中文摘要：

春季基施尿素,种植牧草马唐,采用通气密闭室法研究了我国亚热带红壤旱地氨挥发对施氮水平的响应。结果表明,春季红壤旱地施入纯氮90,160和230 kg/hm^2（分别标记为N90,N160和N230）,氨挥发持续10-17 d,在施肥后6-8 d达到峰值（扣除对照N0）,峰值分别为0.11,0.57和1.84 kg/（hm^2·d）;氨挥发积累量在0.67-5.16 kg/hm^2,占施入氮素的0.74%-2.24%。初步预测氨挥发积累量与施肥量呈现近指数增长关系,指数函数方程为：y=0.1563e0.0146x,R2为0.9513。经显著性检验,N90,N160和N230处理间的氨挥发通量差异达到显著水平（P〈0.05）;氨挥发积累量,N230处理与N160,N90处理之间差异极显著（P〈0.01）,处理N160与处理N90之间无显著性差异。

英文摘要：

The effects of ammonia volatilization on N--applying rates of Digitaria ischaernurn were studied with a closed room method in Spring. The results showed that the ammonia-volatilizing went on for 10--17 days and its peak value were reached after 6 to 8 days of urea application at a rate of 90,160,230kg/ha （N90,N160,N230）,respectively. The peak value of N90,N160 and N230 treatment was 0. 11,0. 57 and 1. 84kg/（hm^2·d）, respectively, after modified from NO treatment. The ammonia-volatilization varied from 0.67 to 5.16 kg/ha among different N--treat- ments,accounting for 0.74%-2.24% of N applied in Spring. The exponential relation was presented between N rates and Ammonia-volatilization, with a correlation equation of y= 0.157 6e^0.0146x （R^2= 0. 951 3）. Besides, the differences of ammonia volatilizing flux were significant among N90, N160,N230 treatment （P〈0. 05）. Meanwhile, the total ammonia-volatilizing amount of N230 treatment were significantly different from N90 and N160 treatment （P〈0.01）, but the difference was not significant between N90 and N160 treatment.