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Show CONSUMPTIVE USE OF WATER IN IRKIGATION 1361 to twenty-five farms. The run-off, Bt, is not given for each farm, but the average, Rf, was &% of the quantity applied. Deducting 6% of the quantity for maximum crops to arrive at the quantity of irrigation water held on each farm and adding arbitrarily an allowance of 0.3 ft. for moisture absorbed from the stored winter precipitation and adding, further, 0.92 ft. for rainfall from April 1 to September 30, there results the farm consumptive use as given in Table 4. How closely this use, as given in the table, approaches the consumptive use is conjectural, as the magnitude of the percolation losses is not known and as it is subject to greater variation in actual farm irrigation than in field plot experiments heretofore reported. TABLE 3.-Fakm Consumptive Use (JJf) as Measured on Field Plots in the Snake Kiver Valley, Idaho, by Lewis. Crop. Vr on plots of high production. Uf on plots of average production 1.78 1.18 1.84 1.45 1.68 1.68 1.66 1.86 1.20 1.20 0.96 1.29 1.63 1.60 2.14 1.54 2.89 2.55 Wheat... Oats..... Barley... Peas..... Beans.... Corn..... Potatoes. Clover... Alfalfa... Mean, if crops are given equal weights.. 1.75 1.53 Investigations of the net duty of water in Sevier Valley, Utah, by Israelsen and Winsor (9) during the 7-year period, 1914 to 1920, gives some information concerning farm consumptive use. In these experiments, the quantities of water found necessary to deliver to the farm for sugar-beets, potatoes, and alfalfa, excluding farm run-off, Rf, were 2.5, 2.0, and 2.8 acre-ft. per acre, respectively. The crop-season rainfall was 0.3 ft., and assuming a draft on the soil moisture of 0.3 ft., the farm consumptive use, Uf, is as follows: Sugar-beets, 3.1; potatoes, 2.6; and alfalfa, 3.4 acre-ft. per acre. Further reference is made to these quantities in connection with a report for Uv for the Sevier Valley. TABLE 4.-Farm Consumptive Use as Determined by Hemphill in Cache la Poudrb Valley, Colorado. Crops. Maximum yield, in tons, or bushels per acre. Farm consumptive use for maximum yield per acre. Average yield, in tons, or bushels per acre. Farm consumptive use for average yield per acre. Sugar-beets............. Potatoes................ Alfalfa................. Barley.................. Wheat.................. Oats.................... 15.1 390.0 4.0 60.0 45.0 80.0 3.6 4.2 5.8 3.4 3.1 3.6 12.6 230.1 2.8 40.7 27.7 48.1 3.0 3.3 3.7 2.3 2.1 1.4 |
