AGE AND KIND OF ANIMAL 151 



pens that the phosphoric acid and potash in the com- 

 mercial 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 

 contained but also because it makes the inert plant 

 food of the soil more available and exercises such a 

 favorable influence on the water supply of crops; hence 

 it is justifiable to assign the same value to the ele- 

 ments in well-prepared farm manures as to those in 

 commercial fertilizers. 



If well-prepared stable manure is not worth $2.50 

 per ton, then too much, accordingly, is paid for com- 

 mercial forms of plant food. 



INFLUENCE OF AGE AND KIND OF ANIMAL 



180. Manure from Young and Mature Animals. — 



The manure from older animals is more valuable than 

 that from young animals, even when fed the same 

 kind of food. This is because more of the phosphoric 

 acid and nitrogenous matters are retained in the body 

 of a voungf 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 of the nitrogen of the food is used for repair pur- 

 poses and subsequently voided in the manure, while 

 with younger animals more of the nitrogen of the food 

 is retained for the construction of new muscular tissue. 



