By Steven Spark and Yvette Jones (AgFirst)
Small scale on-orchard trials are a regular part of the Future Orchards® project and occur across all growing regions. Not only does this encourage innovation at an orchard level but gives growers an opportunity to implement the latest research and development ideas and techniques available to them on-orchard. This article will discuss some of the current FO trials underway in South Australia and Western Australia and outline some of the initial results produced to date and where these trials might be heading in the future. Trial progress and final reports are available in the Future Orchards library. Also, some of these trial results will be presented during Future Orchards walks.
1. Young tree growth project, Adelaide Hills, South Australia
Joel Brockhoff manages the family orchard ‘Otherwood’ which is the South Australia Focus Orchard. The orchard contains 15 hectares of apples and a mixture of avocados, citrus and kiwifruit. Like most orchardists, Joel has expressed an interest in improving yields and packouts as well as identifying ways to improve labour efficiencies across his orcharding operation. One of the trials on Joel’s orchard is to investigate different tree growth treatments to optimise the growth and particularly the height of newly planted trees.
On a newly planted block of Aztec Fuji, six different strategies were used, all with the aim of optimising the growth and particularly height of a newly planted block. Three of the treatments involve pruning trees back to a whip (removing all side branches) with no heading cuts at planting. The other three treatments involved whipping the trees as well as heading (cutting the tree tops back by about 30-50cm) at planting.
Throughout the trial, growth and yield measurements and growth observations were recorded by Paul James, the South Australian Front Line Advisor (FLA). Monitoring will continue to throughout the duration of the trial.
Progress to date
One of the objectives was to get the Aztec Fuji trees to a height of four metres as soon as possible. Fuji trees have been traditionally hard to gain adequate height in South Australia because of readily formed basal branches and weak leaders. The trial is continually looking at ways to overcome this issue and establish tall trees to optimise tree performance on a trellis structure under hail net.
The trial has just completed its second growing season and is already showing some interesting trends:
- The better treatments in the first year were not automatically the best at the end of year two.
- The treatments which were meeting the objectives of the project the best, did appear to be whipped (but not headed at planting) and then whipped again at the end of the first growing season. They also provided the best extension growth in the leaders.
The serious impacts of developing basal branches too early in the development of the trees are already clear. Managing these branches by removing them will continue to ensure that cropping potential of these trees can continue to be maximised. Many of the branches which were trained during the first growing season may need to be removed this coming winter as choke points which weaken the leader growth are already developing.
Chasing early fruit yields at the expense of good tree growth is a problem faced by all growers. This is particularly evident in the control treatment which replicate existing practices. The trial will continue for the next three seasons.
2. Observations of Erger™ use in Adelaide Hills, South Australia
Erger™ is a recently released product that is reputed to promote uniform floral bud break from dormancy. This product is reported to both advance and condense flowering, depending on the application time. It may provide another tool for growers to use in this area.
A trial established on a commercial Open V trellis orchard of Alvina Gala in the Adelaide Hills aimed to provide a demonstration of Erger and its effectiveness. To quantify its effectiveness, the product was applied at commercial rates, several different times before the normally anticipated green tip stage. Treatments included:
- Erger and Calcium Nitrate in 1,000L of water per hectare using a commercial tower sprayer;
- a control treatment of no spray; and
- a treatment of Dormex™ used as a comparison.
The trees were pruned prior to treatments being applied.
During the flowering period the treatments were monitored, photographed and measured weekly with the various phonological stages recorded. As the trial continues, fruit growth and yields will be measured at appropriate stages of growth to determine if a more uniform flowering was achieved compared to the control and the Dormex treatment. Initial findings of the trial will be discussed during a presentation to growers in winter 2017.
3. Evaluating the value of simple, narrow, accessible and productive (SNAP) trees, South West, Western Australia
Around the world there is shift in horticulture, reducing the number of trees planted per hectare by growing more stems per tree. The current trial on the Fontanini focus orchard in South West, Western Australia aims to demonstrate the possibility of improved production using the simplicity of simple, narrow, accessible and productive (SNAP) tree management on a mature Cordon planting system (multiple stems grown on a single trunk). A few rows of old Cordon style trees on the Western Australian Focus Orchard have been used to try out new SNAP tree training system. By using older Rosy Glow and Fuji trees and re-working them to fit the notion of the SNAP system, growers can learn valuable skills sooner than waiting for a newly planted block to come into production. Lessons learnt here can be transferred to newer plantings in the future.
Over the next few years’ trees will be managed using some simple SNAP pruning rules such as:
- Cut out the big branches, 2-3 branches at the top (bench cuts to promote weaker replacement shoots).
- Ideal wood is small, approximately 10mm thick.
- Get rid of big wood that reduces sunlight getting into the tree – create windows of light into the tops of the trees.
- Twelve central leaders per 10 metres of row.
- Straighten up central leaders with staples/tree ties.
- Stagger branch removal over the next few years – only cut 2-3 limbs, next biggest limbs must stay this year.
- Aim to reduce vigour with whatever tools required (fruit/deficit irrigation/Regalis etc.)
- Crop hard but avoid biennial bearing.
- Aiming for 125 fruit per stem/leader (80T).
The driving influence behind the shift to SNAP systems is the ability to increase yields of better quality fruit by re-vitalising existing older plantings. Valuable lessons will be learnt in this orchard demonstration with results expected in June 2017.
4. Leaf defoliation in low chilling environments, South West, Western Australia
One of the issues in Western Australia, is delayed leaf drop in the autumn and the impact that has on the duration of dormancy. Many growers in Western Australia defoliate apple tree leaves in differing ways. The question always asked is; “Does leaf defoliation enable the trees to enter the dormant phase earlier and therefore gain more winter chill in a low chill environment?”
When a sample of orchardists were surveyed about their orchard practices around leaf defoliation some interesting information was collected:
- 70 per cent of Western Australia growers defoliated apple tree leaves.
- 30 per cent did not defoliate the leaves.
When asked why they undertook leaf defoliation?
- 42 per cent were applying nitrogen to boost bud quality;
- 33 per cent felt their trees were entering the dormant phase earlier and therefore gaining more chill;
- 17 per cent undertook the management practice to clean up the orchard as disease prevention; and
- 8 per cent used the opportunity to start pruning earlier.
From the growers that were surveyed, most used a foliar urea at a rate of 40kg/ha with some adding Zinc Sulphate and/or Copper Sulphate. The growers that weren’t following this practise believed the results produced weren’t worth the economic investment.
To further test the surveyed data and the hypothesis, four defoliation treatments were tested across Cripps Pink, Kanzi and Buckeye Gala. Treatments included the described grower standard of Urea or Zinc, a control as well as ProTone (ABA Abscisic Acid) and a Dormex treatment.
Ongoing weekly monitoring has already produced some interesting observations between treatments and between varieties. After the first monitoring round, trees treated with ProTone still had some leaves (30 per cent) to drop compared to Urea which had fully defoliated on the Buckeye Gala and Cripps Pink, with around 10 per cent of leaves remaining on the Kanzi treatment.
Further assessments will be undertaken to see if flowering was positively impacted by defoliating the leaves. It is hoped that these results will be available at an upcoming Future Orchard Walk.
Further information about these trials and others undertaken by participants of the Futures Orchard program is available on the APAL website. Special thanks to Front Line Advisors Paul James South Australia and Susie Murphy White Western Australia, who supplied information for this article and to the Focus Orchards participants of Joel Brockhoff and Jo Fontanini and family.