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Irrigation Control System

Stan Hicks and Robert Lascano


An irrigation control system was developed to calculate potential evapotranspiration (PET), a cotton crop coefficient (Kc ), evapotranspiration (ET), and to control irrigation application using a surface drip system. Irrigation treatments consisted of alternate and every row applications and irrigation application amounts of 0.1, 0.2, and 0.3" per day applied on a 3 day interval. Irrigation applications could not exceed the calculated crop ET minus rain on a 3 day period. The application amounts represent the range of well pumping capacities typical on the Texas Southern High Plains. The experimental design was 12 plots on 4 acres. Water flow to each plot was controlled by a solenoid valve and measured by a flow meter that produced a switch closure pulse for every gallon of water applied. The irrigation control system was a Campbell Scientific CR 10 datalogger with an SDM-CD16AC digital control expansion device and two SDM-SW8A expansion pulse counters. The CR10 recorded air temperature, relative humidity, windspeed and net radiation. PET was calculated by the CR10 based on a Penman-Monteith grass reference standard equation with the exception that net radiation was measured and not estimated. The CR 10 calculated cumulative heat units (HU), the crop coefficient (Kc ), cumulative crop ET minus rain, and water application amount. Every three days the system automatically applied the irrigation amounts for the three irrigation treatments. The CR10 was connected to a remote PC via a cellular phone. Irrigation application could be monitored and controlled by the remote PC computer. This control system is generic and can be adapted to a wide variety of irrigation systems.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pg. 409
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998