The national project will develop tools – backed by science – to guide calcium applications to help deliver best quality avocados, boosting orchard potential and growers’ business resilience and profitability.
The Department of Primary Industries and Regional Development (DPIRD) is supporting the three year Queensland Department of Agriculture and Fisheries (QDAFF) project to increase fruit quality, funded by Hort Innovation’s Avocado Fund.
Calcium is an important part of avocado fruit cell walls, which if compromised can leave fruit susceptible to bruising and disease.
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.
Research scientist Declan McCauley said the department was now in the second year of the project, exploring several options to refine calcium applications to optimise fruit quality.
“There seems to be a 12 week window after flowering where applying calcium can improve the robustness of the fruit,” he said.
“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.
“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.
“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.”
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 for each site – 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.”
QDAFF 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.
This project is a strategic levy investment in the Hort Innovation Avocado Fund.
