Almond productivity: Tree architecture and development of new growing systems (AL14007)

What was it all about?

This investment ran from 2014 to 2019 and worked towards intensifying almond orchard operations across south-east Australia regions. The researchers specifically evaluated a low-cost pruning system to produce almond trees with more light-efficient, narrower canopies that, with minimal additional cost, would increase orchard productivity.

Key findings from this project include:

• Selective limb removal pruning and reflective ground covers  enhanced light and increased cropping in the lower canopy of mature cropping trees in conventional orchards, but did not increase total yield over the four-year duration of this project. Fruit in these lower zones were not ready for harvest until two to three weeks after the main crop, causing further problems downstream for harvesters and processors. Different solutions are required to ensure higher productivity and uniform crop maturity.

• Narrow-pruning of trees when they are two-years old (as a once off practice) was tested as a new approach to create more light-efficient and narrower canopies suitable for high density orchards. Narrow-pruning proved a low-cost option for managing trees in rows planted closer together than is traditional, thus enabling higher orchard yields. 

   

• Planting “unpruned” central leader trees was also an effective step in producing narrow tree canopies. Other benefits of planting central leader trees were the notable resilience to wind damage and ease of maintaining a narrow canopy.

   

• Trunk girdling on young trees as a means to promote flowering and increase cropping was unsuccessful, however the long-term response to girdling was a reduction in tree size with no adverse effect on yield, which may be of interest to growers as an alternative to growth-controlling rootstocks.

   

• Development of a pilot model system for intensification of almond orchards. Based on trees planted in rows 4.5 m wide, with 2.0 m between trees along the rows, the model system will allow for trees to grow to 5.0 m tall and still be suitable for shake harvesting with uniform crop maturity.

   

• High yields were seen on young trees of the new self-fertile cultivars ‘Carina’ and Shasta®. However, high yields put a strain on young trees to support large crops. Narrow pruning with a combination of dormant and in-season pruning starting in year two, helped mitigate some of these problems. Planting "unpruned" central leader trees was a more cost-effective option.

   

• Further identification of successful tree architecture was explored with almond breeders in Australia, California and Spain. This research has promoted discussion on how breeders might change selection criteria when choosing breeding parents and when screening large seedling populations.