Responses of Soil Properties and Yield to Crop Residue Return Under Different Cropping Systems in Rainfed Cropland of Northeast China

Crop residue return is widely used to improve soil conditions in rainfed croplands, but its effects may differ among soil properties and cropping systems. This study evaluated the field performance of crop residue return with three-year consecutive observations in rainfed Northeast China. The field treatments included crop residue removal (R0) and crop residue return (RR) for maize monoculture, fixed maize–soybean strip intercropping, and rotational maize–soybean strip intercropping. The results show that RR significantly decreased soil pH (p < 0.001) and increased available potassium (p < 0.01), particularly in the 0–20 cm soil layer, where mean pH decreased from 8.05 under R0 to 7.59 under RR and available potassium increased from 98.6 to 109.1 mg kg−1. In contrast, bulk density, soil water content, soil organic carbon, total nitrogen, and the C:N ratio showed weaker or less consistent responses across soil depths, cropping systems, and sampling years. Crop yield responses differed between crops. RR significantly increased maize yield overall, whereas no significant overall effect was detected for soybean yield. Overall, crop residue return primarily affected surface-soil pH and potassium availability during the three-year experiment, while its yield effect differed between maize and soybean.