For centuries, agriculture happened outdoors, where crops enjoyed the warmth of the sun and the nourishment of the rain. However, modern farming is increasingly moving under cover – and CCA-treated poles are playing a vital role in supporting this shift.
Undercover farming (or UF) is the production of plants and animals in an environment where growing conditions are controlled. The benefits are supported by agricultural research showing that when conditions are controlled, they can be optimised. This leads to better quality and higher yields.
The latest Sustainable Agriculture Market Intelligence Report from GreenCape notes that in South Africa, the two most common types of UF structures are tunnel systems and shade netting. Glass greenhouses are less common as they are more vulnerable to harsh weather.
GreenCape reports that the number of shade netting and tunnel systems in the Western Cape alone grew by an impressive 329% between 2018 and 2023, to a total of 12 083 hectares.
Better yields, using less water
The Western Cape is South Africa’s most diversified and export-oriented agricultural region. While there are no statistics for other regions, GreenCape’s research indicates that shade netting projects are becoming more widespread across the country – and into other parts of Africa.
“In experiments on the Orri variety of mandarin trees, shade nets resulted in up to a twofold increase in fruit yield (kilograms of fruit per tree) and significantly increased tree water usage efficiency and fruit quality,” Paul Cronjé of Citrus Research International recently told Farmer’s Weekly.
The most common shapes for overhead structures are flat-top, dome-shaped, and pitched. Most shade netting structures are flat-topped because this design is the most cost-effective and has a faster construction time, the report notes.
“These structures are typically supported by CCA-treated wooden poles, so their growing use is good news for our industry,” said Bertus. “Our customers have been reporting on this growth for several years now.”
“We do a lot of work in the agricultural sector, particularly with fruit farmers,” said Ross Holland of Holland and Associates, who acts as environmental consultant to Dolphin Bay. “The feedback from our Western Cape clients is certainly that shade netting is a worthwhile investment. With fruit farming, you have to be globally competitive because most produce is exported. The farmers we’ve spoken to seem to see a much higher proportion of export quality fruit when they produce it under nets.”
Extending the production period
Shade netting allows farmers to control the microclimate more effectively, which is particularly beneficial for citrus fruit. “There is a portion of the day in which citrus trees are productive, and that depends on certain environmental parameters,” Ross explained. “As soon as the environment around the trees falls outside of those parameters, they go dormant and stop producing. Under nets, you can keep your trees within that ideal environment for more hours of the day, which means you get better yields.”
In southern Africa’s hot climate, that’s a game-changer. Here, farmers use shade netting predominantly to protect their plants against sunburn and to reduce evaporation.
The colour of the shade-netting determines the extent to which this is possible. A 2018 master’s thesis from Stellenbosch University found that even a relatively mild shade netting (20% white) significantly altered an orchard microclimate.
“The colour definitely makes a difference,” said Andre van Zyl of shade-netting supplier Knittex, in an interview with the Dolphin Bay Brief. “The darker your shade net, the cooler it is underneath. A lot of our clients – especially in neighbouring countries like Botswana – go for a black 20%, because it gives you more shade and better UV protection.”
“It’s cheaper to insure your netting than to insure your harvest.”
Shade netting also provides protection from weather conditions like hail, sunburn, and wind damage, according to research by the University of Helsinki. This, again, increases the return on investment.
Generally, the capital costs of shade netting range between R220 000 and R350 000 per hectare. The weather protection alone is worth the investment, said Van Zyl. “It’s cheaper to insure your netting than it is to insure your harvest. And if your netting is damaged by hail, for example, it’s much cheaper to fix that than it is to cover the loss of your crops.”
“We are seeing a growing need for agricultural technologies that protect our food security,” said Bertus. “Shade netting is one of those technologies. All the evidence shows that it leads to phenomenal increases in yield. We’re proud to be part of an industry that supports this growth.”
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