in nitrogen than when the
seed was sown. It is thus possible by sowing these crops at suitable
intervals to keep the soil sufficiently supplied with nitrogen to grow
good crops other than legumes, adapted to the locality, without the
necessity for purchasing the nitrogen of commerce in any of its forms.
They may be made to more than maintain the supply of nitrogen,
notwithstanding the constant loss of the same by leeching down into the
subsoil in the form of nitrates, and through the more or less constant
escape of the same into the air in the form of ammonia, during those
portions of the year when the ground is not frozen.

They will do this in addition to the food supplies which they furnish,
hence they may be made to supply this most important element of
fertility, and by far the most costly when purchased in the market,
virtually without cost. The favorable influences which these plants thus
exert upon crop production is invaluable to the farmer. They make it
possible for him to be almost entirely independent of the nitrogen of
commerce, which, at the rate of consumption during recent years, will
soon be so far reduced as to be a comparatively insignificant factor in
its relation to crop production. It is possible, however, and not
altogether improbable, that by the aid of electricity a manufactured
nitrate of soda or of potash may be put upon the market at a price which
will put it within reach of the farmer. The power of legumes to increase
the nitrogen content in the soil should allay apprehension with
reference to the possible exhaustion of the world's supply of nitrogen,
notwithstanding the enormous waste of the same in various ways.

The more common sources of loss in nitrogen are, first, through the
leeching of nitrates into the drainage water; second, through oxidation;
third, through the use of explosives in war; and fourth, through the
waste of the sewerage of cities. When plant and animal products are
changed into soluble nitrates, they are usually soon lost to the soil,
unless taken up by the roots of plants. When vegetable matter on or near
the surface of the ground is broken down and decomposed, in the process
of oxidation, there is frequently much loss of nitrogen, as in the rapid
decomposition of farmyard manure in the absence of some material, as
land plaster, to arrest and hold the escaping ammonia. Through
explosives used in war there is an enormous vegetable loss of nitrogen,
as nitrate salts, w