Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/8/2004
Publication Date: 11/14/2008
Citation: Fisher, D.K. 2008. Simple and inexpensive lysimeters for monitoring reference-and crop-et. Proceedings of the 25th Annual International Irrigation Show, Tampa, Florida. Paper No. IA04-1117, CD-ROM, pg 161-169. Interpretive Summary: In order to properly irrigate cotton, the amount of water that cotton requires throughout its growing season must be known. Crop water requirements, or evapotranspiration (ET), are a function of crop variety, soil conditions, and environmental (weather) conditions. Previous work in quantifying cotton evapotranspiration has been done in other parts of the country, where environmental conditions are very different from those in the humid southeast. To better understand the water requirements of cotton in the southeast, a project was undertaken to measure cotton ET under local conditions. Automated, electronic weighing lysimeters are standard tools for measuring evapotranspiration. Two lysimeters were installed under a grass crop, the standard, reference crop for ET measurements. Two lysimeters were installed under a cotton crop, to measure cotton ET and to develop crop coefficients for use with weather-based ET-estimation methods. Grass reference ET and cotton ET measurements have been collected for two growing seasons and will continue to be collected each season for several more years. More accurate knowledge of cotton water requirements will benefit local producers, irrigators, agricultural extensionists, and researchers. By better understanding the changing water requirements of cotton throughout the growing season, the proper amount of water can be applied. More timely and efficient irrigations can result in more efficient use of water resources, improve yields, and reduce runoff.
Technical Abstract: Weighing lysimeters are standard tools for measuring evapotranspiration (ET). Planted with a grass crop, a weighing lysimeter can be used to verify or calibrate weather-based reference-ET estimates. Planted with an agronomic crop, a weighing lysimeter can be used to measure crop-water use or to develop crop coefficients for use with weather-based ET-estimation methods. Simple and inexpensive weighing lysimeters are being used to help schedule irrigation of cotton in Mississippi. The design, construction, installation, and operation of these instruments are presented.