Abstract: In contrast experiments in sandy soil and clay soil, effects of nitrogen application rates on the concentration of NH4+N in surface water, the loss of ammonia volatilization from paddy field, the production of rice, the nitrogen utilization efficiency and the nitrogen content in soil profile were studied. The concentration of NH4+N in surface water and the amount of ammonia volatilization losses all increased as the nitrogen application rate increased, and peaked at 13 days after nitrogen application. The loss of ammonia volatilization from clay soil was lower than that from sandy soil. The amounts of ammonia volatilization losses after nitrogen application at different stages were as follows: N application for promoting tillering > The first N topdressing for promoting panicle initiation(applied at the last 4thleaf stage) > basal fertilizer > The second N topdressing for promoting panicle initiation(applied at the last 2ndleaf stage). The total loss of ammonia volatilization from clay soil was 10.49-87.06 kg/hm2, accounting for 10.92%-21.76% of the nitrogen applied; the total loss of ammonia volatilization from sandy soil was 11.32-102.43 kg/hm2, occupying 11.32%-25.61% of the nitrogen applied. The amount of ammonia volatilization and the concentration of NH4+N in surface water reached their peaks at the same time after nitrogen application; the maximum appeared at the tillering stage with their ratios from 23.76% to 33.65%. With the increase of nitrogen application rate, rice production and the nitrogen accumulation in plants increased, but nitrogen use efficiency decreased. Rice production and the nitrogen accumulation in plants in clay soil were slightly higher than those in sandy soil. Soil nitrogen content in the depth of 4050 cm was the lowest; soil nitrogen content in the same layers increased with the increasing nitrogen application rate, and soil nitrogen content in clay soil was higher than that in sandy soil. From the view on ammonia volatilization, it is found that the amount of ammonia volatilization would increase quickly when the nitrogen application rate exceeded 250 kg/hm2 in rice growing season. However, from the view on rice production, the suitable nitrogen application rate should be about 300 kg/hm2. Therefore, considering highyield and environment protection, the appropriate nitrogen application rate was from 250 to 300 kg/hm2 in the condition of the experiment.

Key words: ammonia volatilization, nitrogen application rate, soil type, nitrogen utilization efficiency, rice growing season

摘要： 在砂土和黏土两种土壤类型上，研究了施氮量对田面水NH4+N浓度、氨挥发损失量、水稻产量、氮肥利用效率和土壤剖面氮素含量的影响。施氮后田面水NH4+N浓度和氨挥发量都随着施氮量的增加而增加，且在施氮后1~3 d达到峰值，黏土要低于砂土；氨挥发损失量为分蘖肥时期＞倒4叶穗肥期＞基肥时期＞倒2叶穗肥期；黏土上稻季氨挥发总损失量为10.49~87.06 kg/hm2，占施氮量的10.92％~21.76％；砂土上稻季氨挥发总损失量为11.32~102.43 kg/hm2，占施氮量的11.32％~25.61％；施氮后氨挥发峰值和田面水铵态氮峰值同步出现，以分蘖肥时期最大，两者比值范围为23.76％~3365％；随着施氮量的增加，水稻产量增加，氮素积累量也增加，而氮肥利用效率降低；黏土上的水稻产量和氮素积累量要略高于砂土上的；土壤氮素含量在土壤深度40~50 cm处最低，相应各层土壤氮素含量随着施氮量的增加而提高，黏土要高于砂土。从氨挥发损失的角度来看，当施氮量超过250 kg/hm2时，氨挥发损失总量将跃增; 而从水稻获得高产的角度来看，施氮量应为300 kg/hm2左右，因此，试验条件下水稻高产且环境安全的适宜施氮量为250~300 kg/hm2。

关键词: 氨挥发, 施氮量, 土壤类型, 氮素利用率, 水稻生长季