Long-term impacts of nitrogen fertilization and straw incorporation on rice production and nitrogen recovery efficiency under plastic film mulching cultivation

The application of nitrogen (N) fertilizer as base fertilizer in plastic film mulching cultivation (PFMC) system easily leads to soil N deficiency in the late growth period of rice. The combination of N fertilization and straw incorporation was put forward and their impacts on rice yield and grain N recovery efficiency (NRE) based on a long-term experiment in a PFMC system were evaluated. Five N application levels included 0, 45, 90, 135, and 180 kg ha−1 and two subplots were rice straw removal (RSR) and rice straw incorporation (RSI). Moreover, RSR and RSI in a conventional flooding cultivation (CFC) system with 135 kg ha−1 N application rate were also included. The results showed that the optimum N application rate was 135 kg ha−1. At this N application level, the promotion effect on yield and grain N uptake over years in PFMC system was more obvious than that in CFC system. Continuous PFMC might accelerate the mineralization of soil organic matter and the increase of soil N availability. However, RSI had no obvious promotion effect on the increment of yield, grain NRE, and soil available N with years compared with RSR in PFMC system. In conclusion, film mulching with the N fertilizer application rate of 135 kg ha−1 improved soil thermal condition in early growth stage of rice, and thus enhanced the availability of soil N, grain N uptake, and yield. This provides a reference for PFMC application in water-saving rice production system.