Monday, November 5, 2007

Evaluation of Land Application Systems for Swine Manure to Reduce NPS Pollution.

R.L. Rhykerd, Paul Walker, Tim Kelley, and Ken Smiciklas. Department of Agriculture, Illinois State University, Campus Box 5020, Normal, IL 61790

The composition of N and P in swine manure do not match the nutrient requirements for crop production contributing to non-point source pollution (NPS). Alternative methods for managing and land applying liquid manure that reduce NPS and are affordable must be developed. The objective of this study was to evaluate a total systems approach for processing and land application of swine slurry. This systems approach modifies existing equipment and methodologies to effectively and economically reduce the pollution potential of slurry. Following removal of a portion of the separable solids with a gravity screen roll press separator, a polyacrylamide assisted gravity belt thickener was utilized to separate unprocessed raw swine slurry (RS). Following separation, the solids fraction was mixed with woodchips and composted. The separated effluent (SE) was stored in a slurry stored and subsequently land applied to corn using a center pivot irrigator. The unprocessed slurry was composed of co-mingled slurry from a 200 sow operation. During a 5 month period 3785 kL of SE was produced and 2828 kL of SE were irrigated. The RS contained 1.3% DM, 95.4 ml L-1 SS, 878.5 mg L-1 total suspended solids (TSS), 0.0 mg L-1 dissolved oxygen (DO), 57,126.9 mg L-1 chemical oxygen demand (COD), 0.19% N and 0.05% P. The SE had significantly lower DM (69.2%), SS (98.4%), TSS (98.2%,), COD (89.6%), N (60.6), and P (91.7%) concentrations compared to RS. The SE was found to contain 44.9% increased (p<0.05) DO compared to RS. The N/P ratio was changed from 3.8/1 in the RS to 20/1 in the SE. Cost to separate the effluent including polymer, power, labor, and equipment depreciation was $0.0026 L-1 and $0.00026 L-1 to irrigate the SE. These data suggest chemical separation coupled with irrigation can be affordable and environmentally acceptable methods to land apply swine slurry.