Excerpt
Phosphorus (P) loading is considered a primary contributor to surface water eutrophication (Daroub et al. 2009). Phosphorus moves from soil to surface water as dissolved or particulate P. Particulate P is typically not 100% bioavailable, having to enter solution (through dissolution or desorption) before being available for uptake. On the other hand, transported dissolved P is immediately 100% bioavailable to aquatic biota. In addition, dissolved P can be released over very long periods of time from high P source areas on the landscape even when practices are used to control particulate losses. Therefore, dissolved P is generally considered more problematic for water quality, both due to its immediate impact on the ecosystem and difficulties in controlling its movement.
The term “legacy P” is often used to refer to accumulated P that can serve as a long-term source of P to surface waters. Terrestrial P legacies result from past management decisions that lead to high soil P concentrations (Sharpley et al. 2013). Soil P dynamics are such that once soil P concentrations are elevated it can take many years for them to decrease below levels of environmental concern. These high-testing soils are able to release dissolved P for many years, even…
- © 2014 by the Soil and Water Conservation Society
