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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #115554
Title: COMPARING PHOSPHORUS MANAGEMENT STRATEGIES AT THE WATERSHED SCALE

Author
item MCDOWELL, R - PENN STATE UNIVERSITY
item Sharpley, Andrew
item BEEGLE, D - PENN STATE UNIVERSITY

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2001
Publication Date: 8/20/2001
Citation: Mcdowell, R.W., Sharpley, A.N., Beegle, D.B. 2001. Comparing phosphorus management strategies at the watershed scale. Journal Of Soil And Water Conservation. 56(4):306-315.

Interpretive Summary: Agriculture is increasingly linked to water quality concerns. Besides soil and pesticide loss from agriculture, most environmental concerns center on diffuse loss of phosphorus and its role in accelerating freshwater eutrophication. In areas where concentrated animal feeding operations exist, more phosphorus is often applied to crops and pastures than what the eplants actually need. This has led to a build up of soil phosphorus and a increased loss of phosphorus from agricultural lands to surface waters. As a result, the USDA and EPA devised a joint strategy for sustainable nutrient management for animal feedings operations. An important part of this joint strategy outlines how acceptable manure application rates will be determined. The joint strategy describes three options for developing appropriate phosphorus-based nutrient management plans; agronomic soil test phosphorus recommendations, environmental soil test phosphorus thresholds, and a phosphorus index to rank fields according to their vulnerability to potential phosphorus loss. In this study, we compared each option in an experimental watershed in central Pennsylvania, USA, for the development of a watershed scale integrated phosphorus-based management plan. We found that the phosphorus index was the best method to target remedial management to minimize phosphorus export and in the watershed studied impacted less land area than the other strategies.

Technical Abstract: The persistence of water quality problems has directed attention toward reduction of agricultural non-point sources of phosphorus (P). We assessed the practical impact of three management scenarios of the USDA-EPA Strategy for Animal Feeding Operations to reduce P losses from a watershed. Using an agronomic threshold of 50 mg Mehlich-3 P kg-1 soil, 49% of our watershed dwould receive no P as fertilizer or manure. An environmental threshold of 190 mg Mehlich-3 P kg-1 soil, above which P loss in runoff increases, restricts future P inputs to 24% of the watershed. Finally, a site assessment P index was used which accounts for likely source and transport risks. This showed none of the watershed was at high risk of P loss and that areas of medium risk (where remedial measures should be considered) were near the stream channel. We suggest the P index as the best method to target remedial management to minimize P export and in the watershed studied impacted less land area than the other strategies.