Abstract: To clarify the effects of biodegradable film mulching on nitrogen (N) use efficiency and yield of machine-transplanted rice and provide a new planting model for stable and high yield of rice and green efficiency, we carried out a field experiment in 2018 and 2019, under ordinary machine planting with three N fertilization levels (0, 195, 240 kg·hm^-2) and under machine planting with biodegradable film mulching and three N fertilization levels (158.4, 195, 240 kg·hm^-2). The results showed that under the same planting pattern, rice yield increased with increasing N application levels. Under the same N application level, the yield of filmmulched rice significantly increased by 4.1% and 6.1% in 2018 and 2019, respectively. Film mulching increased the dry matter accumulation and N accumulation at each growth stage. Under the same N application level, the N accumulation of film-mulched rice at mature stage increased by 2.5% and 5.8% in 2018 and 2019, respectively. Nitrogen partial factor productivity (NPP), N production efficiency (NPE), and N harvest index (NHI) all decreased with increasing N application level across both years. Under the same N application level, N agronomic efficiency (NAE), N recovery efficiency (NRE), N partial productivity (NPP), and N dry matter production efficiency (NMPE) of rice were higher under film mulching. Film mulching increased the activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) in functional leaves, especially at the late stage of growth, which could effectively delay the decline of their activities. Compared with the control, the film mulched rice significantly increased photosynthetic rate by 6.5% at 10 days after the full heading stage. Under the condition of reducingnitrogen by 18.8%, film mulching significantly improved N utilization and yield of rice. Moreover, biodegradable films avoided the environmental pollution of plastic films, providing a new technical approach for green production, N-saving and efficiency-increasing of rice.

Key words: biodegradable film, nitrogen use efficiency, yield, machine-transplanted, rice.