The South African wine industry is looking towards new technology and adaptive practices to buffer the serious effect of the ongoing drought in the Western Cape, according to wine industry association VinPro.
“The drought situation and water restrictions require wine grape producers to change the way in which they apply water in the vineyard,” said VinPro’s Francois Viljoen.
He said that VinPro and Winetech (Wine Industry Network for Expertise and Technology) presented a series of information days, themed Efficient Irrigation in Periods of Water Scarcity, in the respective wine-growing areas in September.
André Roux, former director of sustainable resource management at the Western Cape Department of Agriculture, said low rainfall and global warming will increase pressure on water resources. The agricultural sector currently uses 60% of the water available.
“There is simply no water available for expansions. We will have to use water more efficiently, for example through the recycling of water for agricultural purposes,” said Roux.
By determining the turning point at which the vine comes under stress, producers can apply water optimally, and even increase quality. Satellite technology such as the Department’s Fruitlook database can be used to determine these stress levels.
“As soon as the plant is under strain, the stomata close and the plant’s temperature rises. Higher temperature ratings in the vineyard can therefore indicate where water should be managed more closely,” said Roux.
The soil type on which a vineyard is planted will also give a clear indication of water conductivity and the applicable management strategy, according to Phillip Myburgh, senior researcher at ARC Nietvoorbij.
Sandy soils ensure better water flow to roots than clay. Clay soils, therefore, do not need frequent irrigation, but sandy soils have to be kept wet.
Vink Lategan, lecturer at Stellenbosch University’s Soil Science Department, said that the timing and volume of water applied can be adapted to manipulate quality and production.
“Applying more water does not equate to higher production. Giving less water than the vine requires at certain stages can even improve quality, without a significant decrease in production,” said Lategan.
Although the grapevine changes its physiology as soon as it is under strain, Lategan warned that vineyards should not be placed under unnecessary stress, especially during berry set and flowering.
Myburgh agreed that irrigation should be timed meticulously.
If only one irrigation is planned, véraison (the onset of ripening) is the appropriate time. If there is enough water for a second round, vineyards can be irrigated during the pea berry stage. If the winter is very dry and there is enough water available for a third irrigation, it can be applied just before flowering to ensure good set.
“Avoid pulse irrigation (short and frequent irrigation), as a lot of water is lost through evaporation. Rather ensure that the entire root volume is wet and allow it to dry before irrigating again. Make sure that the irrigation system functions at optimal pressure without any leakages,” he said.
Producers can also reduce water loss through deep tillage, covering the soil with mulches, removing weeds and keeping canopies small.
“The water scarcity and competition for water resources will be with us in the long term. We would like to urge all wine producers to make use of expanded literature, workshops and advice from industry bodies such as VinPro, Winetech and the Institute for Grape and Wine Sciences (IGWS) to adapt to the drought conditions,” said Viljoen.