The soil must have adequate drainage; otherwise, air may be excluded, and the more beneficial micro-organisms may be destroyed. Soils which have poor drainage are often sour and acid. It will be necessary to improve this acidity by applications of hydrated lime. Wet soils are cold ones, and this means that plant growth is severely retarded. The situation is even more critical in the northern, colder parts of the country. Waterlogged soils cause roots to rot and a combination of all these problems can produce complete failures in some gardens.
Soils which are well-drained have sufficient natural coarse, gritty material or sand and many soils have a high proportion of small stones also. A high humus or organic content will also ensure good drainage. It is usually the clay soils which are the most difficult with regard to drainage, although a
hard ‘pan’ or layer beneath the surface of some soils can also present a problem. Such a pan is usually produced by mechanical cultivation which, in some instances, can consolidate the lower soil layers. Setting the plough or cultivators to cultivate to the same depth season after season will also produce this hard, unbroken layer. Varying the cultivating depth occasionally usually overcomes this difficulty.
Clay soils are composed of finer particles and these tend to pack so tightly together that they soon form a solid mass through which excess water cannot pass easily. Improving the drainage here consists in opening up these fine particles. This can be done by liming the soil. The particles of soil cling together in large granules after this treatment. If sharp, gritty material such as coarse sand or well-weathered cinders is worked in, the clay particles will be separated and made more
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