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Karnataka J. Agric. Sci.,23 (4) : (580-583) 2010

Influence of different plant densities on the growth, yield and economics of Bt cotton (Gossypiumhirsutum L.) genotypes under dryland condition*

M. J. MANJUNATHA, A. S. HALEPYATI, B. G. KOPPALKAR AND B. T. PUJARI

Department of AgronomyCollege of Agriculture, Raichur-584101, India

Email: [email protected]

(Received: February, 2010)

* Part of the M.Sc. (Agri.) thesis submitted by the senior author to the University of Agricultural Sciences, Dharwad-580 005, India

Abstract: A field experiment was conducted at Agricultural College farm, Raichur during kharif, 2008 to find out the performanceof Bt cotton genotypes with different plant densities under rainfed condition. Bunny Bt BG-II recorded significantly higherseed cotton yield (23.55 q ha -1) followed by Bunny Bt BG-I (21.83 q ha -1). Bunny Bt BG-II performed better with respect togrowth components viz., number of sympodial branches per plant (22.53), dry matter production (450.4 g plant -1), leaf area

(106.5 dm2

plant-1

), leaf area duration (177.61 DAS), leaf area index (4.58), AGR (5.18 g day-1

) and crop growth rate (22.4mg dm 2 plant -1). Significantly higher boll weight (3.53 g) and harvest index (0.246) were recorded with Bunny Bt BG-II.Spacing of 60 x 30 cm recorded significantly higher (21.11 q ha -1) seed cotton yield than wider spacing of 90 x 60 cm (15.59q ha -1), 75 x 30 cm (18.85 q ha -1) but it was on par with 90 x 20 cm (20.10 q ha -1). However, the differences in seed cotton yielddue to both Bt hybrids and closer spacings did not differ significantly.

Key words: Bt cotton, genotypes, plant densities

Introduction

Cotton is in predominant position among all cash cropsin India and has retained its unique fame as king of fibre andwhite gold because of its higher economical value among allcash crops. In India, nearly 70 per cent of the crop is cultivatedunder rainfed conditions in the Central and Southern regions of the country and it is essential to investigate the suitablegenotype which performs better under this condition. There ismuch scope to increase the cotton production in India byincreasing the productivity through adoption of appropriateagronomic practices. There is also a need to find out optimumplant density for recently released Bt cotton hybrids to realizethe maximum yield potential. Hence, the present study wasundertaken to find out the potentiality of Bt cotton genotypesand also to save cotton seeds with different plant densitiesunder rainfed condition.

Material and methods

The field experiment was conducted during kharif, 2008at Agricultural College Farm, Raichur situated in North EasternDry Zone (Zone-2) of Karnataka at 16 o 12' N latitude and 77 o 20'E longitude with an altitude of 389 meters above the mean sealevel. The experiment was laid out in split plot design with fourgenotypes (G 1- Bunny Bt BG-II, G 2- Bunny Bt BG-I, G 3- Non Bthybrid and check variety RAS 299-1) in main plot treatmentsand four spacings (P 1: 60 x 30, P 2: 75 x 30, P 3: 90 x 20 and P 4: 90 x60 cm) as sub plot treatments with three replications. Theexperimental field was clayey (56.94 % clay) in texture with the

available nitrogen of 215.9 kg ha -1, phosphorous (27.80 kg ha -1)

and potassium (147.53 kg ha -1) with organic carbon content of 0.49 (%). Sowing was done by hand dibbling as per thetreatments on 30-07-2008.

Results and discussionSignificantly higher seed cotton yield (23.55 q ha -1)

was registered with Bunny Bt BG-II when compared to non Bthybrid (18.35 q ha -1) and check variety (11.92 q ha -1). This maybe due to significantly higher yield attributing characters whichmight have contributed for increased yield (Table 3). The increasein the yield attributing characters with respect to Bunny Bt BG-II might also be due to significantly higher growth componentsand higher amount of dry matter accumulation in reproductiveparts upto harvest. Number of sympodial branches per plantwas significantly higher (22.53) with Bunny Bt BG-II and itinduced higher number of flowers and bolls per plant. Leaf area

being the photosynthetic surface plays a vital role in productionand availability of photosynthates for seed cotton production.Significantly higher leaf area (106.50 dm 2 plant -1) and LAI (4.58)were recorded by Bunny Bt BG-II which might have credited tothe production and supply of sufficient photosynthates uptothe harvest of bolls. Significantly higher leaf area duration wasrecorded with Bunny Bt BG-II (177.61 days) during 91-135 DASand it might be one of the important factors responsible forhigher seed cotton yield obtained in Bunny Bt BG-II bycontributing more assimilates for longer time. Higher values of physiological parameters like AGR, NAR and CGR indicate bettergrowth of plant (Anon., 1973). Significantly higher AGR (5.18 gday -1), NAR (0.169 g dm -2 day -1) and CGR (22.4 mg dm -2 day -1)


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were recorded in Bunny Bt BG-II which might have helped forincreased dry matter production and also its distribution intothe bolls and finally resulting in higher seed cotton yield (Table1 and 2). Dry matter accumulation and its distribution intodifferent plant parts depend upon the photosynthetic ability of a plant which inturn depends on the dry matter accumulation inleaf, leaf area, LAI and leaf area duration. The results on drymatter production and its distribution into different plant partsof cotton genotype followed a set of pattern. At harvest, thehigher values of dry matter production per plant (450.43 g) wererecorded in Bunny Bt BG-II and it was found to be on par withBunny Bt BG-I (443.06 g) but significantly higher than non Bthybrid (421.90) and check variety (403.84). Increased dry matterproduction may be attributed to higher dry matter accumulationin leaves, stem and reproductive parts (Table 2). Significantlyhigher (165.75 g plant -1) dry matter accumulation in reproductiveparts at harvest was registered with Bunny Bt BG-II whencompared to other genotypes but it was on par with Bunny Bt

BG-I (163.46). Higher dry matter production coupled withmaximum partitioning of dry matter into sink decides the yield of

any crop. It is the major factor considered responsible for higheryield in Bunny Bt BG-II. This might have resulted in higherphotosynthesis and higher rate of growth. The dry matterproduction in the early stages and subsequent partitioning intoreproductive parts is essential to achieve higher seed cottonyield. The differences in the yield in both the Bt hybrids did notdiffer significantly because they did not cause significantvariation with respect to all parameters i.e. , growth,physiological and yield parameters. This was also observed byBhalerao et al . (2008). Significantly higher (0.243) harvest indexwas registered by Bunny Bt BG-II followed by Bunny Bt BG-I(0.231) when compared to other genotypes due to highereconomical yield. The maximum gross returns (Rs. 59,583 ha -1),net returns (Rs. 39,152 ha -1) and BC ratio (2.91) were accountedwith Bunny Bt BG-II over rest of the hybrids except Bunny BtBG-I. This may be mainly due to higher seed cotton yield obtainedwith Bt hybrids (Table 3). These results are in line with earlierfindings of Shankaranarayanan et al . (2004).

Significantly higher (21.11 q ha -1) seed cotton yield

Table 1. Growth components, leaf area, leaf area duration and leaf area index of cotton genotypes as influenced by different

plant densitiesTreatments Plant Sympodial Main Leaf area (dm 2 plant -1) Leaf area duration (days) Leaf

height branches stem 135 DAS At harvest 46-90 DAS 91-135 DAS area(cm) per plant nodes per index

plant

Genotypes

G1 - Bunny Bt BG-II

(NCS 145) 117.59 22.53 22.95 106.50 78.8 85.28 177.61 4.58

G2 - Bunny Bt BG-I

(NCS 145) 117.04 22.05 23.12 101.30 75.9 83.65 171.48 4.35

G3 - Hybrid (Non-Bt)

(NCS 145) 110.71 22.05 20.23 94.80 69.6 74.96 157.79 4.08

G4 - Check variety

(RAS 299-1) 107.39 16.95 18.12 90.00 63.0 66.34 145.01 3.87

Mean 113.18 20.07 21.10 98.10 71.82 77.55 162.97 4.22S. Em. 2.07 0.61 0.62 1.75 1.38 1.26 1.99 0.08

C.D. at 5% 7.17 2.12 2.16 6.06 4.79 4.37 6.88 0.28

Plant densities

P1 - 55,555 plants ha-1

(60 X 30 cm) 111.81 19.77 20.97 96.60 71.4 98.48 207.36 5.36

P2 - 44,444 plants ha-1

(75 X 30 cm) 114.06 19.48 21.10 98.10 70.3 80.89 168.60 4.36

P3 - 55,555 plants ha-1

(90 X 20 cm) 111.78 19.12 20.63 96.00 70.1 96.40 203.58 5.27

P4 - 18,518 plants ha-1

(90 X 60 cm) 115.09 21.92 21.72 101.90 75.5 34.47 72.35 1.89

Mean 113.18 20.07 21.10 98.10 71.82 77.55 162.97 4.22

S. Em. 1.64 0.61 0.51 1.35 0.72 0.82 1.56 0.07

C.D. at 5% NS 1.78 NS 3.94 2.10 2.41 4.57 0.19

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was recorded with 60 x 30 cm than wider spacing of 90 x 60 cm(15.59 q ha -1) and 75 x 30 cm (18.85 q ha -1) but it was on par with90 x 20 cm (20.10 q ha -1). Even though, the seed cotton yield per

plant was significantly higher with 90 x 60 cm, it could notcompensate for the loss in number of plants per hectare andthus recorded lower seed cotton yield per hectare (Table 3).Similar results were observed by Narayana et al . (2008). Theultimate seed cotton yield is the manifestation of yieldcontributing characters. These yield attributing characters weresignificantly affected by different plant populations. Thedifferences in the yield characters may be related to thedifferences in the dry matter production and its accumulationinto different plant parts at various growth stages of the crop.At all the stages of crop growth, lower plant population (18,518plants ha -1) with 90 x 60 cm spacing recorded significantly higherdry matter production per plant over higher plant densities(44,444 plants ha -1) with 75 x 30 cm spacing and 55,555 plants

ha -1 with 60 x 30 and 90 x 20 cm spacings. Higher dry matterproduction per plant may further be attributed to the improvementin the assimilation of photosynthates and their accumulation inleaves, stem and reproductive parts at various stages of cropgrowth (Table 2). Further, the fact that higher population with90 x 20 cm, 60 x 30 cm and 75 x 30 cm spacings depressed theplant growth parameters resulting in lower number of sympodialor fruiting branches, leaf area, dry matter production per plantand consequently lower seed cotton yield per plant (Table 1).Significantly higher (160.68 g plant -1) dry matter accumulationin reproductive parts and leaf area (101.90 dm 2 plant -1) wererecorded with 90 x 60 cm spacing when compared with otherspacings. Significantly higher (21.11 q ha -1) seed cotton yieldwas obtained with 60 x 30 cm spacing and this was mainlycontributed by the higher LAI (5.36), LAD (207.36 days), NAR(0.044 g dm -2 day -1) and also by the CGR (20.6 mg dm -2 day -1).Varied plant population at different spacings caused significant

Influence of different plant densities on the growth....Table 2. Absolute growth rate, crop growth rate and pattern of dry matter production of cotton genotypes as influenced by

different plant densities

Treatments AGR (g day -1) CGR(mg dm -2day -1) Pattern of dry matter production (g plant -1)46-90 91-135 46-90 91-135 At 135 DAS At harvest

DAS DAS DAS DAS Leaf Stem Rep. Total Leaf Stem Repr. Totalparts partsGenotypes

G1 - Bunny Bt BG-II 5.18 3.85 22.4 16.7 137.2 133.7 155.9 427.3 127.2 157.4 165.7 450.4

(NCS 145)

G2 - Bunny Bt BG-I 5.15 3.75 22.3 16.4 135.0 132.0 153.4 420.6 125.5 154.0 163.4 443.0

(NCS 145)

G3 - Hybrid (Non-Bt) 4.94 3.67 21.5 15.9 130.1 128.2 147.2 405.6 117.3 149.3 155.2 421.9

(NCS 145)

G4 - Check variety 4.71 3.65 20.4 15.9 128.5 122.5 142.1 393.2 113.6 143.0 147.1 403.8

(RAS 299-1)

Mean 4.99 3.73 21.6 16.2 132.7 129.1 149.7 411.7 120.9 150.9 157.9 429.8

S. Em. 0.09 0.07 0.40 0.3 1.95 1.99 2.20 6.06 1.84 2.43 2.30 6.80

C.D. at 5% 0.30 NS 0.13 NS NS 6.61 7.61 20.96 6.38 8.41 7.97 23.53

Plant densities

P1 -55,555 plants

ha -1 (60 X 30 cm) 4.96 3.71 27.6 20.6 132.2 127.7 148.9 409.8 119.8 149.7 156.8 426.4

P2 -44,444 plants

ha -1 (75 X 30 cm) 4.99 3.73 22.2 16.6 132.7 129.1 149.9 411.8 120.9 150.6 157.3 428.9

P3 -55,555 plants

ha -1 (90 X 20 cm) 4.94 3.74 27.4 20.8 132.2 128.4 147.3 409.0 120.3 149.8 156.7 426.9

P4 -18,518 plants

ha -1 (90 X 60 cm) 5.09 3.74 9.4 6.9 133.8 131.2 151.6 416.9 122.6 153.5 160.6 436.8

Mean 4.99 3.73 21.6 16.2 132.7 129.1 149.7 411.7 120.9 150.9 157.9 429.8

S. Em. 0.04 0.05 0.2 0.3 0.51 1.05 0.88 1.57 0.80 1.22 1.28 1.50

C.D. at 5% 0.11 NS 0.5 0.8 1.49 3.05 2.56 4.59 2.32 3.57 3.75 4.37

DAS- Days after sowing NS- Non significant


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differences in net returns, gross returns and BC ratio. Thespacing of 60 x 30 cm accounted significantly higher net returns(Rs. 30,826 ha -1) when compared with 75 x 30 cm (Rs. 26,317 ha -1) and 90 x 60 cm (Rs. 19,806 ha -1) but it was on par with the

planting geometry 90 x 20 cm (Rs. 28,269 ha -1). The higher netreturns (Rs. 30,826 ha -1) and BC ratio (2.46) with higher plantpopulation were mainly due to higher seed cotton yield obtainedper unit area (Table 3).

References

Anonymous, 1973, Investigation of structure of cereals (Maize andSorghum).A Techl. Rep. PL-480 project, pp.374.

Bhalerao, P.D., Gawande, P.P., Ghatol, P.U. and Patil, B.R., 2008,Performance of Bt cotton hybrids for various spacing underrainfed condition. Agric. Sci. Digest., 28(1): 54-56.

Narayana, E., Hema, K., Srinivasulu, K., N.V.V.S.D. Prasad and Rao,N.H.P., 2008, Performance of Bt Cotton hybrid (NCS-145

Bt.) to varied spacing and fertilizer levels in vertisol underrainfed conditions. J. Indian Soc. Cotton Improv.,33(April),33-36.

Shankaranarayanan, K., Nalayini, P., Prabharaj, C.S. and Dharajothi,2004, Effect of dates of sowing on the productivity of Btcotton hybrids. In: Int. Symp. Strat. Sust. Cotton Prod. AGlobal Vision 2.Crop Production, November 23-25, Univ.Agric. Sci., Dharwad, pp.103-104.

Karnataka J. Agric. Sci.,23 (4) : 2010

Table 3. Yield components and economics of cotton genotypes as influenced by different plant densitiesTreatments Boll Seed cotton Seed cotton Harvest Cost of Gross Net Benefit

weight (g) yield yield index cultivation returns returns cost(g plant -1) (q ha -1) (Rs. ha -1) (Rs. ha -1) (Rs. ha -1) ratio

GenotypesG1 - Bunny Bt BG-II 3.53 76.8 23.83 0.246 20,431 59,583 39,152 2.91(NCS 145)G2 - Bunny Bt BG-I 3.36 68.4 21.55 0.228 21,483 53,875 32,392 2.59 (NCS 145)G3 - Hybrid (Non-Bt) 3.18 59.8 18.35 0.214 23,649 44,040 22,226 1.93(NCS 145)G4 - Check variety 2.81 47.5 11.92 0.184 18,343 27,408 11,449 1.64(RAS 299-1)Mean 3.22 63.1 18.91 0.218 20,976 46,226 26304 2.30S. Em. 0.08 1.58 0.63 0.005 1491 1278 0.09

C.D. at 5% 0.27 5.46 2.17 0.016 - 5160 4421 0.32Plant densitiesP1 - 55,555 plants ha

-1 3.05 52.4 21.11 0.192 21,945 51,635 30,826 2.46(60 X 30 cm)P2 - 44,444 plants ha

-1 3.23 60.3 18.85 0.214 20,808 46,022 26,317 2.27 (75 X 30 cm)P3 - 55,555 plants ha

-1 3.01 51.3 20.10 0.187 21,981 49,117 28,269 2.32(90 X 20 cm)P4 - 18,518 plants ha

-1 3.58 88.6 15.59 0.278 19,173 38,133 19,806 2.02(90 X 60 cm)Mean 3.22 63.1 18.91 218 20,976 46,226 26,304 2.30S. Em. 0.16 1.36 0.48 0.004 1186 1365 0.10C.D. at 5% 0.48 3.97 1.41 0.011 - 3461 3986 0.30

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