PLANTS CHARACTERISTIC OF SOIL TYPES

In addition to classification by chemical and mechanical

analysis, an indication of each type of soil can be obtained

by means of the vegetation found growing on it. On some

types the flora is extremely varied.

Calcareous soils have a profuse and interesting flora, which varies to some extent with the depth of soil. On the deeper chalks, trees and shrubs are found in abundance, ash being the dominant tree in the north and beech in the south of England. Yew is also common. The spindle tree is one of the most noticeable shrubs, but others such as the guelder rose, dogwood, clematis and juniper are to be found in great numbers. Flowering plants are numerous, and chalk soils are notoriously weedy. Among the most common weeds are fumitory, Geranium molle, Scabiosa columbaria, silverweed (Potentilla anserina), bulbous buttercup (Ranunculus bulbosus), Convolvulus arvensis, several vetches and salad burnet (Sanguisorba minor). Typical grasses are Avena pubescens, A. flavescens,. Bromus erectus, Festuca ovina and Carex flacca. Some plants come on to the chalk to avoid acidity, e.g. ash; others which prefer acid conditions will not grow at all, e.g. many heaths. It is quite likely that many plants flourish on chalk soils because of the physical conditions, I.e. dryness of the surface soil and good aeration, rather than from want of calcium carbonate. Most plants that do well on the chalk withstand drought very well.

Heavy loams. Typical weeds are fat hen, chickweed, sow thistle, groundsel, field poppy, spurge, field mint and wild carrot. Owing to the close texture of this type of soil, weeds are less troublesome than on chalk. The flora, to some extent depends upon the drainage. Where this is imperfect such weeds as horsetail flourish. The presence of primroses is an indication of strong land. (Heavy/strong land – heavy horses were needed to plough such soils.)

When dressed with phosphates, pastures are colonised by clovers. Oak is the predominant tree, with hazel as undergrowth. Plants on these soils generally tend to make less fine roots, larger leaves, and short-jointed growth.

Clay loams with 20 to 30% clay are often very fertile and do not present such a big problem as the really stiff clays. Well drained and worked when dry enough, they produce heavy crops of good quality produce, but the crops are often late unless well supplied with phosphates, and nitrogen is given sparingly. Potash is seldom required, but this type of soil responds to lime dressings. The lime neutralizes the acids produced by the decomposition of organic matter, stimulates the formation of nitrates, and also releases potash and

phosphates. Suitable crops are onions, beans, green crops including sprouts and cauliflower, and fruits such as blackcurrants and plums. The culinary varieties of apples do well, and some dessert kinds colour well, e.g. Worcester.

Light sands. The flora is varied and includes plants that are intolerant of lime (calcifuges), and those that appreciate dry conditions (xerophytes). Trees include birch, holly and Spanish chestnut. Conifers also thrive. Among shrubs, members of the Ericaceae and some legumes such as gorse and broom predominate. Sandy soils are subject to abundant weed growth, among the most common being poppies, knotweed, spurrey, creeping buttercup, small bindweed, silverweed, corn marigold and several vetches. Bracken is common on waste land, woodland etc.

Sandy soils are good for seed crops, especially those which ripen late on heavier soils and for early and over-wintering crops. Carrots thrive where irrigation is available against drought. Peas if mulched and irrigated usually crop well.

The peaty sands such as the Bagshot Sands are excellent for Rhododendrons, Heaths, Berberis spp., tamarisks and skimmia. Most of the brooms and lupins can be grown well in a sandy soil.

Moisture retention varies with the average grain size, and with the amount of organic matter which can be supplied and retained.

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