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New Proportional Chemical Injection System for Improved Chemigation Uniformity with Center Pivots

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

Citation:  Paper number  032011,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13988) @2003
Authors:   Bradley A. King, Richard W. Wall, John P. Taberna, Jr.
Keywords:   Chemigation, Center pivot, Application equipment, Sprinkler irrigation, Variability

Constant rate chemical injection into center pivots equipped with an end gun and/or corner watering system results in chemical application errors of 12 to 42% due to system flow rate variations caused by the variable wetted radius of the system. Proportional chemical injection systems for center pivots currently on the market utilize a flow meter to adjust chemical injection rate. The typical installed piping arrangement for a center pivot system is not conducive to accurate and reliable flow rate measurement with flow meters. We have developed a proportional chemical injection system which uses direct measurement of end gun operating pressure and/or status of control valves along a corner watering system to calculate system flow rate for controlling chemical injection flow rate. This approach overcomes reliability problems associated with flow meters. Operation of the proportional chemical injection system was tested with N fertilizer application on a commercial center pivot equipped with an end gun and corner watering system. The proportional chemical injection system reduced the coefficient of variation in N concentration of the applied water by 61% compared to conventional constant rate chemical injection. The components of the proportional chemical injection system are described.

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