$2 THE MANURE HEAP AND SEWAGE 
Fresh and Ripened Manure.—The transformations which we 
have considered constitute what is called the ripening, rotting, or 
composiing of manure. They are clearly similar to those changes 
already considered as taking place in the transformations in the 
humus, but rendered more intense by the concentration of the 
manure heap. It is evident that manure is of no value to plants 
until it has undergone these transformations, and equally evident 
that the transformations may, and some of them do, go on in the 
soil after the manure is mixed with it as well as in the manure heap. 
Indeed, they will probably go on better in the soil, and in some 
important respects it is an advantage to incorporate the manure 
with the soil while fresh rather than to wait for it to ripen. We 
have noticed that the loss from decomposition and denitrification 
is slight when these processes occur in the soil, while they are 
considerably higher when the ripening occurs in the concentrated 
manure heap. ‘The loss is especially large from the liquid manure 
in warm weather, which, if kept in tanks or allowed to accumulate 
with the manure pile, will undergo a very rapid ammoniacal 
fermentation resulting in large losses of nitrogen. If, however, 
it is mixed at once with the soil the ammonia is fixed as fast as 
formed by the soil ingredients, is soon nitrified, and the loss is 
largely prevented. There has thus come to be recommended the 
practice of spreading the manure upon the soil as quickly as con- 
venient, not allowing it to accumulate, and undergo the fermenta- 
tion that inevitably means loss of nitrogen. Whether this will 
always be feasible will depend upon conditions on the individual 
farm; but it is certainly to be highly recommended in all localities 
where climatic conditions and the exigencies of farm occupations 
make it possible. 
It is to be borne in mind that in using manure as a fertilizer 
the soil receives advantages that are not derived from mineral 
fertilizers. Not only does the manure contain a considerable list 
of substances of value to the crops, present in small quantities 
only, and not present in mineral fertilizers, but manure contains 
