AMOUNT OF FERTILIZER APPLIED 



37 



acid, and 3 pounds of potash are carried per 100 pounds of fertilizer. 

 Amount of Fertilizer Applied. No attempt is made to apply 

 enough fertilizer to furnish all the crop needs, as the crop will secure 

 part of its elements from the soil. Nor are the elements applied in 

 the same proportion required by the crop, as the soil is usually 

 most deficient in only one element. Phosphorus is the element most 

 often needed by grain crops. The Indiana Experiment Station rec- 

 ommends a 2-8-4 - fertilizer for wheat, in that state, and the follow- 

 ing table illustrates the relation between the composition of a 20- 

 bushel crop of wheat and 100 pounds of the fertilizer. 3 



Fertility Removed Compared With That Supplied 



Most cereals require fertilizers rich in phosphoric acid, while root 

 crops and legumes require a higher proportion of potash, and grass 

 crops require nitrogen mostly. The following proportions are typical 

 examples : 



Grain crops 2-S-4 to 3-8- 5 



Root crops 2-6-6 to 4-8-10 



Grass crops . . . 4-6-9 to 9-4- 6 



The amount applied varies ordinarily from 100 to 300 pounds per 

 acre. Each farmer must work out the problem by experience on his 

 own land. 



Ordinarily, a complete fertilizer is used, but often only a single 

 element, as phosphorus or potash, is all that is needed. 



2 The formula thus given expresses the fertilizers in percentage in the 

 order given in the above table. 



3 Indiana Experiment Station Circular 23, p. 22. 



