Abstract:

This study aims to lay a foundation for the prevention and control of nitrogen and phosphorus loss in paddy field. The plot experiments were conducted to investigate the effects of different treatments of increasing transplanting density and reducing nitrogen fertilizer on the nitrogen loss by surface runoff, nitrogen utilization efficiency of rice, and soil nitrogen balance. The results show that the total nitrogen loss is significantly reduced due to the decreasing of nitrogen application and the increasing of seedling number. The nitrogen loss before transplanting accounts for more than 60% of the whole growth period. The total nitrogen loss of the conventional treatment (T2) is the highest, reaching 11.80 kg/hm², and those of T3-T6 treatments are reduced by 13.42%-53.52% compared with T2. The agronomic efficiencies of nitrogen fertilizer of T3-T6 treatment increase by 2.86%-28.99% and nitrogen partial productivity increases by 3.40%-24.98% compared with T2. The nitrogen surplus decreases with the decreasing of nitrogen application amount and the increasing of seedling number. The nitrogen surplus of T2 to T6 is 20.55 kg/hm², 15.23 kg/hm², 16.10 kg/hm², 6.33 kg/hm², -10.62 kg/hm², respectively. Therefore, properly increasing seedling density and decreasing nitrogen input could reduce nitrogen loss, improve nitrogen use efficiency and guarantee soil nitrogen balance.

Key words: increasing transplanting density and reducing nitrogen fertilizer, rice, nitrogen loss, nitrogen use efficiency, nitrogen balance