Soil mapping helps winemakers create top tipples

Pyramid Valley vineyard, North Canterbury, showing the four discrete grape-growing plots set among the arid landscape.

In fact about 15 years ago now retired soil scientist Dr Philip Tonkin helped dig thousands of holes over land near Waikari for Pyramid Valley owners Mike and Claudia Elze Weersing in a bid to find the magic mix of limestone and clay. Pyramid’s managing director Caine Thompson said Mike Weersing had spent years searching for the perfect site to grow burgundy-style (pinot noir) and chardonnay grapes. Once he decided on an 80-hectare block at Waikari, Weersing still had to refine the process, because only a small percentage of the land had precisely the correct elements. After exhaustive digging, Tonkin and Weersing established that just 2.2 ha, in four individual blocks across the property, offered what was required. Thompson said the soils were unique. Cattle are run on the remaining land.

Tonkin first began mapping the soils 20 years ago, culminating in a report on the region that has just been presented to winegrowers and makers at a seminar at Black Estate winery. Today the Waipara region is home to at least 70 vineyards growing on distinctive landforms and in an impressive variety of soils, with the Omihi Valley having some of the most fertile in New Zealand.Associate Professor Roland Harrison, director of Lincoln’s centre for viticulture and oenology, said  winemakers could use the information not only to learn about the best areas to plant, but also to use in marketing their wines. “Looking at the whole geology of an area is useful for understanding and telling the ‘story’ of a vineyard. Celebrating differences and variety and diversity is crucial for marketing and the landscape here reflects these,” Harrison said.

The concept of “terroir” – the relationship between wine and the parent materials in which vines grow – was well-recognised by wine growers, winemakers and consumers, although it is tenuous and at times merely anecdotal. However soil attributes were relevant to heat, water storage and drainage, and in this way influence wine qualities. “We are better off thinking about what soil does, for example its influence on growth, than simply about the rocks from which the soils are derived,” Harrison said.

The report was put together over the last two years by Tonkin, associate Professor Peter Almond, current head of the Soil and Physical Sciences Department, Trevor Webb from Landcare Research, and other scientists. Tonkin hopes it will be a blueprint for what can be achieved in other winemaking areas.