CROP-ROTATION 503 



certain types of soil. Cherries and peaches succeed best 

 on a lighter soil than apples may be best grown on. 

 Muck soils are eminently adapted to the growth of celery, 

 onions, etc. With the extension of careful soil and crop 

 surveys, these relations are becoming better known and 

 are extending from groups of plants to species and 

 varieties of plants. By the same methods our informa- 

 tion concerning these relations must be extended until 

 the production of crops rests upon definite knowledge 

 of the plant requirements on the one hand, and the soil 

 capacity and the means available to alter the soil 

 environment on the other hand. Really intelligent hus- 

 bandry can rest only upon the basis of exact knowledge 

 concerning these two groups of facts and principles. 



V. RELATION OF SOIL PRODUCTIVENESS TO CROP- 

 ROTATIONS 



At an early time in the development of agriculture, 

 it was understood that a succession of different crops 

 upon any piece of land gave better returns than one 

 crop raised continuously. The plan of changing the 

 crops grown each year thus became customary, and 

 the universality with which it was practiced by Euro- 

 pean peoples shows that its value must have been dis- 

 covered independently in many communities, as ideas, 

 particularly agricultural ones, traveled very slowly in 

 the middle ages. 



In Great Britain and some of the countries of Europe, 

 crop rotations have been most systematically and effec- 

 tively developed. This has been the natural result of 



