332 



Irrigation and Drainage 



If a soil decreases in fineness of texture as the 

 depth increases, then there may be a considerable 

 lateral spreading of the water due to gravity, and 



Fig. 83. Size and arrangement of soil grains as influencing pore space 

 and capillary waterways. 



this, aided by capillarity, will permit the furrows to 

 be placed farther apart and the water to be run more 

 slowly over the ground. 



Where a fine, loamy soil is underlaid at 3 to 5 feet 

 with a subsoil of much finer texture, through which 

 the water percolates slowly, then water may be led 

 quite rapidly through furrows some distance apart and 

 considerable quantities applied at once, depending 

 upon it to spread laterally by gravity, and to rise by 

 capillarity under the spaces between the furrows, in 

 this way wetting the larger part of the soil of the 



