OD IN THE SOIL

Apparatus required.

_The pot experiments (p. xiii)._

It is a rare sight in England to see land in a natural uncultivated
state devoid of vegetation. The hills are covered with grasses and
bushes, the moors with ling and heather, commons with grass, bracken
and gorse, a garden tends to become smothered in weeds, and even a
gravel path will not long remain free from grass. It is clear that
soil is well suited for the growth of plants. We will make a few
experiments to see what we can find out about this property of soil.

We have seen that a good deal of the soil is sand or grit, and we shall
want to know whether this, like soil, can support plant life. We have
also found that the subsoil is unlike the top soil in several ways, and
so we shall want to see how it behaves towards plants. Fill a pot with
soil taken from the top nine inches of an arable field or untrenched
part of the garden; another with subsoil taken from the lower depth, 9
to 18 inches, and a third with clean builder's sand or washed sea-sand.
Sow with rye or mustard, and thin out when the seeds are up. Keep the
pots together and equally well supplied with water; the plants then
have as good a chance of growth in one pot as in any other.

{42}

[Illustration: Fig. 20. Rye growing in surface soil (Pot 3), subsoil
(Pot 4), and sand (Pot 5)]

{43}

Figs. 20 and 21 are photographs of sets of plants grown in this way;
the weights in grains were:--

Green weight After drying

Rye Mustard Rye Mustard

Plants grown in
top soil (Pot 3) 14.5 17.7 5.6 2.6

" " "
subsoil (Pot 4) 2.9 5.1 1.6 1.1

" " "
sand (Pot 5) 2.0 4.6 0.8 1.0

[Illustration: Fig. 21. Mustard growing in surface soil (Pot 3),
subsoil (Pot 4), sand (Pot 5)]

The plants in the soil remained green and made steady growth. Those in
the sand never showed any signs of getting on, their leaves turned
yellow and {44} fell off; in spite of the care they received, and the
water, warmth and air given them, they looked starved, and that, in
fact, is what they really were. Nor did those in the subsoil fare much
better. The experiment shows that the top soil gives the plant
something that it wants for growth and that it cannot get either from
sand or from the subso