Improving the Chemical Nature of the Soil 83 



BEEF 



MILK 



BUTTER 



STRAWBERRIES 



. Showing the amounts of nitrogen, phosphoric acid, and potash removed 

 from the soil when 1,000 pounds each of beef, milk, butter, and strawberries 

 are sold. 



CORN 



WHEAT 



OATS 



B. Showing the amounts of the three most important plant foods removed 

 from the soil by growing 1,000 pounds each of corn, wheat, and oats. 



ALFALFA 



C. Showing the amounts of the three principal 

 plant-foods removed from and returned to 

 the soil by 1,000 pounds each of cotton 

 lint, cotton seed, and alfalfa. 



COTTON LINT 



COTTON SEED 



- 



Fig. 45. Tables showing the amount of mineral food substances removed and 

 returned to the soil by various crops. 



insoluble combinations that the plants could not absorb 

 it. This would not be the general rule, however. Usu- 

 ally, where the soil analysis shows a high per cent of 

 an essential element, fertilizing with substances con- 

 taining this element rarely give returns above the cost 

 of the fertilizer. The only safe rule by which to learn 



