Asian Journal of Soil Science and Plant Nutrition

A field experiment was conducted during Kharif 2024–25 at the Main Cotton Research Station, Navsari Agricultural University, Surat, South Gujarat, India, to evaluate the effect of integrated nutrient management on nutrient content and uptake of Bt cotton (G. Cot. Hy-10) grown on Vertisols. The soil of the experimental field was clayey in texture, low in organic carbon content (0.44%) and available nitrogen (221.40 kg ha⁻¹), medium in available phosphorus (32.16 kg ha⁻¹) and high in available potassium (570.59 kg ha⁻¹) with pH 7.78, EC 0.42 dS m⁻¹ and bulk density 1.34 Mg m⁻³. The experiment consisted of ten treatments viz., T₁ (100% RDF), T₂ (100% RDN through FYM), T₃ (100% RDN through Biocompost), T₄ (75% RDF + 25% RDN through FYM), T₅ (75% RDF + 25% RDN through Biocompost), T₆ (75% RDF +25% RDN through FYM + Green manuring with sunhemp), T₇ (75% RDF + 25% RDN through Biocompost + Green manuring with sunhemp), T₈ (50% RDF + 25% RDN through FYM + 25% RDN through Neemcake + Green manuring with sunhemp), T₉ (50% RDF + 25% RDN through Biocompost + 25% RDN through Neemcake + Green manuring with sunhemp), T₁₀ (Absolute Control) laid out in Randomized Block Design with three replications. Results revealed that nitrogen and potassium content in  seed and stalk were significantly influenced by treatments (p ≤ 0.05), whereas phosphorus  content remained non-significant. The integrated application of 75% RDF + 25% RDN through biocompost along with green manuring using sunhemp (T₇) recorded the highest nitrogen content in seed (3.10%) and stalk (0.85%) and potassium content in seed (0.60%) and stalk (1.29%). The maximum uptake of nitrogen, phosphorus and potassium in seed (74.18, 16.24 and 14.50 kg ha⁻¹, respectively) and stalk (50.91, 10.91 and 76.96 kg ha⁻¹, respectively) was also recorded under T₇. Iron content in seed (56.81 mg kg⁻¹) and stalk (156.48 mg kg⁻¹) and its uptake in seed (135.56 g ha⁻¹) and stalk (929.47 g ha⁻¹) were significantly improved (p ≤ 0.05) under integrated nutrient management, while Mn, Zn and Cu content and uptake showed non-significant variation among treatments. Absolute control recorded the lowest macro and micronutrient content and uptake. The study concludes that integrated use of organic and inorganic nutrient sources enhances nutrient uptake and supports balanced nutrition in Bt cotton under South Gujarat conditions, India.