is piled against the side of the stable where water from
the roof can drip on it, as is often the case, or if it is piled in an
exposed place where heavy rain can beat on it, the rain water in
leaching through the manure washes out of it nitrogen and potash,
which pass off in the dark brown liquid that oozes from the base of
the pile.

_Loss by heating or fermenting._

When barn manure is thrown into piles it soon heats and throws off
more or less steam and gas. This heating of the manure is caused by
fermentation or the breaking down of the materials composing the
manure and the forming of new compounds. This fermentation is produced
by very small or microscopic plants called bacteria.

The fermentation of the manure is influenced by the following
conditions:

A certain amount of heat is necessary to start the work of the
bacteria. After they have once started they keep up and increase the
temperature of the pile until it gets so hot that sometimes a part of
the manure is reduced to ashes. The higher the temperature the more
rapid the fermentation. This can be seen particularly in piles of
horse manure.

The bacteria which produce the most rapid fermentation in manure need
plenty of air with its oxygen. Therefore fermentation will be more or
less rapid according as the manure is piled loosely or in a close
compact mass.

A certain amount of moisture is necessary for the fermentation to take
place, but if the manure is made quite wet the temperature is lowered
and the fermentation is checked. The water also checks the
fermentation by limiting the supply of air that can enter the pile.

The composition of the manure influences the fermentation. The
presence of considerable amounts of soluble nitrogen hastens the
rapidity of the fermentation.

Now when the manure ferments a large part of the organic matter in it
is broken down and changed into gases. The gas formed most abundantly
by the fermentation is carbonic acid gas, which is produced by the
union of oxygen with carbon of the organic matter. The formation of
this gas means a loss of humus. This loss can be noticed by the fact
that the pile gradually becomes smaller.

The next most abundant product of the fermentation is water vapor
which can often be seen passing off in clouds of steam.

When manure ferments rapidly the nitrogen in it is changed largely
into ammonia. This ammonia combines with part of the carbonic acid gas
and forms carbonate of ammoni