318 SOILS 



the country where live-stock husbandry, in at least 

 one or more of its many branches, is not prac- 

 ticable. There is in progress an evolution toward 

 diversified farming, which is based very largely 

 upon the advantages of combining more or less 

 stock husbandry with all other types of farming. 

 Undoubtedly there are conditions when the keeping 

 of stock is impracticable, or when the same results 

 may be secured more advantageously by the use 

 of green-manures, by buying animal manure from 

 others, or by using commercial fertilisers. But 

 these cases are few as compared with the great 

 majority of American farms upon which stock 

 husbandry, in some form, ought to be one of the 

 chief means of maintaining fertility. Remember 

 the Flemish proverb: "No grass, no cattle; no 

 cattle, no manure; no manure, no crops." 



THE EXCRETORY THEORY OF SOIL FERTILITY 



There has been advocated during the last two or 

 three years a new theory of soil fertility, especially 

 as it relates to the rotation of crops. In the fore- 

 going pages are presented the most commonly 

 accepted beliefs and practices concerning soil fer- 

 tility; what it is and how it may be increased and 

 maintained to best advantage. Now comes a 

 radically different interpretation of the nature of the 

 problem from a few scientists, whose conclusions 

 nave been reached after extended study and 

 are therefore entitled to a very careful hearing. 



Do Plants Excrete? The most important point 

 in the new theory of soil fertility is the positive 

 statement that the roots of plants do excrete sub- 

 stances that correspond in function to the excretions 



