The Spatial And Temporal Distribution Of Nitrogen And Phosphorus In Surface Water Of Paddy Field And Their Performance Of Emission Controlling

During the period of farming, fertilizing and rainfall of paddy rice growth, irrigation-drain experiments were carried out in the paddy field, This article studied the distribution characteristics of nitrogen, phosphorus, suspended solids and other pollutants in the surface water of paddy field and the performance of emission reduction under different controlled drainage experiments in the production process of simulated paddy field, which in order to study the performance and technology, provide scientific basis for controlling agricultural non-point source pollution. The main conclusions are as follows:(1) On the condition of the low, medium and high fertility, after the paddy field plowed, the concentration of nitrogen, phosphorus, suspended solids and other pollutants reached to the maximum at the first 1 hour, and then decreased with the extending of time. In low, medium and high fertility of paddy fields, the nitrogen and phosphorus in the surface water drained after 1 day, which can reduce the emission of total nitrogen about 65.5%.60.8%.32.9%. and total phosphorus about71.5%.68.7%,70.6%:the nitrogen and phosphorus in the surface water drained after 2 days, which can reduce the emission of total nitrogen about 86.2%,65.5%, 50.4%and total phosphorus about 85.3%,73.2%.75.1%.The surface water of paddy field drained after 2 days and kept 3 cm depth, which can reduce the emission of total nitrogen about 50.4%-86.2%and total phosphorus about 73.2%-85.3%. The result showed that after the paddy field plowed; delaying the time of drainage can control emission of nitrogen and phosphorus significantly and reduce agricultural non-point source pollution.(2) During spring plowing, fertilizing four levels of different fertilizer, there were remarkable correlations between the concentration of nitrogen, phosphorus and different levels of fertilizer after fertilizing. The concentration of nitrogen increased at first and then decreased with the extending of time, the concentration of phosphorus decreased with the extending of time. The surface water of paddy field drained after 3 days, kept 3 cm depth, which can reduce the emission of total nitrogen about 18.91%-30.38%and total phosphorus about 58.64%-93.97%. The result showed that after plowed and fertilized with four levels of different fertilizer, if the surface water drained after 3 days, kept several depths surface water of paddy field, which can reduce the loss of nitrogen and phosphorus, and reduce the agricultural nonpoint source pollution effectively.(3) During the period of paddy rice growth, with the extending of time, the concentration of nitrogen increased at first and then decreased after fertilized and met natural rainfall of different intensity, it reached maximum in the 2-3 d, the concentration of phosphorus reached the maximum within 1 hour and then decreased. After different intensity of rainfall, the concentration of nitrogen and phosphorus decreased gradually according to the depth increasing. After moderate and heavy rainfall, the surface water of paddy field drained after 5 days, kept 6 cm depth, which can reduce the emission of total nitrogen about 20.70%-75.22% and total phosphorus about 20.00%-82.30%.The result showed that during the period of paddy rice growth and after moderate to heavy rainfall, controlling drainage can reduce the loss of nitrogen and phosphorus, and reduce the agricultural non-point source pollution.