Long-term application of controlled-release fertilizer enhances rice production and soil quality under non-flooded plastic film mulching cultivation conditions

Agricultural practices that integrate plastic film mulching (PM) cultivation and controlled-release urea have been widely used to conserve water and increase crop yields. The interactive responses of rice productivity and soil quality to long-term plastic film mulching cultivation and controlled-release urea have not yet been comprehensively elucidated, and whether or not plastic film mulching cultivation combined with controlled-release urea is suitable for rice production remains unclear. A 12-year field experiment with two water regimes (continuously flooded [CF] and PM) and three nitrogen (N) fertilization treatments (no N fertilizer, urea, and controlled-release urea) was conducted to explore the long-term effects on rice yield, soil physicochemical and biological properties, and soil quality in a single rice cropping system. Compared to continuously flooded system, the plastic film mulching system maintained rice productivity (CF: 6.9 t ha-1; PM: 7.1 t ha-1) with higher water productivity (CF: 0.9 g L-1; PM: 2.0 g L-1). Controlled-release urea treatments improved rice yield by 11.9% and 44.6% compared to treatments with urea and no N fertilizer, respectively. Random forest analysis indicated that enzyme activity was the main factor affecting rice yield. Compared to continuously flooded system, the plastic film mulching system significantly increased soil pH by 3.4% and decreased soil organic matter content by 9.3%. Moreover, the plastic film mulching system exhibited significantly higher enzyme activity than the continuously flooded system. Principal coordinate analysis of enzyme activities showed that N fertilization influenced enzyme activities considerably more than water regime. According to Pearson's analysis, soil fungal alpha diversity was more sensitive to soil physicochemical properties than bacterial alpha diversity. Overall, treatment with controlled-release urea in the plastic film mulching system resulted in the highest soil quality index values, which were positively correlated with rice yield (R2 = 0.61, p = 0.000). The positive direct effects induced by continuously flooded cultivation (i.e., satisfying the water requirements of rice) were counterbalanced by the negative indirect effects of altered enzyme activity. The N fertilizer type indirectly influenced rice yield by altering soil nutrients, enzyme activity, and microbial diversity. Therefore, controlled-release urea could maintain rice production with high soil quality under non-flooded plastic film mulching cultivation conditions.