IRRIGATION SCHEDULING OF ALFALFA USING EVAPOTRANSPIRATION

This paper describes the Irrigation Scheduling Alfalfa (ISA) model, which is used to determine irrigation timing and amounts for scheduling the irrigation of alfalfa for up to nine cutting cycles. The model uses a water balance approach to estimate changes in soil available water content, which users employ to determine when and how much water to apply. Graphics are employed to assist users with the decision making process. Water stress is quantified as a function of the soil water depletion, and reductions in the actual crop evapotranspiration relative to full crop evapotranspiration are used to estimate yield reductions due to stress. The ISA model was developed using Microsoft Excel. IRRIGATION SCHEDULING ALFALFA MODEL This paper reviews the methodology used in the Irrigation Scheduling Alfalfa (ISA) model, which uses reference evapotranspiration (ETo) and crop coefficient (Kc) values to estimate well-watered crop evapotranspiration (ETc) using the single Kc approach corrected for rainfall and irrigation frequency. Crop coefficient curves are determined for each cutting cycle based on the input cutting dates and recent research. The ISA model includes the calculation of daily stres