WHAT IS MEANT BY DRY FARMING 11 



be produced by the ordinary processes of cultivation. 

 The degree ^of the aridity may be partial or total. It 

 may produce sparse growing shrubs as sage brush and 

 greasewood and even grass, but the production of grass 

 will be quite limited. Even the shrubs that can stand 

 drought best will not grow closely together, as, if they 

 should start thus, the moisture supply would not be 

 enough for each. It may be arid: (1) because of the 

 scant precipitation that falls on it; (2) because of the 

 lack of plant food in the soil ; (3) because of the pres- 

 ence in excess of certain substances in the soil, as alkali, 

 which are so unfavorable to plant life as to make it im- 

 possible to produce, until the substances inimical to 

 vegetation are removed or modified in their chemical 

 properties. These influences may act separately or in 

 conjunction. The more nearly they act in conjunction, 

 the greater is the degree of the aridity. More commonly 

 however, aridity is caused by an insufficient precipita- 

 tion. In the major portion of the area that is arid in the 

 western states, the soil is not only rich in the elements of 

 plant food, but it is in many instances remarkably so. 

 This is especially true with reference to the mineral 

 constituents, and it arises, first, from the store of these 

 in the original rock constituents from which the soils were 

 derived, and, second, from the little loss in the same 

 through leaching. Soils of this class are greatly pro- 

 ductive when irrigating waters are intelligently applied 

 to them. 



The amount of the precipitation- that results in arid- 

 ity is much influenced by the physical character of the 

 soil, by the degree of the evaporation, and by the season 

 at which the bulk of the precipitation falls. A soil un- 

 duly porous calls for more precipitation to render it 

 productive that one that has an amount of porosity most 

 favorable to the retention of moisture, without being 

 antagonistic . to aeration. The longer the season for 



