190 SOILS 



fore and claims, and receives, its due. A large 

 share of the unprecedented progress in American 

 agriculture during the past twenty-five years is due 

 to the more general use of these two coordinate 

 farm practices, each of which has the same general 

 purpose in view to give the crop an adequate 

 and equable supply of moisture. 



The surplus water in a soil, which it is purposed 

 to remove by drainage, all comes from rainfall; 

 but rarely is it only that which falls upon the soil 

 itself. The water may flow upon it as surface 

 drainage from higher land, or it may come from 

 below, being rain that has fallen upon higher land, 

 sunk into the soil, followed a ledge of rock or layer 

 of impervious soil, and finally found its way to the 

 Surface of the lower land as a spring, oozing from 

 a hillside or bubbling up from the subsoil. Quite 

 often level land which is not surrounded by higher 

 land, and which contains only the water that falls 

 upon it, is benefited by drainage because the soil 

 is shallow. In such cases the most beneficial 

 result of drainage may be, not to remove excess 

 water, but to increase the amount of moisture that 

 the soil can hold a seeming paradox that is 

 explained farther on. 



WHEN DRAINAGE IS NEEDED 



Two kinds of soils need draining; those that 

 have too much water, and those that are too shal- 

 low. The signs of poor drainage are obvious. 

 Swamps, marshes, meadows and all other low land 

 on which water stands for any considerable time 

 may be drained, provided there is fall enough to 

 secure an outlet. These low lands may be those 

 which collect surface drainage, or seepage from 



