SOIL PHYSICS 467 



Their roots are often finely branched or divided and the small 

 rootlets are covered with minute hairs (Fig. 284). These root 

 hairs come into close contact with the film of water surround- 

 ing the small particles of soil and absorb the moisture from this 

 film as it is needed for plant growth. As the moisture in the 

 film is thus absorbed, more moisture rises from the deeper 

 portions of the soil to take the place of the absorbed moisture. 

 This moisture rises in the same manner and for the same rea- 

 son as kerosene rises in the wick of a lamp. It is said to rise 

 on account of CAPILLARITY. 



549. Need of Increasing and Conserving Soil Moisture. In 

 most regions, the soil contains sufficient moisture in the spring 

 and the early part of the growing season. But in many re- 

 gions the supply of soil moisture becomes too scanty to insure 

 the most rapid growth and full development of plant life later 

 in the season. In most portions of the United States the 

 farmer, gardener, and fruit grower find it desirable so to pre- 

 pare the soil in the fall or spring as to increase its capacity for 

 moisture and also to conserve the soil moisture as far as pos- 

 sible during the growing season. 



550. Increasing the Capacity of Soil for Moisture. The 

 capacity of soil for holding moisture depends upon several 

 conditions. In regions where the rainfall is likely to be defi- 

 cient, during the growing season, it is of the greatest importance 

 that the soil be so prepared as to increase as much as possible its 

 capacity for holding moisture. There are several ways in 

 which the capacity of the soil may be increased : 



1. Its capacity may be increased by FALL PLOWING . A con- 

 siderable portion of the annual precipitation in many regions 

 occurs during the winter months. If the surface of the soil 

 is left hard, smooth, and compact in the fall, much of the winter 

 precipitation will run off the surface and never enter the soil. 

 Fall plowing leaves the surface of the soil loose and open, rough 

 and broken, thereby tending to prevent the loss of this moisture. 



2. By increasing the amount of HUMUS (Art. 457) in the soil, 

 the capacity of the soil for holding moisture is greatly increased. 



