Effects of mechanical tillage years on the soil physical properties of fluvo-aquic paddy soil

Agricultural mechanization and farming methods are important factors that influence the physical properties of cultivated land. Exploring the changes in the soil physical properties in the fluvo-aquic paddy region of the Jianghan Plain over different mechanical tillage years is essential for clarifying trends in regional soil quality, reasonably improving soil structure of tillage layer, selecting suitable tillage measures, and increasing crop yield and efficiency. In this study, interannual changes in soil characteristics and trends in the physical properties of double-cropping rice planting patterns under different tillage years were simulated and analyzed using in situ simulated tillage experiments in fluvo-aquic paddy soil of the Jianghan Plain. The results showed that: 1) the soil moisture indexes decreased with increasing mechanical tillage years, was generally stable in the soil layer below the plow bottom layer (20–40 cm), and showed a slowly increasing trend in the 30–40 cm layer. 2) Under the action of long-term mechanical tillage, the stability of the soil structure gradually decreased. The breakage rate of soil aggregates increased with the deepening of the profile and the increasing mechanical tillage years, and the stability of the soil structure decreased with increasing soil depth and mechanical tillage years. The soil compactness increased with the deepening of the soil profile, thereafter decreasing slowly due to the thickening and upward movement of the plow bottom caused by long-term mechanical operation. 3) Under long-term mechanical tillage, the overall trend of soil compressive capacity increased first and then tended to be gentle. Preconsolidation pressure showed a decreasing trend in the bottom layer of the plow (10–20 cm), whereas showed an increasing trend in the lower layer (20–40 cm), indicating that soil bulk density and water content are key factors influencing the maximum compression capacity of the soil. These findings provide a theoretical basis for the improvement of soil quality in the rice-planting areas of the Jianghan Plain.