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Evaluation of ET Based “Smart” Controllers

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

Citation:  2011 Louisville, Kentucky, August 7-10, 2011  1111515.(doi:10.13031/2013.38124)
Authors:   Charles L Swanson, Guy Fipps
Keywords:   Landscape Irrigation, Irrigation Scheduling, Smart Controllers, Evapotranspiration, Water Conservation

A smart controller testing facility was established by the Irrigation Technology Center at Texas A&M University in College Station in 2008. The objectives were to (1) evaluate smart controller testing methodology and to (2) determine their performance and reliability under Texas conditions from an end-user point of view. The end-user is considered to be the landscape or irrigation professional (such as the Licensed Irrigator in Texas) installing the controller. This report summaries the performance of eight smart controllers over an eight month (238 day) growing season in 2010. Controllers were programmed based on a virtual landscape that evaluated controller performance using multiple plant types (flowers, turf, groundcover, small and large shrubs), soil types (sand, loam and clay), root zone depths (3 to 20 inches) and other site specific characteristics. Controllers were divided into 2 categories, those which utilize on-site sensors to calculate or adjust ET or runtimes; and those which ET values are sent via cellular, radio or the internet. Controller performance was compared to total ETo, plant water requirement (ETc) and the weekly irrigation recommendation of the TexasET Network ( Results so far indicate that controllers using on-site sensors for calculating irrigation water requirements produced lower water requirements and were more often within the irrigation recommendations of the TexasET Network. Significant seasonal differences in controller performance were also found. Results also indicate problems in quantifying effective rainfall, particularly when using a rain sensor. Continued evaluation of ET based controllers is needed to identify the causes of inconsistency among controllers.

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