114 FIRST PRINCIPLES OF AGRICULTURE. 



In any or all of these lines, however, certain groups 

 of crops may be more profitable than others. This is 

 because it has been found to be more desirable in the 

 long run to have a variety, one following the other in 

 a definite rotation. In the cotton and sugar producing 

 States of the South, and the wheat growing States of the 

 Northwest, rotation is least practised, while in the East- 

 ern States and the Central West, rotations are the rule. 



The practice of growing different crops in rotation, 

 while largely a matter of conditions, does possess cer- 

 tain advantages, based upon scientific principles, as 

 having reference to the character of growth and feeding 

 capacities of plants, and upon business principles, as hav- 

 ing reference to a better division of labor and a more 

 certain income. 



The Advantages of Rotations. The advantages of 

 rotations may be stated as follows : 



1. The feeding capacities of plants differ, certain of 

 them requiring more of one particular element than of 

 another ; certain are surface feeders, and others send 

 their roots deep into the subsoil. The growth of a 

 variety of plants with different capacities, therefore, 

 prolongs the period of profitable culture, or retards soil 

 exhaustion. 



2. The growing of but one crop leaves the soil bare 

 at certain seasons of the year, while a variety permits 

 of a continuous growth and covering of the soil. Soils 

 suffer loss when lying idle; they are improved by the 

 growth of crops. 



3. The continuous growth of one crop renders it more 

 liable to insect attack, and to the development of dis- 



