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Factors Affecting Uniformity of Irrigation-Type Manure Application Systems

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Applied Engineering in Agriculture. 28(1): 43-56. (doi: 10.13031/2013.41285) @2012
Authors:   Z. Liu, G. L. Grabow, R. L. Huffman, J. Osborne, R. O. Evans
Keywords:   Irrigation, Liquid manure, Land application, Field verification, Regression analysis.
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Liquid manure is usually treated through application to agricultural land using irrigation systems. Land application of liquid manure needs to follow established guidelines in order to achieve economic goals as well as to protect the environment. Guidance at the time of this study in North Carolina suggested calibration of land application equipment be performed once every three years by the "catch can" method, a time- and labor-consuming method. The goals of this project were to investigate the relationship between liquid manure application uniformity by using data from historical uniformity assessment trials and from additional trials conducted during the study, and to use the results to provide guidance in developing a simplified field method for uniformity assessment. Trials were performed to test the liquid manure application uniformity for different irrigation system types, sprinkler types and models, nozzle types, nozzle diameters, and nozzle pressures. Wind speed during the trials was monitored. Different sprinkler overlaps were achieved by superposition, thereby allowing for assessment of multiple sprinkler spacings for each trial. Regression models were constructed using historic and study-period trial data and a process of main effect selection, collinearity checking, interaction term and quadratic term selection, parameter estimation, and normality testing of model residuals. The model for stationary systems performed well with an adjusted R2 of 0.72 and predicted application uniformity showed the expected tendencies with changes in predictive factors. The model for traveling gun systems did not perform as well as that for stationary systems; the adjusted R2 was only 0.33. The results of this study were used to amend uniformity assessment requirements to a simple procedure requiring measurement of sprinkler nozzle pressure, wetted diameter, and sprinkler spacing.

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