Standardization of plant geometry of different Bt cotton hybrids for high density planting under drip irrigation

Introduction

Cotton (Gossypium hirsutum L.) is the most important crop in India and plays a significant role in agriculture and industry worldwide. As per data from the USDA, for the year 2024-25, the expected area under cotton cultivation is 31.1 million hectares and the production is 117.40 million bales, each weighing 217.72 kg. This is an increase of 4.4 lakh bales or 3.89% compared to the previous year estimate. The highest producing countries are China, India, Brazil, the United States, and Pakistan. China is largely producing 28.20 lakh bales, India 25 million bales, Brazil 16.90 million bales, the United States 14.30 million bales, and Pakistan 5.50 million bales. The area under cotton production in China was projected to be 2.85 million hectares in 2023-2024. The first advance estimates indicate that the cotton production is 299.26 lakh bales, which is less than the 325.22 lakh bales in 2023-2024. Among the states, Maharashtra is the highest producer with 84.80 lakh bales followed by Gujarat (80.01 lakh bales), Telangana (48.95 lakh bales), Rajasthan (20.42 lakh bales) and Karnataka (18.56 lakh bales). As of September 2024, the area under cotton for 2024-25 is 112.94 lakh hectares, which is less than the 123.70 lakh hectares covered in 2023-24. Maharashtra occupied the maximum cotton area with 40.86 lakh hectares, followed by Gujarat (23.66 lakh hectares), Telangana (17.70 lakh hectares), Karnataka (6.84 lakh hectares) and Madhya Pradesh (6.14 lakh hectares). This experiment was conducted to study the response of different Bt cotton hybrids in different plant geometry on growth, yield attributes, seed cotton yield and fibre quality, nutrients uptake and availability of nutrients at harvest and to study the economics. Bt technology in cotton (2002) could better yield under higher plant densities i.e. high density planting with fewer bolls per plant, synchronized maturity with uniform bursting through Bt cotton genotypes. Nowadays, there is a stagnation in cotton productivity from the year 2014-15 with cotton productivity of only 439 kg lint ha -1 during the year 2023-24 in India. Therefore, there is a need to develop the Bt hybrids suitable for high density planting system for maximization of seed cotton yield. In order to increase the per hectare productivity efforts are being made to develop the hybrids suitable for HDPS. Adoption of HDPS could increase the plant population per hectare which ultimately reflected in increase crop yield. Therefore, it is necessary to standardize the plant geometry for different Bt hybrids. Development of ideal varieties having better adaptation to high density planting with better growth characters and optimum plant population is of paramount importance for this new method of HDPS. Therefore, present investigation was planned and carried out to standardize plant geometry of different Bt cotton hybrids for high density planting under drip irrigation.

Materials and Methods

The field experiment was conducted at the Cotton Research Farm, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola during the kharif season of 2024-25, to standardize the most suitable plant geometry suitable for different Bt cotton hybrids under high density planting (HDP) with drip irrigation, in order to maximize growth, yield and economic returns. Three Bt hybrids viz. AKHH 2022-1 Bt (V1), RCH-971 BG-2 (V2) and SWCH 4823 BG-2 (V3) with three plant geometry viz. 90 cm x 15 cm (S1), 90 cm x 30 cm (S2) and 90 cm x 45 cm (S3) were laid out in factorial randomized block design with three replications and nine treatment combinations. The field had a fairly flat and uniform topography. The soil was black and clayey, belonging to vertisols and had a slightly alkaline reaction (pH 8.10) with available nitrogen (214 kg ha -1 ), medium levels of phosphorus (16.80 kg ha -1 ), fairly high levels of available potassium (308 kg ha -1 ) and organic carbon (4.16 g kg -1 ). The farm used an inline drip irrigation system with 16 mm lateral lines placed at 90 cm intervals and 40 cm dripper spacing. Cotton planting was done on 7 th July 2024. Cotton was planted on 7th July 2024. The recommended dose of fertilizer (RDF) (120:60:60 N:P₂O₅:K₂O kg ha -1 ) was applied through drip fertigation as per the University schedule. Phosphorus was applied as basal, while nitrogen and potassium were supplied in five splits (10% at sowing, 20% at 20 DAS, 25% each at 40 and 60 DAS, and 20% at 80 DAS). The drip system supplied 2.1-3.4 L plant -1 day -1 depending on crop stage, saving 30-40% water and enhancing fertilizer use efficiency.

Results and Discussion

The results and discussion of the present study have been summarized under following heads: Effect of Bt hybrids There were significant differences observed among the Bt cotton hybrids with respect to growth, yield attributes, and seed cotton yield (Table 1). AKHH 2022-1 Bt recorded the tallest plants (127.70 cm), maximum leaf area (36.94 dm 2 ), higher chlorophyll content (28.10), and total dry matter accumulation (237.96 g plant -1 ), which were significantly superior over the other two hybrids. The superior performance of AKHH 2022-1 Bt could be attributed to its robust genetic potential and better adaptability under drip irrigation and high-density planting system. Similar results were reported by Venugopalan et al. (2011) [14] . Similarly, it produced higher number of sympodial branches (23.89 plant -1 ) and picked bolls (22.83 plant -1 ), which ultimately resulted in the maximum seed cotton yield, where Bt cotton hybrid AKHH 2022-1 Bt recorded significantly recorded the highest seed cotton yield (3134 kg ha -1 ), which was significantly superior to the other two hybrids. This was followed by RCH-971 BG-2 (2928 kg ha -1 ), while the lowest seed cotton yield was noted with SWCH 4823 BG-2 (2787 kg ha -1 ). The higher productivity of AKHH 2022-1 Bt could be attributed to its greater plant vigour, higher number of sympodial branches and more picked bolls plant -1 , which ensured higher dry matter partitioning towards economic yield. Similar results were reported by Singh et al. (2010) [10] , Parlawar et al. (2017) [8] and Parihar et al. (2018) [7] . The hybrid SWCH 4823 BG-2 exhibited the lowest growth and yield performance, with significantly reduced plant height (119.27 cm), sympodial branches (20.11 plant -1 ), and seed cotton yield (55.70 g plant -1 ).

Effect of Plant geometry: Among different plant geometry, the highest plant height (127.25 cm) was found in the high density planting with plant spacing of 90 cm x 15 cm. This was followed by lower plant densities with plant spacing of 90 cm x 30 cm (123.20 cm) and 90 cm x 45 cm (117.45 cm). The highest plant height in high density planting was due to more competition between plants. Similar results were reported by Sowmiya and Sakthivel (2018) [12] . [6] , Kumar and Ramchandra (2019) [4] . The yield attributes characters, such as number of picked bolls per plant (25.04) and seed cotton yield per plant (67.49), were found highest in the wider spacing of 90 cm x 45 cm compared to the closer spacing. Similar results were reported by Reddy and Kumar (2010) [9] and Bhalerao and Gaikwad (2010) [1] . However, the lowest number of bolls per plant in closer spacing was made up for by having more plants per hectare, which led to a significantly higher total seed cotton yield (3435 kg ha -1 ) in the closer plant spacing of 90 cm x 15 cm compared to wider spacing of 90 cm x 30 cm (2899 kg ha -1 ) and 90 cm x 45 cm (2514 kg ha -1 ). Similar results were found by Solanki et al.

(2020) [11] and Gouthami et al. (2023) [2] . [3] . (Table 4).

Interaction effect

Treatment combination AKHH 2022-1 Bt and denser spacing 90 cm x 15 cm registered significantly higher seed cotton yield (3744 kg ha -1 ), lint yield (1392 kg ha -1 ) and net monetary returns (182106 Rs. ha -1 ).

Conclusion

The study found that Bt cotton hybrids and plant geometry significantly influenced growth, yield and economics of Bt cotton under high density planting system (HDPS) with drip irrigation. Among the hybrids, AKHH 2022-1 Bt exhibited superior performance in terms of crop growth, yield attributes and seed cotton yield, which resulted in higher GMR, NMR and B:C ratio compared to the other hybrids. Similarly, closer spacing of 90 cm × 15 cm enhanced seed cotton yield on a per hectare basis due to higher plant population, thereby achieving the highest GMR and NMR. The interaction between hybrids and plant geometry was also significant for seed cotton yield, lint yield and economic returns. The combination of AKHH 2022-1 Bt with 90 cm x 15 cm spacing recorded the maximum productivity and profitability, proving its suitability for high density planting systems. Thus, adoption of AKHH 2022-1 Bt at a spacing of 90 cm x 15 cm under drip irrigation is the most effective strategy to maximize yield and economic returns of Bt cotton hybrids and adoption of compact Bt hybrids under high density planting is not only profitable but also regionally suitable, as supported by Latkar et al. (2024) [5] .

References

1. Bhalerao PD, Gaikwad GS. Productivity and profitability of Bt cotton (Gossypium hirsutum L.) under various land geometry and fertilizer levels in rainfed condition. Indian J Agron. 2010;55(1):60-3.
2. Gouthami R, Nagabhushanam U, Ramanjaneyulu AV, Madhavi B, Kamalakar J, Yakadri M. Influence of plant geometry and cultivars on growth, yield attributes and yield of HDPS cotton under rainfed shallow soils. Int J Environ Clim Chang. 2023;13(10):245-50.
3. Kakade SU, Deshmukh V, Gawate AN, Rakhonde OS, Potdukhe NR. Effect of fertigation levels and canopy management practices on growth, yield and economics of Bt cotton (Gossypium hirsutum L.). Pharma Innov J. 2023;12(6):4569-75.
4. Kumar S, Ramchandra T. Growth and yield of cotton as influenced by planting geometry and genotypes under high density planting system. Int J Curr Microbiol App Sci. 2019;8(5):2073-2077.
5. Latkar AS, Surpam AN, Kadam SR, Yadgirwar PV. Bt cotton-based cropping systems suitable for Central Vidarbha zone of Maharashtra. Int J Adv Biochem Res. 2024;8(Suppl):1068-71.
6. Manjunatha MJ, Halepyati AS, Koppalkar BG, Pujari BT. Yield, yield components, nutrient uptake, quality parameters and economics of Bt cotton (Gossypium hirsutum L.) genotypes as influenced by different plant densities. Karnataka J Agric Sci. 2010;23(3):423-5.
7. Parihar LB, Rathod TH, Raut SM, Kahate NS. Impact of genotypes and high-density planting on yield, yield attributes and quality parameters in hirsutum cotton. J Pharmacogn Phytochem. 2018;7(2):2089-92.
8. Parlawar ND, Jiotode DJ, Khawle VS, Kubde KJ, Puri PD. Effect of planting geometry and varieties on morphophysiological parameters and yield of cotton. J Soils Crops. 2017;27(1):152-8.
9. Reddy PRR, Kumar BD. Fertilizer response studies in Bt cotton hybrid. J Cotton Res Dev. 2010;24(1):76-7.
10. Singh K, Singh H, Gumber RK, Rathore P. Studies on the seed cotton yield, growth and yield contributing characters of new Bt cotton hybrids under varied agronomic manipulations. In: World Cotton Research Conference - Technologies for Prosperity. Mumbai: International Cotton Advisory Committee; 2010. p. 237-41.
11. Solanki RM, Malam KV, Vasava MS, Chhodavadia SK. Response of Bt cotton to high density planting and nitrogen levels through fertigation. J Pharmacogn Phytochem. 2020;9(5):1952-8.
12. Sowmiya R, Sakthivel N. Effect of planting geometry on growth and yield of cotton. Madras Agric J. 2018;105(13):30-2.
13. Udikeri M, Shashidhara GB. Performance of compact genotypes under high density planting system at different fertilizer levels. J Farm Sci. 2017;30(4):460-6.
14. Venugopalan MV, Prakash AH, Kranthi KR, Deshmukh R, Yadav MS, Tendulkar NR. Evaluation of cotton genotypes for high density planting systems on rainfed Vertisols of central India. In: World Cotton Research Conference-5, Book of Papers. Nagpur: CICR; 2011. p. 341-6.