Cotton (Gossypium hirsutum L.) is grown on ~3 Mha irrigated alluvial, calcareous soils, with average seed cotton yield of 1.5 t/ha, which is much lower than the potential yields obtained within the country as well the yields in many other countries of the world. In consideration of peculiar chemistry of our cotton soils (i.e., high pH, calcareousness, and low organic matter) coupled with inadequate and imbalanced nutrient management.
Cotton (Gossypium hirsutum L.) is grown on ~3 Mha irrigated alluvial, calcareous soils, with average seed cotton yield of 1.5 t/ha, which is much lower than the potential yields obtained within the country as well the yields in many other countries of the world. In consideration of peculiar chemistry of our cotton soils (i.e., high pH, calcareousness, and low organic matter) coupled with inadequate and imbalanced nutrient management, micronutrient deficiencies were suspected to be amongst the causes of low cotton productivity. Therefore, micronutrient status of farmer-grown crop was monitored in major cotton growing areas of Punjab and Sindh to identify the nature and extent of micronutrient problems. Crop responses to the application of boron (B) and (Zn) fertilizers were also studied.
Technology Development, Demonstration and Recommendation
Extensive soil and plant nutrient indexing of the crop almost in one-half of the cotton growing areas of Punjab and Sindh revealed the incidence of B deficiency in almost 50% and of Zn deficiency in 40% fields. Geostatistics-aided soil fertility contour maps effectively delineated the deficient areas. Subsequently, in multi-location, multi-year field experiments in Multan and Bahawalpur Divisions, soil-applied as well as foliar-fed B and Zn increased boll weight and boll bearing – leading to an average yield increase of 14% over the yield obtained with major nutrient fertilizers only (i.e., urea and DAP). Soil and foliar feeding proved equally effective. Use of B and Zn fertilizers proved high profitable, benefit-cost ratio being 16:1 for soil application and 30:1 for foliar sprays. Fertilizer requirement for correcting the deficiencies was 0.75 kg B/ha and 5 kg Zn/ ha. Contrary to the reported 15–20 mg B/kg as critical level in cotton leaves, NARC research revealed 53 mg/kg as B requirement in youngest matured cotton leaves.
The B+Zn use technology has been extensively demonstrated in major cotton growing areas of the country in collaboration with major fertilizer industry. Farmers’ field days were also organized. Consequently, use of B and Zn for cotton crop got recommended in Punjab in 1998 and in Sindh in 1999.
Prior to cotton sowing, 3.75 kg Borax/Acre or 2.75 kg Granubor/Acre + 6 kg Zinc Sulfate are broadcast applied along with other fertilizers. Uniform field broadcast of small quantities of micronutrient is ensured by premixing with well pulverized soil or granular fertilizers. In case soil application of micronutrients is not made, three foliar sprays of 0.1 % solution each of B and Zn are performed 45, 60 and 90 days after crops sowing. Foliar solution is prepared by dissolving 500 gram Solubor or 600 gram Boric Acid and 300 gram Zinc Sulfate and 50 gram Detergent Powder (like Surf) in 100 Liter of water. Boron and Zn fertilizers can be safely mixed with pesticide solutions.
Rashid, A., and E. Rafique. (2002). Boron deficiency in cotton grown in calcareous soils of Pakistan. II. Correction and criteria for foliar diagnosis: p 357–362, In: Boron in Plant and Animal Nutrition. Kluwer Academic Publishers, New York.
Rashid, A., and E. Rafique. (2006). Boron and zinc fertilizer use in cotton: Benefits and recommendations (Advisory brochure, Urdu). Pakistan Agricultural Research Council, Islamabad. 10 pp.