142 IRRIGATION PRACTICE 



on the cultivated and on the non-cultivated pots were 

 252 and 603; on a sandy clay, 428 and 535, and on an 

 infertile clay, 582 and 750. It so happened that the Col- 

 lege loam was a self-mulching soil, on which ordinary 

 cultivation did not lessen direct evaporation. The favor- 

 able effect of cultivation was shown, however, in the great 

 reduction in the water-cost of dry matter resulting from 

 simple tillage. On every hand the proper cultivation 

 of the soil is shown to be a means of economizing water. 

 It prevents the direct evaporation of water from the soil; 

 it reduces the transpiration, and it makes it possible to 

 produce dry matter at a low water-cost. There is much 

 truth in the statement of the irrigation farmer that culti- 

 vation may take the place of water. Within certain limits, 

 it may be said that tillage is water. Water is indispensa- 

 ble for the production of crops, but the need for water 

 may be tremendously reduced if the upper layer of soil 

 is thoroughly cultivated. 



All other correct treatments of the soil have pretty 

 much the same effect. At the Utah Station, a series of 

 soils were cropped every year for three years, while another 

 similar series, receiving identical treatment, were left 

 bare for three years. The fourth year, all the soils were 

 planted to corn. The soils that had lain fallow for three 

 years invariably produced dry matter at a lower water- 

 cost than did those which has been cropped. The trans- 

 piration ratios for the fallow and the cropped soils were, 

 on the College loam, 573 and 659; on Sanpete clay 550 

 and 889, on clay 1,739 and 7,466. Irrigated soils are 

 cropped every year, and fallowing is scarcely ever prac- 

 tised under irrigation. In fact, none of the established 

 systems of irrigation-farming include the fallow year. 

 Under dry-farm conditions, on the other hand, fallow- 



