Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2002
Publication Date: 11/1/2002
Citation: DAVIS, J.G., IVERSEN, K.V., VIGIL, M.F. NUTRIENT VARIABILITY IN MANURES: IMPLICATIONS FOR SAMPLING AND REGIONAL DATABASE CREATION. JOURNAL OF SOIL AND WATER CONSERVATION. 2002. v. 57 p. 473-478. Interpretive Summary: The variability of nutrient contents in manure makes accurate recommendations for manure application difficult. The objective of this research was to evaluate the variability within and among samples of animal manure. The chemical analysis of feedlot beef, dairy, horse , sheep, chicken and swine manure was determined by sampling 6 to ten different livestock operations for each manure type and comparing the results to values found in the literature. We found that manure in Colorado tended to be drier and have lower ammonium levels then literature values but had higher phosphate (P) and potassium (K) levels. We found that on average, 25 sub-samples must be taken to be within 10% error of the true value of the manure source for nitrogen (N), P and K characterization of solid manures. To evaluate ammonium and nitrate values of the source over 100 sub-samples must be taken for a representative sample which is not, for most cases, practical or realistic. The data-set gives producers and livestock operators an idea of the difficulty in expecting a reliable manure loading rate for crop fields when no sampling is done.
Technical Abstract: The variability of manure nutrient levels within and across farms makes manure sampling and development of reliable tabular values challenging. The chemical characteristics of beef, dairy, horse, sheep, and chicken solid manures in Colorado were evaluated by sampling six to ten different livestock operations for each manure type and comparing the results to values found in the literature. Due to the semi-arid climate of Colorado, manure tends to be drier and have lower ammonium (NH4-N) levels and higher phosphate (P205) and potash (K20) levels than those reported in the Midwest. Within-farm variability was assessed by analyzing ten sub-samples from each of nine manure sources. Coefficients of variation were calculated and the sample numbers necessary to achieve 10% probable error were determined. On average, about 25 sub-samples are necessary for nitrogen (N), phosphorus (P), and potassium (K) characterization of solid manures, but determining NH4-N and nitrate (NO3-N) concentrations requires over 100 sub-samples to form a representative sample, due to their relatively low concentrations. Data from Colorado, Utah, and New Mexico were combined to form a Mountain West Manure Database. The manure types, with a minimum of 72 farms represented in the database, have narrow confidence intervals. Until we have adequate sample numbers (>72 farms) to establish reliable table values based on local data for all manure types, manure sampling will be recommended.