CROPS AND SOIL IMPROVEMENT 



the amounts of nitrogen, phosphoric acid, and 

 potash that he should apply to a particular field, 

 their availability, and their cost. Let us assume 

 that he has found 300 pounds of a fertilizer con- 

 taining 3 per cent nitrogen, 10 per cent phosphoric 

 acid, and 6 per cent potash to be an excellent 

 application for wheat on a thin soil that is to be 

 seeded to clover and timothy. This fertilizer 

 contains 3 pounds of nitrogen to each 100 pounds. 

 He applies 300 pounds of the fertilizer per acre, 

 or 9 pounds of nitrogen. The fertilizer contains 

 10 pounds of phosphoric acid to the 100 pounds. 

 He thus applies 30 pounds of phosphoric acid per 

 acre. The fertilizer contains 6 pounds of potash 

 per 100 pounds, and he therefore applies 18 pounds 

 per acre. What he has really learned, then, is 

 that an acre of this land, when seeded to wheat, 

 needs 9 pounds of nitrogen, 30 pounds of phos- 

 phoric acid, and 18 pounds of potash. It is in 

 these terms he should do his thinking, and the 

 matter of fertilization becomes simple. 



In the general farming of the Pennsylvania 

 experiment station, it is the practice to depend 

 upon nitrate of soda as the source of a fertilizer 

 for wheat. Manufacturers claim that sulphate 

 of ammonia and tankage would be better. The 



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