36 AGRICULTURE FOR BEGINNERS 



after year. This is not a good practice and sooner or later, 

 will wear out the soil completely, because the soil elements 

 that furnish the food of that constant crop are soon exhausted 

 and good crop production is no longer possible. 



Why is crop rotation so necessary ? There are different 

 kinds of plant food in the soil. If any one of these is used 

 up, the soil of course loses its power to feed plants properly. 



FIG. 25. GRASS FOLLOWING CORN 



Now each crop uses more of some of these different kinds 

 of foods than others do, just as you like some kinds of 

 food better than "others. The crop, however, cannot, as 

 you can, learn to use the kinds of food it does not like : 

 it must use the kind that nature fitted it to use. Not only 

 do different crops feed upon different soil foods, but they 

 use different quantities of these foods. 



