Effect of residue management and biochar based slow-release nitrogen fertilizers on growth, yield and economics of wheat under Tarai region of India

Efficient residue and nitrogen management are critical for sustaining wheat productivity in the Tarai region of India, where rice-wheat cropping systems are constrained by residue disposal and low nitrogen use efficiency. A two-year field experiment (2019-20 and 2020-21) was conducted to evaluate the combined effects of residue management and biochar-based slow-release nitrogenous fertilizers (SRNFs) on growth, yield and economics of wheat. The experiment comprised residue removal, residue incorporation and rice straw biochar application, each combined with nitrogen supplied through conventional urea, biochar-coated urea (BCU) and rice straw biochar-based urea (RSBU) at 75 % and 100 % of the recommended N dose. Results revealed that both residue and nitrogen management practices significantly (p < 0.05) affected growth and productivity of wheat. Biochar incorporation enhanced plant height, tiller density and dry matter accumulation compared to residue removal. Among nitrogen treatments, 100 % recommended N rate applied via SRNFs (BCU and RSBU) produced 7-11 % higher dry matter and 6-9 % greater grain yield than conventional urea, while 75 % N through SRNFs achieved yields comparable to N applied via 100 % urea, indicating improved nitrogen use efficiency. Enhanced SPAD, NDVI and Fv/Fm values under SRNFs reflected greater chlorophyll content and sustained photosynthetic activity. Economically, the highest net return and benefit-cost ratio were obtained from the combination of biochar incorporation with 100 % N applied through RSBU, followed by 100 % N via BCU. Despite slightly higher production costs, biochar-based fertilizers substantially improved profitability. Overall, integrating rice straw biochar with biochar-based slow-release urea offers a sustainable and resource-efficient strategy for enhancing wheat productivity and profitability under the Tarai agro-ecological conditions.