IRRIGATION AND DRY-FARMING 713 



face flow, by seepage, and especially by evaporation, 

 without performing any useful service to the plant. 



610. Practices in dry-farming. The practice of dry- 

 farming may be divided into three groups : (1) the main- 

 tenance of such a condition of the soil at all seasons of 

 the year as will insure the complete absorption of the 

 rain- and sno\v-fall ; (2) the conservation of the stored 

 moisture by appropriate methods of tillage ; (3) the selec- 

 tion of drought-resistant crops and of rotations adapted 

 to the small use of water. 



611. Storage of water in the soil. In different regions 

 the rainfall occurs at different seasons. A loose, open 

 condition of the surface soil should be maintained during 

 that period. This may require deep plowing, and if the 

 subsoil is compact it may include subsoiling. Where 

 the precipitation comes as snow, the surface should be 

 rough so as to prevent drifting, in order that the resulting 

 water may be uniformly absorbed by the soil. Fall 

 plowing is an important factor where much of the pre- 

 cipitation comes in winter and the soil is compact. 

 Another reason for the maintenance of a ridged surface 

 is to reduce erosion by the high winds which frequently 

 occur in winter in dry-farming regions and which cause 

 the serious removal of the soil. The roughened surface 

 impedes the wind movement, and the moist soil at the 

 crest of the ridges resists erosion. 



612. Conservation of moisture. The conservation of 

 the moisture in the soil involves two things an increase 

 in the capillary capacity of the soil, and the prevention of 

 evaporation. Where the rainfall is low, the deep subsoil 

 is usually very dry. The rainfall penetrates to a limited 

 distance from the surface. Having loosened the subsoil 

 so that the rainfall is absorbed, the next step is to compact 



