, they are rendered
available.

Sub-soiling is similar to under-draining in continuing the tillering of
grasses, and in getting rid of the poisonous excrementitious matter of
plants.

When the subsoil is a thin layer of clay on a sandy bed (as in some
plants of Cumberland Co. Maine), the sub-soil plow, by passing through
it, opens a passage for water, and often affords a sufficient drainage.

[To how great a depth will the roots of plants usually occupy
the soil?

What is the object of loosening the soil?

How are these various effects better produced in deep than in shallow
soils?]

If plants will grow better on a soil six inches deep than on one of
three inches, there is no reason why they should not be benefited in
proportion, by disturbing the soil to the whole depth to which roots
will travel--which is usually more than two feet. The minute rootlets
of corn and most other plants, will, if allowed by cultivation, occupy
the soil to the depth or thirty-four inches, having a fibre in nearly
every cubic inch of the soil for the whole distance. There are very few
cultivated plants whose roots would not travel to a depth of thirty
inches or more. Even the onion sends its roots to the depth of eighteen
inches when the soil is well cultivated.

The object of loosening the soil is to admit roots to a sufficient depth
to hold the plant in its position--to obtain the nutriment necessary to
its growth--to receive moisture from the lower portions of the
soil--and, if it be a bulb, tuber, or tap, to assume the form requisite
for its largest development.

It must be evident that roots, penetrating the soil to a depth of two
feet, anchor the plant with greater stability than those which are
spread more thinly near the surface.

The roots of plants traversing the soil to such great distances, and
being located in nearly every part, absorb mineral and other food, in
solution in water, only through the _spongioles at their ends_.
Consequently, by having these ends in _every part_ of the soil, it is
_all_ brought under contribution, and the amount supplied is greater,
while the demand on any particular part may be less than when the whole
requirements of plants have to be supplied from a depth of a few inches.

[May garden soils be profitably imitated in field culture?]

The ability of roots, to assume a natural shape in the soil, and grow to
their largest sizes, must depend on the condition of the soil. If it is
finely