The French do not speak of soil, but of terroir, one of those wonderful words which encapsulates many different things. It expresses the coming together of climate, soil and landscape, thereby incorporating the influences of temperature, rainfall, sunlight; of soil depth, structure, pH, minerals and water retention capacity; of slope, aspect and drainage. To the French in particular, terroir assumes almost mystical importance. The late Peter Sichel (former president of the Grand Crus de Bordeaux) said, `Terroir determines the character of a wine, man its quality'.

It lies at the heart of the French appellation system, built up by a thousand years of practical experience which has led to a precisely detailed delineation of quality; to the identification of a limited number of grape varieties especially suited to the terroir (and the climate); and to the exclusion by force of law of all others. It has led to the prescription of pruning methods, the specification of maximum yields (but with such a dose of pragmatism as to render the restraints largely meaningless) and of minimum alcoholic strengths (again largely emasculated by the rampant use of chaptalisation - the addition of sugar to the fermenting wine).

History shows that the vineyards were originally planted by default, in terroir which was too deficient to support other forms of horticulture or farming. In Bordeaux there is a saying, `If these soils were not the best in the world, they would be the worst'. But that in no way diminishes the validity of the subsequent matching of grape and soil, nor of the identification of those microscopic dots on the face of the earth which produce wines of the ineffable majesty of Chateau Petrus (Bordeaux), La Romanee-Conti and Montrachet (Burgundy) and their ilk.

Australasian vignerons may be denied the extraordinary prestige and marketing power of the top French producers, or even the reflected glory which shines on the lesser producers - even poor French wine finds a ready market in many parts of the world. But there are compensations: we are free of the rigidity and constraints of the appellation system, and can (and do) prove that fine wine can be made in a far wider range of circumstances than the French would ever admit.

Maybe ignorance is bliss, but the average Australasian vigneron has made little attempt to correlate specific soil types with particular grape varieties and, outside of certain broad parameters, has made almost no attempt to link soil type and quality. (Such linkage as occurs is between climate, variety and quality.)

Those broad parameters define an ideal soil as a sandy loam, preferably interspersed with gravel or small, fragmented rock. It should be deep, free draining and of low to moderate fertility. Conversely, the most frequently encountered problems are excess clay and excess acidity. Heavy clay is poorly drained, holding too much water after rain or irrigation, and is frequently associated with dense and hard subsoils which roots cannot penetrate.

Excessively acid subsoils are far more widespread than is commonly realised, and have a significant adverse impact on vine health and vigour. The vines roots cannot tolerate the aluminium toxicity which is associated with high acidity (and low pH), which forces them to remain in the shallow topsoils (which are usually less acid), making the vine much more susceptible to drought, even though the rainfall may in theory appear adequate.

Correct moisture supply is all-important, and apart from anchorage and nutrients, is the principal function of soil in determining growth. During early shoot growth up until flowering (early November to late December, depending on region and variety) vines should be well supplied with moisture. By the time the fruit starts to ripen (January to February) available water should tail off, causing vegetative growth to stabilise, and the vine to focus its attention on ripening the grapes by sugar accumulation. (The photosynthetic activity of the vine's leaves causes carbohydrates stored in the system to be converted to sugar in the grapes.)

What is more, Australasian regions tend to contain a wide range of soil types. Coonawarra (at least within the so?called terra rossa boundaries), Eden Valley and Marlborough (at least in the existing vineyards) are regions in which a single (or few) soil type exists. In almost all others, soils vary widely: it is not uncommon to find three or four different soil types on a 15-hectare vineyard.

Next, a large proportion of grapes are grown by farmers who sell to the winemaker. That winemaker may have never visited the vineyard and certainly will lack any intimate knowledge of variation in vine growth within its confines. By contrast, the French winemaker will typically know every vine, every tiny variation in soil. Moreover, that observation will have been repeated over many centuries and handed down through the generations. In Australasia, experience in winemaking is usually confined to a single generation, or perhaps two.

But it does exist in the small estate, and is very probably one of the reasons why the small winery can produce top quality wine to rank with the best the big winery can produce. All observers are agreed that the future of Australasian winemaking lies in the vineyard, and, as a consequence, perhaps more attention will in fact be paid to soil in the future.

So it is that the vineyards of Australasia are established on a wide range of soil types, and, just as with grape varieties, over the years local names for these soils were used with little scientific basis and even less consistency from one region to the next. Dr K H Northcote, of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Soils, was responsible for developing a coordinated classification of soil for Australia, and it is that system which has been used in this book. That for New Zealand is rather less precise, and has been taken from a number of sources.