Microbial trade-off in soil organic carbon storage in a no-till continuous corn agroecosystem

Recent perspective has highlighted the microbial importance of interplay between catabolic breakdown and anabolic synthesis in influencing soil organic carbon (SOC) dynamics and persistence. However, studies on these contrasting activities remain rare, despite value to global discussions on economic and ecologically sustainable ecosystem management. Here we investigate microbial response in a no-till farm in Northeast China after an 8-year manipulation of plant residue returns of varying quantity including control (0%, NT0), low (33%, NT33), medium (67%, NT67) and high (100%, NT100). Topsoil amino sugar biomarker analysis indicated microbial necromass contributed to SOC formation in NT33 and NT67, while the contribution was minimal in NT100. Sequencing data analyses along with subsoil SOC indicated increased microbial degradation of existing SOC upon mulch quantity gradient. We found that a low level (33%) of the previous year's stover return was an optimized trade-off for topsoil (0–5 cm) carbon storage and off-field economic demand for material. This study demonstrates the non-linear relationship between carbon inputs and SOC content, and suggests the importance of the trade-off effects between microbial catabolism and anabolism.