24 DRY FARMING IN RELATION TO RAINFALL AND EVAPORATION, 



The cost of producing an acre of wheat on summer-fallowed land 

 in Utah, including seed and harvesting, is about $7, a which with 

 wheat at 75 cents would be equivalent to about 9 bushels of wheat 

 per acre. On this basis wheat production proved profitable during 

 the three years in Juab and Tooele counties. In San Juan County 

 in 1904 the rainfall was less than 7 inches and the crop was a failure. 

 During the next two years, however, the rainfall was about 20 inches 

 and good yields were obtained. The yields at the other three sta- 

 tions during the three years do not cover the cost of growing the crop. 

 The records of Juab County show clearly the influence of the amount 

 of rain on the yield, the yields varying from 15 bushels with a rainfall 

 of 11 inches in 1905 to 31 bushels with a rainfall of 18 inches in 1906. 

 Jardine emphasizes the importance of having at least 4 inches of 

 rain during the growing season from April 1 to July 20. 



To summarize, in Tooele and Juab counties, Utah, profitable 

 yields were obtained when the rainfall exceeded 13 inches. At the 

 other stations in Iron, Sevier, and Washington counties a rainfall 

 of 15 inches was not sufficient to produce profitable crops. The 

 evaporation from a freely exposed tank of water has been found to 

 be about 42 inches during the six summer months in Juab County. 

 We may conclude, then, that with this amount of evaporation an 

 annual rainfall of 13 inches represents about the minimum under 

 which farming can be profitably carried on in the Great Basin. 6 



MINIMUM RAINFALL NECESSARY FOR WHEAT PRODUCTION IN THE 



COLUMBIA BASIN. 



There is probably no other region in the United States where dry 

 farming is successfully conducted with so low a rainfall as in the 

 Columbia Basin, in southern Washington and northern Oregon. 

 This is the result of a combination of favorable conditions. The 

 evaporation is considerably lower than in the Great Basin, the rains 

 come mainly during the winter season and are not torrential, and 

 the basaltic soils absorb the rainfall readily. As we have already 

 seen, the system of alternate cropping and summer fallow is especially 



« Grace Brothers, who operate a large farm in Juab County, Utah, find the average 

 cost of growing wheat on summer-fallowed land to be $6.85 per acre. This figure 

 includes all charges except an interest charge for the land. (See Second Annual 

 Report Dry-Farming Congress, p. 170.) 



The cost of growing spring wheat on fall-plowed land in Minnesota, as given by 

 E. C. Parker and T. P. Cooper, ranges from $4".30 (on a large farm) to $6.40 per acre. 

 These figures do not include land rental or the cost of hauling the grain to market. 



Other things being •'equal, it is to be expected that wheat production under the 

 system of alternate cropping and summer fallowing would be somewhat more ex- 

 pensive than under the annual cropping system, as in Minnesota, owing to the increased 

 cost of maintaining the summer fallow. 



b Prof. L. A. Merrill, of the Utah station, places the minimum annual rainfall for 

 profitable dry farming in that section at 12 inches. 

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