Shallow plough tillage with straw return increases rice yield by improving nutrient availability and physical properties of compacted subsurface soils

Tillage and straw management are important factors affecting soil quality and crop productivity. However, long-term rotary tillage may form a plough pan in the subsurface (0.1–0.2 m) soil, which limits root growth and crop yields, especially in rice production in the Yangtze and Huai River regions. A 5-year lasting field experiment was conducted to study the effects of three tillage treatments [RT, rotary tillage; SPT, shallow plough tillage (0.15–0.2 m); DPT, deep plough tillage (0.25–0.3 m)], with or without straw return (S) on soil fertility, soil physical properties and rice yields. Olsen phosphorus and available potassium values of the 0.1–0.2 m soil layer were significantly higher (by 36 and 24%, respectively) in SPT + S compared to RT. The soil bulk density of the 0.1–0.2 m soil layer was 13% lower in SPT + S and 9% lower in DPT + S than in RT. Factor analysis revealed that SPT + S had the highest integrated scores of soil fertility for the 0.1–0.2 m soil layer. Rice yields were 10–43% higher in SPT + S compared to RT during the 5-year period. Rice yields were positively correlated with the integrated scores of soil fertility for the 0–0.1 and 0.1–0.2 m soil layers. Our results indicate that shallow plough tillage plus straw return is a promising management strategy for paddy fields following long-term rotary tillage.