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The Effect of Long-Term Organic Amendments on Soil Organic Carbon Accumulation via Regulating Microbial Traits in a Paddy Soil

Jing Ye,Zhaoming Chen,Jinchuan Ma,Junwei Ma,Ping Zou,Wanchun Sun,Feng Wang,Qiaogang Yu,Qiang Wang

Published 2025 in Agriculture

ABSTRACT

Understanding how organic amendments affect microbial carbon use efficiency (CUE) and necromass C (MNC) is crucial for understanding soil organic C (SOC) formation and accrual in paddy fields, but the underlying mechanisms remain largely unclear. In this study, the microbial CUE, MNC, and microbial community composition, as well as SOC fractions and chemical composition, were measured under long-term organic amendments: rice straw (RS), green manure (GM), and pig manure (PM) in paddy soils. Four treatments were included: (1) chemical fertilizers (CF); (2) CF plus RS (CF + RS); (2) CF plus GM (CF + GM); and (4) CF plus PM (CF + PM). The CUE, MNC, and microbial community were determined by 18O-H2O incubation, amino sugars levels, and phospholipid fatty acids (PLFAs) content, respectively. Results showed that SOC, particulate organic C (POC), and mineral-associated organic C (MAOC) concentrations were significantly increased by organic amendments compared with chemical fertilization alone. The O-alkyl C decreased, but aromatic C increased with long-term organic amendments, suggesting enhanced SOC hydrophobicity. GM and PM inputs significantly enhanced microbial CUE, but straw return did not affect microbial CUE compared to CF. Microbial growth and C uptake increased by 25.2–42.4% and 19.8–30.0% under organic amendments relative with CF. Microbial respiration was increased by RS and GM amendments. Turnover time was more rapid in CF + RS and CF + GM than in CF and CF + PM. Compared to CF, organic amendments increased the MNC concentration due to the increase in microbial biomass. In addition, CF + RS and CF + GM enhanced the MNC contribution to SOC, but PM had no effect, suggesting that PM contributed more organic C from non-microbial sources. The SOC, POC, and MAOC increased with microbial CUE and MNC, indicating that microbial traits play a crucial role in SOC accrual. Higher microbial CUE and biomass explained the increased MNC accumulation under organic amendments. Our study highlights the crucial role of microbe-mediated processes in SOC accrual under long-term organic amendments in paddy soils. Our findings show that organic amendments are an effective management practice for accumulating more SOC in paddy soils.

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