|Franklin, Dorcas - Dory|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2007
Publication Date: 5/1/2008
Citation: Butler, D.M., Franklin, D.H., Cabrera, M.L., Tasistro, A.S., Xia, K., West, L.T. 2008. Evaluating aeration techniques for decreasing phosphorus export from grasslands receiving manure. Journal of Environmental Quality. 37:1279-1287.
Interpretive Summary: Surface-applied manures can contribute to phosphorus (P) in runoff, which impairs water quality. Partial disturbance (aeration) of soil in grasslands may reduce P transport by increasing infiltration of rainfall and binding of P with soil minerals. Scientists from the USDA-ARS J. Phil Campbell Sr., Natural Resource Conservation Center, the University of Georgia, and Mississippi State University examined the effects of three aeration treatments and a control (aeration with cores, “no-till” disk aeration perpendicular to the slope, slit aeration with tines, and no aeration treatment) on the loss of sediments, particulate forms of P, and dissolved forms of P in overland flow induced by rainfall. These scientists evaluated this with broiler litter, dairy slurry, and no manure before (January) and after (June) simulated compaction by cattle. Rainfall simulations were done on a typical southeastern clay soil with mixed tall fescue-bermudagrass vegetation on 8 to 12% slopes. Manures were applied to meet P requirements of the vegetation. Core aeration had the greatest potential for reducing all P losses. When broiler litter was applied, export of particulate P was reduced by 55% and dissolved P was reduced by 62% on core-aerated plots compared to controls. Core and no-till disk aeration also showed potential for reducing P export from applied dairy slurry. In well-drained soils, pairing core aeration of pastures with litter application could have widespread impact on surface water quality. This information can be used by land management planners to develop more efficient nutrient management strategies and productive forage systems while reducing contamination of nearby aquatic systems.
Technical Abstract: Given that surface-applied manures can contribute to phosphorus (P) in runoff, a study was conducted to examine mechanical aeration of grasslands for reducing P transport by increasing infiltration of rainfall and binding of P with soil minerals. The effects of three aeration treatments and a control (aeration with cores, “no-till” disk aeration perpendicular to the slope, slit aeration with tines, and no aeration treatment) on the export of total suspended solids (TSS), total Kjeldahl P (TKP), total dissolved P (TDP), dissolved reactive P (DRP), and bioavailable P (BAP) in runoff from grasslands with three nutrient treatments (broiler litter, dairy slurry, and no manure) were examined before (January) and after (June) simulated compaction by cattle. Plots (0.75 x 2 m) were established on a Cecil soil series with mixed tall fescue (Festuca arundinacea Schreb.)-bermudagrass (Cynodon dactylon (L.) Pers.) vegetation on 8 to 12% slopes. Manures were applied at a target rate of 30 kg P ha-1 and simulated rainfall applied at a rate of 85 mm h-1. Although the impact of aeration type on P export varied before and after simulated compaction, overall results indicated that core aeration has the greatest potential for reducing P losses. Export of TKP was reduced by 55%, TDP by 62%, DRP by 61%, total BAP by 54%, and dissolved BAP by 57% on core-aerated plots with applied broiler litter as compared to the control (p < 0.05). Core and no-till disk aeration also showed potential for reducing P export from applied dairy slurry (p < 0.10). Given that Cecil soil is common in pastures receiving broiler litter in the Southern Piedmont, results indicate that pairing core aeration of these pastures with litter application could have a widespread impact on surface water quality.