m 4 to 6 lb. The amounts of nitrogen and mineral matter in
4 lb. of straw are .01 and .23 lb. respectively. The total amount of
nitrogen and ash, therefore, in the farmyard manure produced by a horse
in one day, would be .19 lb. nitrogen and 1.15 lb. mineral matter; or,
if we take the larger quantity of straw, somewhat more.

Taking these figures, we find that the amount of manure produced by a
horse in a year will be from 11,720 to 12,450 lb. (_i.e._, from 5-1/4
to 5-1/2 tons),[152] containing from 69 to 73 lb. nitrogen, and from 420
to 460 lb. mineral matter.[153]

A word or two may be of value regarding the treatment in the stable of
horse-manure. The great object to be aimed at is the prevention of loss
of valuable fertilising constituents. This loss may be due to two
causes. It may be, in the first place, caused by drainage of the soluble
matter of the manure; or secondly, it may be due to volatilisation of
the volatile constituents.

The first of these two sources of loss depends on the precautions taken
in the way of providing a proper impervious flooring to the stable. This
source of loss is extremely difficult to prevent, inasmuch as nearly all
materials used for flooring absorb a certain percentage of urine. The
judicious use of litter, however, will minimise this loss to within a
trifling extent.

Dr Heiden states that the amount of straw used as litter for the horse
in Germany is from 4 to 6 lb. per day. The quantity should be regulated
according to the percentage of water the excreta contain; the more
watery excreta requiring naturally a larger quantity of litter. The most
eminent authorities on this subject recommend that the amount of litter
should equal one-fourth of the food in its natural state, or about
one-third of its dry substance.

The second source of loss, which is due to volatilisation of the
volatile ingredients, may be largely prevented by the use of certain
preservatives.

Horse-dung being, comparatively speaking, of a dry nature, it is
extremely difficult to effect its thorough mixture with the litter. For
this reason the manure formed from horse excreta is particularly liable
to rapid fermentation.[154] In the process of fermentation, as will be
seen more in detail further on, the nitrogen is converted into carbonate
of ammonia. As nitrogen in this form is of an extremely volatile nature,
the risks of loss from this source are considerable. As illustrating
this fact, it may be menti