Weighing Lysimeters for the Determination of Crop Water Requirements and Crop Coefficients

Weighing lysimeters are accurate instruments to measure crop evapotranspiration. Three weighing lysimeters, consisting of undisturbed 1.5- ×2.0-m surface area by 2.5-m depth cores of soil, were constructed and installed at the Texas Agricultural Experiment Station in Uvalde, Texas. Two lysimeters, each weighing approximately 14 Mg, were located beneath a linear irrigation sprinkler system and used in the field production of several crops commonly grown in the area. The third lysimeter was constructed and is used to measure reference ET from a well-watered, grass (ETos) located adjacent to the field lysimeters. Design construction, installation, engineering details and other considerations to ensure acceptable performance of the lysimeters are discussed. The lysimeter facility was developed to accurately assess crop water requirements of vegetables as well as other field crops grown in the Winter Garden region of Texas. Preliminary detection capability of the scale system is also reported.