ARS | Publication request: Changes in soil phosphorus levels on a grazing farm in the Chesapeake Bay watershed

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 20, 2011
Publication Date: July 19, 2011
Citation: Sanderson, M.A., Gonet, J.M. 2011. Changes in soil phosphorus levels on a grazing farm in the Chesapeake Bay watershed. Soil and Water Conservation Society. Meeting Abstract. CD-ROM.

Technical Abstract: A perceived benefit of management-intensive grazing is improved nutrient cycling and reduced soil erosion; however, some management practices, such as increased stocking rates, rapid rotations, and supplemental feeding could affect the soil resource through nutrient additions and the concentration of grazing animals. In this case study, we compiled 30 years of soil phosphorus (P) data for a beef cattle farm in the Chesapeake Bay watershed, which provided an opportunity to compare changes in soil P levels before and after a change from row crops and hay production in the 1980s to management-intensive grazing during 1990 to 2010. Soil P data from detailed farm management records were augmented with spatially explicit soil sampling in 1999, 2003, 2004, and 2010. All soil samples were taken from the 0-15 cm surface soil and analyzed for Bray II P. Pastures on fields that historically had received large amounts of manure and were used for corn silage production changed the most in soil test P (132 mg kg-1 P in 1980 to 70 mg kg-1 in 2010). Soil test P levels in fields used for corn grain production in the 1980s decreased by 30%, fields used for hay production decreased by 26% , and permanent pastures decreased by 17%. The decreases in soil test P probably resulted from less inorganic P imported for use on corn, increased offtake of P in hay and grazed forage, and perhaps redistribution of P around the farm from changes in cropping and grazing management.