French tradition insists that the chemical composition of the soil, especially its mineral content, can contribute to the taste of a wine. Reluctantly, some New World growers are beginning to agree.
"Look at the flinty, mineral character of Chablis, the earthy-gravelly flavors of Graves, or even the slaty taste of Mosel," say the French. Modernists, predominantly New World producers, don't accept the link between soil and flavor, and it has to be said that scientific inquiry hasn't given a lot of support to the traditional view. But New World producers are coming around to it. You should hear riesling producers in Australia's Clare Valley talking about the differences in the soils and the taste of the wines from Watervale and Polish Hill.
What no thinking winemaker now doubts is that the physical properties of the soil have an enormous influence on wine quality and broad style. To produce wine of quality, vines are generally better served by relatively poor soils that encourage the roots to grow, rather than fertile soils that promote foliage growth, ultimately at the expense of fruit-ripening.
Water and heat
Vines need soils that are well drained, but which are capable of holding water at depth for the roots to draw on when necessary. Where irrigation is essential (as it is in much of Australia and South America), this water-retaining capacity is likely to be even more crucial. In the northern hemisphere and other cool regions, the soils also need to be able to store heat - something which stony soils do well. It's no empty coincidence that the chalky Champagne soils, the limestone of Burgundy, the Haut-Medoc gravels, and the clay and gravel layers of Pomerol all fulfill these criteria. Europe, of course, has had centuries to get to know its soil types. Growers didn't necessarily know the science behind the successful soils, but they knew which ones, in which climates, suited which grape varieties, and which parts of which small slope produced particularly fine results. Of course, most of that knowledge is now enshrined in individual appellation controlee rules.
Looking for terroir
In the now more soil- and geology-conscious New World, growers are making up for lost time, exploring new regions, identifying prime sites, and seeing where one grape variety does better or less well than another. These growers are seeking, in the first instance, cooler, less easy climates; but, as the climate becomes more difficult, so the soil has more bearing on vine-growth and quality potential. New World growers may not be using the word terroir, but they are increasingly beating the same drum.