CHAPTER VII. 
RECLAIMING LOST NITROGEN. 
THE LOSS OF NITROGEN. 
In spite of these transformations of nitrogenous compounds, 
and partly because of them, there is a constant loss of nitrates from 
the soil. This loss is from the following sources: 
1. Sewage. Any animal or vegetable material that falls into 
the streams will, unless dissipated into the air, be carried to the 
ocean. Much nitrogen is brought to the city where it is used as 
human food and, as sewage, carried to the river and perhaps to 
the ocean, where it is lost. 
2. Drainage. The rains are constantly percolating through the 
soil and carrying away dissolved material. Since nitrates are soluble, 
large amounts are thus carried off to the rivers which drain the land. 
3. Decomposition and Denitrification. These processes, by 
reducing organic nitrogen to ammonia and by reducing nitrates 
to free nitrogen, cause large losses. These gases of course pass 
from the soil to join the atmosphere. Such processes are going 
on wherever organic matter is found in the river, the soil, the 
manure heap, sewage, and elsewhere. 
4. Direct Chemical Decomposition. A considerable portion 
of the earth's fixed nitrogen is dissipated by direct chemical processes. 
Explosions of gunpowder or other nitrate explosives liberate free 
nitrogen, which goes at once to join the nitrogen of the atmosphere. 
Through all these channels the soil is being constantly deprived 
of its nitrogen. Eventually it all reaches the atmosphere, for 
whether it enters the ocean or dissipates itself in the streams, 
soil, or elsewhere, by means of decomposition it finally allows the 
nitrogen to pass of as a free gas to join nature's inexhaustible supply 
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