Principal Investigator: David L. Cochran (The University of Georgia)
Principal Investigator: Jerry L. Chesness (The University of Georgia)
Sponsor: GWRI
Start Date: 1981-04-01; Completion Date: 1982-06-30;
Keywords: Irrigation, crop water requirements, simulation modeling
Description:
A number of techniques are available for predicting irrigation water demands. However, many are applicable only to arid and semiarid climates where the probability of rainfall during the growing season is low. The rapid increase in irrigated acreage in the southeastern region of the U.S. dictates the need to develop methodologies suitable for humid climates.
A continuous simulation model was developed for predicting seasonal irrigation water requirements of crops. The model was derived by writing water balance equations for successive soil zones in an irrigated soil profile. The quantity of water infiltrating the uppermost zone was the difference between daily precipitation and runoff (according to the SCS equation for runoff volume). Zonal water volumes exceeding field capacity were passed into the next lower zone. Irrigation was called for whenever calculated soil water removal increased soil water tension to a preset level in the profile.
Input data to drive the model are: (1) historical or synthetic daily precipitation and pan evaporation values, (2) crop canopy growth factors; (3) soil water tension-content relationships, (4) irrigation water management depth and level (tension) and (5) SCS runoff curve number.
Daily measured values of soil water tension and irrigation amounts for nine crop (corn and soybeans) seasons were obtained from Dr. James Hook, Assistant Professor, Agronomy Department, Coastal Plains Experiment Station, Tifton, Georgia. Predicted seasonal irrigation water requirements averaged within 11.2% of measured values for eight of the crop seasons.