A Rapid Assessment Tool for Determining Uniformity if Irrigation Type Manure Application Systems

Abstract

Zhengzhong Liu. A Rapid Assessment Tool for Determining Uniformity of Irrigation-Type Manure Application Systems. (Under the direction of Dr. Garry Grabow)

Due to the extent of the animal industry in North Carolina, the treatment of liquid manure is of great importance. Since liquid manure contains plant nutrients, it is usually treated through application to agricultural land through irrigation systems as a substitute or partial substitute for commercial fertilizer. However, land application of liquid manure needs to follow some guidelines in order to achieve economic goals as well as to protect the environment. Current guidences suggest calibration of land application equipment be performed once every three years by the “catch can†method, a time- and labor-consuming method. The research goals of this project were to investigate the relationship between liquid manure application uniformity and application system hydraulic measurements and then make tables of the predicted application uniformity for field use.

Trials were performed to test the manure application uniformity for different sprinkler types, nozzle types, gun models, nozzle diameters, system types, site types, gun models, and nozzle pressures. The wind speed and direction during the trials was monitored. Different overlaps were achieved by superposition, thereby allowing for assessment of multiple sprinkler overlap extents for one trial. The overlaps used for traveling gun systems reflected sprinkler (lane) spacings of 70%, 75%, 80%, 85%, and 90% of the wetted diameter, and those used for stationary systems were 50%, 55%, 60%, 65%, and 70% of the wetted diameter. Including superpositioned data, there were 722 records. Regression models were constructed using trial data through processes of main effect selection, collinearity checking, interaction term and quadratic term selection, parameter estimation, and residual normality testing. The variables “sprinkler spacing in percent of wetted diameter†and “wind speed†exist as quadratic terms in most of the models. Tables were made using predictions from the selected models. The model for stationary systems performs well with an adjusted R2 of 0.75 and tables of application uniformity showing the expected tendencies of application uniformity to predictive factors. The model for traveling gun systems does not perform as well as that for stationary systems. The adjusted R2 is only 0.14, though it is not unexpected due to the sampling variance of the “catch can†method.