Responses of Soil Aggregate Stability and SOC to Different Tillage Modes and Straw Input Level

Straw returning has an effective strategy for improving soil carbon sequestration and aggregate stability, as well as promoting sustainable agricultural development. Although in recent years, predecessors have conducted in-depth studies on the impact of tillage patterns and straw returning levels on soil organic carbon (SOC) and aggregate stability, we remain unclear on which tillage modes and straw return levels were the most suitable combinations in the study area. In view of this, we examined the influence of two tillage modes (tillage with straw returning, TS; no-tillage with straw mulching, NTS) and four straw addition levels (one-time treatment, 3500 kg/ha; two-time treatment, 7000 kg/ha; three-time treatment, 10,500 kg/ha; four-time treatment, 14,000 kg/ha) to soil aggregate size distribution, stability, SOC content, and carbon fractions content by split-plot experiment. The results showed that NTS3 enhanced the proportion of middle macro-aggregates fraction (MM) and unstable macro-aggregates fraction (UM), as well as SOC and hot-water extraction C (HWC) content with NTS mode. TS3 enhanced the proportion of MM, small macro-aggregates fraction (SM) with TS mode. Pearson correlation analysis suggested that the effect of straw input level on SOC and soil aggregates is greater for NTS than TS. In conclusion, considering the aspects of not affecting soil aggregate stability and improving SOC content, we think that NTS plays a significant role in promoting and enhancing the capacity of farmland soil to retain organic carbon in the research area; particularly, NTS3, HWC, and dissolved organic carbon (DOC) serve as indicative indices for SOC changes.