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Show 1360 CONSUMPTIVE USE OF WATER IN IRRIGATION the different irrigations being shown by dotted lines, and the average found by weighting the results according to the number of tests is shown by heavy lines. Harris did not report the seasonal draft of each crop on the soil moisture. For purposes of comparison, this has been assumed to be the same as that found by Widtsoe. Moreover, to make the results still further comparable, the depths of water applied, according to the heavy lines of the charts prepared by Harris, have been selected corresponding to the respective crop yields used in connection with Widtsoe's data, that is, for 21.3 tons of sugar-beets, 267.0 bushels of potatoes, etc. On these bases, Table 2 has been prepared. The values given in this table show fair agreement with those obtained from Widtsoe's work, except for the alfalfa and oats. According to Fig. 5 of Utah Station Bulletin 118, a yield of alfalfa of 4.3 tons per acre would require the same consumptive use as found by Widtsoe for 4.7 tons, namely, 3.3 ft. The maximum yield of oats according to the 17 years' work reported by Harris is slightly less than the 80.7 bushels per acre used in Widtsoe's work. A yield of 74 bushels per acre, according to the curves by Harris, would have been produced by a consumptive use of 2.5 ft., the quantity required to produce 80.7 bushels in Widtsoe's work. TABLE 2.-Consumptive Use Approximations Based on the Field Plot Work of Widtsoe and Harris at the Utah Agricultural Experiment Station. Crops. Yield, in tons or bushels per acre. Depth of water applied, in feet. Depth of soil moisture and rainfall used, in feet. Consumptive use, in acre-feet per acre. Sugar-beets Potatoes.... Alfalfa..... Corn........ Wheat..... Oats........ 21.8 207.0 4.7 99.2 45.7 80.7 1.50 1.67 3.33 1.67 1.83 2.33 0.86 0.52 1.25 0.52 1.15 0.81 2.4 2.2 4.6 2.2 2.5 3.1 Farm Consumptive Use Lewis' Idaho Work.-Lewis (11) measured the quantity of water used by nine important crops in the Snake River Valley, near Twin Falls, Idaho. He divided his observations into two groups: (1) Those on the better plots that produced high yields; and (2) those on which average yields were produced. His data are summarized in Table 3. It will be noted that in the better plpts the seven grain crops and also the potatoes consumed less than 2 acre-ft. per acre. The alfalfa consumed the largest quantity and the clover the next largest, the average for all the crops being 1.75 ft. on the better plots and 1.53 ft. on the average plots. It is probable that these magnitudes represent the farm consumptive use, Uf, for the Twin Falls area more nearly than the consumptive use, U, since the experimental conditions very likely permitted some deep percolation. Hemphill's Colorado Work.-Working in the Cache la Poudre Valley, Colorado, during 1916 and 1917, Hemphill (8) measured the water applied |