Focus Orchard Trial: Optimal Crop Load on 3rd Leaf Pink Lady for
Optimal Canopy Development
Orchard:
Battunga Orchards
Orchardist:
Mark Trzaskoma
Prepared by:
Virginie Grégoire, Fruit Growers Victoria Ldt.
Why we decided on this trial?
Determine the maximum crop load that third leaf Pink Lady trees can bear without compromising
canopy development. Keeping in mind an overall aim to achieve return on investment as quickly as
possible and long term high yields.
Originally, this trial was going to compare 4 different crop loads; 3 fruits/TCA (cm2), 5 fruits/TCA
(cm2), 8 fruits/TCA (cm2) and 12 fruits/TCA (cm2) to really push the limits and see how much fruits
can be produced without compromising canopy development on third leaf.
Block Background
The block is Pink Lady planted 2011 on M26
rootstock. It is being trained on the Auvil V system,
planted at 3603 trees per ha. The trail was run in its
3rd leaf being its first commercial crop. Tree growth in
the first 2 years was quite good as the photo to the
right shows. The block lacks sufficient cross
pollination pressure down the row. It is netted
overhead.
Trial block before blossom 2013
Treatments
This trial contained 3 treatments which consist of 3 different crop loads. Crop loads were set at:
-
3 fruits/TCA (cm2);
5 fruits/ TCA (cm2); (this one is acting as the control) and
8 fruits/ TCA (cm2);
At the time of setting up the trial, 40 trees were randomly selected within one row. The TCA 20cm
above the graft union was measured and the number of fruitlets counted. Unfortunately not enough
trees had enough fruitlets to have a high crop load treatment of 12 fruits/TCA. All trees from each
treatment were hand thinned to the appropriate crop load after the natural drop in December.
On 24th April, prior to harvest, fruit quality and canopy development measurements were taken;
-
Fruit size on 5 fruits/tree, 10 trees/treatment, 150 fruits total;
leader extension on all 40 trees;
Full extension (within three top wires which was generally one year old wood);*
Pressure , Brix and Starch ;
Casual observation of fruit colour
* All two year and older wood had shoots removed twice
during the season, in October and January, making
extension measurements irrelevant on that part of the
tree.
Calcium nitrate and Gibberellic acid were applied on
the entire block as detailed in table on the right.
Results and Discussion
Leader Extension throughout season
80.00
Leader Extension (cm)
73.10
70.00
68.41
65.54
60.00
68.60
62.35
61.45
3 fruits/TCA
50.00
5 fruits/TCA
40.00
30.00
02-Jan-14
8 fruits/TCA
02-Mar-14
02-May-14
We would have expected the lighter crop loads to have resulted in more vegetative extension growth
however the table below shows tat the lightest crop load produced the weakest leader extension of 62
cm.
The 5 fruit/TCA treatment gave the largest leader extension (73cm) and the 8 fruit per TCA still
produced a very acceptable 69cm.
From the first measurement in January, trees with lightest crop load showed smallest average leader
extension. There are two possible explanations:
1. Fertilization and Gibberellic acid applied on all treatments had a greater effect than crop load
on canopy development.
2. Randomly selected trees were allocated a treatment according to their number of flower
clusters, therefore a tree with a very high flower number would be allocated a high crop load
treatment to make the trial possible. That could imply that trees thinned to a low crop load
were weaker from the start.
Extreme treatments like complete fruit removal and no thinning may have had an impact on shoot
growth. In this case, it seems like, Gibberellic acid and maybe calcium nitrate applications had a
greater effect than crop load.
The fruit size outcomes were as expected with the high crop loads producing smaller fruit size.
Graphs below show the low crop load trees (Treatment A – 3 fruits/TCA) achieved 79mm average
fruit size, mid crop load (Treatment B - 5 fruits/TCA) 77 mm and high crop load (8 fruit per TCA)
75mm.
From a marketing perspective the 75 mm average fruit size is more profitable.
In terms of skin colour there was a difference of 12% between low and high crop load, with the higher
crop load having better colour coverage. We can only hypothesis that the higher crop load gave a
better balance within the tree nutritionally resulting in this difference.
Conclusion
In this block the crop load of 8 fruit per cm2 TCA came out the best. At this crop load there was no
significant loss of leader extension and the fruit quality was superior in terms of fruit size and colour.
Unfortunately we were unable to test a higher crop load level of 12 fruit per cm2, however other trials
would indicate that at this cropping level we might have seen negatives in terns of canopy
development in particular.
Setting crop loads on your canopies is critical to the profitability of the block in the current year and
its long term future. Trials such as this that try and quantify the ideal levels provide valuable
information.
Trial block before harvest 2014