Evaluation of net carbon sequestration and ecological benefits from single biochar-incorporated sorghum farmland systems in saline-alkali areas of Inner Mongolia, China

Abstract

Biochar is widely recognized as a soil amendment to reduce greenhouse gas emissions and enhance soil carbon storage in agroecosystems; however, the systematic focus on carbon balance and ecological benefits in cropping systems remains unclear in saline-alkali areas under water-saving irrigation. Here, a 2-yr field experiment with carbon footprint method was conducted to determine soil carbon budgets, biochar carbon efficiency performance, and the economic and ecological benefits of mulched drip-irrigated sorghum production, in an arid salinized region of Inner Mongolia, China. Corn straw-derived biochar dosages of 0 (CK), 15 (B15), 30 (B30), and 45 (B45) t hm^-2 were just applied into the soil in the first crop growing season. A single application of biochar to soil significantly reduced CO₂ emissions for the current and subsequent crop-growing seasons, with 13.1%, 16.7%, and 12.5% reductions for B15, B30, and B45, respectively. Compared with the non-biochar control plots, B15, B30, and B45 also increased NPP by 36.7%, 38.4%, and 27.1%, respectively. The actual effects on improving net carbon sequestration for B15, B30, and B45 in the first year were higher than those in the second year, with mean increases of 1.27, 1.47, and 1.36 times, respectively; however, the efficiencies of biochar for fixing carbon per biochar dosage input for B15 were 72.8% and 64.1% higher than those of B30 and B45, respectively. Net profits were significantly improved by 57.2-87.1% by biochar treatments. The environmental benefits of biochar carbon trading revenues for B15, B30, and B45 increased by 105.9%, 162.1%, and 109.6%, respectively. The minimum observation for carbon productivity and the maximum measurements for both the economic and ecological benefits were B15. The B15 also significantly increased sorghum yield and grain number. Results demonstrate that biochar application in the current growing season helps reduce soil carbon emissions, increases net carbon sequestration for current and subsequent sorghum agroecosystems, and enhances net profit and ecological benefits. The optimal positive synergistic effect was observed at a biochar application rate of 15 t hm^-2 for reducing soil carbon emissions, increasing crop production, and improving the ecological environment.

Keywords: Carbon balance; Carbon footprint; Greenhouse gas; Net primary productivity; Soil organic carbon.