Effects of tillage practices on soil organic carbon, microbial community and necromass in a double rice cropping system

Abstract

No-tillage (NT) can enhance the accumulation of soil organic carbon (SOC), thereby aiding in climate change mitigation and improving soil fertility. However, the relations of soil microbial abundance, composition, and necromass to SOC increase under NT are still unclear, limiting the knowledge of SOC stabilization. We performed a 5-year paddy field experiment in southern China including NT, reduced tillage (RT) and conventional tillage (CT). Soil microbial necromass C (MC, including fungal and bacterial necromass C, FC, and BC) were analyzed, as well as soil bacterial and fungal community composition. At a depth of 0–10 cm, NT increased FC (by 48.6 %–50.2 %, P < 0.05), BC (28.6 %–41.7 %), and MC (38.5 %–45.1 %, P < 0.05) but did not significantly alter the FC/BC and MC/SOC ratios. The increase rate of MC (NT vs. CT and RT) was 12.8–16.2 % higher than that of total SOC. Compared with 0–10 cm and 10–20 cm, the MC/SOC ratio was 12.5 %–14.1 % lower at 20–30 cm. Linear regression indicated significant positive correlations of SOC with MC, BC, and FC, whereas no significant correlation was found between bacterial (or fungal) α-diversity (expressed by Shannon index) and BC (or FC). The Random Forest Model showed that several important fungal and bacterial Amplicon Sequence Variants (ASVs) explained 14 %–73 % of the FC and BC variations. Therefore, the composition of the microbial community may play a pivotal role in driving the accumulation of MC. Short-term NT in rice paddies resulted in increased levels of both MC and SOC. Notably, the rate of increase in MC exceeded that of SOC, suggesting the potential for SOC stabilization.