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Title: FIELD SCALE, PAIRED WATERSHED STUDY: AERATION TO REDUCE RUNOFF AND PHOSPHORUS LOSSES FROM GRASS LANDS FERTILIZED WITH BROILER LITTER

Author
item Franklin, Dorcas
item CABRERA, M - UNIVERSITY OF GEORGIA
item WEST, L - UNIVERSITY OF GEORGIA
item CALVERT, V - UNIVERSITY OF GEORGIA
item REMA, J - UNIVERSITY OF GEORGIA

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2006
Publication Date: 1/9/2007
Citation: Franklin, D.H., Cabrera, M.L., West, L.T., Calvert, V.H., Rema, J.A. 2007. Field scale, paired watershed study: aeration to reduce runoff and phosphorus losses from grass lands fertilized with broiler litter. Journal of Environmental Quality. 36:208-215.

Interpretive Summary: Improved infiltration of rainfall can help extend grass or forage productivity during droughty periods and can retard flooding during periods of heavy rainfall. Application of broiler litter to grasslands may lead to elevated concentration of phosphorus loss in surface runoff which can contaminate surface waters. Management practices are needed to reduce the amount of phosphorus loss in runoff from grasslands fertilized with broiler litter. A practice that may accomplish these results is slit aeration. Slit aeration is the practice of inserting tines into grassland soils to make elongated holes. Researchers from USDA-ARS J. Phil Campbell Sr., Natural Resource Conservation Center and Univ. of GA studied the impact of slit aeration on runoff volume and phosphorus losses in runoff from tall fescue-bermudagrass hay fields fertilized with broiler litter at the field scale. Three pairs of 2-acre watersheds were monitored under similar management from 1995 through 1998, then one of the watersheds in each pair was aerated from 2000 through 2003. Grassland aeration reduced surface-water runoff volume and losses of dissolved phosphorus in runoff by 35% in fields with mostly well-drained soils . In contrast, when poorly-drained soils dominated, grassland aeration increased runoff volume(0.25 inch/runoff event) and losses of total phosphorus(particulate phosphorus plus dissolved phosphorus); 0.22 lbs TP acre-1 per runoff event). This information can be used by natural resource land use managers associated with the poultry industry to more effectively manage runoff and phosphorus losses throughout the Southern Piedmont. In Georgia (number one poultry producing state in the USA), if aeration was done on pastures in the top poultry producing counties(0.5 million acres)and assuming 40% of the pastures were in well-drained soils, dissolved phosphorus losses would be reduced by 450,000 lbs each year. This is not the case if soils are poorly-drained.

Technical Abstract: Management practices are currently needed to reduce the amount of P loss in runoff from grasslands fertilized with broiler litter, and it is important to understand the impact of these practices at the field scale. Study objective was to determine at the field scale, using a paired watershed approach, the impact of slit aeration on runoff volume and P losses in runoff from tall fescue-bermudagrass hay fields fertilized with broiler litter. Three pairs of 0.8-ha watersheds were monitored under similar management from 1995 through 1998, then one of the watershed in each pair received aeration treatment from 2000 through 2003. Results indicated that in fields with mostly well-drained soils grassland aeration reduced surface runoff volume and losses of dissolved reactive P (DRP) in runoff by approximately 35%. In contrast, when poorly-drained soils dominated, grassland aeration increased runoff volume (6.2 mm/runoff event) and losses of DRP and Total P (0.25 kg TP ha-1 per runoff event). Thus, a thorough survey of the soils present in a grassland would be desirable before aeration is used as a management practice to reduce P losses. Additional work should be carried out to further identify the characteristics of soils that respond positively to aeration.