Study On The Nitrogen Transfermation And Rice Growth Under Different Nitrogen Management Methods In The Rice Field

At present,the average utilization rate of nitrogen in China is about 30 to 35 perecnt,which is still lower than that in the developed countries.How to improve the nutrient utilization efficiency and reduce the agricultural non-point source pollution through nitrogen management strategy has been a hot topic in this research field.Three different nitrogen management patterns(the nitrogen fertilization level,organic material of milk vetch with inorganic NPK fertilizer,nitrogen fertilizer added with synergist poly aspartic acid)on rice growth and nutrient absorption,soil nutrient transformation and its environment effect were studied by the data analysis of the long-term located test,field plot and pot experiment.These might be helpful to clarify different nitrogen management patterns on rice yield and the function and mechanism of nitrogen use efficiency,in order to further optimize nitrogen fertilizer management,reduce fertilizer application level,improve fertilizer utilization efficiency and promote agricultural sustainable development.The main research results are shown as follows:(1)The optimal nitrogen fertilization level in the rice field was 200 ~250kg N/ha based on comprehensive factors such as rice yield,nitrogen utilization rate and nitrogen absorption and utilization by rice.Nitrogen application increased the content of available nitrogen,such as soil alkali-hydrolyzed nitrogen,ammonium nitrogen and nitrate nitrogen,promoted the absorption of nitrogen by rice,and thus increased the yield and plant biomassof rice.When the nitrogen application level exceeded 250 kg N/ha,the contents of total nitrogen,ammonium nitrogen,nitrate nitrogen and total phosphorus in the runoff water were significantly increased.Excessive nitrogen application increased the risk of loss of nitrogen and phosphorus in farmland,which had a negative impact on the ecological environment.(2)The combined application of organic and inorganic fertilizers significantly improved the absorption and utilization of nitrogen,phosphorus and potassium in rice,significantly increased the yield of rice,and the nitrogen utilization rate of fertilizer increased by 11.4 percentage points on average.Combined application of organic and inorganic fertilizers can increase the content of soil organic matter,available phosphorus and available potassium,and improve soil fertility.Among them,commercial organic fertilizers have the most obvious effect on improving the content of available phosphorus in soil,and rice straw returning has the best effect on improving the soil available potassium.The combined application of organic and inorganic fertilizers can reduce the total amount of ammonia volatilization and the content of ammonium nitrogen,nitrate nitrogen and phosphate in the paddy field water,reduce the risk of nitrogen and phosphorus runoff loss in the paddy field,and is of great significance to the control of agricultural non-point source pollution.(3)Synergist polyaspartic acid can improve the yield of rice,promote the absorption of nitrogen and other nutrients,and improve the utilization efficiency of nitrogen fertilizer.There was no significant difference in the effect of different concentrations of polyaspartic acid Ca salt.There was also no significant difference between 0.3%polyaspartic acid Ca salt and Zn salt.Polyaspartic acid can improve rice yield and nitrogen utilization efficiency.The main mechanism is that polyaspartic acid can slow down the process of ammonium nitrogen conversion into nitrate nitrogen,prolong the duration of ammonium nitrogen in soil,and thereby facilitate the absorption and utilization of ammonium nitrogen in rice and reduce the loss of denitrification and nitrogen removal.