The Research Of Soil Nutrient Losses Under Different Soil And Water Conservation Measures

Soil erosion is an important form of non-point source pollutions. Different patters of soil and water conservation measures may have significant effects on soil erosion and results in losses of nitrogen and phosphorus. Different patters of soil and water conservation measures in Longfengling Water and Soil Conservation Supervision Station of Mentougou Distric were selected as objects in the research. Stationary monitoring of rainfall-induced runoff was carried out to explore dynamics of agricultural non-point source pollutants in the rainfall-runoff condition and to determine relationship between different patters of soil and water conservation measures with sediments and nitrogen and phosphorus losses. We selected six runoff plots in demonstration garden to conduct the present research. From May to August of2005, series of water samples were collected from the six runoff plots in each rainfall event, and in the meantime, flow rate of the runoff was also measured. Total nitrogen(TN), Total dissolved nitrogen(TDN), Nitrate nitrogen, Ammonia nitrogen, Total phosphorus(TP), Total dissolved phosphorus(TDP), and suspend sediment were measured for the samples.The results showed that:throughout the rainfall event, output of total nitrogen,nitrate nitrogen, ammonia nitrogen,total phosphorus peaked in the early period, but those had declined along with the rain the extension of time. The change trend of total nitrogen,nitrate nitrogen,ammonia nitrogen,total phosphorusis similar to the trend of flow. As the flow of reduce, the output concentrations of total nitrogen,nitrate nitrogen,ammonia nitrogen,total phosphorus were dropping.①,The order of runoff and losses of suspend sediment was bare land>5%vegetation cover rations>10%vegetation cover rations>30%vegetation cover rations>cultivated land>stone dike terrace, under the same rainfall and strength. And the more the vegetation covers, the smaller the runoff and suspend sediment losses. Under single soil and water conservation measure and the more the rainfall and strength, the more the suspend sediment losses.②,Total nitrogen pollutant output varied with different soil and water conservation measuress, stone dike terrace>30%vegetation cover rations> cultivated land>5%vegetation cover rations> bare land>10%vegetation cover rations; Nitrate nitrogen and ammonia nitrogen pollutant output varied with different soil and water conservation measuress, the output of30%vegetation cover rations, stone dike terrace,cultivated land were greater than bare land,5%vegetation cover rations,10%vegetation.③The characteristics of phosphorus loss under six types of cultivation practices were studied in Longfengling Water and Soil Conservation Supervision Station of Mentougou Distric. The results showed that not only runoff and erosion rates followed the order of bare land>5%vegetation cover rations>10%vegetation cover rations>30%vegetation cover rations, but also the phosphorus loss followed the order of bare land>5%vegetation cover rations>10%vegetation cover rations>30%vegetation cover rations. Sediment attached phosphorus accounted most of the P, and it accounted for90%of total soil phosphorus loss. P concentrations responded with rainfall intensity. Output of P peaked in the early period, but the concentrations of P had declined along with the rain the extension of time.Throughout the rainfall event, output of suspend sediment, total nitrogen,nitrate nitrogen, ammonia nitrogen,total phosphorus peaked in the early period, showed that rainfall strongly influenced soil erosion. The more the vegetation covers and there were soil and water conservation measures, the smaller the runoff and suspend sediment losses.