SOIL MOISTURE AND DRY FARMING 81 



ceases, and where ascent may begin, when it becomes cap- 

 illary water, -which is very frequently the case in semi- 

 arid soils. In humid areas it frequently passes down un- 

 til it reaches ground water below, when it may move lat- 

 erally through the soil until it reaches some outlet, as for 

 instance, through springs. When the water table is not 

 too near nor too distant from the surface and when the 

 supply is constant, it renders great service to plants by 

 supplying them with water carried to the roots through 

 capillary action. Water occurs thus not infrequently in 

 the basins of semi-arid countries, more especially where 

 mountains occur. When thus found it comes from 

 higher levels. In its downward movement it finds a 

 stratum of subsoil that is usually sufficiently porous to 

 admit of free movement* laterally. Such movement of 

 water in the soil is spoken of as seepage. The presence 

 of such water at proper levels will frequently maintain 

 good crops in areas where they will completely fail when 

 not supplied from such a source. 



When the air spaces between the soil grains are 

 completely filled, the maximum of gravitational water 

 is present. The capacity of dry farm soils thus to hold 

 this water will, of course, vary, but on the average it 

 is from say 35 to 40 per cent, of the dry weight of the 

 soil. In humid soils such water moves downward after 

 every heavy rain, until it reaches the water table, that 

 is, providing it is not too distant, when it flows out into 

 streams. In dry areas the water table in the ordinary 

 .sense of the term is seldom present. In such areas 

 it goes down as far as the force of gravity can take it, 

 which is, of course, dependent upon the supply. It is 

 thus stored in the subsoil as capillary water until drawn 

 upon by plants in process of growth, in areas that are 

 properly cultivated. The great importance of such wa- 

 ter to the dry farmer cannot easily be overestimated, 

 hence it should be his aim to increase this supply to the 



