New intensification project underway The avocado industry is one of five tree crops, along with almond, citrus, macadamia and mango, set to radically benefit from new research into the possibilities and practicalities of more intensified orchard systems as part of the National Tree Crop Intensification in Horticulture Program (AS18000), funded by the Hort Frontiers Advanced Production Systems Fund, with co-investment from the Queensland Government. The research is being led by the Queensland Department of Agriculture and Fisheries (DAF), in partnership with the Department of Primary Industries and Regional Development (DPIRD) in Western Australia and the Queensland Alliance for Agriculture and Food Innovation- University of Queensland (QAAFI-UQ). It aims to advance understanding of rootstock and scion combinations, plant density, tree structure, training and pruning options in high and medium density plantings to increase the industry’s potential to broadly adopt more intensive orchard systems.
Figure 1. Avocado trees under netting near Carabooda, Western Australia.
The five-year research project is comprised of several components. These include both continuing and new studies on existing planting system and high-density rootstock trials located at the Bundaberg Research Facility (BRF). “It is important to consolidate the findings of previous years (AI13004) by continuing to assess the effects of planting densities, rootstocks and pruning times on maturing orchard systems whilst investigating new options and technologies as part of the current project, AS18000,” Project Leader for DAF, Dr Ian Bally, said. This new research will investigate carbohydrate and resource allocations in trees, canopy light distribution, and patterns of root density, including its effect on yield, in the established seven-year-old planting systems trial on the BRF. Managing vigour in high density avocado plantings is an ongoing challenge, particularly as trees mature. Further insight into these factors and the relationships between them will build understanding of how avocado trees grow and respond to management under a range of planting scenarios and densities. A high-density rootstock trial, comparing nine rootstocks, planted in May 2016 at 4.5m x 2m with trees trained to central leaders on a single plane trellis, found when Ashdot was used as the rootstock, trees yielded twice as much as other rootstocks in the first two years of cropping and demonstrated the highest tree-to-tree yield consistency. New research now aims to focus upon issues of excessive growth that creates a low light environment, causing branch death and low yield. “We will develop our knowledge in how to limit excessive vegetative growth, especially through the use of growth regulator soil drench and tree height limits,” Dr Bally said. A second high-density rootstock trial, planted in 2018 at 4.5m x 2m on a 3m high trellis, was previously established
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Figure 2. The project reference group in the orchard.
to investigate eight rootstock/scion treatments (including Maluma Hass and Gem), adding a structural factor to the trial from 2019 (two-dimensional espaliered trees v threedimensional shaping). Evaluation of fruit-set, yield, fruit quality, total light interception, root investigations and architectural studies will continue in this trial through the AS18000 avocado project. AS18000 will also deliver three new field trials in Queensland and one in Western Australia. The Queensland trials include: 1. a medium density planting using open vase shaping (6m x 3m, 3-4 leaders, 2-3 controlled heights) at BRF, including plant growth regulator product, rate, timing and application methods 2. a demonstration plot at Peirson Farms, also using a medium density open vase shaping 3. high-density trellis planting(s) (4m x 3m) at BRF, including variations of branch structures, pruning timing and nutrition treatments.
TALKING AVOCADOS AUTUMN 2021
