Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2008
Publication Date: 3/6/2008
Citation: Good, L.W., Vadas, P.A. 2008. Estimating surface runoff loss of dissolved phosphorus from manure applications to cropland for the Wisconsin Phosphorous Index [abstract]. American Water Resources Association Wisconsin Section 2008 Meeting, March 6-7, 2008, Brookfield, Wisconsin. p. 10.
Technical Abstract: The Wisconsin Phosphorus (P) Index is a field-level runoff P loss risk assessment tool for evaluating agricultural management practices. It assigns an annual risk ranking to a field by estimating annual sediment-bound and dissolved P losses to the nearest surface water. On cropland with no recent manure or fertilizer applications, the P Index uses the strong relationship between crop land runoff dissolved P (DP) concentrations and soil test P to assess DP loss potential. Simulated rainfall experiments have shown that following unincorporated manure applications, runoff DP concentrations increase and are not related to soil P. In these experiments, the proportion of rain converted to runoff greatly influenced the runoff DP concentrations (r2 = 0.80), as well as loads. We have developed a simple method to estimate DP losses following manure application that uses long-term weather and runoff averages to determine the potential for runoff during the season of manure application. With this method, the P Index appropriately ranked seasonal DP losses following manure application on Wisconsin fields monitored from 2004 to 2006. Winter applications had the highest estimated and measured DP losses. In addition, when the estimated DP losses following manure application were summed with estimated DP losses from the soil for the remainder of the year, this Soluble P Index appropriately ranked fields by DP yields.