dung
and urine of animals fed on turnips, with and without oil-cake, were
examined; but unfortunately, no determination of the total quantity of
the excretions could be made, so that it was impossible to estimate the
increased value. It has been commonly supposed that when cattle are fed
with oil-cake, the increased value of the manure is equal to from
one-half to two-thirds the price of the oil-cake; but this is a rather
exaggerated estimate as regards linseed-cake, although it falls short of
the truth in the case of rape, as we shall afterwards more particularly
see.

Although it may be possible, in this way, to increase the quantity of
nitrogen as a manure, there is a limit to its accumulation, due to the
fact, that it is contained most abundantly in the urine, which can only
be retained by the use of a sufficient supply of litter. Where that is
deficient, the dung-heap becomes too moist, and the fluid and most
valuable part drains off, either to be lost, or to be collected in the
liquid manure-tank. In the well managed manure-heap, the quantity of
litter should be sufficient to retain the greater part of the liquid
manure, and to admit of only a small quantity draining from it, which
should be pumped up at intervals, so as to keep the whole in a proper
state of moisture. Attention to this point is of great moment, and
materially affects the fermentation. When it is too moist or too dry,
that process is equally checked; in the former case by the exclusion of
air, which is essential to it; and in the latter, by the want of water,
without which the air cannot act. The exact mode in which the manure is
to be managed must greatly depend on whether the supply of litter is
large or small. In the latter case the urine escapes, and is collected
in the liquid manure-tank, and must be used by irrigation, and in some
cases this mode of application has advantages, but in general, it is
preferable to avoid it, and have recourse to substances which increase
the bulk of the heap sufficiently to make it retain the whole of the
liquid. For this purpose, clay, or still better, the vegetable refuse of
the farm, such as weeds, ditch cleanings, leaves, and, in short, any
porous matters, may be used. But by far the best substance, when it can
be obtained, is dry peat, which not only absorbs the fluid, but fixes
the ammonia, by converting it more or less completely into humate.
Reference has been already made to the absorbent power of peat