In the De Toren vineyards, water is probably the most valuable and prized commodity. The reason for this is that through means of skilful application of this, these days scarce commodity, has a huge impact on the grape and in essence, wine quality.
At De Toren, we use a few, sensibly strategised methods to manage our water supply not only to nurture berries of the best quality for our range of award-winning wines, but also to use this limited resource as sparingly as possible.
Continuous research is conducted in this regard and with every vintage change, we investigate this subject matter and implement new, more progressive methods and approaches to ensure we entrench best practice guidelines and techniques.
One of the first methods we implemented is Regulated Deficit Irrigation or RDI. This involves restraining the vineyard progressively during growth season, especially during the final ripening phase. The manner in which we apply this restraint is by irrigating slightly less with each irrigation cycle and thus save on water usage. This method not only assists in saving water but also induces the vines to produce fruit that are substantially more concentrated and well balanced. The way we regulate this is by using a plant-based measuring method as opposed to using a soil measuring method. The machine used during this process is called a Scholander Pressure Chamber or more commonly referred to as a pressure bomb.
This measurement tells us exactly how this plant is performing and what the growth rate is and allows us to accurately irrigate the vines to maintain the right level of limitation for a given phenological ripening stage – thus ensuring we do not over-irrigate the vines. The parameters for each of the Bordeaux varietals, planted on our farm, differs greatly, for example, Cabernet Sauvignon can be stressed far more than Merlot. This is very important due to the Fusion V being predominantly Cabernet Sauvignon and the De Toren Z predominantly Merlot based. This approach plays a significant role in determining the wine style by growing the best possible berries in our vineyards.
Controlling the amount of water that is irrigated is just as important as using water-saving irrigation methods to ensure no water is wasted when watering the plants. The method used to manage this is by using drip irrigation instead of the other alternative, namely micro-spray irrigation. The reason for using this technique is due to the concentration and accuracy of drip irrigation to avoid wetting an entire, extended area where water is not necessarily needed. This automatically lowers the amount of evaporation and therefore saves water that would otherwise have been lost in the atmosphere.
An alternative way of saving this water is to increase the humic concentration in the soil. Humic content consists of natural organic matter and is easily increased by using plant material such as the shoots after pruning and adding organic compost, made from the skins of our grapes, to the soil. This result in the water being absorbed and stored in the soil for longer periods until the vine needs to utilise the water. The efficiency of this method is as effective as for every 1% increase in humic content of the soil, another 170 000 litres water per hectare can be stored in that soil.
The latest technique we are currently investigating is inoculating the root zone with fungi, known as Mycorrhizae. This Fungus plays a vital role in forming a symbiotic relationship with the roots of the vines. This particular fungus can reach small crevasses in sand and rock particles where water is accumulated, but vine roots can’t access due the small size of these openings – these Mycorrhizae effectively enlarges the surface area of the roots. The fungi bind onto the roots of the vines and exchanges nutrients. The vine receives water and nutrients from the fungi and the fungi in return receive nutrients from the vine that was produced by photosynthesis which a fungus cannot produce. Mycorrhizae can also hold 10 times their own weight in water which is another way of storing water until it can be utilised by the vines.
By closely monitoring and managing one of our most treasured commodities, water, we are able to produce a range of wines with great complexity, intensity and the perfect balance and at the same time conserve one of our rarest resources.