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United States Department of Agriculture

Agricultural Research Service

Title: Manure Nutrient Content on Vermont Dairy Farms: Long-term Trends and Relationships

Authors
item Jokela, William
item Tilley, Joel - UNIV. OF VT-BURLINGTON
item Ross, Donald - UNIV. OF VT-BURLINGTON

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 23, 2009
Publication Date: March 9, 2010
Citation: Jokela, W.E., Tilley, J.P., Ross, D.S. 2010. Manure Nutrient Content on Vermont Dairy Farms: Long-term Trends and Relationships. Communications in Soil Science and Plant Analysis. 41:623-637.

Interpretive Summary: Manure nutrient analysis is an important component of nutrient management planning on dairy and other livestock farms. The University of Vermont Agricultural and Environmental Testing Laboratory has analyzed approximately 2400 manure samples from dairy farms in Vermont and neighboring states from 1992 to 2006. Annual values for nitrogen and potassium content showed year-to-year variation but no consistent trends. Phosphorus (P) content of manure, however, decreased by about 30% from 1992 to 2005. This presumably reflects a shift in dairy diets to avoid feeding excess P, a practice with both economic and environmental benefits. Most micronutrient levels showed no consistent trends over time. A notable exception was copper in liquid manure, which increased 5 fold, with most of the increase in the past 8 years. This was presumably the result of increased use of copper sulfate in foot baths. While average nutrient values are not reliable for making nutrient management decisions on individual farms, long-term data summaries can be useful to detect trends and to put individual analytical results in context.

Technical Abstract: Manure nutrient analysis is an important component of nutrient management planning on dairy and other livestock farms. The University of Vermont Agricultural and Environmental Testing Laboratory has analyzed approximately 2400 manure samples from dairy farms in Vermont and neighboring states from 1992 to 2006. The lab uses standard methods and participates in the Manure Analysis Proficiency Program. While average or median nutrient values are useful to provide rough guidelines, the high variability among the sample results (CVs of 40 to 80% or more for most nutrients) supports the need for lab analysis rather than reliance on book values for nutrient management planning. Annual values for N and K content showed year-to-year variation but no consistent trends. Phosphorus content of all manure types (liquid, solid, semi-solid), however, decreased by about 30% from 1992 to 2005. This presumably reflects a shift in dairy diets to avoid feeding excess P, a practice with both economic and environmental benefits. However, the last three years showed an unexplained increase in P content. Most micronutrient levels showed no consistent trends over time. A notable exception was Cu in liquid manure, which increased 5 fold, most of the increase in the past 8 years, presumably the result of increased use of copper sulfate in foot baths. While average nutrient values are not reliable for making nutrient management decisions on individual farms, long-term data summaries can be useful to detect trends and to put individual analytical results in context.

Last Modified: 12/22/2014
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