ly not as a direct chemical manure that farmyard manure
is pre-eminently valuable. We must seek for perhaps its most valuable
properties in its indirect influence.

It adds to the soil a large quantity of organic matter. Most soils are
improved by the addition of _humus_. The water-absorbing and retaining
powers of a soil are increased by this addition of _humus_, while it
enables the soil to attract an increased amount of moisture from the
air. This is often of great importance, as in the period of germination
of seed.[177] The influence it exerts on the texture of the soil in the
process of fermentation is also very great. This is especially so in
soils whose texture is too close, such as heavy clayey soils. It opens
up their pores to the air, and renders them more friable. Where such an
influence is most required, as in clayey soils, the manure ought to be
applied in a fresh condition, so that the maximum influence exerted by
the manure in this direction may be experienced. On light soils, on the
contrary, whose friability and openness are already too great, and which
do not require to be increased, the manure will be best applied in a
rotten condition. It adds, further, greatly to the heat of the soils by
its decomposition. Thus on cold damp soils it effects one very marked
benefit. The influence it exerts in its decomposition upon the
fertilising ingredients present in the soil is also by no means
inconsiderable. In the process of its fermentation large quantities of
carbonic acid gas are generated. This carbonic acid probably acts in a
double capacity. It will, in the first place, greatly increase the
solvent power of the soil-water, and thus enable it to set free an
increased amount of mineral plant-food; and secondly, it will help to
conserve a certain quantity of the soil-nitrogen, by preventing its
conversion into nitrates.

As its indirect and mechanical properties are greatest when in its fresh
condition, it will be better to apply it in that condition to soils most
lacking in these mechanical properties. We may therefore say that
farmyard manure is best applied in a rotted condition to light sandy
soils, and to soils in a high state of cultivation, where its mechanical
properties are not so much required.

An important point still remains to be discussed--viz., the rate at
which the farmyard manure should be applied. This, of course, should
naturally depend on a variety of circumstances--the amount of art