This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

The Australian avocado industry had a long focus on improving quality to the consumer by developing better production, harvesting, storage, ripening and retail practices.

The main avocado fruit quality problems were rots and flesh disorders which caused browning of the flesh. Most of the research in recent years had been to grow fruit which could better prevent rots and disorders development. This approach also help reduce the use of chemicals during production and after harvest.

In many fruit crops, fruit with higher calcium (Ca) concentrations often had less rots and disorders. Previous research had confirmed that this relationship also existed in avocados. Therefore, the Australian avocado industry, along with Hort Innovation (which was then Horticulture Australia Limited) and the Queensland Department of Primary Industries and Fisheries funded a four-year programme to develop Ca fertiliser recommendations with a view to improving fruit Ca and quality.

The research suggested that, contrary to commonly-held views, Ca was not held very well in most avocado growing soils, so that leaching of added Ca could easily occur. More frequent applications of smaller amounts of Ca reduced this risk, however even with this strategy the reseaercher had difficulty improving fruit Ca concentrations and quality.

It appeared that other factors were involved in fruit Ca nutrition, especially potassium (K) nutrition, the genetics of the tree, and tree yield. The results again confirmed that Ca was important in fruit quality, but that it was difficult to manipulate.

Further work was recommended to reduce K nutrition to minimise competition with Ca, and assisting growers to improve overall tree yield to improve fruit quality. Harvesting fruit specifically from higher yielding blocks or trees could have provided fruit for more distant markets where longer transport and storage times were often required.

More information could be obtained from the 2007 summer edition of Talking Avocados.