Oat– Sesbania Rotation Boosts Oat Yield and Profit via Soil Nutrient Buildup and Dual Harvest

ABSTRACT Oat and Sesbania have complementary growth, enabling eco‐friendly rotation for autumn‐sown oat. Nevertheless, how different Sesbania utilization practices regulate soil conditions, crop productivity and comprehensive benefits remains poorly quantified. A four‐year field experiment was conducted at two sites (WJ and CZ), encompassing three cropping treatments: oat‐fallow (O + F, control), oat‐ Sesbania rotation with Sesbania harvested as forage (O + SFH) and oat– Sesbania incorporated as green manure (O + SGM). We measured soil physicochemical properties, oat yield, quality and economic benefits, and adopted partial least squares path modelling (PLS‐PM) to reveal driving mechanisms. Compared with O + F, O + SGM and O + SFH significantly increased soil organic matter (SOM) and total and available nutrients (N, P, K) in 0–20 cm soil at WJ. Oat dry matter yield (DMY) increased by 6.86–39.23% under O + SGM and 3.96–29.21% under O + SFH, consistent trends were found at CZ. Improved soil nutrient accumulation facilitated crop nutrient absorption and dry matter production. Both rotations boosted economic returns, with O + SFH demonstrating greater economic performance due to extra forage gains. This study quantitatively compares different Sesbania utilization modes in oat rotations and clarifies soil–crop‐economic synergistic mechanisms. The findings support region rotation schemes to lower chemical fertiliser input and improve land use efficiency.