Fig. 46. A wheat field in May. The large patch in the centre where the crop is doing badly lay under water for much of the winter because of the bad drainage
SUMMARY. The various things we have learnt in this Chapter are:—
Autumn and winter cultivation are needed to loosen the soil so that rain can soak in and not lie about in pools, and also to facilitate working in spring.
The soil has to be broken down very finely and made rather dry for a seed bed. The seed has to be rolled in and then left entirely alone.
As soon as the little plants are up the soil must be hoed, and the more often this is done the better. Hoeing keeps the soil cool and moist in hot weather, the loose layer acting like a mulch of straw. Anything else that shields the soil from the sun or the wind has the same action but is not so effective as the mulch. Further, hoeing keeps down weeds, which successfully compete against almost any cultivated plants. Humus also prevents the loss of moisture from soils.
Drainage may be necessary to remove excess of water.
Liming or chalking the soil is beneficial, not only because of the improvements mentioned in Chap. III., but also because certain injurious substances are thereby removed. There are, however, some plants that will not tolerate lime.
[1] At great depths below the surface the temperature rises again from quite another cause.