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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #93066
Title: ASSESSING THE IMPACT OF MANAGEMENT INTENSIVE GRAZING ON WATER QUALITY

Author
item Stout, William
item FALES, S. - PENN STATE UNIVERSITY
item MULLER, L. - PENN STATE UNIVERSITY
item Schnabel, Ronald
item Elwinger, Gerald
item Weaver, Stefan

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Many small- to medium-sized dairy farms in the northeast U.S. have adopted management intensive grazing (MIG) to reduce costs and improve farm profitability. It has been assumed that MIG was by nature an environmentally friendly practice that would have a minimal or even positive impact on water quality. This paper uses experimental data on N leaching loss from animal excreta and information from the literature to synthesize the relationships that illustrate the impact MIG has on water quality under northeast U.S. conditions. The paper shows that, even under relatively low stocking rates, that water quality standards cannot be met using MIG.

Technical Abstract: Stocking rate is the key determining effect of management intensive grazing on dairy farm profitability. However, increased stocking rate can increase N leaching from pastures. Increasing stocking rate affects NO3-N loss through leaching because the bulk of the N consumed by the animal is excreted unevenly in concentrated areas of the pasture in the urine. We used experimental data from the northeast U.S. and the literature to illustrate the relationships between stocking rate and NO3-N leaching losses beneath an intensively grazed pasture. A relatively low cumulative seasonal stocking rate of only about 200 mature Holstein ha-1 would result in a 10 mg l-1 NO3-N concentration in the leachate beneath a fertilized intensively grazed pasture. This means that while management intensive grazing can improve the farm profitability, it is not inherently environmentally friendly, and N management techniques need to be developed if profitability and water quality goals are to be met.