Periodic straw-derived biochar improves crop yield, sequesters carbon, and mitigates emissions

Increasing soil carbon sequestration is one of the main measures to mitigate greenhouse gas (GHG) emissions in agricultural systems, and straw-derived biochar returning has the potential to increase soil carbon sequestration and crop yield, mitigate GHG emissions, but its application is largely restricted due to the high input. It remains unclear whether periodic application of straw-derived biochar could effectively meet these challenges. To explore the appropriate mode of straw-derived biochar returning which aims to achieve the goal of increasing yield and carbon sequestration without reducing economic benefits, a 7-year site experiment was carried out to compare the effects of conventional tillage, wheat straw returning and straw-derived biochar returning on winter wheat yield, soil organic carbon (SOC) contents, GHG emissions and economic benefits on the Loess Plateau of China. The highest average yield over the 7-year experiment was found under straw biochar, and average yield over the 7-year experiment was increased by 9.94 % and 2.28 %, as compared with conventional tillage and wheat straw, respectively. Meanwhile, under straw biochar the SOC content was significantly increased by 24.61 % and 12.57 % than conventional tillage and wheat straw after 7 years (p < 0.05). In addition, compared to conventional tillage and wheat straw, straw biochar increased the annual cumulative CO2 emissions, but reduced the annual cumulative N2O emissions; the net global warming potential under straw biochar decreased by 7.7 and 1.1 times (p < 0.05), and the greenhouse gas emission intensity decreased by 8.6 and 1.6 times (p < 0.05), those were mainly due to the fact that straw biochar increased wheat yield and SOC, but reduced N2O emissions. The 5-year cumulative net income and cumulative net ecosystem economic benefits under straw biochar were significantly increased by 12.16 % and 20.27 % compared to the conventional tillage, while the 7-year net ecosystem economic benefits was comparable to the wheat straw (p < 0.05). Taken together, our results suggest that the application of straw-derived biochar every five years could effectively increase carbon sequestration and mitigate GHG emissions, while maintaining the income simultaneously. Therefore, that the periodic straw-derived biochar returning could be an effective approach in rainfed agriculture of dryland, considering both economic and environmental effects.