Modelling soil, plant and fertilizer relationship to optimize nutrient management for chilli (<i>Capsicum annuum</i> L) under <i>Alfisols</i> of Southern India

India is the largest producer, consumer and exporter of chilli, which covers 20% of the total area in Southern India. The imbalanced use of chemical fertilizers has detrimental effect on soil physico-chemical and biological properties thereby affecting soil and crop quality. In accordance with this concept, the field experiments were conducted to develop and validate fertilizer prescription equations for chilli crop under rainfed condition. The experiments were conducted in three phases. The basic parameters to develop the targeted yield equations were derived. Further, the developed targeted yield equations were validated in comparison with soil fertility rating approach and general recommended dose (GRD). The results revealed that 4.50, 1.76 and 2.95 kg of N, P2O5, and K2O, respectively were required for producing 100 kg of dry chilli. The STCR approach, with or without FYM, at the targeted yield of 1.30 and 1.00 t ha−1 enhanced the yield over GRD and soil fertility rating approach. The STCR approach also exhibited a higher NPK uptake, use efficiency, microbial biomass carbon and nitrogen, dehydrogenase, acid and alkaline phosphatase activity along with better profitability. Hence, STCR-targeted yield approach could improve the yield, nutrient use efficiency, soil microbial properties and economics of chilli crop.