Scheduling Irrigations Using Climate-Crop-Soil Data

Recent studies of surface irrigation systems (16,21,29) 4 indicate that irrigation scheduling practices, tithing and amount applied, have not changed significantly from those observed about 25 yr ago by Israelson, et al. (11). Attempts to relate observed irrigation efficiencies to field, soil, crop, and management characteristics generally have not been successful because the factors causing the large variations in timing and amount of water applied at each irrigation are so diverse that the resulting irrigation efficiencies appear to be random events with a broad, uniform distribution. The potential for better irrigation water management has; however, increased substantially during the past 15 yr because of better water control and measurement facilities (24), improved system design criteria (2), more reliable methods for estimating evapotranspiration (13), increased knowledge of each crop's response to soil moisture levels (9), and commercially available soil moisture instrumentation for timing irrigations (10)