The addition of chalk or lime to soil was found in Chap. III. to improve it very much by making it less sticky and less impervious to air and water. Chalk or lime does more than this. It puts out of action certain injurious substances or acids that may be formed, and thus makes the conditions more favourable for plants and for the useful micro-organisms; farmers and gardeners express this by saying that it "sweetens the soil." A United States proverb runs: "A lime country is a rich country." Very many soils in England are improved by adding lime or chalk. There are considerable areas in the south-eastern and eastern counties where the soil is very chalky; here you find a wonderfully rich assortment of flowers and shrubs. Where there is too much chalk the soil is not fertile, because it lets water {98} through too easily, as was shown on p. 26: but for this very reason it is admirable for residential purposes. There are some exceptions to the rule that plants need lime. Some plants will not tolerate it at all; such are rhododendrons, azaleas, foxgloves, spurrey, and broom; wherever you see these growing you may be sure that lime is absent. Lime really differs from chalk, but changes into it so quickly in the soil that the action of both is almost, though not quite, the same. [Illustration: 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. {100} CHAPTER X THE SOIL AND THE COUNTRYSIDE In this chapter we want to put together much of what we have learned about the different kinds of soil, so that as we go about the country we may know what to look for on a clay soil, a sandy soil, and so on.