Change of tillage system affects the soil carbon pools characters, reduces carbon emissions and improves maize yield in the Loess Plateau

Understanding the response of soil aggregates and soil carbon pools to different tillage practices is an important way to illustrate the role of conservation tillage in climate change mitigation. Therefore, a long-term tillage experiment was conducted from 2007 to 2020 with four tillage practices: 1) The rotational tillage practice consisting of no-tillage in the first year, conventional tillage in the second year, subsoiling in the third year and a cycle of three years (NCS); 2) no-tillage (NT); 3) subsoiling (ST); and 4) conventional tillage (CT) to explore the relationship among soil aggregates, soil carbon pools, soil carbon sequestration and emissions. After long-term experiment, NCS and NT improved the soil total organic carbon (TOC) stock by 14.4% and 9.0% compared with CT in the 0-40 cm soil depth. Meanwhile, NCS, NT, ST decreased carbon emissions by 18.6 similar to 36.6% during the observation period, when compared with CT. Partial least squares path model revealed that soil aggregates structures and soil carbon pools stability were the main causes of soil carbon sequestration and emissions affected by conservation tillage. NCS, NT and ST increased soil aggregates proportion, mean weight diameter, geometric mean diameter and aggregates associated carbon compared with CT. Meanwhile, NCS and NT improved the carbon pools management index (CPMI) by 11.1% and 16.5%, respectively. The increased stability of soil aggregates and the improvement of soil carbon pools reduced soil carbon emissions and increased soil carbon sequestration. However, NT and ST significantly increased the TOC stratification ratios (SR) by 38.8% and 30.1% in the 0-10 and 10-20 cm soil depth compared with NCS, which was not conducive to the vertical distribution of TOC. In additional, NCS, NT and ST increased yield by 16.7 similar to 22.6% compared with CT. Collectively, based on the combined effects of environmental protection, production, and soil physicochemical property improvement, we recommend NCS (with highest comprehensive index: 6.76) as a sustainable tillage practice that can improve yield with ecological effects.