Response of nitrogen fertilizer productivity of spring maize on the Loess Plateau to different tillage measures: a meta-analysis

This study aimed to clarify the effects of different tillage measures, including mulch planting, straw returning, subsoiling, and no-tillage, on the partial productivity of nitrogen fertilizer (PFP_N) of spring maize in the Loess Plateau and explore the factors driving the change in PFP_N under different tillage measures. Meta-analysis, regression analysis, and random forest analysis were performed. Compared with traditional tillage measures (such as, bare land planting, straw-free returning, and plowing), mulching, straw returning, and subsoiling tillage increased PFP_N by 38.8%, 10.3%, and 8.4%, respectively, whereas no-tillage had no significant effect on spring maize PFP_N. The random forest model showed that the average annual rainfall and growing season rainfall were two relatively important factors affecting the PFP_N of spring maize under mulching and straw returning, and that the average annual rainfall and test duration were important factors under subsoiling. Subgrouping and regression analysis showed that in the areas where the average annual rainfall was ≤400 mm, growing season rainfall was ≤300 mm or average annual temperature was <7 ℃, mulching increased the spring maize PFP_N by 77.7%−99.5%, and PFP_N was negatively correlated with average annual rainfall, growing season rainfall, and average annual temperature. In areas where the average annual rainfall was 400−500 mm or the growing season rainfall was 300–400 mm, straw return could increase PFP_N by 10.2%−16.3%. When the average annual rainfall was 400–500 mm and the duration of the subsoiling experiment was less than 3 years, the PFP_N was increased by 14.1% to 14.6%. Therefore, according to the regional and climatic characteristics, adopting appropriate tillage measures can further improve the PFP_N of spring maize and promote the realization of the goal of sustainable crop production in arid areas. This study provides a reference for improving the PFP_N of spring maize in the Loess Plateau and formulating agricultural production strategies for regional sustainable development.