Impact of STCR Based Fertilizer Application on Soil Chemical Properties of Rabi Onion in Inceptisols

A field experiment for fertilizer equation validation was conducted during the Rabi season of 2022–23 under the AICRP on STCR farm, PGI farm, and AICRP on IWM farm, MPKV, Rahuri, to evaluate the effect of STCR-based fertilizer application on the soil chemical properties of Rabi onion. The experiment was laid out in a randomized block design with ten treatment combinations: Absolute Control, GRDF, As per Soil Test, STCRC target for 250 q ha⁻¹ without vermicompost, STCRC target for 300 q ha⁻¹ without vermicompost, STCRC target for 350 q ha⁻¹ without vermicompost + Biofertilizer, STCRC target for 250 q ha⁻¹ with vermicompost, STCRC target for 300 q ha⁻¹ with vermicompost, STCRC target for 300 q ha⁻¹ with vermicompost + Biofertilizer, and only 5 t ha⁻¹ vermicompost. The research findings indicated that treatment T9 significantly increased electrical conductivity (0.24 dS m⁻¹) and soil organic carbon content (0.59%). Similarly, treatment T9 resulted in the highest residual soil available nitrogen and phosphorus levels, measuring 199.21 kg ha⁻¹ and 16.12 kg ha⁻¹, respectively. On the other hand, the highest soil available potassium level (475.29 kg ha⁻¹) was recorded in treatment T6, which was comparable to treatment T9 (471.76 kg ha⁻¹). Combining vermicompost with biofertilizers (Azospirillum and PSB) boosts nutrient use efficiency, reduces losses, and improves residual nutrient content compared to treatments without them.