Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/20/2000
Publication Date: 2/20/2001
Citation: Mcdowell, R.W., Sharpley, A.N., Condron, L.M., Haygarth, P.M., Brookes, P.C. 2001. Processes controlling soil phosphorus release to runoff and implications for agricultural management. Nutrient Cycling In Agroecosystems. 59(3):269-284. Interpretive Summary: Phosphorus is required to maintain plant growth. Phosphorus was considered fixed and immobile in the soil and any losses to water were considered incidental from an economic standpoint. Furthermore, manure applications have been based mostly on crop nitrogen requirements, resulting in more phosphorus applied than crops need. This increases the potential transfer of phosphorus from soil to solution and eventually surface water. Increased phosphorus concentrations in fresh waters can accelerate eutrophication and impair water use for recreation, drinking, and industry. The amount of phosphorus that reaches fresh waters can be simply viewed as a function of how much is in the soil and soil hydrological conditions that transport phosphorus to surface waters. If we are to mitigate phosphorus loss from soil to water, we must understand soil phosphorus dynamics and how it interacts with soil hydrology. As it is impossible to control natural rainfall and difficult to influence soil hydrology, this review is more concerned with the movement of soil phosphorus from soil to solution and how it can be integrated with hydrology to manage phosphorus.
Technical Abstract: Phosphorus (P) loss from agricultural land to surface waters is well known as an environmental issue because of the role of P in freshwater eutrophication. Much research has been conducted on the erosion and loss of P in sediments and surface runoff. Recently, P loss in subsurface runoff via agricultural drainage has been identified as environmentally significant. High soil P levels are considered as a potential source of P loss. However, without favourable hydrological conditions P will not move. In this paper, we review the basis of soil P release into solution and transport in surface and subsurface runoff. Our objectives are to outline the role of soil P and hydrology in P movement and management practices that can minimize P loss to surface waters. Remedial strategies to reduce the risk of P loss in the short-term are discussed, although it is acknowledged that long-term solutions must focus on achieving a balance between P inputs in fertilizers and feed and P outputs in production that is of low risk of P loss.