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Predicting Dissolved Phosphorus in Runoff from Manured Field Plots

^a USDA-ARS, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA 16802-3702
^b USDA-ARS, Poultry Production and Product Safety Research Unit, 203 Engineering Hall, Fayetteville, AR 72701

View larger version (26K): [in a new window]   Fig. 1. Relationship between water to manure ratio (W; cm3 g–1) and manure water-extractable phosphorus (WEP), as expressed relative to WEP extracted at a W of 250:1. Data are from Haggard (unpublished data, 2005), Kleinman et al. (2002), and our current study. The symbol *** designates significance at the 0.001 probability level.

View larger version (25K): [in a new window]   Fig. 2. Relationship between dissolved inorganic P release from manure to simulated rain water as measured by Sharpley and Moyer (2000) and as predicted using Eq. [1] and [2]. The symbol *** designates significance at the 0.001 probability level.

View larger version (27K): [in a new window]   Fig. 3. Relationship between dissolved inorganic P concentrations in runoff from soil boxes and field plots where manures had been surface-applied and subjected to simulated rain. Data are as measured by Haggard et al. (2003), Kleinman et al. (2004), and Smith et al. (2004), and as predicted by Eq. [3] and [4], using either (a) measured runoff to rain ratios or (b) calculated P distribution fractions to distribute P released from manure into runoff or infiltrating water. The symbol *** designates significance at the 0.001 probability level.

View larger version (29K): [in a new window]   Fig. 4. Illustration of the method used to calculate P distribution fractions, which is the fraction of manure water-extractable phosphorus (WEP) released by rain during a storm that is transported in surface runoff. Data are from Smith et al. (2004). W, water to manure ratio.

View larger version (27K): [in a new window]   Fig. 5. Data from Haggard et al. (2003), Kleinman et al. (2004), and Smith et al. (2004) showing the empirical relationships between measured runoff to rain ratios and (a) calculated P distribution fractions and (b) error in predicted dissolved P in runoff calculated as (measured/predicted values). The symbol *** designates significance at the 0.001 probability level.

View larger version (24K): [in a new window]   Fig. 6. Relationship between dissolved inorganic P concentrations in runoff from field plots where manures had been surface-applied and subjected to simulated rain as measured by Kleinman et al. (2001) and as predicted by Eq. [3] and [4], using (a) P distribution fractions predicted from runoff to rain ratios with the relationship in Fig. 5a, or (b) measured runoff to rainfall ratios adjusted based on the relationship in Fig. 5b. The symbol *** designates significance at the 0.001 probability level.