50 THE PRINCIPLES OF AGRICULTURE 



69. The free water of the soil is found at 

 varying depths. Frequently it comes to the sur- 

 face and oozes out as springs. Again it is many 

 feet below the surface. The supply is main- 

 tained by rainfall, that part which is not held 

 by capillary attraction or removed by surface 

 drainage passing down to the level of the free 

 water. In soils which are very porous and 

 open, as gravelly soils, a large part of the rain- 

 fall passes down quickly, and such soils are 

 said to be "leachy." With soils that are fine 

 and compact and impervious, as in many clays, 

 the water runs off by surface drainage, and 

 not only is the supply of capillary water not 

 increased to any perceptible degree, but the 

 surface flowing removes valuable plant -food, 

 causes erosion, and increases dangers from 

 floods. Under these circumstances rainfall may 

 be a detriment. 



3. How the Moisture -holding Capacity of the 

 Soil May be Increased 



3a. The capacity of the soil 



70. The first step toward utilizing the water 

 of the soil is to so fit the land that the rainfall 

 may be stored. In the winter months a large 

 percentage of the rainfall is removed by surface 



