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Orchard trials shape future management strategies

Research & Extension

Author: Richard Pentreath &
Kevin Manning
AgFirst
+64 6 872 7080
hawkesbay@agfirst.co.nz

Over the last two seasons over twenty five trials have been carried out in association with the Future Orchards® program. Each trial has been designed and implemented collectively by growers, front line advisors and consultants with the aim of finding practical solutions to common challenges and constraints that limit orchard productivity.

Trial outcomes provide valuable information that growers require before they can adopt a new management strategy with confidence or test a new strategy for themselves. The results of each trial can be found in the members’ area of the APAL website and have been widely communicated via orchard walks, trial reports and industry publications. Orchard trials or ‘demonstration trials’ are typically designed to test a product or management approach in the ‘real world’ context, allowing growers to evaluate results for themselves and easily translate the outcomes to their own circumstances. Running a demonstration trial means that certain elements cannot be controlled such as frost and adverse seasonal conditions and it is often difficult to achieve the high level of replication and randomisation that characterises scientific trials. However, when orchard trials are well designed and Mother Nature is kind, orchard trials can provide the physical evidence that growers require to determine whether the strategy offers a practical solution that they are willing to try for themselves. With the odd exception, Future Orchards trials have run to completion and produced meaningful results and in many cases generated valuable recommendations for the wider industry. So what has been learnt over the past two years of trials? There are too many trials and outcomes to discuss in detail but we can look at what was learnt from some of the trials that share common themes and had similar objectives. These included vigour management to improve young tree growth and development and secondly, vigour control techniques to improve fruit quality and yield in mature blocks.

Improving young tree growth and development

If young trees can develop good structure and fill their allocated space quickly, yields can be increased sooner and the grower achieves a better return on their investment. However there are a number of factors that often limit young tree development including replant disorders, soil type, water availability, nutrition, training and crop load. A number of Future Orchards trials have been carried out to assess different management strategies that may help to overcome these constraints and help produce strong productive trees in the shortest possible time. Some of the strategies employed were more successful than others and some valuable lessons were learnt.

Give trees a good start

In a trial with young re-plant Kanzi® trees in SA, the effects of not fumigating soil prior to planting could not be overcome in the second season by applying a range of nutritional amendments. A second trial carried out on ‘Royal Gala’ on M26 rootstock also aimed to improve tree growth following three years of poor growth after planting. None of the treatments were able to produce an acceptable level of growth, thus reinforcing the message that trees must be given the best possible start at the time of planting.

Use an effective soil treatment

In a trial comparing soil fumigants and bio inoculants in Southern Victoria, Chloropicrin was found to be superior to Basimid as a soil fumigant and the addition of bio inoculants, Plant Mate and Radifarm further improved tree growth.

Implement suitable thinning techniques

Two trials were carried out to assess the impact of crop load on second and third leaf Pink Lady™ trees. In order to maximise tree height on second leaf trees, three treatments were compared. The control treatment was a standard chemical thinning program, treatment 2 included removal of all flowers in the top 0.5m of the tree in addition to the standard chemical thinning program and in treatment 3 all fruit were removed from the trees. Treatments 2 and 3 resulted in the greatest leader extension and shoot length. In another trial, three specific crop loads were compared including three, five and eight fruit/TCAcm2. In this trial a crop load of eight fruit/TCAcm2 produced the best result overall with no loss of leader extension and superior fruit quality in terms of fruit size and colour. It should be noted however, that the optimal amount of fruit removal on other orchards will depend on rootstock, the training system used, planting density and the desired tree structure at full maturity.

Figure 1: Enhancing Young Tree Growth trial, Stanthorpe, QLD. Photo taken 18th November 2013 showing a control tree that received no treatment. Photo Credit: Orchard Services

Giberellic acid improves tree growth

Giberellic acid (GA3) resulted in improved extension growth and canopy development of young treated Kanzi trees on M26 rootstock in a trial conducted in South Australia. A similar Queensland trial also produced improved extension growth on young Pink Lady trees. A third trial in Southern Victoria highlighted the need to ensure that spray solution is acidic (-pH 5) when spraying GA3.

Managing vigour in mature trees

Depending on rootstock and growing conditions, mature trees will often require intervention to manage excessive vegetative vigour. A combination of pruning strategies as well as chemical and root pruning strategies were evaluated in orchard trials. Again, some strategies were more effective than others but some exciting and some very useful outcomes were achieved, some of which have led to further investigation and others that have provided immediate and practical recommendations.

Time Regalis® use wisely

A Queensland trial was designed to assess the importance of timing for the initial application of Regalis®. Interestingly, all three early applications proved to be equally effective as the recommended timing (60% petal fall, shoots 4-6 cm) where the average reduction in shoot length was 26%. However, applying the first application only six days after recommended timing when shoots were 10-12cm long resulted in only 4% reduction in shoot length. Whilst early applications were successful, growers were cautioned that when following 28 day spray intervals the final application may be too early to restrict late season growth.

Root pruning delivers benefits

Figure 2: Enhancing Young Tree Growth trial, Stanthorpe, QLD. Photo taken 18th November 2013 showing a tree that received treatment with giberillic acid (ProGibb®). Photo Credit: Orchard Services

Several root pruning trials were carried out over the last two years of the Future Orchards programme. The following benefits were observed;

  • effective vigour management when applied correctly
  • a positive effect on return bloom
  • shorter shoot length and more open canopies resulting in better light distribution
  • minimal impact on crop yield

When considering root pruning, growers need to be mindful that root pruning can result in significant reduction of the effective root area and ensure that irrigation requirements can be met.

A way to reduce biennial bearing

A combination of summer NAA sprays and root pruning was trialled in Adelaide Hills, South Australia. The combined treatments significantly reduced the impact of biennial bearing on mature ‘Fuji’ trees by increasing return bloom and restricting vegetative vigour. After a 50 ton/ha yield the previous season, gross yield from the untreated control trees was 36.9 ton/ha versus 53.8 ton/ha from the treated trees.

Acknowledgements

AgFirst would like to acknowledge the growers, front-line advisors and local advisory groups who have made these trials possible. Full reports on all Future Orchards trials can be found within the members section of the APAL website.

Tagged:
crop load and thinning Future Orchards Vigour Young tree development

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