Temporal variation of SOC storage and crop yield and its relationship - A fourteen year field trial about tillage practices in a double paddy cropping system, China

Carbon (C) sequestration in agricultural systems is recommended as a beneficialmeasure for climate change mitigation and food security. Despite much research, the relationship between soil organic carbon (SOC) storage and sustainable crop productivity has not been identified for various agricultural ecosystems, especially in the paddy ecosystem where conservation tillage has been adopted. Thus, a long-term experiment was conducted to evaluate the effects of tillage practices on SOC storage, yield, and their relationship in a double-cropped rice (Oryza sativa L.) paddy in Southern China from2005 to 2018. Four tillage systemswere investigated: no-tillwith residue retained on the soil surface (NTS), rotary tillagewith residue retention (RTS), plowtillage with residue retention (CTS), and plowtillage with residue removed (CT). The SOC accumulation in the 0-20 cm layer in tillage systems included two stages: the rapid accumulation stage (2005-2007) and the slow fluctuation stage (2007-2018), with a tendency for C saturation. After reaching C saturation, the increase in SOC storage was not obvious, even with continued C input, and the SOC storage under different tillage systems was inconsistent. In general, SOC storage under NTS was the greatest. Interannual changes were not significant, while cumulative yield (2005-2018) was highest under CTS (162.13 t ha(-1)), followed by RTS (158.46 t ha(-1)), NTS (153.99 t ha(-1)), and CT (149.70 t ha(-1)). Tillage practices had no effect on the yield stability of late rice, but a significant difference in early ricewas noticed between CTS and RTS. A non-linear relationship between rice yield and SOC storagewas significant (P < 0.0001). With increasing SOC, yields tended to increase first and then decrease. Thus, innovative tillage strategies (such as NTS) could increase SOC storage before it reaches C saturation, but maintaining SOC storagewithin a reasonable range and optimizing SOC distributionmight bemore beneficial for crop productivity than a higher SOC storage, especially in C-rich paddy fields. C() 2020 Elsevier B.V. All rights reserved.

Automated summary

The study showed that the choice of tillage practices in paddy fields can impact soil organic carbon storage and crop yield, especially in the paddy ecosystem. Retaining residue through tillage practices can increase soil organic carbon storage, but it is important to maintain it within a reasonable range.