Abstract: A field experiment was conducted to explore the effects of reduced application of nitrogen fertilizer on yield formation and nitrogen uptake and use efficiency of rice (cultivar Wuyunjing 31), by setting different nitrogen application treatments and deep application of basal fertilizer with machine at root side. The results showed that, during two seasons of rice in 2017 and 2018, compared with spraying application of basal fertilizer (N1), deep application of basal fertilizer at root side and 10% reduction in nitrogen application (N3) significantly reduced the number of panicles per unit area and increased the spikelets per panicle and filled grain percentage, which ensured the high yield of rice. Compared with the N1 treatment, N3 treatment significantly reduced the biomass of rice; however, its yield was not decreased due to the higher economic coefficient. There were no differences in rice nitrogen accumulation, nitrogen use efficiency of biomass and nitrogen use efficiency of grain yield between N3 and N1 treatments. Under deep application of basal fertilizer at root side, with the decreasing nitrogen application level, N use efficiency of biomass and grain yield of rice gradually improved. Compared with the N1 treatment, N3 treatment increased rice agronomic efficiency, average recovery efficiency, physiological efficiency and partial factor productivity of nitrogen fertilizer by 8.9%, 8.3%, 0.6% and 10.5%，respectively. There was no difference between N3 and N1 treatment in soil available nitrogen content at rice maturity stage. Our results indicated that, in comparison with artificial application of basal fertilizer, deep application of basal fertilizer at root side and 10% reduction in nitrogen application could ensure high rice yield, improve both the efficiency and rate of nitrogen uptake and use, and maintain soil fertility.

Key words: side position of root, deep application of basal fertilizer, rice, yield formation, nitrogen uptake and use efficiency.