Effect Of Water Level On Ammonia Volatization In Paddy Field

Ammonia volatilization is one of the most important forms of nitrogen loss in paddy field.Strengthening the control of ammonia volatilization in paddy fields has far-reaching significance for improving nitrogen use efficiency,reducing agricultural economic losses,and solving environmental problems which was caused by agricultural production.Water level has impacts on the ammonia volatilization in paddy fields.However,the effect of water level on ammonia volatilization and its mechanism are still unclear.Traditional agricultural control of paddy field water level is relatively extensive which is hard to control ammonia volatilization.Based on laboratory column experiments and continuous air-flow enclosure method,this study monitored the dynamic changes of ammonia volatilization in paddy fields under various water levels,and explored the effect of water level on ammonia volatilization in paddy fields and its mechanism,in order to analyze the water level management to reduce ammonia volatilization loss and optimize nitrogen use efficient in paddy fields.Research results are as follows:（1）The rate of ammonia volatilization and ammonia volatilization accumulation at 1 cm water level were both higher than 3 cm and 5 cm water level,after applying base fertilizer and tillering fertilizer under the same fertilization amount.During base fertilizer period,1 cm water level showed stronger ammonia volatilization,the highest ammonia volatilization flux value was 1.997 kg·hm^-2·d^-1;ammonia volatilization accumulation at 1 cm water level was 8.08 kg·hm^-2,and the proportion of ammonia volatilization in total nitrogen application was 27%.After the application of panicle fertilizer,the highest ammonia volatilization flux value and ammonia volatilization accumulation was under the water level of 5 cm,respectively came to 1.807 kg·hm^-2·d^-1and 5.23 kg·hm^-2（17%）.（2）There are significant differences from water temperature and dissolved oxygen under different water levels.The peak temperature of 1cm treatment was usually 1.1-1.9℃higher than that of 3 cm treatment and5 cm treatment.The dissolved oxygen of 1 cm treatment was higher than that of 3 cm treatment and 5 cm treatment 1-2 mg·L^-1.（3）Low water level has weak dilution ability and higher NH₄⁺-N concentration,which causes significant ammonia volatilization.After the application of basal fertilizer,the peak concentration of NH₄⁺-N under 1cm water level was 7.147 mg·L^-1,which was higher than that in 3 cm and5 cm treatments.After applying panicle fertilizer,dissolved oxygen supply at high water level was slow,which suppressed the nitrification of NH₄⁺-N and was beneficial to ammonia volatilization.（4）The nitrogen content of rice treated in 1 cm water level was 14.312g·kg^-1,which was higher than that of 13.301 g·kg^-1 and 12.173 g·kg^-1treated in 3 cm and 5 cm water levels.Low water level promoted to assimilate nitrogen in rice and reduce ammonia volatilization.（5）Low NH₄⁺-N concentration and low water temperature caused by high water level were the main factors for ammonia volatilization reduction after base fertilizer and tiller fertilizer were applied;and the high nitrification intensity in low water level was an important element associated with the inhibition of ammonia volatilization after the application of panicle fertilizer.It is recommended that adopt a higher water level during the application of base fertilizer and tiller fertilizer,and lower the water level when applying panicle fertilizer to reduce ammonia volatilization.In summary,water level plays a key role in ammonia volatilization of paddy fields.Ammonia volatilization can be reduced under reasonable control of water level.This study provides a theoretical basis and application reference for optimizing rice production models and reducing ammonia volatilization.