Winning the Berg River Table Grape Block Competition is no mean feat, but doing it with a cultivar that’s considered difficult to grow, makes it even more of an achievement. Marius Wagener, table grape manager at Kloovenburg Estate in the Western Cape, won with his block of Prime Seedless grapes. Wouter Kriel reports.
Kloovenburg and its sister farm, De Hof in Riebeek Kasteel are protected by the northeastern slopes of Kasteelberg. According to owner Pieter du Toit, there have been good and bad years, but never a crop failure on these two farms. Table grapes are established on 29ha with Prime taking up 1,7ha under net protection. “In the Western Cape, Prime Seedless needs to be under net cover to be successful,” table grape manager Marius Wagener explains. “It’s a wind-sensitive cultivar and a low-vigour grower.
This means it holds onto its seed, resulting in small and uneven berries. Net covering costs more than R30 000/ha, but can result in 2 000 to 3 000 more cartons per hectare being packed, returning the net investment within two seasons.” Nets also significantly reduce the labour needed to prepare this cultivar, as leaders do not have to be tied and there is less seed rubbing to perform. “Rubbing out of seeds is by far the most labour-intensive aspect of Prime Seedless cultivation, but we have minimised that with net protection. Any form of stress encourages the vine to hold onto its seeds as a means of survival and by removing stress factors such as wind, the seeds drop by themselves, resulting in labour savings,” Marius says. “The net covering also saves 15% in water.”
Fertigation, spraying and irrigation
Organic fertiliser is applied after each harvest and care is taken with weak spots in each block. “We mark these spots with red paint and by applying extra fertiliser, the soil is built up over a three-year period. Viewed in isolation, this might seem like unnecessary trouble, but it makes a substantial difference to our production figures,” says Marius. Lime at 2,4t/ha is applied in three-year intervals, maintaining that soil at a pH of 6. I rrigation is by 0,6m drip irrigation, delivering 3,5â„“/hour per dripper. The drip interval was shortened from 1m to 0,6m to encourage better root distribution. Marius uses tensiometers together with the more modern and advanced AquaCheck soil moisture sensing technology.
“I’m familiar with tensiometers and will keep on using them while familiarise myself with the new system. also a believer in the simple soil bore,” he explains. “Vines should be slightly stressed during veriason, as this will yield in grapes with a longer shelf life.” Marius uses a computerised spray programme that has several advantages, if used correctly. It’s connected to a local weather station and spray recommendations are made over a 10-day weather forecast. This allows Marius to practise preventive disease control, requiring in less spraying, while withholding periods and appropriate active ingredient concentrations are incorporated for each cultivar. “We don’t spray any organophosphates, but use biological control measures where possible,” says Marius. “We also have wind socks in the vineyards, which are simple and effective tools to determine when strong winds will make spraying ineffective. The important thing is to understand the spray programme and to realise that it’s not simply boring paperwork. And if the programme says spray on Saturday evening eleven-o-clock, you have to do it exactly then.” The programme also keeps a register that serves as a backup when Kloovenburg is audited by the certifying bodies.
The importance of girdling
Girdling is essential but difficult to perform on Prime Seedless due to its low growth vigour. “Timing is of the essence,” stresses Marius. “The vine must be in a strong growth phase and there must be no water stress when girdling is performed. Clusters in the front should have berries of 8mm to 10mm in diameter, while clusters at the rear should be 6mm to 8mm in diameter.” Due to this difficulty, many farmers have stopped girdling on this cultivar, but Marius believes that it’s essential for good production and berry size. “After a few good years, I will adapt my fertiliser application if growth vigour declines, or maybe skip one year’s girdling,” Marius says. Marius advises Prime Seedless producers to plan all manipulations very carefully and not to be tempted to do preparations too early. “Never girdle before seeds have set completely,” he says.
The timing of gibberellic acid spray is absolutely crucial. “I do a bunch count and divide the grapes into three categories depending on their stage of development – early bloom, full bloom and completed set. “The gibb spray will cause the early bloom category to develop very loose and small bunches, so these grapes are destined for packaging as punnets. “Punnets are currently doing very well, but they pack slower than normal boxes, so we aim for 20% to 30% of total production to go this way, otherwise our packhouse will bottleneck.” The gibb spray delivers the best results on bunches that are in full bloom, so Marius tries to have as many as possible in this category. “But it gets complicated in your rows with an east-west orientation, as ripening stage variation within a row is likely,” he explains.
“By managing girdling and gibberellic acid application, we produce an evenly spaced berry set and looser bunches with larger berries, reducing labour-intensive berry-trimming work.” Production figures on Kloovenburg for Prime Seedless are impressive with the winning block producing 5 800 cartons per hectare for the 2007/08 season. Prime Seedless is the most profitable cultivar for Kloovenburg, due to the current good prices for seedless cultivars, the farm’s good production figures, and the low labour cost component. Contact Pieter de Toit or Marius Wagener at Kloovenburg on (022) 448 1635. |fw
