CHAPTEE V. 



SOIL IMPROVEMENT BY DRAINAGE AND IRRIGATION. 



Water in the soil is essential to the growth of crops. 

 There are soils which are barren simply from lack of 

 sufficient moisture. An excess of water in the soil is 

 always injurious, sometimes fatal to crops. There are 

 plants which thrive in soils saturated with water, or 

 even covered with it, but these are not the common 

 crops of the farm. Before any land can be used to 

 the best advantage it must be able, either naturally 

 or by artificial means, to rid itself of surplus water. 



The rain-fall is the primary source of the water in 

 the soil. If a jfiece of land is too wet, it is because 

 the water which comes to it cannot readily enough 

 flow off or through it. The immediate source of the 

 water may be either the direct rain-fall or water which 

 flows from higher lands. This last may flow down 

 over the surface, or come up from below in springs; 

 in some cases it may ooze out from hillsides or up 

 from the sub -soil. 



Some soils have good natural drainage, even when 

 the rain-fall is abundant. The natural tendency of 

 water is to flow downward, either directly into the 

 soil, or over the surface if this be inclined. If the 

 surface soil admits water freely and the sub-soil is 

 open to a considerable depth, or if a porous soil be 

 underlaid with rocks with many crevices in them, even 

 level land will rid itself readily of surplus water. In 

 such soils there will be little or no water, even after 

 heavy rains, in holes dug in the ground; there may 



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