Dynamic Variation of Nitrogen and Phosphorus Under Optimize Fertilization and Slow-release Fertilizer in Paddy Field Surface Water

This paper explores the effect of nitrogen fertilizer applicated in several times and slow-release fertilizer work on dynamic changes of nitrogen and phosphorus in paddy fields on the condition of natural rainfall and irrigation through field experiment.the results showed that the TN concentration of the surface water reached the maximum on the first day after fertilization and NH+4-N in the second day.With the conversion of nitrogen,NO-3-N concentrations peaked in the 4th day.NH+4-N was the main formation of nitrogen of surface water generally,and irrigation and natural rainfall could significantly increase the proportion of NO-3-N.The TP concentration peaked on the 2nd day after fertilization and rebounded on the 7th day after fertilization or in 2～3 days when the field was disturbed by irrigation or rainfall.The irrigation and natural rainfall could also decreased the soluble phosphorus of surface water and increase the proportion of particulate phosphorus.The TN,TP of the runoff were relatively high in the early stage of the growth of rice,far beyond the standard limit of Ⅴ water of the surface water quality standards(TN 2.0 mg/L,TP 0.2 mg/L of lakes and reservoirs).Compared to the treatment of conventional fertilization,using nitrogen in several times and slow-release fertilizer could decreased by 22.98%～42.88% of TN concentration.