138 COItN CB0P8 



The problem of production on soils of this class is to 

 increase availability through use of manures and organic 

 matter, but in many cases the addition of some mineral 

 supplement is now necessary. 



FERTILIZERS FOR CORN 



99. Theory of fertilizer dosage. — If a perfectly sterile 

 sand were used as a medium for growing crops, and it were 

 desired to add fertilizing material, the logical method 

 would be to ascertain the relative amount of mineral 

 constituents in the plant under culture and add the minerals 

 in the same relative proportion. For example, the three 

 principal mineral constituents in the corn crop is shown in 

 Table XXVI to equal, in a 50-bushel corn crop, 74.0 pounds 

 of nitrogen, 11.5 pounds of phosphorus (or 26.3 phosphoric 

 acid), and 35.5 pounds of potassium (or 42.6 potash) ; 

 or the ratio would be about 6 : 2 : 3 for nitrogen, phos- 

 phoric acid, and potash. 



If the amount of fertilizer applied were to equal the 

 expected crop, then for a 50-bushel corn crop we should 

 apply about the following formula : 



74 lb. nitrogen = 400 lb. sodium nitrate 

 11.5 lb. phosphorus = 190 lb. acid phosphate 

 35.5 lb. potassium = 85 lb. muriate of potash 



Fertilizer for corn would not, however, be apphed to a 

 sterile soil, but to a soil usually containing enough miner- 

 als and nitrogen in an unavailable state for fifty to one 

 thousand crops. Organic matter and lime, and thorough 

 tillage, assist in making minerals available ; but after all 

 reasonably good treatment has been given, some one or 

 more elements may be found available only in such small 

 amount that the crop is limited. 



