2020 Plum and Apricot Results
Plum' Angeleno'
Science paper: Effect of cropload management and canopy architecture on yield and fruit quality of late-season plum 'Angeleno'
- High cropping levels reduce fruit weight and lowered packout performance
- Irrespective of training and cropping level combination, fruit sweetness was high with low variability
- Over half of all fruit grown on Tatura trellis exceeded º18 Brix, compared to ≤38% on vase.
- For vase trained trees, fruit maturity and firmness were similar across cropload treatments. However, for the Tatura trellis training system, high cropping levels produced more immature and firmer fruit.
International Society for Horticultural Science: O'Connell, M. and Stefanelli, D. (2020). Effect of crop load management and canopy architecture on yield and fruit quality of late-season plum 'Angeleno'. Acta Hortic. 1281, 227-234
DOI: 10.17660/ActaHortic.2020.1281.31
https://doi.org/10.17660/ActaHortic.2020.1281.31
Abstract: The Australian summer fruit industry has identified that sales growth is impeded by low consumer satisfaction with fruit quality, leading to low prices and static consumption. Crop load is known to affect fruit size of plum, but few studies have been reported on fruit quality. The effect of crop load on fruit quality was studied in an experimental orchard at Tatura, Australia. The objective of the study was to identify crop load management practices, under Tatura trellis and vase training systems, to enable plum to maximise uniformity in fruit quality attributes. Different thinning regimes were implemented in season 2016/17 to establish the following crop load treatments: 1) high: minimally thinned; 2) medium (commercial standard as control): moderately thinned and; 3) low: heavily thinned. Larger canopies occurred on Tatura trellis compared to vase, despite identical tree density and age. Larger tree size was reflected in trunk cross-sectional area and canopy radiation interception (fPAR), providing capacity to support greater fruiting levels and high yields. Mid-season fPAR was ~68% under Tatura Trellis compared to ~52% for vase trees. Fruiting level did not affect full bloom date in spring 2016 and spring 2017 or fPAR in summer 2017 for a given canopy architecture. However, trunk growth was higher under low crop load on Tatura trellis. Overall, high cropping levels reduced fruit weight and lowered pack-out performance. Irrespective of training and cropping level combination, fruit sweetness was high (≥17.2 °Brix), with low variability (CV≤11%). Over half of all fruit grown on Tatura trellis exceeded 18 °Brix, compared to ≤38% on vase. For vase trained trees, fruit maturity and firmness were similar across crop load treatments. However, for Tatura trellis training system, high cropping levels produced more immature and firmer fruit.
Apricot 'Golden May'
Crop load and canopy design affect ‘Golden May’ Apricot quality and yield (4 seasons)
Download PDF document Apricot ‘Golden May’ - Tatura Trellis out yield’s vase in establishment years (Note: this document does not meet WCAG 2.0 accessibility guidelines.)
Agriculture Victoria research indicated the need for manipulation of canopy design and fruiting levels to achieve high yield, large sweet fruit, maximum pack-out of domestic/export quality fruit and minimal vegetative (pruning) growth in ‘Golden May’ apricot.
Trees were planted in winter 2014, trained as Tatura Trellis and vase at 4.5 m row & 1.0 m tree spacing. The research used a sensor equipped fruit grader with stringent fruit quality metrics to determine the number of ‘premium’ grade fruit. Premium grade fruit was defined as fruit size ≥ 36 g, maturity < 1.2 *IAD and sweetness ≥ 12 °Brix of individual fruit (~ 17,000 fruit per season). This following information summaries production results for 4 seasons from 2016/17 to 2019/20.
*IAD: index of absorption difference. The DA meter measures the flesh greenness by reflectance of two wavelengths (670 and 720 nm) of light, near the chlorophyll-a absorbance peak. The reflectance is expressed as an index of absorption difference (IAD) scaled from 0 to 3 (green). Comparison of IAD with fruit ethylene production for many cultivars has shown a strong inverse relationship supporting the DA meter as a tool to measure fruit maturity.
Key points
- Fruit size and sweetness can be improved by reducing fruiting levels in Tatura Trellis and Vase trained trees.
- Tatura Trellis resulted in more uniform fruit weight outcomes than Vase trees
- The Vase architecture (free-standing training system) produced smaller trees and lower yields in establishment years.
- Tatura Trellis trained trees were larger. They had a bigger canopy and greater light interception. This gave them the ability to carry a greater fruit number, hence greater yields than the vase trees
- Trunk diameter was not impacted by crop load management on either Tatura Trellis or Vase trees.
- In canopies that have poor light distribution in the lower parts of the tree, we suggest maximizing fruit numbers in higher part of the canopy and reducing the number at the base of the tree to improve the uniformity in fruit quality and size.
Varying crop load resulted in several results:
- High crop loads failed to achieve ‘premium’ grade production outcomes primarily due to a combination of poor fruit size and low sweetness irrespective of tree training system. For Tatura Trellis and vase trained trees, high crop load reduced fruit weight, lowered sweetness and delayed fruit maturation. Low crop load produced large sweet fruit, but penalised yield and grew more vegetative growth that required more pruning, irrespective of training system.
- Less seasonal variability in fruit quality was found in the Tatura Trellis trained trees. In season 3, no fruit in the vase trained trees met the premium grade due to low fruit sweetness compared to ≥ 80% of fruit meeting 'premium' grade in the Tatura Trellis trained trees.
- The vase architecture (a free-standing training system) produced smaller trees and lower yields in establishment years. Figure 1 highlights that Tatura Trellis produced higher cumulative yield (seasons 1 – 4) for each crop load treatment (Low, Medium and High) than vase trained tree.
Figure 1. Cumulative yield (seasons 1 – 4) under crop load treatments in vase and Tatura Trellis trained trees
- Crop load management clearly impacted the distribution and uniformity of fruit size, sweetness, maturity and firmness on Tatura Trellis and vase trained trees (see Figure 2)
- For each crop load treatment (Low, Medium and High), Tatura Trellis resulted in more uniform fruit weight outcomes than vase trained trees (see Figure 2)
Table 1. Croploads modified through fruit thinning on both Vase and Tatura trellis trees, and outcomes of cropload treatments
| Low crop load: | Medium crop load | High crop load: |
|---|---|---|
| heavy removal of fruit on trees to avoid competition for available nutrients | moderate removal of fruit on trees to minimise competition for available nutrients | minimal removal of fruit on trees to maximise competition for available nutrients |
| large sweet fruit, penalised yield, grew more pruning biomass | (control) standard or recommended commercial practice | poor fruit size and low sweetness |
- The Medium crop load treatment (control) had a target of 1 fruit per 10 cm of fruiting lateral.
- The Low crop load treatment had approximately 20 % less fruit per tree than the Medium crop load treatment.
- The High crop load treatment had approximately 40 % more fruit per tree than the Medium crop load treatment.
- Fruit was hand thinned early in the season (< 12 mm diameter) to maximise cell number and final fruit size. Fruit thinning consisted of initial removal of fruit from end of branches, ‘doubles’, small, disfigured & damaged fruit followed by even thinning of remaining fruitlets to desired crop load target.
The graphs in figure 2 present distributions of fruit size, sweetness, maturity and firmness under crop load treatments (high, medium and low) in season 4 on Vase canopy (graphs in left column) and Tatura Trellis (graphs in right column). Figure 1 illustrates, that for each fruit quality variable, crop load management clearly impacted the distribution and uniformity. For each crop load treatment (Low – Medium – High), Tatura Trellis resulted in more uniform fruit weight outcomes than Vase trees.
Figure 2. Graphs show the distributions of fruit size, sweetness, maturity and firmness under crop load treatments (high, medium and low) in season 4 on Tatura Trellis and Vase trees.
Measuring fruit maturity
Fruit maturity was measured with a DA meter (IAD) to guide harvest logistics. The DA meter measures the flesh greenness by reflectance of two wavelengths (670 and 720 nm) of light, near the chlorophyll-a absorbance peak. The reflectance is expressed as an index of absorption difference (IAD) scaled from 0 to 3 (green). Comparison of IAD with fruit ethylene production for many cultivars has shown a strong inverse relationship supporting the DA meter as a tool to measure fruit maturity.
How to use the DA meter and reference values for cultivars see database: DA meter IAD maturity classes
Project acknowledgement
This research (SF12003 Increased stone fruit profitability by consistently meeting market expectations; SF17006 Summerfruit Orchard Phase 2) was funded by Agriculture Victoria with co-investment from Horticulture Innovation Australia Limited using the Summerfruit levy and funds from the Australian Government.