Soil Fertility and Its Preservation 39 



FIG. 22. Hillside land that once was farmed. The topsoil is rapidly being 

 carried away by rains. 



of artificial cropping in a few years ? An answer to this 

 question may suggest a mode of farming more in keep- 

 ing with the ways of Nature, which will not deplete the 

 soil. 



If it were universally true that a long-used field How we 

 became valueless, the prospect before us would be dis- farmlands 

 couraging. But there are regions which under careful may be kept 

 management have been producing good yields for many 

 centuries. Indeed, some of the worn-out farms of the 

 East are now, with modern scientific treatment, being 

 made profitable again. 



Three reasons can be assigned for the continued 

 fertility of the Western prairies. First, the sod, formed 

 by a close mesh of grass roots, served as a sponge to hold 



