A continuous airflow enclosure chamber method was used to study ammonia volatilization from paddy field under the rice-wheat rotation system in South Jiangsu and effects of rate and method of nitrogen fertilizer application on ammonia emission from the field during the rice and wheat growing periods.Results showed that ammonia volatilization could be obviously reduced under the rice-wheat rotation system by optimizing fertilization,N loss through ammonia volatilization accounted for 7.05%±1.37% and 9.81%±0.38%,respectively,of the total N applied for optimized and traditional ways of fertilization.The difference in ammonia volatilization between the rice season (water-logged) and the wheat season (dry) was notable.During the rice season N loss through volatilization rose with the application rate of nitrogen fertilizer,showing a power relationship while during the wheat season,a linear relationship.In the rice field,ammonia volatilization lasted short,and took place within a week after N application,while in the wheat field,it lasted longer for about ten days.Almost 50% of the ammonia volatilization took place during the basal dressing period in either rice or wheat season.