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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF WATER MANAGEMENT TECHNOLOGICES FOR THE MID SOUTH

Location: Crop Production Systems Research Unit

Title: Simple weighing lysimeters for measuring reference and crop evapotranspiration

Author
item Fisher, Daniel

Submitted to: International Journal of Agricultural and Biological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 9, 2012
Publication Date: N/A

Interpretive Summary: Knowledge of crop evapotranspiration (ET) is important in scheduling irrigations, optimizing crop production, and modeling evapotranspiration and crop growth. The ability to measure, estimate, and predict evapotranspiration and crop water requirements can result in better satisfying the crop’s water needs and improving water use efficiency. Weighing lysimeters have been used for many years to measure and study water use, and to develop crop-coefficient functions necessary in estimating ET. Lysimeters were designed, constructed, and installed to monitor ET from a reference (grass) surface and from a cotton field to quantify water use in the humid southeast region of the United States. Daily water use of grass and cotton, in mm/day, have been collected for three growing seasons and will continue to be collected each season for several more years. The data will be used to evaluate weather-based ET models and to develop crop coefficient functions suitable for use under local conditions. Local producers, irrigators, agricultural extensionists, and researchers will benefit from more accurate knowledge of cotton water requirements. Better understanding of the changing water requirements of cotton throughout the growing season, and the ability to estimate and predict water use, will result in more timely and efficient irrigations, more efficient use of water resources, and improved yields.

Technical Abstract: Knowledge of cotton crop evapotranspiration is important in scheduling irrigations, optimizing crop production, and modeling evapotranspiration and crop growth. The ability to measure, estimate, and predict evapotranspiration and cotton crop water requirements can result in better satisfying the crop’s water needs and improving water use efficiency. Weighing lysimeters have been used for many years to measure and study water use, and to develop crop-coefficient functions necessary in estimating evapotranspiration. Electronic weighing lysimeters, consisting of a steel outer tank and inner tank, electronic loadcell assemblies, and a PVC drain system, were designed, constructed, and installed. Each lysimeter cost approximately US$1700 (in 2001) in materials, required two people and 40 hours of labor to construct, and were installed by two people using minimal excavation and hand tools. Evapotranspiration data have been collected beginning in 2003, under grass and crop covers on a daily and seasonal basis. The design, construction, installation, and performance of these simple, electronic weighing lysimeters are described and discussed.

Last Modified: 8/27/2014
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