In 2000, farmer Wilfred Stephan became one of the first producers in the Western Cape to grow table grapes offline, and the system provides multiple benefits. He talked to Glenneis Kriel about how he adjusted the infrastructure to save costs and increase efficiency.
Sixteen years ago, Vredendal farmer Wilfred Stephan severely damaged his table grape crop due to birds. The loss prompted him to invest in a new technology at the time in the Western Cape: the net. He soon discovered that these nets can not only resist birds, but also create a more favorable microclimate for the production of table grapes, and also play a role in wind protection.
“These nets have caused our export packaging volume to increase from about 4,000 boxes/ha to about 5,000 boxes/ha, and the size of the berries has also increased significantly,” Wilfred recalled. "We also save labor because there is no longer a need to tie the vines to protect them from the wind."
Over the years, Wilfred has significantly improved his netting system. One of the problems is that vineyards tend to grow into a network.
“We started with a small house structure and used a net to form a triangular roof above the vineyard, because we thought it would provide better wind protection than a flat structure. Later we found that the net was too low-vines and branches tend to grow into nets. It causes the net to tear," he explained.
Wilfred then converted into a tall and flat structure in which the net was spanned 3.6m in height and the vine canopy was kept at 1.6m. This is much cheaper than having to erect hut-shaped poles high enough to prevent plants from growing into them. It was also found that the wind did not pose a problem for the flat structure after all.
Infrastructure Wilfred uses wires and cables on the roof of his structure, previously he used wood. Wires and cables are better because they are more flexible," he explained.
Using cables and wires is also about 30% cheaper than using wooden frames.
The support poles that keep the infrastructure in place are no longer planted in the soil, but remain on the soil. Wilfred said this saves labor a lot, because the farm's soil is mainly composed of durisol (dorbank), which is difficult to cultivate. Protection System
A strong anchor is needed to keep the infrastructure in place. Each is composed of 4m long, 125mm diameter wooden angle poles with a planting depth of 600mm. It is held in place by 16 mm builder steel cables and 6 mm connecting steel cables. To fix the cables, Wilfred filled old pesticide containers with concrete and planted them about 1.4m in the soil.
"One of the main benefits of using cables instead of wires in anchors is that it does not stretch, so the possibility of infrastructure collapse is low. As the vineyard gets older, the wires tend to stretch over time. In fact, It becomes heavier," he explained.
Traditional vineyards have a pole every 6m or so to support the trellis, but Wilfred's system uses a pole every 4m. The second rod in each row is used to carry the weight of the net; these rods are all 80 mm in diameter and 3.6 meters in height. The spare rod is smaller, with a diameter of 65 mm and a height of 2.1 meters, and is only used to support the grid.
Use two wires to fix the cordon in place: one goes through a 2m high work row, the other is fixed to a 1.6m high pole and turned over the top wire to form a slight V shape. Wilfred said this is flat The structure is very suitable for table grape production.
The vineyard is operated by pruning so that all the grapes grow along the first 50 cm of the vine.
"In any other system, you have to pick everywhere. Here, the grapes are concentrated in one area and are easy to get. The picking speed is more than 10% higher than that of the vineyard, and the workers must also pick at high places."
Wilfred only uses knitted mesh, because other materials tend to be lost due to small tears. He tried four pure colors—white, red, blue, and transparent—but did not find significant differences in production and cost. In the end, he chose white nets because they seemed to show the most light. Temperature control Because it is difficult to maintain crop quality, many farmers no longer plant flame seedless varieties. In contrast, Wilfred is expanding his production of these popular grapes.
"It is generally believed that grapes will burst in warm and humid seasons, but I think this is more related to extreme fluctuations in temperature," he said.
To manage the temperature under the net, Wilfred added a drip pipe on top of the lattice roof. The emitters are spaced 100 cm apart, the same as the emitters used on the vineyard floor in the row. The temperature of the water in the dripper line is usually about 17°C. When the ambient temperature is below 12°C, open the top dripper to increase the temperature.
In summer, when the ambient temperature rises above 35°C, the dripper is used to cool the vineyard. This "water treatment" is usually carried out for 10 minutes every hour until the ambient temperature returns to its optimal state.
The use of overhead dripper lines causes the roots of the vines to develop into the middle between the rows, making them more resistant to thermal stress.
"Usually, when you plant vines under drip irrigation, the roots are concentrated in the dripping area. By using another dripper line between the rows, we encourage the roots to spread over a wider area. This means that the vines are resistant to water stress. The sensitivity is lower than normal, and they can get nutrients in a wider area. The ideal state for any type of fruit production is always to maintain a good balance between growth above and below the soil."
Production skills Wilfred introduced two other production techniques. He covered the lowest part of each young vine with a plastic bag so that he could apply contact herbicides in the row without damaging the vines. He leaves weeds, such as tumbling weeds, in the work rows of young vineyards, because they help prevent sand from blowing on the vines. According to him, sand can cause serious damage to young vines.
Email Wilfred Stephen at [email protection]