Planting single-leader trees at ultra-high density – Mardouw Olive Estate in the Western Cape is experimenting with a novel alternative to the Mediterranean orchard system, and after four years returns look promising. Wouter Kriel spoke to farm manager Schalk van Eeden.
Situated halfway between Swellendam and Ashton in the Western Cape and dominated by the Langeberg mountain range, Mardouw Olive Estate is pioneering ultra-high-density olive production in SA. Owner André Verder, a European industrialist, believes there are golden opportunities in the international olive industry.
Under farm manager Schalk van Eeden, what used to be a traditional grape farm is being transformed into a cutting-edge olive production unit. A fter consulting with Carlo Costa, an olive expert at the ARC, it was decided to establish olives in ultra-high density groves. Tree spacing was reduced from a traditional 6m x 6m to 1,5m x 4m.
The trees are pruned to have only one leader trunk, and fixed on a wire trellis system. Tree height is restricted to 3m. radical shift “This is a radical mindshift,” says Schalk. “In the orchard layout we inherited from traditional olive production in the Mediterranean countries, trees are allowed to become huge in a dryland system.
We’re planting 1 660 trees per hectare instead of 277/ha. With a traditional low-density olive-orchard business plan, breakeven is attainable after eight years, but we’re working on achieving it in seven. Yield per hectare has increased dramatically, even though our input costs are significantly higher.” single-leader tree shape is a relatively modern trend, and somewhat controversial.
Traditionally olive trees were allowed to grow without pruning, resulting in huge trees that made harvesting difficult. Olive trees only bear fruit on second-year growth. means that if a tree isn’t pruned, its olive-producing area keeps moving to the outside of an ever-larger tree.
U sing the bushy structure of an olive tree as a guideline, it has become the norm to prune trees in a vase shape. It’s considered important to open the inside of the tree for better light penetration, says Schalk. Maintaining the single-leader tree shape requires intensive pruning. Schalk uses the rule of thumb that a dove should be able to fly through a correctly-pruned tree.
Mechanical pruning is an option, but Schalk prefers hand pruning as it gives better control over tree shape. “Don’t prune severely during the first two years, only focus on establishing the correct single-leader shape,” he says. Experiments and expertise The first 4ha of trees were established in 2002, using 1,5m x 4m spacing and a trellising height of 3m. With subsequent plantings Schalk lowered the tree height to 2,6m, greatly improving harvesting efficiency as workers no longer need ladders. Tree spacing was adjusted to 2m x 4m, allowing for 1 200 trees/ha.
In the near future mechanical harvesting with a grape harvester-type machine will be possible for oil cultivars, but for now everything is done by hand. Schalk explains that table olives, like the Kalamata variety, need to be hand-harvested to prevent bruising.
Orchard layout is critical for maximum production. “Southern slopes are better than northern slopes,” Schalk advises. “Olives are wind-pollinated and partially cross-pollinated, so establish the correct combination of cultivars, keeping wind patterns in mind. Strong wind will damage the slender leader trees, so establish windbreaks if necessary.” As an experiment, nine cultivars were established to see how different trees would react to the ultra-high density environment. So far only the Coratina variety struggles. Schalk suspects this is due to the system’s increased irrigation demand.
“Wet feet” could hamper some trees more than others.
Olive trees are very sensitive to poorly-drained soil, and root rot can set in quickly. All orchards are established using a double drip line irrigation system. Schalk recommends ridging in a poor draining situation. “We’re four and a half years into this experiment and initial results are very promising,” he says. The average yield for four-year-old trees was 5,5t/ha. “Eventual production should be between 12t/ha and 15t/ha.” This takes into account the olive tree’s tendency to bear heavy and light crops alternately. “If this experiment is unsuccessful, we can remove every second tree and continue in a more conventional way,” says Schalk.
Mardouw on the march
He’s excited about the future. There are plans to establish 100ha of trees, which amounts to 120 000 trees, with an estimated production of 1 200t and more. A factory that will process the harvest into 30% table olives and 70% oil is planned for 2009, and consumers can expect to see the Mardouw label on olives and olive oil in the near future. Contact Schalk van Eeden on (023) 616 2783 or e-mail [email protected]. |fw