A Technique To Estimate Release Characteristics And Runoff Phosphorus For Agricultural Land#

Abstract

Using soil tests to estimate phosphorus (P) released from agricultural soil by runoff had limited success because P loss is a function of source and transport parameters. There are good procedures applying these parameters, but they are lengthy, expensive and demand numerous laboratory and field data. The objective is to develop reliable exploratory technique to estimate runoff P for agricultural land. Various forms of P like moisture are held by soil particles at different energy levels. Kinetic energy exerted by raindrops on surface soil plays a major role in releasing P. The Soil Survey Laboratory suggests an anion exchange resin (AER) method to determine P release characteristics (PRC) for soils. In this method, different levels of energy are applied by water on soil particles when soil suspension is shaken for various periods. Understanding the relationship between shaking and rainfall energy enabled us to use the AER method to predict P released by rainfall. USDA/NRCS (SCS) runoff equation is applied to determine the relationship between rainfall and runoff for agricultural watersheds. Soil hydrology, rainfall, and type of vegetation are parameters utilized by the runoff model. We propose a technique implementing the AER method and runoff equation to estimate runoff P for agricultural land. The estimated runoff P for 24 soils investigated ranged between 0.09 and 8.3 (fallow), 0.06 and 7.5 (cropland), and 0 and 6.0 kg P/ha/y for grassland. Field studies on different benchmark soils of the United States are in progress to estimate runoff P by using rainfall simulators. These data could be used to verify and calibrate the technique. #The submitted manuscript has been authored by a contractor of the U.S. Government. Accordingly, the U.S. Government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.