Objectives The regional effects of straw return on maize yield, nitrogen (N) uptake, soil N leaching and runoff in China and its dominant driving factors were studied, so as to provide a scientific basis for the rational application of straw return.

Methods A total of 1775 valid observations were collected from 97 published articles in which field experiments were conducted in China across 1990−2023. Meta-analysis and random forest modeling was employed to quantify the effects of straw removal vs. straw return on maize yield, N uptake and N transport in soil profile (0–20 cm, 20–40 cm, 40–60 cm) under contrasting management practices and climatic conditions. The variation characteristics of soil N leaching and runoff losses were dissected, and their dominant driving factors were analyzed.

Results Compared to straw removal, straw return significantly increased maize yield by 7.9% and N uptake by 10.1%. In the 0–20 cm layer, soil nitrate-N (NO₃⁻-N), ammonium-N (NH₄⁺-N) and total N (TN) contents rose by 19.8%, 7.3% and 11.7%, respectively. Across the 20–40 cm profile, NO₃⁻-N and TN increased by 20.0% and 13.3%, whereas NH₄⁺-N had no significant difference between the two treatments. In the 40–60 cm horizon, TN still increased by 9.3%. Straw return reduced TN leaching and runoff losses by 21.3% and 21.8%, respectively. Random-forest analysis identified initial soil TN, soil organic C (SOC) and pH as the dominant drivers of maize yield, whereas N uptake was primarily driven by water management and soil NH₄⁺-N. In the 0–20 cm layer, initial SOC (contribution rate 23.0%) and initial TN (contribution rate 21.4%) were the principal factors regulating NO₃⁻-N content, NH₄⁺-N was most strongly influenced by soil initial TN (contribution rate 19.4%), and surface TN was regulated by initial TN (contribution rate 34.6%), pH (contribution rate 31.3%) and initial SOC (contribution rate 30.6%). In the 20–40 cm layer, mean air temperature during the growing season (contribution rate 16.6%), soil texture (contribution rate 16.6%) and N fertilizer rate (contribution rate 24.3%) were the key drivers of NO₃⁻-N, NH₄⁺-N and TN, respectively. In the 40–60 cm layer, mean air temperature (contribution rate 21.8%) and precipitation (contribution rate 13.0%) during the growing season predominantly governed NO₃⁻-N and NH₄⁺-N, whereas TN was jointly controlled by precipitation (contribution rate 21.7%) and temperature (contribution rate 18.6%) and N fertilizer rate (contribution rate 18.2%).

Conclusions Returning straw significantly increased maize yield and N uptake while reducing soil N leaching and runoff losses in China. The initial soil total N, SOC content, and pH were crucial factors influencing the yield response to straw return. Water management and initial NH₄⁺-N were the primary drivers affecting N uptake. In soils with high total N content, moderate to low organic C levels, and slightly acidic pH, straw return substantially enhanced maize yield potential. Additionally, integrating straw return with deep plowing, irrigation, and optimized N fertilizer application significantly mitigated the downward leaching potential of N within the plough layer. Mean air temperature and precipitation during the growing season were identified as the major drivers regulating deep soil NO₃⁻-N and NH₄⁺-N dynamics.