People as a rule run away with the idea that the soil for the grape must necessarily be of a rich character. Even the farmer, thinking of wheat growing, and the market gardener, thinking of his turnips, are apt to entertain a similar belief. But the truth is that the vine is a hardy plant and will grow in almost any place that is not water-logged or otherwise unsuitable. In America the definition of a soil adapted for the grape is expressed in the following phrase: - "Land that is suitable for vine-growing is land that is not suitable for anything else." This is of course an extravagant way of stating the matter, still it is worth recalling. We may say this much, however, that almost any soil will do for the vine, provided that it does not bake and crack in the summer, nor get wet and boggy in the winter. A simple test is said to be adopted by the vine-growers of the Rhine. A specimen of the soil is put into an earthenware vessel, into which boiling water is poured to cover it, after which it is undisturbed for three days. If the water on being tasted gives a mouldy or salty taste, the soil is believed to be unsuitable.
In considering the soil we must pay heed to its physical and its chemical characters. By its physical characters we mean its looseness or stiffness, its depth, and its colour. This looseness is a matter of much importance. It fulfils the great indication required in a soil for grape-growing; that is, a soil which will not remain damp after having been well wet. There is a marked difference between a stiff clayey soil which dries up and cracks in summer, and a loose soil which is always moist a little below the surface.
The depth of the soil is a matter that varies in accordance with the climate. In warm districts the vine requires more room for development, and goes deeper. In the cooler regions it has a sufficiency of moisture, and can content itself with a shallower soil. The colour of the soil, like its depth, is a matter of consequence according to the climate. A dark soil absorbs heat, becoming hotter consequently, while it reflects but little on the plant above. On the other hand, a light-coloured soil absorbs very little heat, but reflects almost the whole of the rays upwards upon the vine. From this it follows that a dark soil is better in a cooler climate, because there is generally an excess of moisture; while a light colour is more suitable in the warm regions, for the moisture is then retained.
The chemical constituents of the soil play no inconsiderable part in assisting the development of the vine. Of these, however, there are only five - namely, nitrogen, phosphorus, potash, calcium, and iron - to which it is necessary to draw attention. For the successful cultivation of wheat and other cereals a richly nitrogenous soil is invaluable; for turnips and maize one rich in phosphorus is of great advantage; but for the vine potash is of considerable importance. It is true that nitrogen and phosphorus are necessary for the production of the vine wood, but it is for the fruit itself that the potash is so much required. As it is well known, the deposit known as winestone or "cream of tartar," on the inside of the cask by the fermentation of wine, is really tartrate of potash. In a similar way the potato is a plant which requires a supply of potash, and without it there is a manifest diminution in the crop. But in the case of the vine, unless there is a sufficiency of potash, the leaves do not attain to their full development; the stem is stunted to one-fourth of its natural size; and there is little or no fruit at all. Calcium or lime has a marked effect in increasing the strength of the wine. For this reason, therefore, this element is more necessary in the cooler than in the warm regions. And finally, there is that other chemical constituent of the soil, which deserves a brief notice, and it is iron. Now, the presence of iron therein has a distinct effect in deepening the colour of a Avine. This is without doubt the reason why our Australian wines, as a general rule, are so rich in colour.