Scheduling irrigation events based on crop use allows growers to meet the water demands of crop production wile reducing both the risks of over- and underwatering. Together with improvement of irrigation system efficiency, the integration of the crop water use concept to irrigation scheduling may additionally aid growers in adhering to policies designed to conserve water.
UCCE has partnered with the Department of Water Resources (DMR) to generate weekly Etc reports for almond, pistachio, citrus, raison grapes, wine grapes, walnuts, and stone fruit. The Etc report is an estimate of the weekly soil moisture loss for each crop based on weather data gathered from CIMIS (California Irrigation Management Information System) stations. For the southern San Joaquin Valley, the report is based on data from the following six CIMIS stations: Merced, Parlier, Lemon Cove, Panoche, Five Points, and Stratford. For each crop, local UCCE farm advisors have monitored leaf out in the spring to make estimates of when to start the current irrigation season. Because leaf out may vary extensively by variety, the leaf out date estimates are selected at the approximate midpoint for a given crop. To use the Crop Water Use Report, select the crop of interest as well as the closest CIMIS station to the block in question to determine the approximate water use for the past week as well as the accumulated water use in the current season. Additionally, the report allows growers to estimate water use in irrigation systems with varying efficiencies, and to estimate the number of gallons applied per tree or vine over the prior week. Last, the Water Use Report provides an estimate of the next week's ETc based on an average from previous years.
The Crop Water Use Report is located on the UCCE Tulare County website (https://cetulare.ucanr.edu/) under the agriculture section in the Nut, Prune, and Olive Programs. It is also emailed out weekly from the UCCE Fresno County office. If you would like to be added to that electronic mailing list, please send an email to Mae Culumber (cmculumber@ucanr.edu).
The Etc reports provide valuable estimates of crop water use but are not a substitute for a grower's direct measurement of water stress using tools such as the pressure chamber. The water use report, however, does provide a “cheat sheet” for growers to use as a reference for their irrigation practices. Growers should consider local weather conditions, the exact leaf out dates of varieties under their management, the efficiencies of their irrigation systems, soil type, and historic water use and crop production information to customize irrigation practices at each site.
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