Contrasting effects of biochar and compost on greenhouse gas emissions and the global warming potential of semi-arid cropping systems

Abstract

Abstract Agroecosystems in arid and semi-arid regions face growing risks of climate extremes and soil degradation. The addition of exogenous carbon can restore degraded soils by adding soil organic carbon, but its effects on greenhouse gas (GHG) emissions and global warming mitigation remain elusive. This study evaluated emissions of three major GHGs–nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and methane (CH 4 )–following soil amendment with biochar, compost, and a biochar + compost (BC) mixture. Biochar application reduced cumulative N 2 O–N and CH 4 –C emissions by 52% and 16%, respectively. Soil CH 4 –C emissions were generally negative, being lowest with biochar and highest with compost. During the crop season, average CO 2 –C and N 2 O–C emissions were 75% and 45% greater, respectively, while CH 4 –C was 66% less compared to the no-crop season. Increasing soil moisture content increased N 2 O–N emissions ( R 2  = 0.39), while soil temperature influenced CH 4 –C emissions ( R 2  = 0.37). Among amendments, biochar-treated soil had the lowest cumulative N 2 O–N and CH 4 –C emissions, reducing net global warming potential (GWP) by 43% and 30%, respectively, compared to compost-treated soil and control (CTRL). Biochar amendment can be a climate-smart strategy for semi-arid regions as it improves soil health and mitigates GWP by reducing N 2 O and CH 4 emissions.