Optimizing Nutrient Management for Kodo millet (Paspalum scrobiculatum L.) in the Alfisols of Southern India through Modeling Soil, Plant, and Fertilizer Interactions

Abstract Achieving an optimal balance of nutrients is crucial for sustainable agriculture. In this context, soil test crop response (STCR) experiments on kodo millet were conducted from 2020–2022 to assess relationships between yield, soil, plant, and fertilizer nitrogen (N), phosphorus (P), and potassium (K) and calibrate optimum fertilizer doses for attaining yield targets. The Basic parameters, i.e., nutrient requirements, contributions of nutrients from fertilizers, soil, and organic manure were derived. The NPK nutrients required to produce one kg of grain yield were 0.049, 0.0047 and 0.035 kg, respectively, under the STCR NPK alone and 0.050, 0.0046 and 0.037 kg, respectively, under the STCR NPK + FYM approach. The STCR NPK + FYM approach for the targeted yield of 1700 kg ha–1 resulted in a higher grain yield (1710 kg ha–1), which was significantly greater than the general recommended dose and soil fertility rating approach. The developed STCR equations are valid, as the percent deviation of the grain yield from the targeted yield was within ± 10%. The implementation of the STCR approach not only surpassed the effects of the other fertilizer recommendation approaches in terms of grain yield but also increased NPK uptake, nutrient use efficiency and economic returns.