High-rate pelletized straw return with rotary tillage enhances soil fertility and maize yield in Northeast China

The severe topsoil degradation poses a critical threat to sustainable agricultural production. The combination of annual high-rate pelletized straw return and rotary tillage has the theoretic potential, while it has not been validated to enhance topsoil fertility and crop yield. Therefore, a three-year field experiment was conducted in degraded soil of Northeast China to explore straw management strategies, i.e., annual pelletized straw application via rotary tillage at 15 and 45 Mg ha −1 (PS15 and PS45), straw mulching at 15 Mg ha −1 (SM15), and no straw return as control (CK), on soil physicochemical properties and maize agronomic traits. Results showed that soil total and readily oxidizable carbon were increased by straw input and experimental duration; their contents under PS45 were 62% and 38% higher than CK in the third year, respectively. PS45 also improved other soil properties, including soil total and available nitrogen, phosphorus, and potassium. In addition, PS45 enhanced soil mean weight diameter and the proportion of >0.25 mm aggregates by 64% and 38% compared to CK, respectively. The improved soil physiochemical properties were positively correlated with maize growth and thus increased maize yield by 23% compared with CK in the second year. Notably, SM15 improved soil fertility, while it decreased grain yield by 22% in the first year, with 18% reduction in ear number. In addition, the relationships between soil properties and yield-related parameters differed substantially among years. Grain yield was mainly driven by ROC-improved harvest index in 2021, while both harvest index and aboveground biomass were enhanced by ROC and NO 3 − -N in 2022. In 2023, the increase in ROC further elevated harvest index, thus boosting grain yield. This study confirmed that high-rate pelletized straw return combined with rotary tillage is a feasible way to enhance agricultural sustainability and highlights great benefits through innovating straw return strategy.