Estimating Phosphorus Loss in Runoff from Manure and Fertilizer for a Phosphorus Loss Quantification Tool

Authors: Vadas, Peter; GOOD, LAURA - UNIV OF WISCONSIN-MADISON; Moore, Philip; WIDMAN, NORMA - USDA-NRCS, WASHINGTON DC

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2009
Publication Date: 6/24/2009
Citation: Vadas, P.A., Good, L.W., Moore Jr, P.A., Widman, N. 2009. Estimating Phosphorus Loss in Runoff from Manure and Fertilizer for a Phosphorus Loss Quantification Tool. Journal of Environmental Quality. 38:1645-1653.

Interpretive Summary: Non-point source pollution of ponds, lakes, and reservoirs by phosphorus (P) is a concern because it can cause dense growth of algae and plants, which can use up oxygen in the water when they die and decay. Qualitative P Indexes have been developed in the USA and Europe to estimate the risk (as high, medium, or low) of P loss from agricultural fields. Because these Indexes often have practical and technical limitations, we believe a simple tool that quantifies annual field P loss using readily available information is a better option. First we developed new methods to predict annual P loss in runoff from surface-applied manures and fertilizers. Then we incorporated these manure and fertilizer P runoff loss methods into an annual, field-scale P loss quantification tool that estimates dissolved and particulate P loss in runoff from soil, manure, fertilizer and eroded sediment. Our results show it is possible to reliably quantify these P losses using simple methods and readily obtainable inputs, especially if sufficiently accurate estimates of runoff and erosion are available. Thus, a runoff P loss quantification tool does not necessarily require greater input data than existing P Indexes. The same P loss tool can also reliably quantify P loss across a wide variety of management and fertilization practices, soil types, climates, and geographic locations. Such flexibility has not been demonstrated for existing P Indexes.

Technical Abstract: Non-point source pollution of fresh waters by phosphorus (P) is a concern because it contributes to accelerated eutrophication. Qualitative P Indexes that estimate the risk of field-scale P loss have been developed in the USA and Europe. However, given the state of the science concerning agricultural P transport, a simple tool to quantify annual, field-scale P loss is a realistic goal. We developed new methods to predict annual dissolved P loss in runoff from surface-applied manures and fertilizers and validated the methods with data from 21 published field studies. We incorporated these manure and fertilizer P runoff loss methods into an annual, field-scale P loss quantification tool that estimates dissolved and particulate P loss in runoff from soil, manure, fertilizer and eroded sediment. We validated the P loss tool using independent data from 28 studies that monitored P loss in runoff from a variety agricultural land uses for at least one year. Results demonstrate it is possible to reliably quantify annual dissolved, sediment, and total P loss in runoff using relatively simple methods and readily available inputs. However, appropriately accurate estimates of runoff and erosion are needed. Thus, a P loss quantification tool that does not require greater degrees of complexity or input data than existing P Indexes can accurately predict P loss across a variety of management and fertilization practices, soil types, climates, and geographic locations. A P loss quantification tool also offers the opportunity to be able to validate prediction results with field data and to link them to measurable water quality goals.