CALCIUM additives at the growing stage could be the secret to avocados surviving the supply chain in better condition.
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Calcium is an important part of avocado fruit cell walls, which if compromised can leave fruit susceptible to bruising and disease.
Western Australian researchers are looking into how the addition of calcium fertiliser can improve the robustness of avocados as they move toward the consumer.
The national project will develop science-backed tools to guide calcium applications to help deliver the best quality avocados.
The Western Australian Department of Primary Industries and Regional Development (DPIRD) is supporting the three year Queensland Department of Agriculture and Fisheries (QDAF) project to increase fruit quality, funded by Hort Innovation's Avocado Fund.
DPIRD's component of the Growing Robust Avocados project will build on evidence about the influence of calcium fertiliser applications, in the form of gypsum, on avocado robustness.
The department is now in the second year of the project, exploring several options to refine calcium applications to optimise fruit quality.
The department is doing trials with three commercial Hass avocado orchards at Pemberton, Busselton and Carabooda to evaluate various rates and timing of calcium applications to improve fruit robustness.
Research scientist, Declan McCauley, said there seemed to be a 12-week window after flowering where applying calcium can improve fruit robustness.
"The first harvest from the Carabooda site showed variability in fruit robustness between trees, suggesting variability between trees may be a driver of whether fruit robustness is adequate or not," Mr McCauley said.
"We are also exploring whether potassium in the soil inhibits calcium take up by avocado trees to help optimise fertiliser treatments and inform future orchard management strategies."
Testing and gathering data
THE measurement requirements for the project are considerable during and after harvest, with the team evaluating up to 720 avocado fruit multiple times for weight, firmness and ripening progression, before dissecting the fruit to appraise flesh damage.
The post harvest assessment even includes dropping some avocados from a height of 30 centimetres to deliberately cause damage to help determine the robustness of the fruit.
Additional measurements are also being taken of fruit and stem growth to determine the relationship between tree growth and calcium movement into the tree.
These measurements will be integrated with digital, real time, continuous monitoring to help growers identify the optimal timing of intervention to improve fruit robustness.
DPIRD is also collecting data for statistical modelling by the Queensland team to determine how changes in soil and plant mineral status during the growing season relates to future fruit robustness.
"So far we have found each site has unique soil mineral properties that result in unique plant mineral quantities - despite all sites using the exact same avocado variety," Mr McCauley said.
"This will help the Queensland team to determine how soil and plant mineral status affects future fruit robustness from a wide range of growing environments.
"Together, these and other project initiatives will all help growers to predict when best to undertake early intervention to improve fruit robustness."
QDAF senior principal horticulturalist, Daryl Joyce, said the DPIRD team's involvement in the Growing Robust Avocados project was invaluable.
"This work is integral to our national effort to sustainably supply high fruit quality, quantity, and consistency into our expanding overseas markets," Dr Joyce said.
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