76 THE MANURE HEAP AND SEWAGE. 
not allowing it to accumulate, and undergo the fermentation that 
inevitable 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 
considerable organic material in a partly decomposed condition 
that aids in forming a permanent humus. The texture of the soil 
is improved by this so that the final result is a soil superior to that 
containing only mineral fertilizers. The soil thus treated becomes 
more tenacious, richer, washes less with rains and is generally to 
be preferred. Mineral fertilizers, with the exception of nitrates 
may be mixed with manure. The nitrates, if thus mixed, would 
be lost by denitrification. 
SALTPETER PLANTATIONS. 
These nitrifying forces are not confined to the soil, but may 
occur in other localities, always resulting in the production of nitrates. 
Before the discovery of the nitrate beds of South America it was the 
custom of agriculturists to prepare their own nitrates by a simple 
process, not then understood, but now known to be due to nitrifying 
bacteria. The places where nitrates were thus formed were called 
saltpeter plantations, and the saltpeter was produced by exactly the 
processes we have already considered. The method was as follows: 
Masses of chalky soil were mixed with various organic bodies 
and the whole heaped into a pyramidal pile, rendered somewhat 
porous by the admixture of brushwood. The heap was still further 
furnished with fermentable nitrogen by frequently watering it with 
liquid manure. In this heap occurred the various kinds of nitrogen 
decomposition already mentioned, and later the nitrification process 
