How different nitrogen application rates affect yield composition and nitrogen uptake of rice (Oryza sativa L.) in a saline-sodic paddy field

Abstract

Planting rice (OryzasativaL.) is an effective and feasible approach for improving salt-affected soils, especially in saline-sodic soils. Improved rice is the main biological measure for rapid treatment and utilization of a saline-sodic paddy field. Reasonable application of nitrogen fertilizer is an important measure for obtaining saline-sodic soil high yield. Dongdao 4 (D-4), Dongdao 2 (D-2), Changbai 9 (C-9), and Baijing 1 (B-1)) were studied by a field experiment in this paper. On the growth, yield, and yield component responses of different nitrogen levels (150 kg N/ha, 225 kg N/ha and 300 kg N/ha), and the nitrogen uptake of four saline-tolerant rice cultivars at different nitrogen application levels was calculated, which provided a useful reference for the rational application of nitrogen fertilizer in a saline-sodic paddy field. The results showed that: biomass of four kinds of rice accumulates over time and reached their maximums in September, with the biomasses of D-2 and D-4 reaching the maximum of 225 kg N/ha, and C-9 and B-1 reaching the maximum at 300 kg N/ha, which is related to rice varieties; the yields of four salt-tolerant rice plants reached the highest in 150 kg N/ha; applied nitrogen fertilizer reasonably was beneficial to increase the number of spikes and the number of effective grains per spike, in this experiment, the optimum amount of nitrogen is 150 kg N/ha, and the number of spikes and the number of effective grains per spike also were major factors in increasing production. With 1000-grain weight, primary and secondary branches made no significant contribution to the yield; the N uptake of four kinds of rice gradually increased over time and reached the maximum in September. There was no significant difference in the nitrogen grain production efficiency of 4 rice varieties under different nitrogen application rates; with the increase of nitrogen application rate, partial productivity of nitrogen fertilizer nitrogen of 4 rice varieties all decreased. Therefore, reasonable application of nitrogen fertilizer promoted the uptake and transfer of nitrogen to the plant.