Effects of Long-Term Conservation Tillage on Soil Properties and Crop Yield

Long-term conservation tillage can alter soil properties and crop performance in a depth-dependent manner. We evaluated a 2 × 2 factorial experiment combining tillage practice (conventional plowing vs. no-tillage) and organic manure application (without vs. with organic manure) in rainfed winter wheat on the Loess Plateau. Soil nutrients, aggregate stability, N2-adsorption-derived surface and pore properties, and bulk density were measured at 0–10, 10–20, and 20–40 cm, and grain yield was analyzed from 2011 to 2025. Two-way ANOVA showed that no-tillage generally increased surface-soil nutrient contents and aggregate stability, with the strongest responses at 0–10 cm. Significant tillage × organic manure application interactions for several nutrient properties indicated manure-dependent responses to tillage. These effects generally weakened with soil depth, demonstrating pronounced vertical stratification. Management effects on N2-adsorption-derived surface and pore properties were limited, whereas no-tillage increased bulk density mainly within the upper 20 cm. Based on the descriptive 15-year yield analysis, NT had the numerically highest mean and cumulative yields and the lowest interannual variability. Overall, no-tillage enhanced surface-soil fertility and aggregate stability, but nutrient stratification and increased soil consolidation should be considered when optimizing long-term management.