PLANT GROWTH IN DRY AREAS 107 



in the soil and carrying it down out of the reach of 

 plant roots and into the drainage water before it can be 

 taken up by the plants. The other is, excluding the air 

 when the soil becomes saturated. In such a condition 

 the transformations referred to practically cease. Satura- 

 tion also stays the process of tillage. In dry areas such 

 excess of water is seldom, and in a great majority of 

 instances never, present. Thus far, therefore, soils in 

 dry areas have a great advantage over soils in humid 

 areas. 



In the early part of the season, it aids in warming the 

 soil, which in turn favors germination and early growth. 

 These results follow the greater degree of warmth in the 

 water that falls at that season than is possessed by the 

 soil. When the soil becomes unduly warm, as in summer, 

 water falling on it from the clouds cools it, and such cool- 

 ing at that season promotes growth. It is only when mois- 

 ture, heat and air are present in the soil that the bac- 

 teria in the same can fulfill the ends for which they ex- 

 ist. Should any one of these be absent beyond a certain 

 degree, their activity ceases. 



Water is also the medium through which food is car- 

 ried to plants. This food is dissolved through the ac- 

 tion of water, and is held in solution by the same. While 

 in this condition it is taken up by the minute hairs which 

 are attached to the rootlets of plants, and is thence con- 

 veyed through the plants for their support and upbuild- 

 ing. The importance, therefore, of a sufficient supply of 

 water in the soil to accomplish this end will be appar- 

 ent, from whatsoever source it may be obtained. 



Reducing the loss of water. Since water in the soil 

 is so precious in dry areas, the importance of practical 

 measures that may be adopted for its maintenance cannot 

 be easily over-estimated. In various ways its loss may 

 be reduced. Prominent among these are the following: 

 (1) by storing it deeply in the soil; (2) by surface cul- 



