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Table 2. Mta ll\A01 ]ULOOT DEPTII I7? AVATER USE <br /> <br />CROP <br />ROOTING: DEPTH* (FT) WATER INCHES USED/WEEK** <br />(May through September) <br />Alfalfa 4 1-2 <br />Corn 3.5 0.75-1.75 <br />Small Grains 3 1-2 <br />Pasture Grass 2 1 - 1.5 <br />Turf sass 1 or less 0.75-1.25 <br />*Adapted from: Sprinklers, Crop Water Use and Irrigation D"me, Weber County, Utah State University <br />Extension, ENGIt/BIEAVM/14, April 2001. <br />*"Adapted from Consumptive Use of Irrigated Crops in Utah, Utah Agricultural Experiment Station Research <br />Report No. 145. October 1994. <br />Consider a pasture in loam soil. The loam is estimated to absorb 0.5 inches (average intake rate of 0.3 - 0.8) of water per <br />hour (fable 1). Since loam soils need to be irrigated with linch of water/ foot (Table 1), and pasture roots are 2 feet <br />deep, (Table 2), apply 2 inches of water. <br />Sprinkler: If the sprinkler system puts out 0.25 inches of water per hour, run it for 8 hours to apply 2 inches. (0.25 <br />inches/hour x 8 hours =. 2 inches) <br />Flood: Since 2 inches of water will need to be applied, and the soil absorbs 0.5 inches/hour, water should flood the soil <br />for 4 hours. (0.5 inches/hour x 4 hours = 2 inches) <br />How talteim to Uvigaw? <br />Utah Weather Bureau data indicates that alfalfa uses 1 to 2 inches of water per week during the irrigation season of May <br />through September. The majority of alfalfa roots are in the top 4 feet of soil. If it is growing in a loam soil, it will have <br />access to 1 inch of usable water per foot. Thus, it has a potential soil water reservoir of 4 inches of water to draw from <br />without suffering drought-stress. In the middle of the summer when alfalfa is using 2 inches of water a week, it needs to <br />be irrigated every 2 weeks with 4 inches of water. In contrast, turfgrass has a 1-foot rooting depth, and in the same <br />soil needs to be irrigated once a week with 1 inch of water, or twice a week with 0.5 inches. ,Developed March 2003 <br />FOR MORE INFORMATION: <br />Utah. State University Extension <br />t/ <br />http://extension.tisu.edu/droujzh <br />Utah Division of Water Rights home page: <br />I7tt :Ia/na wnl,nr.state.ut.us/ then select "Publications" and <br />then "Consumptive Use '.Cables". <br />WATER UNITS & CONVERSIONS <br />one cubic foot = 7.48 gallons <br />one acre inch -= 3630 cubic feet <br />= 27,154 gallons <br />one acre foot 12-acre inches <br />Utah State University web site: sprinkler management = 43,560 cubic feet <br />information at httn_/iext.onsion.usu.edu/public:a then select = 325,851 gallons <br />"Irrigation Engineering". <br />450 gal./minute = 1 acre inch/hour <br />1 cubic foot/second <br />'r'ze4*d4v,9, 1 SW ea. ?race" <br />Utah State University Extension, is an equal opportunity employer, provides programs and <br />services to all persons regardless of race, age, sex, color, religion, national origin or disability. <br /> <br />62