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United States Department of Agriculture

Agricultural Research Service

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

Authors
item VAN KESSEL, JO ANN
item Reeves Iii, James

Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 1999
Publication Date: N/A

Technical Abstract: Nutrient analyses performed rapidly, on the farm could be useful for determining appropriate manure application rates. This study was designed to evaluate Quick Tests for their accuracy in estimating manure N (total) or NH4+-N concentrations. Evaluated Quick Tests were the hydrometer, electrical conductivity meter and pen, reflectometer, Agros N Meter, and Quantofix-N-Volumeter. The hydrometer predicts total N and P and the other tests predict NH4+-N. Manure samples (107) were collected from dairy farms in five states. Samples were analyzed for total N and NH4+-N by traditional laboratory methods, and for total N or NH4+-N using each of the Quick Tests. Manure dry matter (DM) ranged from 1.4% to 38.6%; total N was 0.09% to 0.94%; and NH4+-N was 0.02% to 0.47%. Quick Test estimations of N or NH4+-N were regressed against laboratory estimates. In all cases, linear regressions were significant (P < 0.01). The strongest relationship for prediction of NH4+-N was with the Quantofix-N-Volumeter (r2 = 0.95; slope = 0.98). The Agros N Meter and the reflectometer also predicted NH4+-N with relative accuracy (r2 = 0.81 and 0.91; slope = 0.99 and 0.84; for Agros and reflectometer, respectively). The r2 for the relationship between conductivity and NH4+- N was 0.87 and 0.89 for the meter and pen, respectively. The hydrometer did not perform well as a predictor of total N (r2 = 0.48; slope = 0.56). Samples were also split into high (> 12%) and low (ó 12%) DM groups. In all cases, the regression of the predicted vs. laboratory N value was significant (P < 0.01), and the r2 was higher for the low DM group than for the high DM group. These data indicate that several Quick Tests are viable options for measuring NH4+-N in dairy manure.

Last Modified: 9/10/2014
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