CHAPTER III. 



SOIL MOISTURE AND PREPARATION OF THE SOIL. 



y^.— SOIL MOISTURE. 



It is evident from the foregoing experiments 

 that the particles of soil and, therefore, of the 

 spaces between them, vary in size. When the 

 soil is dry most of the spaces are filled with air, 

 but when the soil becomes wet the air is driven 

 out by the water. 



I. Kinds of Moisture. 



1. Ground U^ater. — The water which perco- 

 lates through the soil under the influence of 

 gravity until it reaches an impervious layer of 

 hard-pan, or rock, is called the free or ground 

 water of the soil. Above the hard-pan, or rock, 

 is a layer — varying in thickness — of saturated, 

 or water-soaked, soil. It is from this free water 

 that the supply is obtained for springs and wells. 

 In dry weather it is drawn upon by capillary 

 action to furnish the moisture for vegetation, 

 but if this free water is allowed to stand too 

 near the surface of the soil it is injurious to 

 most plants. In soils of close texture it be- 

 comes necessary to remove the surplus water by 

 drainage. 



2. Capillary Water is that which is held in 

 the spaces between the soil particles by capillary 



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