NATURAL MANURES. 55 



teen per cent of organic matter. The ash contains from 

 eight to ten pounds each of phosphoric acid and lime, 

 and six to eight pounds of potash ; while the organic 

 matter contains from eight to ten pounds of nitrogen. 



Its indirect value, however, is often quite as great as, 

 and frequently greater than, its direct value, — first, be- 

 cause of its vegetable matter, which materially improves 

 the absorbing and retaining power of soils ; and second, 

 because of the lower forms of life, or bacteria, contained 

 in it, which induce useful fermentations in the soil. 

 Not including the lime, the average ton of city manure 

 contains but twenty-eight pounds of actual fertilizer con- 

 stituents. 



Solid and Liquid Portions. — The nitrogen digested 

 from the food, as well as a large part of the potash, is 

 found in the liquid portions of the manure ; while the 

 nitrogen in the undigested portions, as well as a large 

 part of the phosphoric acid, is contained in the solid 

 residue. The nitrogen in the urine is largely in the 

 form of '^urea,'' a compound soluble in water, and is 

 easily decomposed; the potash is also soluble in water. 

 These constituents are, therefore, the most active. 



Sources of Loss in Manures. — Manures are sus- 

 ceptible to two direct sources of loss, the first of which 

 is due to fermentation, which results in the loss of ni- 

 trogen ; and the second is due to leaching, which may 

 finally result in a loss of all the constituents, though it 

 is confined largely to the soluble nitrogen and potash. 

 By fermentation, *he nitrogen in the manure is changed 

 to ammonia, usually in the form of a carbonate, which 

 is volatile, and escapes into the atmosphere. 



