Planting a vineyard is a long-term investment, and the decisions you make today will have a big influence on future success.
Where is the best place to plant you next vineyard block? What cultivar, clone and rootstock is the best combination for a specific piece of land? How will the vineyard grow here, or will it grow at all? How is the wine going to taste if I plant a vineyard block here?
Producers continuously grapple with these questions, for the exact reason that the decisions made today will determine the success of the next 20 years. To make these decisions, it is necessary to be well informed about the soil, terrain and climate you are working with.
Know your terroir
The South African wine industry is located on one of the world’s oldest landscapes. The soils in which our vineyards grow, are so diverse that we have had to develop our own soil classification system. With an abundance of mountain ranges and hills, we have no lack of topography. And when it comes to climate, there are few places on earth with as much variation as we have in our country.
This combination of variables has a major influence on the growth of the vine and the possible quality of grapes and style of wine that can be produced. The interaction of the environment on the ultimate product has captivated winemakers and viticulturists for hundreds of years. As it is a difficult concept to grasp, with so many variables which collectively have an effect on the final product, the French have named it “terroir” – their broad term for land.
To better understand terroir, the concept must be broken down into its individual elements. If soil is the starting point, a detailed soil map becomes one of the most important basis maps on which planning can be done. A soil map indicates soil differences in homogeneous soil mapping units (HMUs). Each HMU has a map symbol which describes the soil contained therein. It usually consists of an abbreviation of the soil form that predominantly occurs in the HMU, followed by a numerical figure that involves a further division within the soil form, based on family level, effective depth, stone percentage etc.
Each HMU has its own challenges and advantages, and an experienced agriculturist can make various deductions from studying such a map. Informed decisions, like the necessity of drainage, ridging actions, soil preparation actions, irrigation type and scheduling, and much more, can subsequently be made. Representative soil samples are then taken according to the soil variation to identify chemical limitations and deficiencies and make recommendations.
Each cultivar, and especially rootstock, has its own soil requirements and tolerances. If the soil characteristics and limitations are known, the rootstock that will perform best in the specific soil type can be chosen.
The next element that has a significant influence on the vine, is climate. Climate is a very broad term that can also be broken down into individual indices, like the average February temperature and annual rainfall. Although data from the nearest weather stations is very useful to better understand the climate of the immediate area, it cannot point out climatic differences on individual farms.
The biggest drivers of climatic differences on farm level is solar radiation, wind and topography. These can be mapped by means of a terrain analysis to illustrate the differences. Climate determining characteristics, like altitude, aspect, slope, solar radiation, daylight length, slope form and flow accumulation, are very useful to depict the finer differences in climate on farm level. This information is very valuable, as cultivars tend to show significant differences when it comes to climatic requirements. This data is obtained through the processing of contour and other terrain data in a GIS system to create a digital terrain model. Terrain information, like slope form and flow accumulation, is also helpful to draw soil boundaries, because it predicts the groundwater conditions.
These big decisions do not have to be taken alone and it is recommended to involve a soil scientist and viticulturist to help with the process.
Collectively, informed block layouts can be drawn on detailed soil and terrain maps in order to create homogeneous blocks with the correct cultivar and rootstock choices.
There are free websites available like Cape Farm Mapper of the Department of Agriculture and TerraClim, which is funded by Winetech, where basic soil, climate and terrain data of a farm can be obtained.
FIGURE 1. Example of a block layout based on a soil map.
– For more detailed information and personal support, the Vinpro Consultation Service can be contacted at 021 276 0429 to help make the block layout process easier by means of soil mapping, terrain analyses and viticultural consultations.