @ 450 kg ha- ' . The nutrients were judiciously blended on the basis of predetermined site-specific requirement to yield target of 50 tonnes ha- ' bananas. SSP and MOP were applied in two split doses (first as a basal dose and the second at two months after plantation), while urea was applied through drip irrigation on daily basis up to sixth months to respective treatments. Each plot of 25 production units with a spacing of 1.5 m x 1.5 m for each treatment was replicated seven times as per randomised block design (RBD) on approximately 0.12 ha of University Research Farm. Drip irrigation was resorted to as recommended by Shinde et ai

(1996). The post-plantation care was taken as per routine agricultural practices used by banana growing farmers (Patil, 1996).

Two months later, the per cent mortality was replaced by planting fresh sword suckers. Growth profiles (height, girth and chlorophyll contents) were monitored after emergence of peduncle at 81h month (shooting stage) (Deo et ai, 1998; Jayaraman, 1996). After the harvest, quality and quantity of banana were evaluated and average sword suckers, recyclable pseudo-stem waste per production unit and water contents of biomass (% w/w) were recorded as a treatment-wise function. Total banana production per ha was the product of average bunch weight and 4000 production units by considering 10% probable failure due to unavoidable environmental and cultural constraints.

Rhizospheric soil samples were collected 25 cm away and deep from the base of the pseudo-stem nearby the populated hairy roots from banana plants at shooting stage in different plots. Pooling three sub­samples around a plant derived each sample, and such randomly selected three samples from a replication were thoroughly mixed to get composite sample for the replication. These were analysed for V AM spore density and nematode population per gram by wet sieving and decantation techniques (Gerdemann & Nicolson, 1963). VAM spores were identified as per the method of Schenck & Perez, 1990, by preparing slides in polyvinyl alcohol (PV A) and under stereozoom and compound microscope.

Hairy, absorbing root samples were similarly collected, cleared with 10% KOH solution for 40 min to remove phenolic compounds and stained with trypan blue (Phillips & Hayman, 1970). The per cent mycorrhizal infection of the roots was determined by root slide technique.

Prior to plantation, physico-chemical soil analysis was done as per the method of Somwanshi et ai (1997). The macroelements were analysed from a composite foliar sample from the above selected three plants. Third healthy leaf laminae from the apex , chosen for analysis, were washed, dried and dehydrated in temperature controlled and fan ventilated oven at 65°C±1 for 24 hrs. They were mixed in equal gravimetric parts, homogeni sed and digested in perchloric acid (Jones et ai, 1991 ). Nitrogen contents were determined by Kjeldahl procedure, P contents by colorimetric method using vanado-molybdo-phosphoric acid and K by flame photometry (Bhargava & Raghupath, 1993).

282 INDIAN J BIOTECHNOL, JUL Y 2002

All the data were analysed statistically and tested for its significance. Means were compared by Student's t-test, and for each treatment, relationships of per cent mycorrhization were established with other sets of observed features by calculating correlation coefficients (P ~ 0.05).

Results and Discussion The soil used at University Research Farm was

alkaline, nitrogen and phosphorus deficient, with reduced organic carbon and moderate water holding capacity (Table l).

Diversified species of AM and V AM fungi were found in all treatments and their replicates (Table 2). V AM fungal species found in banana orchard, representing the typical soi l type of Jalgaon di strict were anticipated to be well adopted to humid, sub­tropical climate and could survive, nourish and protect the plant in these soils by tolerating frequent, longer droughts (annual and unpredictable rainfall 45-70 cm, temperature range 10-47°C), soil salinity due to irrigation with salty ground water, toxicity of heavy metals unavoidably augmented through application of high doses of phosphoric and potash fertilisers and varying seasonality of banana plantation.

Among the treatments, (a) control served as natural negative comparison, receiving none of the inputs, (b) chemical served as posi tive comparison, receiving the nutrient dose totally through chemical fertilizers recommended for traditional Indian banana cultivation (Pawar et al, 1997; Souvenir, 1999), and (c) IPNM served as test, receiving balanced nutrition

predetermined by site-specific nutrient budgeting through well optimised cultural practices (Phirke et al, 1999). All treatments affected the mycorrhizal infection and spore densi ty, resulting in varied effects on vigour, nutrient uptake, yield and biomass.

Mycorrhi zal spore density and per cent infection were highest in the IPNM treatment and it was superior to that of control (Table 3). Both these characteristics declined in chemical treatment plots . Thi s resulted in considerable decrease in nematode population in IPNM plots. Increased AM and V AM spore density and decreased nematode population effected increased plant survival rate in IPNM system.

Among the morphological profiles, height in chemical and IPNM treatments was fo und higher than the control. Girth of the pseudostem was not found significantly affected. Chlorophyll contents were found highest in IPNM and it was significantly different from control and chemical treatments.

In Jalgaon district, the crop was attacked by nematodes, Radopholus similis and Helicotylenchus species (Patil, 1996). Such infection is combatible, as shown in the present investigation. Mycorrhizae have attributes such as penetration along with the root system, and therefore, providing increased absorptive surface. This ramification with root system permitted enhanced nutrient uptake from the soil rhizosphere and thereby, minimised transplantation shock on nutritional and moisture stress.

The NPK uptake, average bunch weight, functional sword suckers (which can be propagated for new plantation) and recyclable bio-waste have been

Table 2-Exploration of AM & YAM species in banana mycorrhizosphere

No. Experiment

1 Control

2 Chemicals

3 rPNM

No. Glomus

1 G. fasciculatum 2 G. fueg ianum 3 G. geosporum 4 G. intraradices 5 G. macrocarpum 6 G. mosseae

Gigaspora

G. decipiens G. margarita

Sclerocystis

Sclerocystis sp.

Scutellospora

Scutellospora sp.

Table 3--Yi tal profiles of rhiwspheric YAM and YAM banana plants

YAM Spores Per cent root Nematodes Plant Height Girth (g-I soi l) colonisation (g-I soi l) mortality (%) (cm) (cm)

52.4a, b 60.8 a, b 5.6 a 26 a 140.2 42.8 a, c

39.3 a 49.2 a 5.5 a 23 a 163.7 a 59.2 a, b

68.7 b 78.4 b 2.1 12 161.4 a 67.8 b. c

Chlorophyll (!igg- I)

316 a

523 a

778

Each value represents the mean of seven replications. Each mean within a column, not followed by the same lener, is statistically different (p<0.05) as per Student's t-test.

PHIRKE et al: V AM FOR IMPROVING BANANA YIELD THROUGH IPNM 283

indicated in Table 4. The uptake of P was highest in severely V AM infected IPNM treatment, while K increased with increase in nitrogen, so also nitrogen uptake as compared to the control. Average bunch weight was also highest in IPNM treatment. This is in accordance with the findings that AM and V AM fungi were responsible for increasing the uptake of other nutrients that move to the root surface primarily by diffusion (Abbot & Robson, 1984). Subsequently , in a comparative experiment on the effectiveness of P supply on banana growth, the intensity of mycorrhization decreased with an elevated P level (Lin & Fox, 1992). DeClerck et al (1994) found significant rise not only in P content, but also K content in mycorrhizal banana plants.

According to the Soil Testing Laboratory at Jalgaon, average fertility indices for available P20 S

(1.10) and available K20 (2.98) for the district for 1981-97, illustrate the scarcity of available P and higher contents of available K. To alleviate these constraints, banana cultivation in Jalgaon district has ample scope for optimal exploitation of native vesicular-arbuscular mycorrhizal flora for maximal benefits through IPNM system. This is supported by

the DARE/ICAR Annual Report ( 1995-96) by stating that V AM fungi and phosphate solubilising microbes could enhance banana productivity by 20% and save about 25% of SSP.

Mycorrhization and number of V AM spores in control and IPNM system were comparable (Table 5) but the quality of produce in control was poor with shorter, thinner, deformed fingers, with finger weight unacceptable in the international or metropolitan market. Chemical treatment produced moderate quality bananas, having longer, broader, heavier fingers and with lesser defects than control, while IPNM treatment yielded superior quality produce of longest, broadest and heaviest fingers with minimal defects and malformation among all the treatments, revealing that bunches are properly nourished. Also, control treatment showed early emergence of inflorescence due to stress conditions of soil fertility, while chemical and IPNM treatments indicated comparable days required for emergence and flowering.

Application of half the recommended level of chemical fertilizers together with soil conditioners (organic matter) favoured the build-up of native VAM

Table 4-Nutrient uptake and productivity of VAM banana plants

No. Experiment N P K Avg bunch Healthy suckers/ Recyclable Water (% w/w) (%w/w) (%w/w) wt (kg) production unit biowaste contents in

(kg) biomass (%)

Control 2.74 a 0. 19 a 4.26 3.4 4 .1 10.7 88.0 a

2 Chemicals 3.18 a, b 0.24 a 6.3 1 a 11 .7 8.8 a 29 .3 a 87 .2

3 IPNM 3.62 b 0 .3 1 6.45 a 18.0 8.7 a 36.6 a 87 .9 a

Low 2.5-3.4 0.15-0. 19 3.0-3.7

Sufficient 3.5-4.5 0.2-0.4 3.8-5.0

High >4.5 >0.4 >5.0

Each value represents the mean of seven replications. Each mean with in a column, not fo llowed by the same letter, is statistically different (p<O.OS) as pcr Student 's t-test. Interpretative values on dry weight basis for foliar analysi s after 8 months old banana (Joncs et ai, 1991).

Table 5--Average days for flowering, number, length, girth and finger weight

No. Experiment Days for Number of Le ngth of fingers Girth of fin gers (cm) Finger wt (g) flowcrin g fingers/bunch (cm)

Control 267 .8 40.3 13.4 9.6 a 84.4

2 Chemicals 358.6 a 94.5 19.2 a 12.2 a, b 123.8 a

3 IPNM 342.1 a 137.6 2 1.6 a 12.4 b 130.8 a

Each value represents the mean of seve n replications. Each mean within a column, not followed by the same letter, is statistically different (p<O.OS) as per Student' s t-test.

284 INDIAN J BIOTECHNOL, JULY 2002

Table 6--Quality, quantity and financia l profiles of V AM banana plots

No. Experiment Quality of Production Relative banana Financial investment on Net income fingers (tonnes ha·J

) * productivity ** chem fert (US $) *** (US $ ha- J) #

I Control Poor 13.6 nil 605 .20

2 Chemicals Moderate 46.8 68.3% 453 .00 2083.00

3 IPNM Superior 72.0 76.5% 227.00 3204.00

*Production (tonnes ha- J) = Average bunch weight per plant (kg)/IOOO x 4000 plants (10% of total production units 4400 h- J with

1.5m x 1.5m spacing, were considered as failure due to unavoidable cultural and environmental factors) . **Relative banana productivity = {(difference between the avg. weights of dry biomass of treatment and that of control)/avg. weight of dry biomass of the same treatment) x 100 ***Financial investments on chemical fertilisers (US $) were calculated by considering its prevailing prices in Indian market during April-October, 1998. #Net Income (US $ ha- J

) was determined by selling the bananas @ US $ 44.5/MT to Jalgaon-based Fruit Sale Co-operative Society during April-October, 1999.

population in sub-tropical soils (Harinikumar & Bagyaraj, 1998). Therefore, active association of fertilizers with roots has been known to afford more uptake of moisture that increases per cent water contents and help the banana plant to survive during droughts. Per cent root colonisation was found related moderately positive with spore density, chlorophyll contents, nutrient uptake, fruit weight and recyclable bio-waste, while moderately negative with per cent mortality of plants, nematode population and duration for emergence. No correlation was established with height, girth, average bunch weight, fruit size and suckers produced by plants. Thus, cumulatively, IPNM treatment showed better nourishment, robustness and improved productivity than other treatments.

IPNM treatment gave maximum production per ha, followed by chemical fertilisers and least by control (Table 6). Between IPNM and chemical treatments, IPNM showed higher relative banana productivity, which could be defined as the capacity of an experimental variety of banana to produce maximally through applied system of fertility at a study site (Patil, 1996). Highly V AM dependent IPNM plots thus, (i) saved half of the financial investment made on traditional way of cultivation, (ii) improved fertiliser use efficiency, (i ii) conserved soil and underground water table from potential havoc of pollution, and (iv) brought more income in favour of farmers.

Conclusion Management of native V AM flora in conjunction

with application of soil conditioner, effective rhizospheric plant growth promoting microbes, fly ash

and reduced fertigation provided environs for sustained growth, nullified the toxicity of heavy metals and improved productivity at lower cost by remunerative way in favour of farmers, consumers, government and environment. Thus, through these cumulative scientific traits, mycon·hizae not only imparted higher rate of survival, but also promoted higher rate of growth and eventually higher yield of banana, without compromising sustainability of soil for productivity.

Acknowledgement The authors are grateful to the Development Board

for the Rest of Maharashtra (DBRM), Mumbai, for providing financial support and Professor S F Patil, Vice-Chancellor, North Maharashtra University, for providing research farm facility. Dr Alok Adholeya (TERI, New Delhi) and Professor Ajit Varma (JNU, New Delhi) are gratefully acknowledged for offering valuable training and guidance to NVP in V AM techniques, its management and R&D.

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