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United States Department of Agriculture

Agricultural Research Service

Research Project: Management Strategies to Sustain Irrigated Agriculture with Limited Water Supplies

Location: Water Management Research

Title: Using models to determine irrigation applications for water management

Author
item Trout, Thomas

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 16, 2012
Publication Date: October 21, 2012
Citation: Trout, T.J. 2012. Using models to determine irrigation applications for water management. ASA-CSSA-SSSA Annual Meeting Abstracts. Cincinnati, OH Oct 21-Oct 24, 2012.

Technical Abstract: Simple models are used by field researchers and production agriculture to estimate crop water use for the purpose of scheduling irrigation applications. These are generally based on a simple volume balance approach based on estimates of soil water holding capacity, irrigation application amounts, precipitation, and daily estimates of crop evapotranspiration. Crop ET is estimated from ET of a reference crop, usually based on a version of the Penman-Monteith equation, and a crop coefficient that is commonly based on days or growing degree days since planting. This approach is common in the Western U.S. and is often referred to as the FAO-56 method. The approach requires daily data from a weather station, which is available in many irrigated areas in the western states. Since errors in daily ET accumulate over time, it is recommended that the method be supplimented by periodic soil water content measurements. The main weakness of the method is determining appropriate crop coefficients for the crop and conditions.

Last Modified: 12/21/2014