he same principle, the sub-soil plow renders the compact
lower soil sufficiently fine for the requirements of fertility.

[Why are the benefits of sub-soiling not permanent on wet
lands?

Does sub-soiling overcome drought?

How does it deepen the surface soil?]

Notwithstanding its great benefits on land, which is sufficiently dry,
sub-soiling cannot be recommended for wet lands; for, in such case, the
rains of a single season would often be sufficient to entirely overcome
its effects by packing the subsoil down to its former hardness.

On lands not overcharged with water, it is productive of the best
results, it being often sufficient to turn the balance between a gaining
and a losing business in farming.

It increases nearly every effect of under-draining; especially does it
overcome drought, by loosening the soil, and admitting air to circulate
among the particles of the subsoil and deposit its moisture on the
principle described in the chapter on under-draining.

It deepens the surface-soil, because it admits roots into the subsoil
where they decay and leave carbon, while the circulation of air so
affects the mineral parts, that they become of a fertilizing character.
The deposit of carbon gives to the subsoil the power of absorbing, and
retaining the atmospheric fertilizers, which are more freely presented,
owing to the fact that the air is allowed to circulate with greater
freedom. As a majority of roots decay in the surface-soil, they there
deposit much mineral matter obtained from the subsoil.

[Why is the retention of atmospheric manures ensured by
sub-soiling?

Why are organic manures plowed deeply under the soil, less liable to
evaporation than when deposited near the surface?

How does sub-soiling resemble under-draining in relation to the
tillering of grasses?

When the subsoil consists of a thin layer of clay on a sandy bed, what
use may be made of the sub-soil plow?]

The retention of atmospheric manures is more fully ensured by the
better exposure of the clayey portions of the soil.

Those manures which are artificially applied, by being plowed under to
greater depths, are less liable to evaporation, as, from the greater
amount of soil above them, their escape will more probably be arrested;
and, from the greater prevalence of roots, they are more liable to be
taken up by plants.

The subsoil often contains matters which are deficient in the
surface-soil. By the use of the sub-soil plow