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0018F\ "There are a number of new developments in technology and management which I feel will have a sizeable impact on water use by irrigated agriculture in the next several years, particularly as the value of water increases and the supply becomes more limiting. Some examples that come to mind are as follows: I. Subirrigation using perforated or porous underground pipe has the potential of being a new irrigation system that can reduce water application in the neighborhood of one-half. This will be an expensive system which may be largely restricted to higher-valued crops. 2. Major developments are being made in automation of irrigation systems, both sprinkler and surface systems. One important application for surface systems is the possibility of automating a cutback-furrow stream for graded furrows which would minimize or eliminate tail water runoff, 3. Recent research is indicating considerable potential for increasing the water-storage reservoir available to plant rooting and the ability to recharge the reservoir by deep tillage and profi Ie modification of slowly permeable soils. Those practices can reduce water application by reducing the frequency of irrigation and increasing soil-water storage from rainfall. 4. Improved timing of fewer irrigations in relation to critical stages of plant development and expected rainfall can considerably reduce irrigation water application and increase water-use efficiency. With many cropping system-rainfall conditions, rainfal I can be relied upon to furnish moderate to adequate soil moisture at planting time, thus el iminating the need for a preplant irrigation which may account for one-fourth to one- third of the total water used to grow a crop. Applying fewer irrigations wi II increase the potential for beneficial storage and use of rainfall, When such an approach is combined with applying a limited number of irrigations in relation to critical stages of plant development, particularly for such grain crops with drought tolerance I ike wheat and sorghum, both irrigation and rainfall are efficiently used except for rainfall that occurs soon after irrigation, The limited-irrigation approach can considerably reduce irrigation water appl ication while insuring sufficient water for an adequate yield, 5, Soil-water evaporation accounts for 40 to 50 percent of water lost during the crop-growing season as evapotranspiration from irrigated land and about 70 to 80 percent of rainfall during nongrowing periods, (Rainfall evaporation will be higher during nongrowing periods following an early preplant irrigation.) Reducing soil-water evaporation constitutes a major potential for reducing irrigation water needs. It can be done by using soil covers and mulches. A practical approach that I am interested 19.