452 MISCELLANEOUS FARM SUBJECTS 



To illustrate this : Suppose one applies 200 pounds to the acre 

 of the average commercial fertilizer, and then harvests a crop of 60 

 bushels of corn. He will remove in the corn crop about twice as 

 much phosphorus, ten times as much potassium, and twenty-five 

 times as much nitrogen, as he applied in the fertilizer. The facts 

 are that he has not only removed more plant food than was fur- 

 nished in the fertilizer, but he has taken more from the soil itself 

 than he could have taken without the fertilizer, because the quick 

 acting fertilizer has stimulated the early growth of the plants and 

 enlarged the root systems and thus enabled the crop to draw more 

 heavily upon the soil. Besides this, the fertilizer contains manu- 

 factured landplaster, which is one of the most powerful soil stimu- 

 lants. Suppose the farmer grows oats the next year without fertiliz- 

 ing, applies another 200 pounds per acre for the following wheat 

 crop, and then with no further additions grows two crops of timothy 

 and clover hay. He can thus wear his soil out more rapidly than 

 he could without the stimulating action of the fertilizer. This 

 would not be the case if he would apply more plant food than his 

 crops remove. 



There is a third way in which commercial fertilizers may possi- 

 bly injure the soil. The value of steamed bone meal and of raw 

 rock phosphate is due to the tricalcium phosphate which they con- 

 tain. When these materials are treated with sulfuric acid, the in- 

 soluble, neutral tricalcium phosphate is converted into soluble, acid 

 monocalcium phosphate; and, at the same time the sulfuric acid is 

 converted into calcium sulfate, which is essentially the same com- 

 pound as plaster of Paris, a well known material with strong ce- 

 menting properties. It is a fact, that with the long continued use of 

 acid phosphate, alone or in mixed fertilizers, the soil usually becomes 

 harder and more compact. That is to say, it develops a bad physical 

 condition. In large part, this is probably due to the destruction of 

 humus or organic matter, but to some extent it is very possibly due 

 to this manufactured cementing material. 



There are, indeed, cases in which, apparently, the fertilizer has 

 been injurious. A farmer, for example, finds that the application 

 of 200 pounds per acre of acid phosphate will increase his crop con- 

 siderably. He makes this application for three or four years, then 

 finds that his crop is smaller than it was to start with, or he dis- 

 continues the application of fertilizers and does not get much of a 

 crop. Apparently, the acid phosphate had injured the soil. 



The injury has been caused by the method of farming and not 

 by the fertilizer. The acid phosphate supplied only phosphoric acid 

 to the soil. The increased crop increased the demand for nitrogen 

 and potash so that the quantity in the soil has diminished until it 

 is no longer the phosphoric acid but the nitrogen or potash which 

 controls the yield of the crop. The one-sided application of plant 

 food has aided in the exhaustion of the soil in the other plant food. 

 The other plant foods can, of course, be restored by using fertilizers 

 containing them. 



