National tree crop intensification program (AS18000)
What it was all about?
The National tree crop intensification program marked a transformative step for Australian horticulture, targeting almond, avocado, citrus, macadamia, and mango industries. Over five years, the project delivered robust, regionally relevant research on high-density orchard systems, innovative canopy management, rootstock and cultivar selection, and economic viability. Through a network of experimental and demonstration sites, the project evaluated new genetics, planting designs, and management strategies, providing growers with practical tools and knowledge to boost productivity and profitability.
Key achievements include the identification of cultivar–rootstock combinations suited to intensive systems, the development of pruning and training techniques for higher yields, and the demonstration of early and sustained productivity in several crops. The project also pioneered the use of automated phenotyping platforms for canopy assessment and delivered comprehensive economic analyses, highlighting both the opportunities and challenges of intensification.
Growers benefited from field days, workshops, videos, and industry publications, enabling them to observe outcomes firsthand and make informed decisions about orchard redesign and investment. The project’s collaborative approach, engaging researchers, growers, and industry bodies, ensured that outputs were relevant and immediately applicable. While barriers remain, such as machinery adaptation and market acceptance for alternative cultivars, AS18000 has laid a strong foundation for future innovation, resilience, and sustainability in Australian tree crop industries. Its legacy is a more informed, confident, and connected grower community, ready to adopt advanced systems as conditions and markets evolve.
For more information on the crop-specific activities in this program, you can view their individual project pages on the right-hand side of this page.
Over the past year, the National Tree Crop Intensification program continues to progress research on vigour, light, crop load, and orchard systems. Long-term field trials established earlier, in this, or the previous project (AI13004), continue to provide insights to the key themes mentioned above and their integration into orchard systems.
The second face-to-face AS18000 all Teams Forum was held in April 2023 in Bundaberg, Queensland. It proved a great opportunity to meet the new personnel, share successes and challenges and to discuss the progress of the whole program through a very interactive session focused on the mid-term review.
Avocado
Managing tree vigour continues to be a significant barrier to intensifying avocado orchards. Research on managing tree vigour with applications of plant growth regulators (PGRs) is investigating how soil drenches affects vegetative and reproductive growth in two avocado varieties with distinctly different growth habits. A new research field trial to be planted on the Bundaberg Research Facility will continue this research.
Macadamia
Discussions of the 9-year-old macadamia planting system trial by the Project Crop Reference Group found it is still providing useful production data for mature macadamia orchards planted at higher densities. The trial will be continued. A second macadamia planting system, now 3-years-old, targeting vigour management and tree architecture has cropped for the first time. These planting system trials will help us understand precocity and yield efficiency of intensive macadamia orchards. A modelling approach was also used to investigate the productivity of macadamia planted at high density. The modelling deducted that suppressed yields per hectare are more likely due to high fruit drop rather than differences in light interception. This suggests the important role of light distribution and carbohydrate dynamics within the canopy in high density planted trees, rather than solar energy captured at orchard scale.
Mango
The nine-year-old mango planting systems trial is continuing to provide useful production and fruit quality data in mature trees. Yields per hectare this past season (2022/2023) were the highest measured over the 7 years of cropping, with the cultivar ‘Keitt’ achieving over 79 tons per ha in the high-density, conventional hedge. The second mango rootstock trial is expected to be planted in September 2023. This trial will investigate the performance of the most promising rootstocks identified in the first rootstock trial on the main commercial scion cultivars.
We are currently recruiting two research staff for the Bundaberg Research Facility to work on the project. A Principal Research Scientist to lead Avocado research at Bundaberg and a Senior Technical Officer to provide technical expertise in the day-to-day management of field research trials. The Principal Scientist will replace Col Douglas who vacated the position in February 2023. Dr Emma Carrié has been appointed as Postdoctoral Research Fellow with the QAAFI/UQ team for horticultural plant physiology and modelling at UQ (Brisbane). Dr Carrié finished her PhD last year with CIRAD in Reunion Island (France), she will conduct tree growth modelling research as part of the QAAFI/UQ team.
Almond
This research program aims to intensify the growing systems for almonds in Australia (more trees per hectare) in order to increase productivity and profitability.
The almond research team, comprising scientists from both Plant & Food Research (PFR) and SARDI, has established a series of field trials both in the research orchard at the Almond Centre of Excellence (ACE) in Loxton and in commercial orchards across the main almond-growing regions. These trials include over 20 cultivars, eight rootstocks and a variety of growing systems, to provide the almond industry (breeders, nurseries and growers) with recommendations on genotypes, tree architecture, scion and rootstock combinations, planting distance, pruning strategies and general management of higher density plantings in Australia.
SARDI is contributing to the almond component of AS18000 through its high-density (H2-H3 Optimization) orchard at the Almond Centre of Excellence (ACE). Project activities included canopy training and evaluation operations plus the 2023 harvest assessments for each of the trials 72 experimental plots.
The research team has established a network of trials on orchards both in a research environment (Almond Centre of Excellence in Loxton) and in commercial settings. The New Zealand Institute for Plant and Food Research Limited (PFR) trials are located across three states (SA, VIC and NSW) and include 20 cultivars and eight rootstocks.
This network of trials is providing breeders, nurseries, and growers with recommendations on genotypes, tree architecture, scion and rootstock combinations, planting distance, cost of trees, pruning strategies and general management of higher density plantings in Australia.
Some of this information has been published and links to those publications are provided below:
- Almond planting and early tree establishment in the nursery (part 1)
- Almond planting and early tree establishment in the orchard (part 2)
- Almond planting and early tree establishment- establishment of canopy (part 3)
The South Australian Research and Development Institute (SARDI) is contributing to the almond component of this project through its high-density (H2-H3 Optimisation) orchard at the Almond Board of Australia (ABA) Almond Centre of Excellence (ACE).
Project activities during this reporting period were dominated by winter orchard maintenance, processing of season 2022 data and communications to both industry and the broader AS18000 consortium.
Since the last milestone report in October 2021, some key activities have been achieved:
- Field and lab research was conducted, and viroid, pruning and arboretum experiments established and measured.
- Case studies were completed on commercial high density citrus orchard in August 2022. Two growers in each citrus growing regions, Riverina and Sunraysia, were interviewed about their canopy management problems, challenges and pathways growing high density citrus. Two case studies have been prepared in draft form.
- Data is being collected that will record the time of pruning experiments and allow growers to manipulate the costs associated with each input cost and activity.
- Extension materials have been produced and submitted to relevant industry outlets. A video of mandarin pruning practices of a Citrus Crop Reference Group member, has been published on the NSW DPI website: QLD mandarin pruning practices videos (nsw.gov.au). Another video series was published on the pruning trials in Sunraysia and the Riverina have been developed and the Sunraysia videos have been published on the NSW DPI website: Navel orange pruning methods and trial (nsw.gov.au).
- The annual Program Team Forum was held in July 2022 at Dareton Primary Industries Institute, NSW Department of Primary Industries. More than 30 program team members attended across each of the five target crops.