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United States Department of Agriculture

Agricultural Research Service

Title: The Use of on-Farm Quick Tests to Estimate Dairy Manure Nitrogen

Authors
item Van Kessel, Jo Ann
item Reeves Iii, James

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2000
Publication Date: August 1, 2001

Interpretive Summary: Manure nutrient analyses performed rapidly, on the farm could assist farmers in applying appropriate levels of manure to cropland. An experiment was conducted to evaluate six Quick Tests for their accuracy in predicting manure nitrogen concentrations. Quick Tests included the hydrometer, electrical conductivity meter and pen, reflectometer, Agros N Meter, and Quantofix-N-Volumeter. Samples (107) were collected from dairy farms in five northeastern states. Samples were analyzed by traditional laboratory methods and using each of the Quick Tests. Estimated N concentrations determined by each Quick Test were regressed against laboratory-determined values. The hydrometer performed poorly as a predictor of total N, however, Quick Test prediction of ammonia-N was accurate. The strongest prediction was with the Quantofix-N-Volumeter followed by the Agros N Meter, the reflectometer, and the electrical conductivity meter and pen. When the samples were split into slurries and solids, predictive equations were stronger for the slurries than for the solids. These data indicate that, several Quick Tests are viable options for estimating N in dairy manures.

Technical Abstract: An experiment was conducted to evaluate six Quick Tests for their accuracy in predicting manure nitrogen concentrations. Quick Tests included the hydrometer, electrical conductivity meter and pen, reflectometer, Agros N Meter, and Quantofix- N-Volumeter. The hydrometer was used to predict total N, while the remaining tests were used to predict NH4+-N. Samples (107) were collected from dairy farms in five northeastern states. Samples were analyzed for total N and NH4+-N by traditional laboratory methods and using each of the Quick Tests. Manure compositions ranged from 1.4% to 38.6% DM, 0.09% to 0.94% total N, and 0.02% to 0.47% NH4+-N. The estimated concentration of N or NH4+-N determined by each Quick Test was regressed against laboratory-determined values. The hydrometer did not perform well as a predictor of total N, however, Quick Test prediction of NH4+-N was accurate. The strongest prediction of NH4+-N was with the Quantofix-N-Volumeter followed by the Agros N Meter, the reflectometer, and the electrical conductivity meter and pen. When the samples were split into high (> 12%) and low DM (£ 12%) groups, the r2 for the regression equations were higher for the low DM group than for the high DM group. These data indicate that, several Quick Tests are viable options for estimating NH4+-N in dairy slurries and solids.

Last Modified: 10/25/2014
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