Tillage strategies optimize SOC distribution to reduce carbon footprint

Tillage methods and nitrogen (N) application are critical for soil organic carbon (SOC) sequestration and crop production. However, both tillage and N are the main contributors to the carbon footprint (CF) in agricultural production. A 6-year-long field experiment was conducted under a winter wheat-summer maize cropping system in Northern China to test how tillage methods (RT, annual rotary tillage; DT, annual deep tillage; and TT, RT applied annually with a DT interval of two years) and N rates (300 kg ha(-1), N300; 225 kg ha(-1), N225; 165 kg ha(-1), N165) affect SOC sequestration, greenhouse gas (GHG) emissions, and annual grain yield. And, the CF was used to evaluate ecological sustainability. RT preferentially sequestrated SOC in the 0-10 cm soil layer. In the 10-30 cm soil layers, 2.87-3.82 and 1.85-2.53 Mg ha(-1) greater SOC were respectively observed under DT and TT than RT, which was conducive to maximizing annual grain yield with less N application (N225) relative to traditional farming practice (RT-N300). Both increasing N rate and deep tillage resulted in obvious increases in the total GHG emissions. N fertilizer production and transportation were the greatest contributors, accounting for 40.4-47.0% of the total GHG emissions, followed by direct N2O and CH4 emissions (23.5-30.5%). TT-N225 significantly reduced CF (CF including SOC sequestration was 0.49 Mg CO2 eq ha(-1) year(-1) lower than DT -N225, and was 1.87 Mg CO2 eq ha(-1) year(-1) lower than RT-N300) and maintained high crop productivity while creating appropriate soil conditions and thus may be a much cleaner agricultural strategy in Northern China. And, the strategy of reducing N application in agricultural production by improving soil properties of the plow layer in this study can also be referred to in other ecological regions.

Automated summary

This study investigated the effects of different tillage and nitrogen fertilizer application on soil organic carbon sequestration, greenhouse gas emissions, and annual crop yield. The findings suggest that deep tillage can increase soil organic carbon sequestration and reduce nitrogen fertilizer application, but it leads to higher greenhouse gas emissions. However, reducing nitrogen fertilizer application while improving soil quality can lower the carbon footprint and maintain high crop productivity.