Improved soil structural stability under no-tillage is related to increased soil carbon in rice paddies: Evidence from literature review and field experiment

Improving soil structural stability (SSS) and soil organic carbon (SOC) are critical for soil health and environmental pollution mitigation. No-tillage alters many soil properties (e.g., SOC), however, its effects on SSS in rice paddies are unclear. Therefore, we used field experiment and meta-analysis to determine the effects of no-tillage on wet stability of aggregates (WSA), clay dispersibility (ClayDis), mean weight diameter (MWD), and aggregate SOC distribution and mineralization in rice paddies. The field experiment included four tillage practices: no-tillage, rotary tillage and moldboard plow tillage with rice straw retention (NTS, RTS and CTS respectively), and moldboard plow tillage with rice straw removal (CT). The WSA at 0-5 cm soil depth was significantly higher under NTS compared with CTS. The ClayDis at 5-10 cm soil depth under NTS was 36% lower (P < 0.05) than CTS. The relationship between SOC and WSA fits a broken stick model, with an inflection point of clay/SOC ratio at 12.5. Higher SOC under no-tillage might result from the protection of >2 mm aggregates (macroaggregates) and lower SOC mineralization of < 2 mm aggregates. Additionally, the meta-analysis showed that no-tillage increased (P < 0.05) the macroaggregate content, WSA and MWD. However, the current research regarding tillage effects on paddy ClayDis is insufficient. In rice paddies, the increased macroaggregate content may contribute to increasing SOC, which improves SSS under no-tillage. (C) 2021 The Author(s). Published by Elsevier B.V.