PHYSICAL PROPERTIES OF SOILS 



soil many spaces which are capable of taking up water 

 in the same way. . The height to which water can be 

 raised by capillarity de- 

 pends upon the size and 

 arrangement of the soil 

 particles, it may be to a 

 height of several feet. 

 Ordinarily, however, the 

 capillary action of water 

 is confined to a few feet. 

 The arrangement of the 

 soil particles influences 

 greatly the capillary power 

 of a soil. Usually from 

 30 to 60 per cent of the 

 bulk of a soil is air space ; 

 by compacting, the air 

 spaces are decreased ; by 

 stirring, they are increased. 

 In soils of close texture, 

 as heavy clays, an increase 

 in air spaces results in an 

 increase of capillary spaces 

 and of water-holding capacity, while in other soils, as 

 coarse sandy soils, increasing the air spaces decreases 

 the capillary spaces and the water-holding capacity. 

 The best conditions for crop production exist when the 

 soil contains water to the extent of about 40 per cent 

 of its total capacity for saturation. 



FlG. 13. Showing Rise of Water in 

 Capillary and other Tubes. 



