578 SOILS: PROPERTIES AND MANAGEMENT 



conserve their excreta. Yard manure generally refers 

 to mixed manures. The mixing usually occurs during 

 storage, either for convenience in handling or for the pur- 

 pose of checking losses and facilitating fermentation. 

 Thus, horse and cow manures are commonly mixed, since 

 the too rapid fermentation and probable loss of ammonia 

 in the former is checked, while at the same time a more 

 rapid and much more complete decay is encouraged in 

 the latter. 



The ordinary manure consists of two original compo- 

 nents, the solid and the liquid portion. As these con- 

 stituents differ greatly, not only in composition but also 

 in physical properties, their proportions must appreciably 

 affect the quality of the excreta and its agricultural value. 

 Litter added for bedding or for adsorptive purposes is 

 almost always an important factor, for while it prevents 

 losses of the soluble constituents it may at the same time 

 lower the value of the product for a unit amount. 



Farm manure ordinarily fulfills two functions which 

 are usually not so simultaneously yet clearly developed 

 in any other material that of a direct and that of an 

 indirect fertilizer. Consisting of 73 per cent of water 

 and only 27 per cent of dry matter, the percentages of 

 plant-food are necessarily low. As mixed farm manure 

 contains on the average 1 0.50 per cent of nitrogen, 0.25 

 per cent of phosphoric acid, and 0.60 per cent of potash, 

 considerable quantities of plant-food elements are added 

 in an ordinary application. Ten tons of average manure, 

 even if only one-half of the nitrogen, one-sixth of the 

 phosphorus, and one-half of the potash are readily avail- 

 able, is equivalent to 300 pounds of sodium nitrate, 60 



!See Analyses, Storer F. H. Agriculture, pp. 237-248. 

 New York. 1910. 



