To target high quality fruit, strategic crop load management practices are currently being investigated in designed field experiments at Agriculture Victoria, Tatura, in the stonefruit experimental field laboratory.

  • Apricot, Nectarine, Peach and Plum:
    • High, medium and low crop loads
    • Tree training systems: Tatura trellis, Vertical leader & Vase - all have same planting density, micro-drip irrigation.
    • Research parameters: light interception, trunk size, tree performance, yield, fruit number, fruit quality - Brixº, maturity, firmness, colour, size

Topics:

2020

Protocols - Crop load management in stonefruit

Researcher: Mark O'Connell, Agriculture Victoria, Tatura
  • Flower and fruit thinning are agronomic practices aimed at changing the ratio of carbon partitioning between leaves and fruits.
  • Thinning dictates the number of fruit per tree and directly influences tree growth and development, yield and fruit quality outcomes.
  • Thinning activities contribute to the cost of orchard production via labour required; however, optimal crop loads can save $ through reduced picking, packing and transport costs.
  • Excessive crop loads result in small fruit size, delayed maturity and poor fruit quality despite yielding higher. Therefore, optimal crop load management is required to achieve high marketable yield and good quality fruit outcomes whilst maintaining sufficient vigour and return bloom to sustain long-term yield.
  • Research into crop load management on peach, nectarine, plum and apricot at Tatura has found average fruit weight and fruit sweetness (°Brix) decreases rapidly with increasing crop load. Fruit maturity (flesh firmness, colour development) is delayed under high crop load. Low fruiting levels increase tree vigour (shoot length, pruning weight, trunk diameter).

Protocol Download PDF in new window (Note: this document does not meet WCAG 2.0 accessibility guidelines)

2020

Results from the Canopy - Crop load study

Production results (yield, fruit quality) from crop load treatments (high, medium, low) for trees in Vertical Leader, Vase and Tatura Trellis canopy systems.

2020

Plum' Angeleno'

Science paper: Effect of cropload management and canopy architecture on yield and fruit quality of late-season plum 'Angeleno'

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  • High cropping levels reduce fruit weight and lowered packout performance
  • Irrespective of training and croppling 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.
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 loadHigh crop load:
heavy removal of fruit on trees to avoid competition for available nutrientsmoderate removal of fruit on trees to minimise competition for available nutrientsminimal 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 practicepoor 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

2019

  • Plum
  • Apricot
  • Peach and Nectarine
Plum 
Video: stonefruit cropload experiments on Plum Angeleno - Tatura trellis versus vase
  • 'These plums have high sweetness, high brix values around the 17-18 brix, irrespective of canopy system or crop load.'
  • 'The crop load treatments we've had on these trees have also impacted the yield, fruit size and fruit quality outcomes.'
  • 'Tatura trellis trees are basically larger trees. They've got bigger canopy, higher lighting interception and that gives them the ability to carry a greater fruit number and hence greater yields.'
Dr Mark O'Connell, from Agriculture Victoria, discusses stonefruit cropload experiments on Plum Angeleno - Tatura trellis versus vase
Video transcript: stonefruit cropload experiments on Plum Angeleno - Tatura trellis versus vase

I'm standing in the summer fruit experimental research orchard here at Tatura, and beside me we have plum crop load experiments where we're comparing Tatura trellis system under a high density system, next door with the vase, high density, freestanding trees. Angelino is the cultivar and we've been looking at different crop loads, different fruit number per tree, and then impact on yield, fruit quality. The tree density is exactly the same. They're both one metre tree spacing on a 4.5 metre row spacing. Both micro-irrigated through in line drip. Over the last two to three seasons we've been monitoring yield, fruit number and fruit quality. In particular, brix, maturity, firmness, colour etc. We also, during the season, measured light interception and trunk size and other vegetated indicators, as well as the tree performance in terms of yield and quality. The Tatura trellis trees are basically larger trees. They've got bigger canopy, higher lighting interception and that gives them the ability to carry a greater fruit number and hence greater yields. The crop load treatments we've had on these trees have also impacted the yield, fruit size and fruit quality outcomes. These plums have high sweetness, high brix values around the 17-18 brix, irrespective of canopy system or crop load.

Apricot
Video: stonefruit cropload experiment on Apricot Golden May -  Tatura trellis versus vase
  • 'the Tatura trellis intercepts more light. They can support a higher crop load compared to the free standing vase trees.'
  • 'In terms of fruit quality, we're getting big differences due to the crop load effect in both canopy systems. It's to do with fruit number. Obviously the crop load is affecting fruit size and then that follows on with effects on the pressures, the firmness for example and the brix.'
Dr Mark O'Connell, from Agriculture Victoria, discusses the stonefruit cropload experiment, Apricot Golden May - Tatura trellis versus vase
Video transcript: stonefruit cropload experiment, Apricot Golden May -  Tatura trellis versus vase

I'm standing in the stone fruit experimental orchard here a Tatura. And today I'm going to present some information on the apricot canopy crop load experiments. Beside me we have a Tatura trellis system, canopy system compared to the freestanding vase system. They're both the same tree age, same soil preparation, same root stocks, same tree spacing. And what we've been doing over the most recent years, once these trees reached maturity, we've been varying the crop load, the number of fruit tree. And we've been looking at the yield, fruit size, and in particular fruit quality aspects. So overall we've been comparing tree performance and fruit quality and include things like light interception and biomass from the prunings, the yield, the fruit quality, the fruit size across these two experiments, one on Tatura trellis and one on the freestanding vase. The crop load effects have really been quite prevalent. We've seen huge changes with fruit size. Obviously if you have higher fruit number, the smaller the fruit, but higher the yield, which isn't desirable because we need some minimum standards there. Around about the thirty six grams of fruit, is the base standard in apricot. Light interception wise, obviously the larger the tree, as you can see here with the Tatura trellis intercepts more light. They can support a higher crop load compared to the free standing vase trees. They're both the same age, planting density and other management inputs are the same. In terms of fruit quality, we're getting big differences due to the crop load effect in both canopy systems. It's to do with fruit number. Obviously the crop load is affecting fruit size and then that follows on with effects on the pressures, the firmness for example and the brix. Overall though we're getting around the 9 to 12 brix in this cultivar.

Peach and Nectarine
Effects of low, medium & high crop load treatments on Fruit Weight and Brix

2017

Crop Load Management Results
  • Peaches
  • Nectarines
  • Apricots
  • Plums
Video: Results for Peaches, Nectarines and Apricots
  • 'Early thinning when fruit diameters are less than 15 millimetres in size, is a good practice to maximize cell number in the fruit flesh and thus final fruit size at harvest.'
  • 'To target fruit quality outcomes in peach and nectarine, our data to date suggests setting a cropping level of one fruit per 12 to 15 centimetres fruiting lateral.'
  • 'In canopies that have poor light distribution in the lower parts of the tree canopy, we suggest maximizing fruit numbers in higher part of the canopy, reduce the number at the base of the tree to improve the uniformity in fruit quality and size.'
Dr Mark O'Connell discusses the results from the crop load management experiments (7min, 18 sec)
Video transcript

To target high quality fruit, strategic cropload management practices are currently being investigated in designed field experiments at DEDJTR, Tatura, in the stonefruit experimental field laboratory. Manipulating fruit number per tree, offers the ability to regulate available assimulate, to maximize fruit size and fruit quality. Removal of fruit may involve a combination of orchard techniques. They include pruning, blossom thinning, and hand fruitlet thinning practices. Typically commercial peach and nectarine orchards set a target for a number of approximately 1 fruit per 10 centimetres of fruiting lateral.

At Tatura, in the experiment orchard cropload fruiting level treatment treatments being investigated are, high, medium and low cropload targets. The high treatment is minimally thinned fruit to levels to maximize competition between the fruit and available assimulate. The medium fruiting level is a moderately thin fruit to minimize competition between fruit and available assimulate, and a low thinning level treatment is heavily thinned fruit to eliminate competition between fruit and available assimulate. The high cropload treatment is minimal fruit removal, and were we only removed from clusters that are thinned. The medium cropload treatment mimics typical commercial practice where we target fruit number approximately one fruit per 10 and that's per fruiting lateral. Low treatment has most fruit removed from the tree. The Tree architectures being investigated at Tatura in the cropload management experiments include vase configuration trees, vertical Leader trees and Tatura trellis trained trees. The crops being studied include nectarine, peach, apricot and plum.

Results to date show cropping levels have marked impacts on yield, fruit size and in most cases fruit sweetness, fruit maturity and fruit firmness.

The results from the 2016-17 season for nectarine Rose Bright, early season cultivar, under different cropload regimes, can be seen in those two data graphs. For fruit size we have a range of histograms for high, medium and low cropload treatments. For fruit sweetness, high, low and medium cropload treatments. We can see the distributions for that. Going back to fruit size, we had a major shift in the size of our fruit, on the high, low and medium cropload treatments where we can see the red line here, the low treatment, for example, had overall larger fruit and a high portion of larger fruit. Conversely, the high cropload treatment, produced many small fruit. When we look at the profiles of fruits sweetness. we get again, a shift to the right under less fruit per tree, so the low cropload treatment having sweeter fruit, overall.

The data for peach August Flame, a mid-season cultivar, similar sort of trends under high, low and medium cropload. We've also got two canopy configurations, a vertical leader system and a Tatura trellis system. So when we look at fruit size, under the high, low and medium, we're getting a major shift in our fruit size profiles when we have a high crop low treatment compared to the low and medium treatments. There's not as much distinguishing features in the fruit sweetness profiles. That's with the vertical leader. Similar sort of trends in the Tatura Trellis under high, low and medium cropload where the high cropload had smaller fruit and not as sweet. Another example of some data we have on nectarine Autumn Bright, another mid-season variety, under both vertical leader and Tatura trellis. Again we're getting shifts in both fruit size and fruit sweetness profiles with their cropload management for both Tatura trellis and vertical leader systems. Last season data for plum under 2 canopies, we had three standing vase trees and a Tatura Trellis canopy configuration. For the vase, fruit size differences with less distinguished, and similarly fruit sweetness was very similar, under the three regimes cropload but under the Tatura trellis however, we definitely got major shifts in fruit size profiles when we went from high fruit number per tree to the medium at low levels. And it looks like we're getting an improvement in our sweetness percentages as well.

Similar canopy configurations under apricot, last season we had a vase system compared to a Tatura trellis system under high and median croploads. Again, similar story, we have a shift in fruit size profile as we have less fruit per tree, but not much change in fruit sweetness and that occurred also in Tatura trellis as well as the vase.

Overall fruit thinning and tree management strategies for improved fruit quality include, adjusting cropload to maximise fruit size and fruit sweetness. When economically viable i.e. if financial returns are higher for better quality fruit. Early thinning when fruit diameters are less than 15 millimetres in size, is a good practice to maximize cell number in the fruit flesh and thus final fruit size at harvest.

To target fruit quality outcomes in peach and nectarine, our data to date suggests setting a cropping level of one fruit per 12 to 15 centimetres fruiting lateral.

In canopies that have poor light distribution in the lower parts of the tree canopy, we suggest maximizing fruit numbers in higher part of the canopy, reduce the number at the base of the tree to improve the uniformity in fruit quality and size.

Plums

Plum experiments 9 - 10*: Effect of crop load management and canopy architecture on yield and fruit quality of late-season plum 'Angeleno’

Objective: to identify crop load management practices, under Tatura trellis and vase training systems, to enable ‘Angeleno’ plum to maximise uniformity in fruit quality attributes.

Scientific Poster: *Result presented at the 30th International Horticultural Congress (August 2018 - Istanbul Turkey)

(Download poster)

Introduction and experiment design

2015/16

Investigations in the Stonefruit Field Laboratory for Experiments 3 - 10

Manipulating fruit number per tree offers the ability to regulate available carbohydrates (assimilates), to maximize fruit size and fruit quality.

Cropload fruiting level treatments being investigated are high, medium and low cropload targets:

  • high cropload level is minimally thinned fruit treatment to maximize competition between the fruit and available assimilate.
  • medium fruiting level is a moderately thin fruit treatment to minimize competition between fruit and available assimilate, and
  • low cropload level is heavily thinned fruit to eliminate competition between fruit and available assimilate.
Introduction to research - see videos for Peach, Nectarine, Apricot and Plum experiments:

Introduction: Peach cv. August Flame on Vertical Leader tree training

Experiment 3

Introduction: Peach cv. August Flame on Tatura trellis tree training

Experiment 4

Introduction: Nectarine cv. Autumn Bright on Tatura Trellis tree training

Experiment 5

Introduction: Nectarine cv. Autumn Bright on Vertical Leader tree training

Experiment 6

Introduction: Apricot cv. Golden May on Vase and Tatura trellis tree training

Experiments 7 & 8

Introduction: Plum cv. Angeleno May on Vase and Tatura trellis tree training

Experiments 9 & 10

Table 1 Canopy crop-load experiments

Exp.FruitRoostockTreatmentTrainingDensityDate
planted
3Peach cv. August FlameNemaguardCrop Load (high, medium, low)Vertical Leader2222 trees/ha2013
4Peach cv. August FlameNemaguardCrop Load (high, medium, low)Tatura Trellis2222 trees/ha2013
5Nectarine cv. Autumn BrightNemaguardCrop Load (high, medium, low)Tatura Trellis2222 trees/ha2013
6Nectarine cv. Autumn BrightNemaguardCrop Load (high, medium, low)Vertical Leader2222 trees/ha2013
7Apricot cv. Golden MayMyrobalan H29CCrop Load (high, medium, low)Tatura Trellis2222 trees/ha2014
8Apricot cv. Golden MayMyrobalan H29CCrop Load (high, medium, low)Vase2222 trees/ha2014
9Plum cv. AngelenoMyrobalan H29CCrop Load (high, medium, low)Tatura Trellis2222 trees/ha2014
10Plum cv. AngelenoMyrobalan H29CCrop Load (high, medium, low)Vase2222 trees/ha2014

Virtual Orchard Tours

Virtual Tours

360 degree photos of tree structures in the stonefruit research orchard.

Time series videos

Every few weeks photos were taken of each experiment, and produced into a video to show the resulting growth of tree canopies and fruit development.

Time series videos experiments 3 to 8

Crop load and fruit position influence variability in nectarine quality

Crop load and fruit position

This study looks at the influence of crop load and fruit position on size and soluble solids concentration.

The effects of canopy architecture and crop load on non-structural carbohydrate in young stone fruit trees

Understanding the effects of canopy architecture and crop load on non-structural carbohydrate (NSC) in stonefruit trees is fundamental to boost early bearing and ensure consistent fruit size and quality.

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.