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