Focus Orchard Trial: Ruby Pink fruit quality when grown in singles vs. two or three fruit per cluster
Orchard: H & LM Sanders
Orchardist: Peter Sanders
Prepared by: Virginie Grégoire, Fruit Growers Victoria Ldt.
Why we decided on this trial?
We wanted to determine if fruit quality could be improved, (mainly fruit colour, fruit size and pressure), when most clusters are reduced to one fruit each compared to leaving two or three fruits per cluster.
As a standard practice, Sanders winter prune Pink Lady trees reasonably heavily to achieve a ratio of buds to fruit number relatively low, ie 1.0 to 1.5 buds per fruit. Theoretically this practice should allow growing apples in singles. That is, if every bud flower’s and if at least one flower per cluster sets. Environmental conditions being unpredictable as they are, we know this theory never actually happens and this means Sanders end up having to grow fruit in 2s and 3s to achieve commercial yields. Is it worth leaving more buds on when winter pruning and having to spend more time hand thinning after fruit set to make sure most fruits can be grown in singles? Does the fruit quality improve significantly enough to justify a practice change and is the change economical?
Some details on the trial
Treatment 1: Apples grown in singles (one fruit per cluster) as much as possible. Some fruits may have been left on occasion in 2s to achieve the set crop load per tree.
Treatment 2: Apples grown in 2s and 3s (2 or 3 fruits per cluster) as much as possible. As for treatment 1, some fruit naturally singled may have been left on occasion to achieve the set crop load per tree.
All 20 trees (10 per treatment) were from the same row and selected randomly. Treatment distribution was based on the number of flower clusters, trees with most clusters to bear fruits in singles and trees with least clusters to bear fruits in 2s and 3s. All trees were hand thinned to 120 fruits per tree.
Results and discussion?
As predicted fruits are consistently larger when thinned down to one per cluster with an average difference of 2 mm.
The difference in fruit colour between the two treatments was not significantly different, fruits in twos and threes showing on average 3% more red skin surface. Fruits grown in single were expected to be redder (higher proportion of red skin surface) and finding an explanation for this result is difficult. Amongst the most plausible:
- In that particular canopy fruits may not be the main shading factor when grown in twos and threes.
- One must keep in mind that fruit colour evaluation is very subjective.
On the other hand, treatments that had multiple fruits per cluster seemed to have a larger range of redness overall. They were therefore more varaiable.
Fruits grown in twos and threes were slightly firmer, only 0.20 kg difference. This small probably insignificant difference most likely due to their smaller size rather than the number of fruits per cluster.
Fruit sugar and starch level don’t show any significant difference between the two treatments other than a wider variation of sugar level when grown in pairs, as shown in graph below.
Conclusion
The trees that carried fruit predominately in singles produced larger average fruit size with a similar level of colour, pressure and brix. Our expectation that fruit quality would also improve did not eventuate however it was certainly not negative.
Fruit colour is often disadvantage by inter-fruit shading which in theory reduces when a crop is carried in singles.
On the contrary the more wood and leaf in the tree the more shading is caused by foliage hence our goal is to try and find the correct banana that maximise Class 1 yield per tree or per ha.
Assuming that fruits are always bigger when grown in a single, next it will be interesting to see if trees cropped in singles can support higher total fruit numbers per tree and hence higher total yield so the same fruit size. And will the higher fruit numbers per tree result in similar fruit quality. of better quality when grown in single compared to fruits grown on bunch.
While this trial hasn’t solved the issue categorically, were convinced that in a perfect season, a canopy that carries its crop load predominantly in singles will produce a better financial outcome. However total crop load is critical as pink lady value drops with oversize fruit, therefore if crop loads are short, it is sensible to carry the crop in 2’s and 3’s.
Our aim must be to try and use management techniques that minimise the need to hand fruit in multiple clasters.