Afourer project update

Afourer canopy management project re-cap

A Horticulture Innovation Australia funded project led by Steven Falivene from New South Wales Department of Primary Industries (NSW DPI) aims to develop best practice canopy management techniques. The project will improve long-term yields and minimise alternate bearing in Afourer mandarins.

Afourer mandarins are recognised for producing high yields (60-90 tonnes per hectare) during the early years of production, sometimes peaking over 100 tonnes per hectare. However, as the trees grow large, their yield declines and alternate bearing becomes more prominent. Some growers of mature trees have reported average yields of 35 to 40 tons per hectare in ‘off years’.

Excessive vigour and unmanaged water-shoot growth are thought to contribute to yield decline in Afourer trees by shading the lower canopy. Alternate bearing contributes to yield decline because the low crop load in ‘off’ years reduces long-term average yields. In the short-term, alternate bearing produces low-value small fruit in high crop load years, and in low crop load years leads to oversized fruit.

The project will investigate pruning strategies through replicated trials and demonstrations to minimise vigour and water-shoots to improve long-term yields and reduce alternate bearing. Most of the trials are on growers properties in Sunraysia and the Riverina.

This project has two objectives:

to develop best practice canopy management techniques to improve long-term yields and minimise alternate bearing in Afourer mandarins
to develop capacity of Afourer growers in Australia by collating information locally and overseas, case studying growers, implementing on-farm trials and linking growers.

Andrew Creek (NSW DPI Citrus Development officer) will be coordinating activities in the Riverina and Rachelle Johnstone (WA Department of Primary Industries and Regional Development) will be coordinating activities in WA.

Demonstration trials

Demonstration trials have been set up on growers’ properties around Australia, including the Southern Cross-managed farm at Ellerslie (Sunraysia) in collaboration with Rebecca Grant, David Lyell, Jason Plant and Matt Short. Treatments include heavy topping (~1.5 m) every second row, half tree hand pruning (Figure 1), north-west window pruning and intensive pruning.

At the Nutrano farm, Tom Braybrook and David Stevens have established several demonstration trial sites including heavy pruning and high nutrition treatments (Figure 2).

Figure 1. Half tree hand pruning treatment at the Southern Cross managed farm at Ellerslie.

Figure 2. David Stevens standing in front of a tree (25 November 2020) that was heavily pruned in late spring 2020.

Replicated trials

Seven replicated trials have been established: four on mature tree blocks and three on young tree blocks, each has four or five replicates. Five replicated trials are in Sunraysia and two are in the Riverina.

Sunraysia mature tree replicated trial treatments:

Light hedging annually (LH): annual light hedging sides for row access, topping might be done every second year for height control.
Half tree hedging (HH): cut one side of the tree hard and let it grow and crop until it causes row access issues then cut the alternate side.
1M: pruning after harvest, traditional one-minute pruning, open a door into the tree and remove some centre limbs (Figure 3).
1×: intensive pruning, intensive side window pruning after harvest and no regrowth management during summer.
3×: intensive pruning and regrowth management; intensive side window pruning after harvest and regrowth management during summer.

Riverina mature tree replicated trial treatments:

Light hedging annually (LH): annual light hedging sides for row access, topping might be done every second year for height control.
1M centre limb pruning: annual light hedging sides for row access and traditional one or two centre limbs removed.
Centre limb pruning + regrowth management: annual light hedging sides for row access, traditional one or two centre limbs removed and regrowth management in summer and autumn.
3× pruning and regrowth management; intensive side window pruning after harvest and regrowth management in December and autumn (Figure 4).

Figure 3. An intensively pruned tree in the Sunraysia replicated trial (few days after pruning). Pruning aimed to form a structure of well-spaced limbs. This treatment will have a yield reduction in the first year and pruning next season is expected to be easier and quicker.

Figure 4. Young mature trees pruned intensively in spring in the Riverina have grown a good number of new shoots. Andrew Creek, trial coordinator and pruner, said that the trees look bare, similar to the photo of the Sunraysia intensively pruned trees.

Young tree pruning

Three replicated young tree trials were implemented; Nutrano (VIC Sunraysia), KW Orchards (NSW Sunraysia, formerly Belah heights) and Mick Cuzzillo (Riverina). The treatments include no pruning, centre limb pruning (Figure 5) and intensive pruning and are replicated five times. The intensive pruning treatment removes centre or side branches that are expected to be problem limbs and providing adequate space between the limbs. In other words, the intensive pruning treatments aim to prevent the trees from growing ‘wild’ by the time they reach maturity.

Figure 5. Young tree pruning replicated trial at Nutrano; centre pruning treatment.

Field days

November 2020 Sunraysia farm walks

Two farm walks occurred in Sunraysia to inspect pruning trial sites, overview grower Afourer practices and general discussion. A follow-up visit will occur in late summer or early autumn.

A farm walk was held on 24 November at KW Orchards (formerly Belah heights; Figure 6), which is managed by Lyn Tonsin and Toby Hederix. Toby discussed that his trees have been growing and producing well for the first 10 years, however they have reached maximum size and need to be pruned for row access. The trees have been pruned similarly to the one-minute pruning treatment in the replicated trial.

Figure 6. Farm walk participants inspecting replicated trial trees at KW Orchards. Steven Falivene is holding an electric chainsaw that was used to implement pruning trials.

A farm walk occurred on 25 November at Nutrano SunWest that is managed by Tom Braybrook along with consultancy from David Stevens. The farm has one of the oldest Afourer trees in the region and Tom and David discussed the challenges of managing the highly vigorous trees (Figure 7). Managing their trees is mostly by mechanical pruning and some hand pruning where relevant. Tom indicated that the trees yielded very well during the early years and then as the trees matured and needed annual pruning for row access, average yields started to decline. Tom and David, with the help of Racheal McKenzie (field technical officer), are actively running numerous trials to help understand the best option for their circumstances (reported in project demonstration trials).

Figure 7. Farm walk participants inspecting replicated trial trees at Nutrano.

General trail and demonstration trial/case study farm walks

General short farm walks inspecting trial sites (replicated and grower demonstration) are planned for late Autumn. Afourer growers wishing to join the project and participate in activities can contact Steven Falivene on 03 5019 8405, 0427 208 611, or steven.falivene@dpi.nsw.gov.au.

South Africa Zoom meetings: pruning and carbohydrate sampling

Four Zoom meetings occurred with South African citrus specialists Paul Cronje (Citrus Research International), Hans Bester (Citrus Research International) and Jackie Standers (Philagro). A report of the zoom meetings is published in the ‘Project Planning Background Information report’ previously circulated.

A second Zoom meeting occurred with Marne De Vries (Agri Technovation) and Jakie Stander (Philagro) discussing carbohydrate leaf and root sampling for predicting and managing crop load (Figure 8). Notes from the zoom meeting are available upon request.

Figure 8. Left: Jakie Stander (Philagro), Right: Marne De Vries (Agri Technovation).

Funding Acknowledgment

This project has been funded by Hort Innovation, using the citrus research and development levy, co-investment from NSW DPI, and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. Afourer grower project members providing their time and trial blocks in-kind; special thank you to Nutrano, Southern Cross, KW Orchards and Mick Cuzzillo for your collaboration in replicated trials.

Contacts

Sunraysia and South Australia
Steven Falivene
NSW Department of Primary Industries
Citrus Development Officer
DARETON 2717 AUSTRALIA
P 03 5019 8405, M 0427 208 611, E steven.falivene@dpi.nsw.gov.au

Riverina
Andrew Creek
NSW Department of Primary Industries
Citrus Development Officer
Yanco NSW 2703 AUSTRALIA
M 0428 934 952, E andrew.creek@dpi.nsw.gov.au

Western Australia
Rachelle Johnstone
Department of Primary Industries and Regional Development
Horticulture Research Scientist
Bunbury WA 6230 AUSTRALIA
P 08 9780 6158, E mailto:rachelle.johnstone@dpird.wa.gov.au

March 2021.