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Clay Soils

clays, crops, alumina and substances

CLAY SOILS derive their character from the alumina which they contain in a state of mixture, as well as in chemical combination with other substances. Some soils contain as large a proportion of alumina as 40 per cent, hut generally the proportion is much smaller. The feldspar which chiefly yields the alumina of clay soils contains also soda and potash, substances essential to vegetables, and which tend to render clays fertile when under cultivation. The physical characters, however, of the different varieties of clay soils arising from the varying proportions of silica, and other substances mixed with the alumina, are chiefly concerned in their relative fertility. Calcareous matter exercises a considerable influence on their powers of producing crops.

In Scotland, clay soils are chiefly found on the coal-measures, the bowlder-clay, and as alluvium in the valleys. Those derived from the coal-measures are generally unkindly, being tenacious and difficult to labor. In the eastern counties, these are usually farmed on a five or six course shift, according to their quality. In the western, the moister climate is less suited for cultivating them to advantage, and dairy husbandry usually prevails where they are found under culture. The clay soils derived from the bowlder clays are also generally coarse, and inferior in quality. The richest clay soils arc found along the margins-of the rivers, and go under the name of carse clays, which have already been described under that bead. In the n. of England, the alurninous shales of the coal

measures yield soils very similar in their properties to those in Scotland. England also abounds in clay soils derived from other geological formations. The chief of these are the London, plastic, weald, Gault, and blue liar clays. The stubborn character of many of them is such that they are not suitable for tillage, but form excellent meadows and pastures. In the dry climate of Suffolk, strong clays are cultivated with great success on the four-course shift.-1. Seeds; 2. Wheat; 3. Fallow or roots; 4. Barley. Thorough drainage has greatly increased the value of clay soils under cultivatiou. Being so much sooner dry in spring, a longer period is obtained for preparing the land for putting in the crops. Weeds, too, are much more easily extirpated, and the strength of the soil is more entirely directed towards the raising of the crops. Wheat, beans, and clover are the crops which clay soils carry in greatest perfection. Clay soils have been long known to be retentive of moisture as well as of manure. Recent chemical investigations have shown, that clay soils have remarkable powers for absorbing ammonia, potash, and other substances, which constitute the food of plants. This property, it is now pretty well ascertained, arises from surface attraction.