SCIENCE WADES IN
SA’S frequent periods of water shortage have drawn the attention of researchers, who have offered innovative solutions to mitigate the effects of drought
Unisa scientist Neil Stacey has developed a technology to reduce global water usage drastically by approaching the matter from an unusual angle: he looked at where water ends up.
Two of Stacey’s research articles, published in international scientific journals, have shown that more than 90% of the water used in agriculture is lost to evaporation. And since 70% of global water usage is for agriculture, those evaporative losses exceed losses from all other forms of water usage put together.
Stacey and his team set out to find ways to minimise these losses. By using a greenhouse as a model they demonstrated that there is a limit to the reductions that are achievable through conventional means.
Plants require carbon dioxide, which they obtain from the air. Huge airflows are needed to supply enough of the crucial CO², as it is highly dilute in air at just 400 parts per million. That airflow drives evaporation, because all that air has to be brought to the warm, humid conditions that plants require.
Stacey’s proposed solution is to use CO² enrichment to decrease the flow of air needed to supply enough of the crucial carbon, thereby cutting down evaporation and potentially reducing water usage to a fraction of present levels. Stacey’s preferred method of CO² enrichment is by using inorganic silica membranes to separate a high-co² stream from the open air. It is a modular approach that can be implemented on any scale.
Farmers could potentially boost revenue with this method as well; operating at higher levels of CO² results in faster plant growth
and increased crop yields.
In the case of some popular crops, the yield increase is over 20%. So a farmer can expect a revenue boost along with the water savings.
Still in its early stages, the project has nonetheless gone beyond just the scientific; Stacey’s business model is in the running to be one of the top 50 projects selected by the Elsevier Foundation Green & Sustainable Chemistry Challenge. Elsevier is the world’s largest scientific publisher. Each year it selects the most commercially promising, sustainable chemistry projects, offering prizes of €50,000 and €25,000 to those in first and second place respectively.
What it means: Agricultural groups say they are aware of the extent of their water usage and have been putting measures in place to reduce it
Despite the apparent commercial potential of CO² enrichment, Stacey’s team has placed the concept in the public domain rather than holding on to a patent, choosing instead to focus on commercialising the practical aspects of the technology.
Stacey (31), a researcher at the Unisa Science Campus, is no stranger to innovative thinking; just over a year ago he was in the news for breakthroughs in biofuels production. He is also overseeing a project aiming to replace the coal used in iron ore reduction with environmentally friendly alternatives, including biomass and waste plastics.
SA’S urgent need for technology to improve agricultural water efficiency is well known, with agricultural groups saying they are well aware of the extent of their water usage and have for a while been putting various measures in place to reduce it.
Niël Joubert, a director at Vinpro and organised business group Agri SA, and who farms with wine grapes and stone fruit, says winemakers have various water-saving strategies in place.
“Fruit and wine farms are, and have always been, acutely aware of their dependence on sustainable water resources to be able to produce a good-quality product and in the process create jobs, not only on farms but also in the value chain — right up to the shelves of chain stores and even [the stands of] informal hawkers who earn a living by selling farm produce,” says Joubert. “Furthermore [many] rural towns [depend on] responsible farming and water usage.”
Drought conditions have been present in the Western Cape for a third consecutive season. Most producers depend on water from irrigation schemes, and this water has been rationed since early in the 2017 growing season. Quotas have been cut by 50%-80%.
The Olifants River region is worst affected by the drought. Producers in this region have been allocated less than 17% of their usual water quota from the Clanwilliam Dam. The Orange River region is the only wine region not experiencing water shortages.
Over the years major changes have taken place in technology.
Joubert says irrigation practices have changed from sprinklers and micro-irrigation to variations of drip technology, depending on where the farm is. Water stress levels are monitored by sophisticated equipment to allow precise scheduling of watering hours and volumes in individual blocks according to soil type, canopy size and wine style.
The scientific approach extends to every decision, from soil preparation and the choice of rootstock and cultivar for a specific terroir to the cover crops that are used.