AGRICULTURE. 21 



of capillary moisture takes place rapidly, but can only be maintained 

 through a relatively short soil column. In such soils the water table 

 may remain within a few feet of the surface without danger of alkali 

 accumulation. In the case of the alluvial soils of finer texture and 

 compact structure the capillary movement takes place more slowly, 

 but is capable of being maintained through a much greater vertical 

 distance. In this case it becomes necessary to lower the water table 

 to a greater depth, which should generally be from 6 to 10 feet, de- 

 pending upon rapidity of drainage, cultural methods employed, and 

 the character of crops for which the land is used. 



In the southern and west-central parts of the valley of good slope 

 and covered by the San Luis series occasional open ditches, accom- 

 panied with cultural and irrigation practices designed to prevent 

 waste of water, would probably prove sufficient to control the 

 drainage conditions. In the more northern districts covered by the 

 heavier soils of compact structure, installation of underground drains 

 will be necessary in places, although the prevailing conditions could 

 be greatly improved by open ditches. Stream courses could be 

 utilized to some extent as drainage outlets, but some enlargement and 

 straightening of these channels would prove advisable. Efficient 

 and comprehensive drainage of the northern portion of the valley 

 would call for organization on the part of the landowners and super- 

 vision by competent engineers. The available fall measured along 

 the trough of the valley is relatively slight, amounting to about 65 

 feet between Moffat and the Rio Grande. To obtain this, consider- 

 able excavating in the southern part of the valley w r ould be necessary. 

 To justify the expense incurred in operations of this magnitude, the 

 profit accruing from increased productiveness of the soil must be 

 more than sufficient to bear the original cost with interest charges 

 thereon. With the rapid advance in values of western irrigated 

 lands and the agricultural opportunities offered in this valley, a 

 comprehensive project for draining the entire district should be 

 feasible. Transmission of electric power from adjacent mountain 

 water-power sites at a cost low enough for pumping from shallow 

 subsurface waters also offers some future possibilities in connection 

 with irrigation and drainage. 



Besides drainage surface flooding will be necessary for the recla- 

 mation of lands badly affected with alkali. In this process a system 

 of checks must be formed in order that water may be held on the land 

 constantly during the leaching process. The efficiency of this method 

 of alkali removal has been demonstrated by the Bureau of Soils in 

 a number of cases involving much greater difficulties than would be 

 encountered in the San Luis Valley. 1 



*See Bulletins 42, 43, and 44 and Circulars 11 and 12, Bureau of Soils, U. S. Depart- 

 ment of Agriculture. 



