[Effects of Tillage and Straw Return on the Distribution of Soil Aggregates and Integration of Organic Carbon in Farmland Soil].

Abstract

Farmland management practices， especially tillage depth and straw return， are among the most important factors affecting farmland soil aggregates and soil organic carbon （SOC）. However， the mechanism of their interaction on SOC in farmland soil aggregates remains unclear. Therefore， in consideration of China's dryland farmland ecosystem and with the help of Meta-analysis technology， 71 published research papers were integrated and analyzed to explore the effects of tillage and straw return and their interactions on farmland soil aggregates and SOC. The results showed that tillage depth significantly affected the distribution of soil aggregates and SOC content. The mass fraction of macroaggregates increased by 36.55% under the no-tillage （NT） condition （shallow tillage > deep tillage）. In particular， shallow tillage increased the SOC of macroaggregates by 60.98% （P < 0.05）. Compared with traditional tillage， straw return could increase the input of organic matter and also promote the transformation of small- and medium-sized aggregates to large-sized aggregates， thus increasing the mass fraction of soil aggregates and its SOC. In particular， the mass fraction of large aggregates increased by 15.1% （P < 0.05）， and the SOC of large aggregates increased by 16.61% （P < 0.05）. In addition， the interaction between tillage depth and straw return had significant effects on soil aggregate distribution and aggregate SOC. Shallow tillage with straw return （STS） had the most significant effect； it increased the mass fraction of macroaggregates and the SOC of macroaggregates by 71.3% （P < 0.05） and 60.3% （P < 0.05）， respectively. Furthermore， the increase of SOC under different tillage depths after straw return was closely related to the stability of soil aggregates and the change of SOC in soil aggregates. Geometric mean diameter had the largest contribution rate to soil aggregate stability， and soil microaggregate SOC made the largest contribution to soil aggregate SOC. Therefore， in China's dryland farmland ecosystem， tillage depth and straw return and their interaction affect the distribution of soil aggregates and SOC. For total SOC， geometric mean diameter and microaggregate SOC have the highest contribution rates. In conclusion， shallow tillage straw return may be an important agricultural management measure to improve soil stability and carbon sequestration capacity.