Variable-Rate Chemigation via Center Pivots
Publication: Journal of Irrigation and Drainage Engineering
Volume 145, Issue 7
Abstract
Center pivots can be used to achieve variable-rate chemigation—applying spatially variable dosages of agricultural chemicals within the same field. This paper first presents equations specifying how a center pivot and the associated chemical injection pump can be operated to vary chemical dosages among sectors of a circle or among arc-shaped zones. This paper then introduces a software tool that facilitates computations for variable-rate chemigation. This paper finally documents two field tests of commercial, uncustomized variable rate chemigation systems. In the catch can test, mean absolute relative error in zone-average adjusted chemical dosage was 17%. In the flow-proportional chemical injection test, the system chemical concentration remained within 5% of the average value despite a fivefold range in water flow rates. With rising popularity of variable-rate application and increasing development of variable-rate chemigation equipment, the time is ripe for applied research and extension of variable-rate chemigation via center pivots.
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Acknowledgments
Funding for a portion of this research was provided by the National Institute of Food and Agriculture, USDA, under award number 2016-68007-25066, Sustaining Agriculture through Adaptive Management to Preserve the Ogallala Aquifer under a Changing Climate. Funding for the other portion of this research was provided by the Daugherty Water for Food Global Institute through its graduate student support program. The chemical injection system was jointly sponsored by Agri-Inject and by University of Nebraska–Lincoln Testing Agricultural Performance Solutions (UNL-TAPS) program. The authors appreciate the assistance of Joshua Krautkramer at Agri-Inject in the installation and repair of the chemical injection system. The authors are grateful to Dr. Derek Heeren and Alan Boldt at University of Nebraska–Lincoln (UNL) for lending their collection of catch cans. The authors thank Turner Dorr and Jacob Nickel at UNL, Mike Nesbitt and Cooper Bollman at the Upper Republican Natural Resources District, and Glen Bowers at the Twin Platte Natural Resources District for their help with field testing. The authors are grateful for the input of the reviewers, which improved the manuscript.
Disclaimer
Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Nebraska–Lincoln is implied.
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Information & Authors
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Published In
Journal of Irrigation and Drainage Engineering
Volume 145 • Issue 7 • July 2019
Copyright
©2019 American Society of Civil Engineers.
History
Received: Dec 22, 2017
Accepted: Jan 22, 2019
Published online: May 11, 2019
Published in print: Jul 1, 2019
Discussion open until: Oct 11, 2019
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