chapter  4
24 Pages

Basic Approaches to Modeling Phosphorus Leaching

Leaching is an active process in the phosphorus (P) cycle, thereby affecting P transport in agroecosystems. Although subsurface P transport is not the predominant loss pathway in most regions (Hansen et al. 2002; Lemunyon and Daniel 2002; Osborne and Kovacic 1993; Peterjohn and Corell 1984), there is increasing evidence of vertical P movement in soils when P applications exceed crop P removal over extended periods of time. For example, many studies have documented elevated subsoil P concentrations

resulting from repeated waste applications (King et al. 1990; Maguire et al. 2000; Mozaffari and Sims 1994; Nelson et al. 2005; Novak et al. 2002; Sharpley et al. 1984a). Leaching processes affect P distribution within the soil, removing P from surface horizons where it would be available for crop uptake or loss through runoff and erosion. In soils with low P sorption capacities, leaching can potentially remove more P from the root zone than crop uptake (Nelson et al. 2005).