The nonpoint source pollution can be controlled by implementing various best management practices (BMPs) in the watershed. However, before such practices are adopted, their effectiveness at various spatial and temporal scales must be evaluated. Though the effectiveness of individual BMPs has been usually assessed in standard plots, it is necessary to quantify the impact at a wider range (eg. at the watershed scale) to ensure that practices taken will be sufficient to meet EPL (the environmental protection law) targets. In this paper, we compare the characteristics and suitability of different approaches (direct measurement, nutrient budgeting, risk assessment and model simulation) to assess the effectiveness of actions to mitigate sources and transport of nitrogen (N) and phosphorus (P) from agricultural land to water. Nutrient budgets are most commonly used to quantify nutrient management by evaluating inputs and outputs over a defined time period. Automatic calculations under spreadsheets or other user friendly interfaces are used as accounting procedures to obtain the nutrient surplus or deficit values. System boundaries are flexible, resulting in a range of methodologies applicable from plot to national scale including farm gate, soil surface and soil system budgets. The limitation of this method that it currently fail to consider the timing and transport aspects of mitigation and assume a direct causal relationship between
With the development of point source pollution control, Agricultural Non鄄point Source Pollution (AGNPS) issues have become increasingly prominent worldwide. Non鄄point source pollution is difficult to control because it comes from the everyday activities of many different people, such as fertilizing a lawn, using a pesticide, or constructing a road or building. Recently, the agricultural non鄄point source pollution control has become a hotspot in the water research. As a common tool used to reduce non鄄point source pollution, Best management practices (BMPs) have been widely adopted to improve water quality problems associated with agricultural nonpoint source pollution, however, there have been few realistic efforts to assess their effectiveness in reducing AGNPS pollution. The effectiveness of BMPs must be evaluated at various spatial and temporal scales before adoption. Models are more comprehensive that can reflect choice of mitigation at a widely range of scales and then to achieve the best cost鄄effectiveness selection and placement of BMPs for non鄄point source
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