BOARD OF NATURAL RESOURCES AND CONSERVATION

Abstract: Biweekly and total irrigation amounts and irrigation scheduling practices were monitored at representative sites in central Illinois during the 1988 and 1989 growing seasons. The purpose was to gather baseline information on average quantities of irrigation water used in normal and drought years and on the general efficiency of irrigation operations in the subhumid climate of Illinois. Soil water-holding capacity is the most important factor in determining irrigation amounts, explaining about 65 percent of the variability in irrigation totals. Other important factors in explaining irrigation variations include weather changes, individual farmer idiosyncrasies, and crop differences. In general, irrigation farmers in Illinois appear to be applying appropriate amounts of irrigation water at appropriate times in the growing season, based on their soil type, crop type, and total evaporative losses