Effect of Nano Fertilizers on Yield, Nutrient Uptake, Soil Nutrient Status and Fertilizer Use Efficiency of Bt Cotton

Aims: Foliar application of nano fertilizers aims to reduce the need for conventional fertilizers. Nano fertilizers enhanced crop growth, yield and quality by improving nutrient uptake. They enable precise nutrient delivery that aligns with the crop's growth stages, while their increased surface area facilitates faster metabolic reactions. This, in turn, boosts photosynthesis, leading to greater dry matter production and higher yields. Foliar application of nano fertilizers during the flowering, boll initiation and boll development stages meets the nutrient requirements of the plant, resulting in improved productivity and quality. By combining conventional fertilizers with nano fertilizers in a balanced manner, it is possible to achieve higher crop productivity in a sustainable way. Place and Duration of Study: A field experiment was conducted during Kharif 2023 at AICRP on Cotton, Haradanahalli farm, Chamarajanagar. Study Design and Methodology: The experiment was laid out in split plot design with three replications comprising three levels of conventional fertilizers in main plot viz., 50%, 75% and 100% RDNP and four dosages of nano fertilizers in subplot viz., nano urea @ 2 ml L-1 and 4 ml L-1, nano DAP @ 2 ml L-1 4 ml L-1, respectively sprayed at 40, 60 and 80 DAS. Results: The results revealed that among different levels of conventional fertilizers, application of 100% RDNP noticed significantly higher total number of bolls (47.3 plant-1), good opened bolls (42.2 plant-1), seed cotton yield (1453 kg ha-1) and stalk yield (2562 kg ha-1). The same treatment recorded higher nutrient uptake (120.96, 37.27, 97.48 kg NPK ha-1, respectively). And soil nutrient availability (203.14, 57.66, 153.75 kg N P2O5 K2O ha-1, respectively). Significantly higher fertilizer use efficiency was noticed with 50% RDNP (15.86 kg N kg-1, 31.53 kg P kg-1), whereas higher potassium use efficiency was recorded in 100% RDNP (19.37 kg K kg-1). Among the nano fertilizers, application of nano DAP @ 4 ml L-1 at 40, 60 and 80 DAS resulted significantly higher total number of bolls (46.7 plant-1), good opened bolls (41.9 plant-1), seed cotton yield (1420 kg ha-1), stalk yield (2497 kg ha-1) and nutrient uptake (116.91, 37.37, 96.57 kg NPK ha-1, respectively), similar trend was observed with fertilizer use efficiency also. where, foliar spray of nano urea at 2 ml L-1 recorded higher available nitrogen, phosphorous and potassium content in soil with 194.41, 54.48 and 152.48 kg ha-1, respectively.