THE ROTATION OF CROPS 



Such a yield of crop would take from the soil the 

 following amounts of plant food per acre : 



Now suppose we sell the lint of the cotton, keep- 

 ing all the rest of the plant, including the seed, on 

 the farm and turning it back into the soil. 



Of the corn suppose we sell one-half the grain 

 and keep the other half and the fodder for use on 

 the farm. 



Suppose the oats be made into oat hay and be fed 

 on the farm and the cowpeas be turned under. 



Assuming that the cowpeas take half their nitro- 

 gen from the air. 



This will mean that in the course of three years 

 we take out of the soil of each acre in the crops : 



Nitrogen. 

 258 pounds. 



Phosphoric Acid. 

 103 pounds. 



Potash. 

 219 pounds. 



but we return to the soil in crop refuse and manure 

 from the stock: 



Nitrogen. 

 256 pounds. 



Phosphoric Acid. 

 87 pounds. 



Potash. 

 197 pounds. 



