FARM MANURES * 169 



number of years must be considered and also its in- 

 fluence in permanently increasing the value of the land. 



It is sometimes stated that the phosphoric acid and 

 potash in stable manure i$ not so soluble as that in 

 commercial fertilizers, and consequently is worth less. 

 While not so soluble in the form of manure, it fre- 

 quently happens that the phosphoric acid and potash 

 in the commercial fertilizers become, through fixation 

 processes, less soluble when mixed with the soil than 

 the same elements in stable manure. 



Stable manure is valuable not only for the fertility con- 

 tained but also because it makes the inert plant food of 

 the soil more available and exercises such a favorable in- 

 fluence on the water supply of crops ; hence it is justi- 

 fiable to assign the same, if not a higher, value to the 

 elements in well-prepared farm manures as to those in 

 commercial fertilizers. 



INFLUENCE OF AGE AND KIND OF ANIMAL 



187. Manure from Young and from Mature Animals. 

 -The manure from older animals is somewhat more 

 valuable than that from young animals, even when fed 

 the same kind of food. This is because more of the 

 phosphoric acid and nitrogen are retained in the body 

 of a young animal. It is not so much a difference in 

 digestive power as a difference in retentive power. In 

 older animals the proportion of new nitrogenous tissue 

 produced is much less than in young animals, and more 



