Strip Tillage with Straw Retention Alters the Associations Between Maize Yield Components and Grain Yield Across Seven Soil Types

Soil degradation constrains cropland productivity in Northeast China, where conservation tillage has been widely adopted to improve soil structure and sustain maize (Zea mays L.) production. However, previous studies have focused mainly on single soil types or regional-scale assessments, and the applicability of conservation tillage across contrasting cultivated soil types remains inadequately characterized. From 2021 to 2023, field experiments were conducted across geo-ecological zones within mid-temperate sub-humid and mid-temperate sub-arid climatic regions, encompassing seven typical cultivated soil types: Aeolian sandy soil, Bielic, Black soil, Chernozem, Histosol, Inceptisol, and Mollisols. A strip-tillage with straw return treatment (ST) was compared against no-tillage with straw mulching treatment (CK) to systematically evaluate the effects of strip-tillage on (i) soil physical properties (bulk density and porosity), (ii) soil chemical properties (organic matter and total nutrient contents), and (iii) maize yield components. Across the full dataset, ST significantly reduced soil bulk density and increased total porosity relative to CK; however, soil-type-specific comparisons showed that significant responses were detected only in some soil types. By contrast, soil chemical properties were significantly influenced by the treatment × soil type interaction: SOM and STN contents increased significantly in Inceptisol under ST, STP increased significantly in Mollisols, and STK increased significantly in Histosol. A PCA-derived composite physicochemical score, based on six standardized soil indicators, was higher under ST than CK in six of the seven soil types relative to CK, with the most pronounced improvements occurring in Aeolian sandy soil (+1.23), Bielic (+0.87), and Black soil (+0.65); significant maize yield increases under ST were detected in Aeolian sandy soil and Black soil, with mean increases of 7.07% and 10.94%, respectively. The associations between maize yield components and grain yield differed between ST and CK, with 1000-kernel weight showing a stronger association with grain yield under ST. Collectively, these findings indicate that ST can improve soil physical structure, but its effects on soil chemical properties, maize yield, and yield-component associations are soil-type dependent.