Biochar mediated residue and nitrogen management for sustaining crop productivity and soil health in rice wheat cropping system

Abstract

The present investigation was carried out during 2019-2021 in two different sets of newlineexperiments i.e. in laboratory and field conditions. In laboratory, biochar from rice straw was derived at newline450°C and characterized for its physical and chemical properties. Further it was used for developing newlinecarbon based slow release N fertilizers. High surface area, porosity, pore size and distribution were the newlinecritical characteristics of biochar, owing to which it was used as a nutrient carrier. The intercalated newlinebio-urea composite i.e. rice straw bio-urea (RSBU) derived with 2:1 urea: biochar ratio; contained 28% newlineN while, biochar plus gum acacia and paraffin wax coated urea i.e. biochar coated urea (BCU) showed newline40% N content. Soil column studies were carried out to examine the nitrogen desorption behaviour of newlinebiochar based slow release nitrogen fertilizer (SRNF). Under commercial urea, the N release continued newlinefor 17 days with 50% release within 2 days and 75% in 9 days. However, for BCU and RSBU the newlinecontinuous release was observed beyond 30 days with 50% release in 5 and 9 days and 75% in 13 and newline21 days, respectively. newlineThe field experiment with three residue management options (residue removal, residue newlineincorporation and residue as biochar) and six nitrogen treatments (control, 100% N through Urea, 75 newlineand 100% N through RSBU, 75 and 100% N through BCU) replicated thrice was carried out in split newlineplot design. A significant increase in growth of rice and wheat was recorded with biochar application newlinefollowed by residue incorporation. The biochar application gave around 12.0% and 3.8% higher system newlineproductivity over no residue and residue incorporation, respectively during second year of the newlineinvestigation. The nitrogen management through SRNFS showed significant effect on growth and yield newlineof rice and wheat. The highest yield of rice was recorded under RSBUat100%N, while that of wheat newlineunder BCUat100%N. Application of 75% N through SRNFS gave comparable or higher grain yield newlineover commercial urea (100% N) for both rice and wheat. N source 100% RSBU gave 18.9% higher newlineagronomic NUE efficiency than 100% Urea for rice while for wheat, the increment was 13.7% with newline100% BCU during second year of study. newlineResidue and nitrogen management practices significantly influenced the soil properties and newlinecarbon fractions. Residue recycling through biochar and direct residue incorporation increased the SOC newlinestock by 23.7% and 11.0%, respectively while increment in soil TOC stock was 21.3% and 11.4%, newlinerespectively over control (residue removal). A significant improvement in carbon passive pool was newlineobserved when residue was used as biochar compared to its direct incorporation into the soil. newlineThe biochar based SRNFs out yielded commercial urea as well as improved soil properties. newline25% reduced application of nitrogen through SRNFs gave comparable yield to commercial urea newline(100% N) thereby saving 25 kg N/ha. Therefore, biochar application has proved a viable option to newlineenhance the soil physical properties (porosity, bulk density) and chemical properties newline(CEC, organic carbon and recalcitrant carbon fractions), while positively influencing crop growth and newlineestablishment under rice-wheat system and increasing carbon sequestration. newline