THE MOISTURF IN THE SOIL 55 



have already seen (57, 75-78) that draining in- 

 cn^ases tlu' (h^jtth of the soil ; so do«^s dtH'j> plow- 

 ing. I'apillarity is incroasod hy lincly dividing 

 or pulverizing the snii. 



S(i. Incn'asing the capillarity increases the 

 inoisturL'-holding capacity of soils in two ways : 

 it enables the soil to actually hold more inois- 

 tiir<' jt'T square inch ; it enables it to draw 

 up ninisturc from the free water of the lowei- 

 subsoil (t ).')). 



SI. I5y the action of cajtillary attraction, 

 moisture moves from one layer of soil to another 

 (()«)), usually from the lower to the u]>per, to 

 »nj>j>ly the place of that whi<'h has Ixmmi used 

 by plants, or which has been lost by ev;i]»oia- 

 tjoii. The rapidity of movement and the force 

 .with which it is held depend ujion various 

 <M)nditions. A soil in whicli \\\r particles are 

 soniewhat large, as in sandy or gravelly soils, 

 may, if well compa<'ted, show «'onsiderable ra- 

 pidity of movement, but weak jiower to retain 

 moisture. The tiner the division <»f the soil 

 particles the greater is the surface presented. 

 In linely divid«'d clay soils, the movement of 

 capillary water is slow but the retaining power 

 is great. Occasionally it happens that the par- 

 ticles are so fine that the spaces ilisappeai-, and 

 there is produced a condition through which 

 moisture and air cannot pass. This state of 



