Rice-pigeon pea biochar influences nutrient cycling, microbial dynamics, and onion performance in organic production system: insights from Alfisols of the Eastern Plateau and Hill Region of India.

Organic agricultural practices are increasingly recognized for promoting sustainable soil–plant-environment interactions. However, the specific impact of soil additives in organic systems on nutrient and microbial dynamics, and their subsequent effects on crop performance, are still relatively unexplored. This study sought to address this gap by investigating the screening of suitable rice-legume residue combinations for biochar (BC) production and assessing the effect of incorporating BC as a soil additive in organic soil nutrient management. A two-year field experiment was conducted with six organic soil treatments comprising farmyard manure (FYM) and vermicompost (VC) as organic nutrient sources (equivalent to 100 kg N ha⁻¹), along with BC and Jeevamrit (J-Con) as soil additives, and a non-fertilized control to evaluate their impacts on nutrient cycling and crop performance. The rice-pigeon pea crop residue combination was found to be the most suitable for BC production (BC-RP), maintaining favorable nutritional quality and conversion efficiency. Among the soil treatments, T5 (50% FYM + 50% VC + BC) emerged as the most effective for enhancing soil pH, carbon content, and nutrient and microbial dynamics, followed by 50% FYM + 50% VC + J-Con (T6). This treatment also notably improved crop (onion) parameters, including growth, yield, quality, and production economics. The incorporation of BC as soil additive in 50% FYM + 50% VC significantly enhanced nutrient and microbial transformations in the soil, resulting in improvements of 7–25% in crop parameters. The findings of the study thus may be useful for achieving sustainable onion production by enhancing synchronized soil–plant interactions within an organic production system. [ABSTRACT FROM AUTHOR]