Spatially distributed control netowork for flow proportional chemical injection with center pivot irrigation

King, B.A. and Wall, R.W. and Taberna, J.P, Jr. (2009) Spatially distributed control netowork for flow proportional chemical injection with center pivot irrigation. Applied Engineering in Agriculture. 25(5):677-683.

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Abstract

The agricultural production practice of injecting a chemical into an operating irrigation system and applying it
to the field area with the water is known as chemigation. Chemigation is a widely adopted practice with center pivot sprinkler
irrigation. However, the practice of chemical injection at a constant rate with center pivot sprinkler irrigation systems
equipped with an end gun and/or swing‐arm corner watering system results in systematic chemical application errors ranging
from 7% to 21% due to systematic changes in system flow rate. Chemical injection proportional to center pivot sprinkler
system flow rate is one approach to reduce systematic chemical application errors. The objective of this project was to test
the feasibility of using real‐time monitoring of center pivot sprinkler irrigation system operating status to control chemical
injection rate proportional to calculated system flow rate, thus minimizing systematic chemical application errors. A spatially
distributed control network was developed to facilitate real‐time monitoring of end gun and swing‐arm corner watering
system operating status and pressure. The spatially distributed control network consisted of three network nodes at specific
locations along a center pivot sprinkler irrigation lateral that used the 480 VAC 3‐phase power cable on the center pivot
sprinkler irrigation system as the communication medium. The spatially distributed control network was installed on a
commercial 460‐m (1510‐ft) long center pivot sprinkler system equipped with an end gun and swing‐arm corner watering
system. Performance of chemical injection proportional to calculated flow rate based on real‐time center pivot sprinkler
irrigation system operating status was evaluated by injecting Rhodamine WT dye into the center pivot sprinkler irrigation
system water supply and measuring its concentration in the applied water. Mean dye concentration varied by 26% under
constant rate chemical injection and 2% under flow proportional chemical injection due to systematic changes in center pivot
sprinkler irrigation system flow rate. Use of the flow proportional chemical injection system reduced the coefficient of
variability in measured dye concentration of applied water by 54% from 0.100 to 0.046. Use of the spatially distributed control
network for calculating center pivot sprinkler system flow rate eliminates the need for straight sections of unobstructed piping
at the chemical injection site. Display and/or data logging of real‐time center pivot sprinkler operating status is an added
benefit of using the spatially distributed control network. This information provides the ability to monitor, diagnose, and
troubleshoot center pivot sprinkler system operation. Commercialization and adoption of the technology could reduce
systematic chemical application errors and facilitate maintenance and operation of center pivot sprinkler irrigation systems
equipped with an end gun and/or swing‐arm corner watering system.

Item Type:	Article
NWISRL Publication Number:	1328
Subjects:	Irrigation > Sprinkler irrigation > Center pivot Water
Depositing User:	Users 6 not found.
Date Deposited:	08 Jan 2010 03:38
Last Modified:	14 Oct 2016 14:51
Item ID:	1351
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/1351