DETERMINATION OF CROP COEFFICIENTS (Kc) FOR IRRIGATION MANAGEMENT OF CROPS

摘要

Weighing lysimeters are used to measure crop water use during the growing season. By relating the water use of a specific crop to a well-watered reference crop such as grass, crop coefficients (Kc) can be developed to assist in predicting crop needs using meteorological data available from weather stations. Seven lysimeters, consisting of undisturbed 1.5 x 2.0 x 2.2 m deep soil monoliths, comprise the Texas Agricultural Experiment Station -^sUvalde lysimeter facility. Six lysimeters, weighing about 14Mg, have been placed each in the middle of a one hectare field beneath a linear LEPA irrigation system. A seventh lysimeter was established to measure reference grass ETo. Corn, sorghum, spinach, onion, cotton, and wheat were grown over the last five years in the lysimeter fields. Daily water use was measured on 5-min intervals. Crop water requirements, KC determination, and comparison to existing FAO KC values were determined over a 2 or 3 year period depending on the crop.