Integrating Nano-DAP and inductive cum targeted-yield equations to improve maize productivity and nutrient use efficiency in Alfisols of Karnataka

Introduction Soil-specific nutrient management is critical for improving maize ( Zea mays L.) productivity in Alfisols , where imbalanced fertilization and low nutrient use efficiency often limit yields. This study aimed to develop and validate Soil Test Crop Response (STCR)-based fertilizer prescription equations integrating conventional fertilizers, farmyard manure (FYM) and foliar nano-diammonium phosphate (nano DAP) to enhance nutrient use efficiency and profitability in maize. Methods Field investigations comprised a fertility gradient experiment, a main experiment to derive nutrient requirement and contribution parameters and verification trials conducted across low, medium and high fertility strips at ZARS, GKVK, Bengaluru. Fertilizer prescription equations were formulated for NPK alone and NPK + FYM, with nano DAP applied as a foliar spray. Verification trials compared STCR yield targets (9 and 10 t ha −1 ) with the general recommended dose and soil fertility rating approaches using a randomized complete block design. Results STCR-based NPK + FYM treatments consistently produced higher kernel yields (~9.7–9.9 t ha −1 ) and stover yields (13.7–14.4 t ha −1 ,), along with significantly greater N, P and K uptake compared to conventional nutrient management practices. The average nutrient requirement was 1.20–1.28 kg N, 0.48–0.52 kg P, and 1.68–1.77 kg K per quintal of grain yield. Integration of FYM and nano DAP reduced inorganic fertilizer requirements and improved fertilizer contribution, recovery efficiency, partial factor productivity and agronomic efficiency of N, P and K. Validation through response yardstick and percent deviation approaches confirmed the accuracy of the equations within ±10% tolerance, while value–cost ratios demonstrated economic viability. Discussion The results demonstrate that STCR-based targeted yield prescriptions integrated with FYM and nano-fertilizers substantially enhance maize productivity, nutrient use efficiency and profitability in Alfisols . This approach supports sustainable intensification of maize production systems by optimizing fertilizer inputs and improving resource-use efficiency.