84 DRY FARMING 



soil is not the least important of the problems of the dry 

 farmer. It may be considered under two heads : 



1. How to keep a supply of it continuously available 

 to the seeds in the soil or to plant roots, and 



2. How to make it serve its purpose most efficiently. 

 Of the three forms in which moisture occurs in the 



soil, viz., free water, capillary water and hygroscopic 

 water, only that in the capillary form is of immediate 

 value to growing plants. The small portion known as 

 hygroscopic moisture, which is present about the soil 

 particles when they are air dry is held so firmly that 

 plants cannot extract it. The free water, that portion 

 found filling the spaces between the particles of a soil 

 which is flooded, is of very great value as a source of 

 supply even though it cannot be drawn upon directly 

 and is sometimes harmful to plants. Free water when 

 present in the subsoil may be changed to capillary or 

 film water, in which form it may move up or down or 

 in any other direction or be held by the soil even against 

 gravity. It is in the capillary form only that water may 

 be drawn upon by plants. 



In the practice of crop growing it frequently hap- 

 pens that something is done which either lessens the 

 chance of the plant getting at the moisture in the soil or 

 what is of equally serious concern, makes it difficult or 

 impossible for the moisture in the subsoil to move to 

 where the seeds or plant roots are. Thus when coarse 

 manure or long stubble are plowed under in fall or 

 spring in preparing for a crop the next season, loose 

 open spaces are created between the seed bed and the 

 subsoil and the availability of even the capillary moist- 

 ure is interfered with. Similarly when coarse clods are 

 plowed under, or the plowing left in rolls, or the fur- 



