Effects Of Organic Fertilizer On Ammonia Volatilization And Nitrogen Use Efficiency In Coastal Paddy Field

Rice is one of the important food crops in China.The use of a large amount of nitrogen fertilizer during planting and the high temperature and high humidity environment cause ammonia volatilization.The presence of a large amount of ammonia in the atmosphere promotes the formation of fine particulate pollutants and reduces air quality.After ammonia is deposited into water and soil,it will also lead to ecological and environmental problems such as eutrophication and soil acidification.In order to build Shanghai coastal into a world-class ecological island,reduce agricultural ammonia volatilization and improve the quality of ecological environment,coastal local governments have vigorously promoted the use of organic fertilizers,but the effect is not clear.Therefore,based on the main rice planting areas in coastal areas,three treatments of chemical fertilizer(CT),organic fertilizer(OT)and no fertilizer(CK)were set up in this study.The field fertilization experiment of ammonia volatilization in coastal paddy fields was carried out by intermittent pumping method in closed chamber.The characteristics of ammonia volatilization and the main influencing factors in different fertilization periods of paddy fields in coastal areas,as well as the effects of organic fertilizer and chemical fertilizer on rice growth and nitrogen use efficiency were studied.The results are as follows:(1)The ammonia volatilization characteristics of different treatments in different fertilization periods of coastal paddy fields were different.Except that the CT treatment showed the characteristics of ’long peak duration’ in the base fertilizer period and the ’first decrease and then increase’ in the OT treatment in the base fertilizer period,the other periods showed the law of ’single peak,rapid decrease,and decreasing rate from high to low’.Ammonia volatilization in each period reached the peak within 1-2 days after fertilization,and basically ended within 6-9 days after fertilization.The accumulation of ammonia volatilization in different fertilization periods of coastal paddy fields was divided into two stages:rapid increase period and slow growth period.The rapid increase period of ammonia accumulation after fertilization was 1-6 days after fertilization,except that the base fertilizer period of CT treatment was 1-8 days after fertilization,and the base fertilizer period of OT treatment was 1-4 days after fertilization.(2)The cumulative amount of ammonia volatilization in the whole growth period of rice treated with CT,OT and CK were 243.42 kg/hm2,144.42 kg/hm2 and 78.92 kg/hm2,respectively,and the difference between the treatments was significant.Compared with CT treatment,the ammonia volatilization accumulation of OT treatment in the whole growth period of rice decreased by 99.02 kg/hm2,a decrease of 40.68%.Organic fertilizer mainly reduced the amount of ammonia volatilization in base fertilizer,the first topdressing period and the.second topdressing period,and the reduction rates were 63.20%,53.94%and 66.65%,respectively.(3)The main influencing factors of ammonia volatilization in different fertilization periods of coastal paddy fields are different.Among the influencing factors,meteorological factors had little effect on ammonia volatilization in paddy fields.Soil ammonium nitrogen content,soil nitrate nitrogen content,soil organic matter content,ammonium nitrogen concentration in surface water,total nitrogen concentration in surface water,and pH of surface water had a greater impact on ammonia volatilization in coastal paddy fields.Compared with single application of chemical fertilizer,organic fertilizer mainly reduced soil ammonium nitrogen content,ammonium nitrogen concentration in surface water,total nitrogen concentration in surface water by 27.51%,41.25%and 43.23%,respectively,and increased soil organic matter content by 42.82%,reducing the production of ammonia volatilization.(4)The grain yield of rice treated with CT,OT and CK were 8.77 t/hm2,8.31 t/hm2 and 5.75 t/hm2.Compared with CT treatment,the rice yield of OT treatment decreased by 5.21%,and the nitrogen absorption and utilization rate,nitrogen physiological utilization rate,nitrogen agronomic utilization rate and nitrogen partial productivity of rice decreased by 1.55%,2.71 kg/kg,0.77 kg/kg and 0.78 kg/kg,respectively,which did not reach significant level.However,about 48.06%of the fertilizer nitrogen in the OT treatment remained in the soil,and only 4.24%was lost to the environment through other ways except for 30.63%of the rice absorption and 17.07%of the ammonia volatilization loss.In addition to 32.18%of the rice absorption and utilization and 43.29%of the ammonia volatilization loss,the remaining 24.53%of the fertilizer nitrogen in the CT treatment was lost to the environment through other ways and reduced the soil nitrogen stock by 4.35%.Therefore,organic fertilizer can reduce ammonia volatilization in coastal paddy fields and increase soil nitrogen stock without significantly reducing rice yield,which has promotion significance.