CHAPTER XVI. 



MANUKIAL VALUE OF FEEDING STUFFS. 



In many parts of the United States the soil is now so depleted of 

 fertility that those who till it are forced to use commercial fertilizers 

 in order to secure remunerative crops. The commercial fertilizers 

 sold in this country during the year 1907 amounted to 4,451,523 

 tons. 1 At $20 per ton, a reasonable valuation, we have a total of 

 nearly $90,000,000 paid in a single year by farmers, planters, and 

 gardeners, principally in the Atlantic and Gulf States, for com- 

 mercial fertilizers. In the year 1907 there were purchased in Massa- 

 chusetts 85,000, in Ohio 140,000, and in California 21,000 tons of 

 commercial fertilizers, while Georgia led all the states, using nearly 

 800,000 tons. 



376. Composition and value of fertilizers. Of the constituents 

 which plants remove from the soil, only three need ordinarily be 

 replaced, viz. nitrogen, phosphoric acid, and potash. Phosphoric 

 acid and potash, when naturally lacking, or when they have been 

 carried off in crops or animals sold, must be replaced by buying 

 fertilizer or by applying the manure made from feeds. The nitro- 

 gen may, however, be indirectly obtained from the air by raising 

 legumes. In practice much nitrogen is purchased along with phos- 

 phoric acid and potash. 



Barnyard manures benefit the soil because the vegetable matter 

 they contain forms humus, helps retain moisture, improves its phys- 

 ical condition, etc. ; but for directly feeding the plant their worth 

 is in the nitrogen, phosphoric acid, and potash they contain. The 

 selling price of a commercial fertilizer is based on its content of 

 nitrogen, phosphoric acid, and potash, and because of the enormous 

 quantity used thruout the civilized world each of these constituents 

 has a recognized price, which fluctuates no more than that of any 

 other standard article of worldwide commerce. In this country 

 the average price of these ingredients to those who buy in large 

 quantities is about as follows : Nitrogen 18, phosphoric acid 5, and 

 potash 5 cents per Ib. 



The officials of the Ohio Station, 2 after much practical work, give 

 to the elements of fertility in farm manures the same value they 



1 American Fertilizer, Jan. 1909. 2 Bui. 183. 



17 241 



