If there is one reason more than any other why the wine industry should sorely reach to colossal dimensions, it is that the climate is naturally adapted for the cultivation of the vine. Although human effort and human skill can overcome what looked to be almost insuperable difficulties, they cannot, as we know, fight against climate. Hence, having a climate created, as it were, for the growth of the grape, there can be no possible excuse offered for its neglect. Indeed, as I have already shown, the suitableness of the climate for this purpose directly attracted the attention of the first arrivals, and as a consequence the vine was actually planted a few years after the discovery of Australia.
There are three constituents, namely, heat, light, and moisture, which in varying proportions make up what is known as climate. The first two, heat and light, are derived from the same source—the sun—and may, therefore, be conveniently considered together. The more heat and light a vine receives the more vigorously it grows. What is more important, however, is that the wine from it becomes stronger. It gains in strength because the percentage of glucose increases in the must: the must being the juice pressed from the grape, but in which fermentation has not commenced. Accordingly we find that the wines of the warmer regions in new South Wales, Victoria, and South Australia are much stronger than those from the cooler parts.
It is important to remember that the unripe berries of the grape contain several acids, notably tartaric, citric, and malic acids. As the fruit begins to ripen, these acids act upon the various substances, namely, starch, gum, dextrine, lignine, cellulose, &c., also contained within it, and grape sugar or glucose is formed in consequence with the advent of ripening, therefore, the fruit becomes richer in sugar and poorer in acids; part of the acids, in addition, is neutralised by the mineral salts which are absorbed by the roots. These acids, however, are not so thoroughly neutralised in a cooler climate, and as a result the wine has often a sour, crude taste. The warmer the climate the more alcohol the wine will contain; indeed, it may become too strong. On the contrary, the cooler the climate the more of acid there will be, and it may possess in consequence a crude, sharp taste. But these are matters which can be rectified by choosing the right varieties of grape for the different localities, and by their proper cultivation.
The third element concerned in the climate, namely, moisture, has now to be considered, and it is important from the fact that in a moister climate the percentages both of glucose and of acids in the grape are diminished. It is also important for another reason, namely, that while heat and light are unalterable, moisture may be produced by irrigation. This constitutes one of the vexed questions connected with viticulture, and the most diverse opinions have been expressed about it. Some believe that irrigation is of great value, while others cannot say enough against it. But it would seem that when judiciously employed it is of unquestionable advantage. It renders the cultivation of the grape possible in places where it would otherwise be impossible; it largely increases the yield; and, what certainly must not be forgotten, it enables a lighter wine to be produced in the warmer regions. And another argument in favour of irrigation is this, that there is far more fertilizing matter in river water than in rain water. Hence it is that irrigation greatly enriches the land and increases the yield. It is thus a powerful aid, and because its advantages have been abused, that is no reason why it should not be made use of in a rational and scientific manner.
There is still another matter connected with this question of climate, namely, the aspect of the vineyard, which should be referred to because many different views are held upon it. But, as in all similar cases where there are such decidedly antagonistic opinions, it will be found that the arguments are not maintained from the same standpoint. So in this case the importance or non-importance of the aspect depends altogether upon the climate, and upon the locality—whether it be level or hilly. On level ground the aspect is not nearly so important. On hilly land it makes a considerable difference, from this circumstance, that in Australia the northern side of a hill is always hotter than that facing the south. In the hot regions, therefore, a hill slope facing towards the south is preferable; while in the cooler districts, since more warmth is required, a situation with a northern aspect is necessary. It is often said that hilly ground is better for the cultivation of the vine than level land. This is certainly true as far as cold localities are concerned, because a warmer aspect can then be chosen, and there will also be more shelter and better drainage.
THE SOIL.
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-glowing 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 wine. This is without doubt the reason why our Australian wines, as a general rule, are so rich in colour.