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Updated: Aug 1, 2026
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Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds
Published on: September 26, 2017
Water quality and the grazing animal
R K Hubbard1, G L Newton, G M Hill
1Southeast Watershed Research Laboratory, USDA-ARS, Tifton, GA 31793, USA. hubbard@tifton.usda.gov
Journal of Animal Science
|October 9, 2004
Summary
Grazing animals impact water quality through nutrient and pathogen runoff. Proper pasture management is crucial for mitigating negative effects on soil and water resources.
Area of Science:
- Environmental Science
- Agricultural Science
- Water Quality Management
Background:
- Grazing animals and pasture production present dual impacts on water quality, both beneficial and detrimental.
- Effective forage production management can protect soil surfaces from erosion, contrasting with conventional crop production methods.
- Negative impacts stem from erosion, sediment transport, nutrient (nitrogen and phosphorus) from animal waste and fertilization, and pathogen contamination.
Purpose of the Study:
- To provide a comprehensive overview of water quality issues associated with grazing animals.
- To highlight the significance of evaluating grazing impacts at both field and watershed scales.
- To discuss the primary concerns of nutrient loading and pathogen contamination.
Main Methods:
- Evaluation of water quality impacts at field and watershed scales.
- Analysis of nutrient loadings per land area and nutrient removals via livestock harvests.
- Measurement of nutrient loads in surface runoff from grazed lands and comparison with other land uses (row crops, forestry).
- Regression analysis of discharge concentrations against grazing animal units per land area.
Main Results:
- Erosion and sediment transport are linked to high-density stocking and poor forage stands.
- Nitrogen (N) and Phosphorus (P) are key nutrients of concern; elevated N can cause methemoglobinemia, while P contributes to eutrophication.
- Watersheds with concentrated livestock populations can discharge 5-10 times more nutrients than cropland or forestry watersheds.
- Pathogens from animal waste pose a significant risk, especially when animals access surface waters.
Conclusions:
- Grazing management significantly influences water quality outcomes.
- Mitigating negative impacts requires careful consideration of stocking density, forage health, and exclusion of animals from water bodies.
- Integrated watershed management approaches are essential for sustainable grazing practices and water resource protection.
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