Maluma Symposium: dwarfing rootstocks, high density planting and trellising to improve yield efficiency of avocados
At the annual Maluma symposium a large avocado producer throws its doors open, giving a generous insight, free of charge, into the workings of Allesbeste Boerdery.
The Maluma avocado is an open cultivar, not a club cultivar. There is strong brand development around the avocado (at this stage particularly well-advanced in Australia through Coles supermarket) but it is not obligatory, albeit beneficial to join the brand.
“It’s not a case of selling the Maluma to people, but we’re trying to show them we’re moving in a direction and we’d like to invite them to come on this route with us and we’ll get there faster,” explained Zander Ernst, director of marketing and production at Allesbeste Boerdery around Tzaneen. They are taking the apple industry as an example, both in terms of its use of dwarfing rootstocks like the M9 as well as its intensive trellising and pruning practices to find the optimal leaf:fruit ratio.
Search for dwarfing avocado rootstock
At every Maluma symposium updates are given on the various activities related to the new cultivar (commercially launched 11 years ago), for instance their search for rootstocks with dwarfing characteristics in order to optimise yield efficiency (the cubic production capacity of the tree) and spatial use.
At Allesbeste Nursery, where Abraham de Villiers and his team propagate avocado trees using the microclonal method (which has been called “the Everest of plant propagation”), four trials have been on the go for much of the past decade, three of which compared Maluma’s performance in high density plantings on the three well-known avocado rootstocks in use in South Africa: Dusa, Duke 17 and Bounty. They have been surprised by their results.
“Duke 7 was the rootstock that brought us here, an American rootstock. Dusa is presently very, very popular, also in the clonal world. We always believed that Dusa was best for virgin soils but now for replant we have found that Bounty is extremely good,” Dr André Ernst told delegates visiting the trial orchards. “I have no doubt that Bounty is showing up as among the best rootstocks for Maluma.”
A trial with 28 rootstocks, among them 10 new promising rootstocks identified by Allesbeste, supplemented by a number of other new South African and international rootstocks, have shown which rootstocks possess the dwarfing characteristics needed to optimise yield efficiency (measured as kg of fruit per m3 of tree volume), among them Bounty. A fifth trial is due to start to test Maluma on 60 rootstocks of Allesbeste and international provenance.
Trellising of avocados
Another facet, closely related to the search for a rootstock with dwarfing characteristics, is the exploration of high and even ultra-high density avocado planting. The tendency of the Maluma towards willowy growth, makes trellising a natural progression in avocado cultivation. Last year the first commercial avocado orchard on a trellis system was established.
Newly established avocado orchard on vertical trellising in August 2017
“As soon as you go into higher density with the precocious cultivars, the branches tend to droop down, and you struggle to fill the zone within the row,” Zander Ernst explained. “Our experience has shown: the closer we go with the trees, the more we struggle to close that gap because we’re putting more production on the tree as we’re pruning it better and the more the branches droop down. That reduces production on the lower branches. We need to get sunlight in there.”
Their trials are showing that both trellis systems give higher production that conventional orchards, with Tatura outperforming as the productive tree area is doubled. “It enables you to walk into an orchard and easily identify which branches need pruning,” Zander said. “I like to walk into an orchard and being able to see all of the trees at once.”
The Tatura system has double the establishment costs, because of the cost of wire, but the diagonals of the system keep the fruit shaded, reducing sunburn problems.
Tatura trellising of avocados
After a few years of trialling their trees in this way, they’re able to state that there is definitely higher production, but that it was too early to say whether it had an effect on fruit size. As for pruning, they’re relieved to note that growth vigour hasn’t proven an impediment and that vegetative growth can be kept under control. They will get their first harvest on the trees on wire spacing this year.
Their ideal is trees that evenly carry fruit from the bottom branches to the top.
At the symposium, the Allesbeste team gave delegates a detailed account of an orchard established on a steep slope, starting with soil maps to model water flow and design the flow of rows along terraces (closer spacing on higher slopes to maintain manageability of trees) and, importantly, accessibility for vehicles and pickers. (“We’ve rolled enough tractors and mist blowers on steep slopes. It’s an expensive exercise.”) They regard 100m as the ideal length of a row. Every single decision is discussed and explained at the symposium, to the level of giving tips on cheaper versions of super-expensive geo-positioning technology or sharing the hard lessons they have learned: it’s a big mistake to build a road first and then the terraces around it.
Every single tree planted on their farms has a geopositioning reference number.
“Drip irrigation has changed my life,” Zander Ernst of Allesbeste told delegates, noting how common over-irrigation is in the South African context, especially on heavy soils, and upon replanting of young trees.
A number of participants at this year’s symposium commented on the generosity of information available at the symposium which has no entry fee. “They just gave all of the knowledge that took them months to gather, to us for free,” a technical advisor noted. “All kinds of information which other producers are keeping close to their chest, but at this symposium they share everything they have learned.”
All presentations delivered at the symposium, as well as previous years’ symposia, are available here: http://blog.maluma.co.za/presentations-2/