| In recent years, with the point source pollution control capability improved,the severity of agricultural non-point source pollution has gradually emerged,which accounted for a large proportion on the impact of eutrophication.Excessive use of fertilizers and irrational water management are the main reasons for agricultural non-point source pollution.This paper studied the distribution Characteristics of nitrogen and phosphorus 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, in order to provide experimental basis on controlling the emission of nitrogen and phosphorus in paddy field drainage.It was also expected to provide a theoretical basis for the purpose of achieving energy conservation and protecting river water quality,while controlling the total amount of pollutants emitted by paddy field from the agricultural non-point source pollution perspective. The main results were as follows:1. Irrigation-drain experiments were carried out in the paddy field with different drainage heights,while simulating the main agricultural activities in the process of spring tillage. The result showed that:Applied compounding base fertilizer and spring tillaging one hour later, TN concentration in the surface water of the paddy field increased rapidly,and reached the maximum whin 2-3 days,then decreased as time elapsed.The potential loss of ammonia-based was gradually insteaded by that of TN-based in the surface water drainage.TP concentration in the surface water of the paddy field was during 0.32～0.86mg/L in the first hour and reached the maximum in the 24th hours, during 2.19-3.27mg/L, then also decreased as time elapsed..The main potential loss of phosphorus is soluble in the surface water drainage.Considering the requirements for the depths of the surface wate of paddy field in the process of spring tillaging and transplanting seeding, in order to reduce the emission of nitrogen and phosphorus in the paddy field drainage and improve the utilization of water resource, the paddy field should not drain immediately after fertilizing and tillaging. Keeping appropriate depths of surface water in the paddy field and draining delayly did favor to control pollutants emission in the paddy field. If the paddy field drained delaying 5days and keeping the surface water in 6cm depth, compared with conventional water management after spring tillaging, it could reduce the emission of TN 32.59%-75.87% and TP 53.42%-90.44%.2. Store-drain experiments were carried out after spherical fertilizer was deeply applicated at different depths, comparing to spreading the fertilizer to the paddy filed when rice was in the period of turning green.The result showed that:Urea was deeply applicated one hour later in the form of mud ball, TN concentration in the surface water of the paddy field reached the maximum, was during 20.54-24.71mg/L. Then, TN concentration decreased as time elapsed. While urea was spreadly applied to the paddy field one hours later, TN concentration in the surface water of the paddy field was relatively low, it was 8.84mg/L. And TN concentration reached the maximum in the 24th hour, was80.74mg/L.Then TN concentration decreased as time elapsed. The potential loss of nitrogen was TN-based in the surface water drainage in three depths treatments in the paddy field using deep fertilization,but the potential loss of TN-based was gradually insteaded by that of ammonia-based in the surface water drainage using surface fertilization.TP concentration in the surface water of the paddy field reached the maximum in the first hour both applicated in the form of mud ball and applied spreadly, then also decreased as time elapsed.;The main potential loss of phosphorus were both particulate in the surface water.After spherical fertilizer was deeply applicated when rice was in the period of turning green, if suffering rainfall,in order to reduce the amounts of nitrogen and phosphorus emitted into the surrounding water environment, the paddy field could store the rain water and drain delayly. If the paddy field stored the rain water and drained after 2days, compared with the conventional water management that did not store rain water and drained immediately, it could reduce the emission of TN 26.72%-49.31% and TP 20.33%～31.25%. 3. Store-drain experiments were carried out after spreading the fertilizer to the paddy filed fitted with different drainage heights when the young panicle was forming. The result showed that:Urea spreadly applied one hour later, TN concentration in the surface water of the paddy field were was relatively high, and reached the maximum in the 24th hour, then decreased as time elapsed. The potential loss of nitrogen was TN-based in the surface water of paddy field.After urea spreadly applied, TP concentration in the surface water of the paddy field was in a low level, and reached the maximum in the first hour, then decreased as time elapsed.The main potential loss of phosphorus was particulate in the surface water of paddy field.After urea spreadly applied when the young panicle was forming if suffering rainstorm, in order to reduce the amounts of nitrogen and phosphorus emitted into the surrounding water environment, the paddy field could store the rain water and drain delayly. Compared with the conventional water management that did not store rain water and drained immediately, if the paddy field stored the rain water in 10cm depth and drained after 5days, it could reduce the emission of TN 60.93% and TP 64.29%; if the paddy field stored the rain water in 10cm depth and drained after 7days, it could reduce the emission of TN89.19% and TP67.86%. |
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