Effect of potassium management through foliar nutrition on yield, quality and economics of Bt cotton (Gossypium hirsutum L.)

Introduction

Cotton (Gossypium hirsutum L.) is one of the most important commercial fibre crops and plays a major role in the textile and agricultural economy (Malinga, 2021) [8] . India has the largest area under cotton cultivation and ranks second in cotton production. During 2024-25, cotton was cultivated over 114.84 lakh hectares with a production of 297.24 lakh bales (PIB, 2026) [12] . However, cotton productivity remains comparatively low, particularly because of the predominance of rainfed cultivation, erratic climatic conditions, imbalanced nutrient management and other biotic and abiotic stresses (Ministry of Textiles,2025) [10] . Potassium is an essential macronutrient required in large quantities by cotton, particularly during flowering, boll formation and boll development. It plays an important role in maintaining plant water balance, regulating stomatal activity, activating enzymes, improving photosynthetic efficiency and facilitating the translocation of photosynthates towards developing bolls. Adequate potassium nutrition therefore contributes to better boll development, yield formation and fibre quality. Foliar application provides an additional approach for supplying nutrients during periods of high crop demand. Potassium nitrate (KNO 3 ) and potassium sulphate (K 2 SO 4 ) are important potassium sources used for foliar application in cotton. Previous studies have reported improvements in yield attributes and seed cotton yield with foliar application of KNO 3 . Meena et al. (2017) [9] recorded higher seed cotton yield with foliar KNO 3 application, while Amarjeet et al. (2018) [1] reported increased seed cotton yield with three sprays of 1 per cent KNO 3 . Similarly, Dhadge et al. (2018) [3] observed higher seed cotton yield with four sprays of 3 per cent KNO 3 . Foliar application of K 2 SO 4 has also been reported to improve cotton productivity and profitability. Hussain et al. (2020) [5] reported better economic returns with 2 per cent K 2 SO 4 compared with foliar application of KNO 3 and KCl, while Basavanneppa et al. (2015) [2] observed higher seed cotton yield, net returns and benefit-cost ratio with foliar KNO 3 application. These findings indicate that foliar potassium application can supplement soilapplied potassium during critical reproductive stages and may improve yield and economic returns. Therefore, the present investigation was undertaken to study "Effect of potassium management through foliar nutrition on yield, quality and economics of Bt cotton (Gossypium hirsutum L.)"

Material and Methods

A field experiment was conducted during the Kharif season of 2025 at the Main Agricultural Research Station (MARS), University of Agricultural Sciences, Raichur. The experimental site was situated in the North-Eastern Dry Zone (Zone 2) of Karnataka at a latitude of 16°12′ N, longitude of 77°20′ E and an altitude of 407 m above mean sea level. The soil of the experimental field was deep black soil. The initial soil available nitrogen, phosphorus and potassium were 223.10, 29.70 and 260.50 kg ha -1 , respectively. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. The genotype used was SWCH 4749 BG II (US 7067). The gross plot size was 7.20 m × 4.80 m and the net plot size was 3.60 m × 3.60 m, with a spacing of 90 cm × 60 cm. The recommended fertilizer dose was 180:90:90 kg N: P 2 O 5: K 2 O ha -1 , with recommended nitrogen and phosphorus kept common for all treatments.

The treatments were: T 1: Recommended NPK (100%) (kg ha -1 ) T 2: 75% recommended potassium + 1% K₂SO₄ spray at 50 and 75 DAS T 3: 75% recommended potassium + 1% K₂SO₄ spray at 50, 75 and 100 DAS T 4: 75% recommended potassium + 2% K₂SO₄ spray at 50 and 75 DAS T 5: 75% recommended potassium + 2% K₂SO₄ spray at 50, 75 and 100 DAS T 6: 50% recommended potassium + 1% K₂SO₄ spray at 50 and 75 DAS T 7: 50% recommended potassium + 1% K₂SO₄ spray at 50, 75 and 100 DAS T 8: 50% recommended potassium + 2% K₂SO₄ spray at 50 and 75 DAS T 9: 50% recommended potassium + 2% K₂SO₄ spray at 50, 75 and 100 DAS T 10: Recommended NPK (100%) (kg ha -1 ) + 1% KNO₃ spray at 80 and 100 DAS (recommended practice) T 11: Control (without potassium).

The crop was sown on 3 rd July 2025 by dibbling two seeds per hill at a spacing of 60 cm between plants and 90 cm between rows. Seed cotton yield was recorded separately from each net plot at every picking, and the total yield was computed on hectare basis. Yield attributes including number of good opened bolls, boll weight and seed cotton yield plant -1 and quality parameters viz. lint yield, ginning outturn, staple length, fibre strength and micronaire were also recorded as per standard procedure described in the experimental methodology. The cost of cultivation was calculated by considering the prevailing prices of seed, fertilizers, plant protection chemicals, labour and other inputs. Gross returns were calculated based on seed cotton yield and market price, while net returns were calculated by deducting the cost of cultivation from gross returns. The benefit cost ratio was calculated as the ratio of gross returns to cost of cultivation. The data were statistically analysed as described by Panse and Sukhatme (1978) [11] , and critical difference values were calculated when the F-test was significant.

Results and Discussion

Application of different levels of potassium through soil and foliar nutrition significantly influenced the yield attributes and seed cotton yield of Bt cotton. Treatment T 10 , comprising 100 per cent recommended NPK + 1 per cent KNO 3 spray at 80 and 100 DAS, recorded the higher values for major yield attributes, seed cotton yield, lint yield and ginning percentage (%). Whereas treatments T 5 and T 4 , involving 75 per cent recommended potassium supplemented with 2 per cent K 2 SO 4 sprays, also performed better and were comparable with T 10 for the major yield parameters.

Yield attributes and seed cotton yield

Treatment T 10 recorded significantly higher number of good opened bolls plant -1 (27.5) followed by T 5 (27.0) and T 4 (26.8), which were found on par with T 10 . The control treatment T 11 recorded the lower number of good opened bolls plant -1 (16.1) as shown in Table 1 and figure 1. The better performance of T 10 may be attributed to adequate potassium availability during the reproductive phase, which supported boll development, retention and translocation of photosynthates towards developing reproductive sinks. The comparable performance of T 5 and T 4 indicated that foliar application of 2 per cent K 2 SO 4 could effectively supplement reduced soil-applied potassium during flowering and boll development. Similar improvement in yield attributes with foliar potassium application was reported by Saravanan et al. (2012) [15] , Sekhon and Singh (2013) [16] and Howard et al. (1998) [4] . T 10 recorded significantly higher boll weight (6.00 g), seed cotton yield (165.3 g plant -1 ) and seed cotton yield (3060 kg ha -1 ). It was followed on par by T 5 with 5.96 g boll weight, 161.00 g plant -1 seed cotton yield and 2981 kg ha -1 seed cotton yield, and T 4 with 5.93 g, 159.00 g plant -1 and 2944 kg ha -1 , respectively. The control treatment T 11 recorded the lower boll weight (5.18 g), 83.7 g plant - 1 seed cotton yield and seed cotton yield (1551 kg ha -1 ) as shown in Table 1 and figure 1. The higher seed cotton yield under T 10 may be attributed to the cumulative improvement in yield components, particularly higher boll number, greater number of good opened bolls and higher boll weight together with fewer bad opened bolls. The close performance of T 5 and T 4 indicated that repeated foliar application of K 2 SO 4 partially compensated for reduced soilapplied potassium and maintained reproductive productivity. Similar improvement in seed cotton yield with foliar KNO 3 and K 2 SO 4 application was reported by Basavanneppa et al. (2015) [2] , Meena et al. (2017) [9] , Amarjeet et al. (2018) [1] and Hussain et al. (2020) [5] .

Quality parameters Lint yield and ginning percentage

Application of different levels of potassium through soil and foliar nutrition significantly influenced lint yield and ginning percentage, whereas staple length, fibre strength and micronaire value were not significantly influenced. T 10 recorded significantly higher lint yield (1145 kg ha -1 ) and ginning percentage (37.43%), followed by T 5 (1098 kg ha -1 and 36.83%, respectively) and T 4 (1079 kg ha -1 and 36.64%, respectively). The control treatment T 11 recorded the lower lint yield (468.00 kg ha -1 ) and ginning percentage (30.15%) as shown in table 2. The higher lint yield and ginning percentage under T 10 may be attributed to adequate potassium availability during the reproductive phase, which favoured boll development, lint production and greater lint recovery. The comparable performance of T 5 and T 4 indicated that foliar application of 2 per cent K₂SO₄ was effective in supplementing reduced soil-applied potassium. Similar improvement in lint yield with foliar potassium application was reported by Jagdish et al. (2011) [6] and higher ginning percentage with foliar application of Polyfeed + Multi-K was reported by Saravanan et al. (2012) [15] , while Jyothi and Hebsur (2018) [7] recorded higher ginning outturn with soil and foliar potassium application.

Staple length, fibre strength and micronaire

The staple length varied from 29.40 to 30.70 mm, fibre strength from 29.45 to 31.05 g tex -1 and micronaire from 3.55 to 4.20, with T 10 recording the higher values for all the three characters (30.70 mm, 31.05 g tex -1 and 4.20, respectively), followed by T 5 (30.65 mm, 30.65 g tex -1 and 4.10, respectively) as shown in table 2. However, the differences were non-significant, indicating that these fibre quality parameters were comparatively stable under the different potassium management practices. The narrow variation in staple length suggested that foliar potassium application was not sufficient to produce a statistically measurable change in this fibre character. Similarly, the limited variation in fibre strength indicated that the additional KNO 3 and K 2 SO 4 applications did not strongly alter this trait. Rajendran et al. also reported that foliar nutrition did not significantly influence fibre strength in cotton. The non-significant response of micronaire indicated comparatively little influence of potassium treatments on fibre fineness under the prevailing conditions. Ratna Kumari et al. (2014) [14] reported no significant differences in fibre quality characters with foliar application of urea, DAP and KNO 3 along with RDF, whereas Shanmugam and Bhat (1991) [17] reported improvement in fibre fineness, fibre maturity and strength with adequate potassium concentration in cotton leaves.

Economics

The economic parameters differed with different potassiummanagement treatments. The higher cost of cultivation was recorded with T 5 (Rs. 90,540 ha -1 ), while the lower cost was recorded in the control T 11 (Rs. 77,865.00 ha -1 ). T 10 recorded significantly higher gross returns of Rs. 2,35,952 ha - 1 , followed by T 5 (Rs. 2,29,861 ha -1 ) and T 4 (Rs. 2,27,008 ha -1 ) which were found on par with each other. The control T 11 recorded the lower gross returns of Rs. 1,19,556 ha -1 and T 10 recorded significantly higher net returns of Rs. 1,50,287 ha -1 , followed by T 4 (Rs. 1,39,418 ha -1 ) and T 5 (Rs. 1,39,321 ha -1 ), which were found on par with each other. Although T 5 recorded slightly higher gross returns than T 4 , its higher cost of cultivation resulted in slightly lower net returns. The control treatment T 11 recorded the lowest net returns of Rs. 41,691 ha -1 as shown in table 3 and figure 2. Significantly higher BC ratio was recorded with T 10 (2.75), followed by T 4 (2.59) and T 5 (2.54), which were found on par with each other. Whereas control treatment i.e T 11 recorded lower BC ratio (1.54) as shown in table 3 and figure 2. The higher economic returns under T 10 were mainly associated with its higher seed cotton yield, while the favourable economic performance of T 4 and T 5 demonstrated the potential of supplementing reduced soil-applied potassium through foliar K 2 SO 4 . Similar improvement in economic returns through foliar potassium application was reported by Amarjeet et al. (2018) [1] and Hussain et al. (2020) [5] .

Conclusion

The application of 100 per cent recommended NPK + 1 per cent KNO₃ spray at 80 and 100 DAS (T 10 ) recorded significantly higher yield attributes, seed cotton yield, lint yield and economic returns and was superior to the other treatments. It recorded 3060 kg ha -1 seed cotton yield, 1145 kg ha -1 lint yield, Rs. 2,35,952 ha - 1 gross returns, Rs. 1,50,287 ha -1 net returns and BC ratio of 2.75. The treatments receiving 75 per cent recommended potassium supplemented with 2 per cent K 2 SO 4 spray at 50 and 75 DAS (T 4 ) and 50,75 and 100 DAS (T 5 ) also performed well and were comparable with T 10 for major yield and economic parameters and T 4 may potentially substitute to reduce 25% of soil applied potassium.

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