tailieunhanh - Modeling phosphorus in the environment

Statistical models are empirical. Although they are derived from observations, the relationship described must have a basis in our underlying understanding of processes if we are to have faith in the predictive capabilities of the model (National Research Council 2000). | Section I Basic Approaches 2007 by Taylor Francis Group LLC 1 Modeling Phosphorus Movement from Agriculture to Surface Waters Andrew N. Sharpley . Department of Agriculture-Agricultural Research Service University Park PA CONTENTS Types of Process-Based Export Coefficient Statistical or Empirical How Models Simulate P Dissolved Particulate Fertilizer and Manure Spatial Data Requirements for Defining Future Best Management How Models Simulate Fluvial Processes and Impact of P in Surface Fluvial Surface Water Impacts . 14 Summary. 14 References. 15 INTRODUCTION Phosphorus P an essential nutrient for crop and animal production can accelerate freshwater eutrophication which is the most ubiquitous water quality impairment in the . with agriculture a major contributor of P Sharpley 2000 . Geological Survey 1999 . Environmental concerns from harmful algal bloom outbreaks 3 2007 by Taylor Francis Group LLC 4 Modeling Phosphorus in the Environment Burkholder and Glasgow 1997 and regulatory pressure to reduce P loadings to surface waters via implementation of Total Maximum Daily Loads TMDLs . Environmental Protection Agency 2000 have increased the urgency for information on the impacts of agricultural management specifically conservation practices and best management practices BMPs on P loss. Because of the time and expense involved in assessing P loss models are often a more efficient and feasible means of evaluating management alternatives. In their most comprehensive form models can integrate information over a watershed scale to identify BMPs and critical source areas where BMPs are most likely to affect watershed-scale P losses. A common limitation to model application is the lack of detailed parameterization data on soil physical chemical and .