The effect of potassium, humic acid and foliar fertilizer applications on yield and fiber quality traits of cotton (gossypium hirsutum L.)

This study was conducted to determine the effects of potassium, humic acid, and foliar fertilizer applications on yield and fiber quality characteristics of cotton (Gossypium hirsutum L.). The experiments were conducted in the Kılıçlı neighborhood of Harran district, Şanlıurfa province, during cotton growing seasons of 2020 and 2021. The study was conducted using a randomized complete block design with split plot arrangements and three replications. The cotton variety 'Fiona', potassium, humic acid, a micronutrient mixture, and a specially formulated foliar fertilizer solution included the materials of the study. Potassium doses were kept in main plots, whereas foliar applications were randomized in sub-plots. Results indicated that seed cotton yield varied between 4506.2 - 6307.2 kg ha-1, whereas plant height differed between 82.80 and 98.97 cm. Similarly, number of monopodial branches were in the range of 0.92-1.55 plant-1, while number of sympodial branches varied between 10.35 and 13.25 plant,-1.Likewise, number of bolls ranged from 9.12 to 11.47 plant-1, whereas boll weight differed between5.85 and 6.99 g. In the same way, boll seed cotton weight ranged between 4.87 and 5.87 g, while ginning turnout differed between 43.05 and 44.17%. Likely, 100 seed weight varied from 9.13 to 9.95 g, while fiber index differed between 7.16 and 7.66 g. Similarly, fiber length was in the range of 31.16-32.92 mm, whereas fiber fineness ranged between 4.71 and 4.90 micronaire. Fiber elongation differed between 31.21 and 34.85 g tex-1, whereas short fiber ratio (SFI) ranged from 4.89 to 6.33%. Fiber elongation was in the range of 6.45-7.08%, whereas uniformity index varied between 84.49 and 87.29%. Fiber brightness (Rd) ranged from 75.53 to 78.30% and the yellowness value (+b) was in the range of 6.95-7.42. While potassium × foliar applications interaction exerted statistically significant effects on the seed cotton yield, plant height, number of monopodial and sympodial branches, number of bolls and yellowness rate, non-significant effects were recorded on boll weight, boll seed cotton weight, ginning turnout, 100 seed weight, fiber index, fiber length, fiber fineness, fiber elongation, short fiber index, fiber elongation, uniformity index and fiber brightness. The highest seed cotton yield, plant height, number of monopodial and sympodial branches, number of bolls, boll weight, boll seed cotton weight, ginning turnout and fiber strength values were recorded from K21×U3, K7×U3, K21×U3, K14×U2, K7×U2, K21×U3, K21×U3, K14×U3 and K14×U3 interactions, respectively. It is concluded that applying 21 kg da⁻¹ of potassium sulfate (K₂SO₄) to the soil at planting in a single dose, and foliar applications of specially formulated solution consisting of 0.5 kg urea + 0.5 kg potassium sulfate + 0.1 kg zinc sulfate + 0.1 kg Micro Active Combi per 100 liters of water can be recommended during the square initiation, flowering initiation, and peak flowering growth stages.