32 MOISTURE IN THE SOIL 



Free water. Water occurs in the soil as free water. 

 The water in a well, or which stands in a post hole 

 when dug in a wet time, comes from the free water in 

 the soil. The free water of the soil finds its way out 

 by drainage, appearing as springs where it comes to 

 the surface. For most crops free water should not 

 come closer to the surface of the soil than from two 

 to four feet. 



Water brings food to plants. Water is the carrier 

 by which plants obtain their food from the soil. A 

 constant current is slowly passing upward from the 

 roots and evaporating from the leaves into the air. 

 Thus a large amount of soil moisture passes from the 

 ground into the growing plants and then into the air 

 as water vapor. One half of all the moisture that falls 

 on the land in the form of rain or snow soon evaporates 

 directly from the soil. As the moisture evaporates 

 from the surface of the soil, more soil water moves 

 up from below, and thus much moisture is lost which 

 might be used by the growing crop. One of the objects 

 of tillage, by making a mulch of loose soil, is to prevent 

 evaporation at the surface of the ground, and thus save 

 the soil moisture for the crop. 



Sources of water. In humid regions, the moisture 

 is stored in the soil by the falling of rain or snow. In 

 the farm lands of dry regions, water is applied to the 

 soil by irrigation. Snow or rain falls upon the moun- 

 tains in the arid regions, and the water is carried by 

 streams from the mountain slopes through the more 



