214 BACTERIA AND SOIL FERTILITY 



the soil better than will equivalent quantities of commercial fer- 

 tilizers. This is true in the case of continuous wheat, barley, 

 potatoes, mangels, and sugar-beets. 



The value of the manure produced in the United States can 

 be seen from the following: 



"According to recent statistics there are in the United States in 

 round numbers 19,500,000 horses, mules, etc., 61,000,000 cat- 



Pic^ 43. — Beets grown on manured and unmanured soil. (Photo by Pittman.) 



tie, 47,000,000 hogs and 51,600,000 sheep. Experiments indi- 

 cate that if these animals were kept in stalls or pens throughout 

 the year and the manure carefully saved, the approximate value 

 of the fertilizing constituents of the manure produced by each 

 horse or mule annually would be $27, by each head of cattle 

 $20, by each hog $8, and by each sheep $2. The fertilizing value 

 of manure produced by the different classes of farm animals of 

 the United States would, therefore, be for horses, mules, etc., 

 $526,500,000; cattle, $1,220,000,000; hogs, $376,000,000; 

 and sheep, $103,200,000 — or a total of $2,225,700,000. 



''It is conservative to state that fully one-third of the manure 



