SECTION XL MOISTURE IN THE SOIL 



THE difference between a rich and a poor soil consists 

 largely in the fact that a rich soil is usually able to maintain 

 enough moisture, but not too much ; while the unproductive 

 soil does not hold enough water for the use of the plant 

 during periods of dry weather, and becomes too completely 

 saturated during wet weather. 



Clay soils hold water. Soils differ widely in the 

 amount of moisture that they can hold. Test this by filling 

 two tomato cans of equal size with thoroughly dried soil, 

 one of them with nearly pure sand and the other with the 

 stiffest clay you can find. Pack both soils thoroughly, and 

 gradually add equal amounts of water to each. Before 

 any dripping from the clay occurs, water will have begun 

 to drip freely from the sandy soil through the holes in the 

 bottom of the tin can. Thus it is seen that clay will hold 

 much more water than sandy soil. 



Capillary moisture. The water that drains away from 

 the soil is called free water. It is spoken of as free be- 

 cause it always flows toward the lowest point. If cans of 

 soil are allowed to drain for a day or two, although most 

 of the free water will be removed, the soils will still be 

 moist. The moisture remaining in the soil is called ctip 1 - 

 il la ry moisture. It is spread out over the surface of the 

 soil grains in such thin layers or films that it cannot col- 

 lect in drops and drain away. If a bag of pebbles is 



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