Coefficient of Variation of Discharge from Liquid Manure Applicator Distribution Manifolds

Uniformity of liquid manure application across the tool-bar points is important to ensure proper nutrient supply for crop growth, to maintain producer confidence in nutrient availability, and for addressing water quality concerns. To date, no research has been performed at field-scale to determine the variability of liquid distribution across the tool-bar points, transverse to the direction of travel. In this project, six commercially-available, tank-mounted manifolds for liquid manure distribution were tested for coefficient of variation. Testing was performed using water and coefficients of variation were determined for application rates ranging from 18,708 liters per hectare to 56,124 liters per hectare by setting the manifolds under field conditions and using manufacturer specifications for operation. The tests were performed under three different slope conditions of 0, 3, and 6 percent to simulate cross-slope manure application. Coefficient of variation, calculated for the average application rate as measured across the tool-bar, was less than 20 percent for three of the six manifolds tested for the five application rates for all three slope settings. Only one of the manifolds tested had coefficient of variation less than 10 percent for all of the test settings. On the opposite end, coefficient of variation for one of the manifolds exceeded 100 percent. Results of the testing indicate that caution should be exercised to select the appropriate manifold when applying manure such that the lowest possible coefficient of variation is achieved