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Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/20/2005 Publication Date: 3/10/2006 Citation: Vadas, P.A. 2006. Distribution of phosphorus in manure slurries and its infiltration upon application to soils. Journal of Environmental Quality. 35:542-547. Interpretive Summary: Phosphorus (P) transfer from soils to surface waters is an environmental concern. Computer models help identify areas with high P transport potential, but widely-used models do not simulate P transport directly from surface-applied manures to runoff. As part of an effort to model such P transport, we determined how much slurry P will likely infiltrate into soil upon application, thus becoming less available to runoff. We separated dairy and swine slurry by sieving, centrifuging, and suction filtering, and analyzed bulk slurry and separated liquids and solids for dry matter and P. Suction filtering allowed the most P in separated liquids, followed by sieving and then centrifuging. We applied slurries to soil columns and analyzed un-infiltrated solids for dry matter and P and underlying soils for P. About 40-65% of manure slurry P remained in un-infiltrated solids, which was similar to filter separation results. Applying slurries always increased soil P in the top 0-2 cm of soil, but rarely below 2 cm. Results can be incorporated into models to simulate slurry P infiltration into soils upon their surface application. Technical Abstract: Phosphorus transfer from agricultural soils to surface waters is an environmental concern. Computer models help identify agricultural areas where P transport potential is high, but widely-used models do not simulate surface application of manures and P transport directly from manures to runoff. As part of an effort to model such P transport, we conducted manure slurry separation and soil infiltration experiments to determine how much slurry P will infiltrate into soil upon application, thus becoming less available to runoff. We separated dairy and swine slurry by sieving, centrifuging, and suction filtering, and analyzed bulk slurries and separated liquids and solids for dry matter, water extractable inorganic (WEIP) and organic P (WEOP), and total P (TP). Suction filtering allowed the most WEIP, WEOP, and TP in separated liquids, followed by sieving and then centrifuging. We also applied dairy and swine slurries to soil columns and analyzed un-infiltrated solids for dry matter and P and underlying soils for P both 24 and 96 h after slurry application. The fraction of bulk slurry WEIP and WEOP remaining in un-infiltrated dairy and swine solids was similar to filter separation results. For dairy slurry, bulk slurry TP in un-infiltrated solids was between that observed for suction filtering and sieving, while TP in un-infiltrated swine solids was less than observed for both filtering and sieving. Applying slurries always increased soil P in the top 0-1 cm of soil, frequently in the 1-2 cm depth, but rarely below 2 cm. Overall, 40-65% of manure slurry WEIP will infiltrate into the top 2 cm of soil, and mostly in the top 1 cm, upon application, and will decrease in availability to runoff until soil P chemical equilibrium is reached. |
