Nitrogen use efficiency and ammonia volatilization from urea applied to wheat on a paddy field in Taihu Lake region.

Through setting up different amount of urea treatment,ammonia volatilization losses from urea applied during basal dressing,reviving-top dressing and jointing-top dressing stages were measured with the continuous airflow method in a wheat field in Taihu Lake region.The results showed that ammonia volatilization rates(percentage of the ammonia volatilization amount to the applied nitrogen fertilizer) were 1.51%～3.07%,the N losses in three top dressing periods were ranked as basal dressingjointing-top dressingreviving-top dressing,and ammonia volatilization mainly occurred in 10~12 days after fertilization.With the increasing of the nitrogen rate,both the nitrogen apparent and physiological using efficiency were decreased,at the same time,the yield was increased in some degree.The maximal yield occurred in the 200 kg·hm-2 treatment(N3),and when the nitrogen fertilizer rate reached 250 kg·hm-2,the yield started to decrease.In general,the yield differences between treatments were not significant,but differences between the control and the treatments were significant(P0.01).