Research on canopy design options for stone fruit at Tatura SmartFarms has shown for peach nectarine, plum, and apricot that using vase and trellis systems has found the canopy selection affects the tree growth and vigour, and impacts yield and fruit quality. So canopy architecture and design are important orchard business management decisions made before crop establishment. Canopy type and design influences tree density, and tree size and shape, and governs yield, and orchard management practices like infrastructure, designs, costs, irrigation, nutrient, pest and disease management, labour inputs, and effects the vegetative growth and development of the trees, and impacts fruit quality and production potential.

Open vase freestanding canopy design is the most common in the industry and represents the industry standard for peach and nectarine in Australia. Canopy systems can range from low density, freestanding vase trees, right through to modern high-density two-dimensional hedge row vertical trellis systems, and three-dimensional V trellis systems.

So for apricot Golden May and plum Angelino comparisons were done between vase and Tatura Trellis. The results show for plum and apricot, that Tatura Trellis out yielded vase in the establishment years due to having higher tree size, light interception and that capacity to carry more fruit number. Tatura Trellis resulted in more uniform fruit weight and more uniform maturity compared to the vase canopy systems in both plum and apricot. Greater vegetative growth, pruning biomass, trunk size occurred under the vase trees despite having lower light interceptions. Looking at peach and nectarine under vertical leader and Tatura Trellis systems, similar production outcomes were observed between the vertical leader and the Tatura Trellis canopy systems. From a vegetative growth perspective, trunk size was not different between the vertical leader and Tatura Trellis canopy systems. However, greater pruning biomass occurred under Tatura Trellis. Greater and more uniform light interception occurred under Tatura Trellis canopies despite of having taller trees under the vertical leader trees. These light interception regimes and responses reflect the canopy design and architecture of each training system, i.e., the vertical 3D shape of Tatura Trellis compared to the 2D hedge row of the vertical trellis.

Hello, I'm Mark O'Connell, senior research scientist at Agriculture Victoria based at Tatura SmartFam.

Research at the experimental stone fruit orchard at Tatura, has shown that crop load management on peach, nectarine, plum and apricot, shows that average fruit weight and fruit sweetness decreases rapidly with increasing crop load. Fruit maturity, that being firmness of the flesh and colour development is delayed under high crop load scenarios. At the low fruiting levels we've seen increases in tree vigour and vegetative growth, including pruning biomass and trunk size.

Cropload management in stonefruit at Tatura has shown that fruit thinning, the agronomic practice aimed at changing the ratio of carbon partitioning between the fruits and the leaves, crop load management dictates the number of fruit per tree and directly influences tree growth development, yield and fruit quality outcomes.

Fruit thinning activities contribute to the cost of orchard production, via the labour inputs required, however, optimal crop loads offer a savings through reduced picking, packing, and transport costs. Nowadays, modern high density orchard systems offer early greater cumulative yield, improved light distribution within the canopy and mature trees fill their allotted space quicker.

However, excessive crop loads can result in small fruit size, delayed maturity and poor fruit quality outcomes. Therefore, optimal crop load management is required to achieve high makeable yields, good quality fruit outcomes, and trees being more sustainable in the longterm.

Hello, I'm mark O'Connell, senior research scientist at Agriculture Victoria based at Tatura SmartFarm.

Stonefruit trees set more fruit than they can support to full maturity. Flowers and fruits naturally thin themselves (known as fruit drop); however, stonefruit crops (peach, nectarine, plum and apricot) require thinning for improved horticultural outcomes: yield, fruit quality and tree health.

Excessive fruit numbers result in greater fruit competition for limited available energy (carbohydrates), poor production outcomes such as low fruit weight and reduced quality, limb breakage, biennial bearing and ultimately tree health is reduced.

Flower thinning is usually down mechanically (e.g. Darwin string thinners) and fruit thinning is most often down by hand. Hand thinning of fruit is more precise but has higher labour costs. Winter pruning is also a form of fruit thinning as it sets the level of tree fruiting structures for each season.

Canopy accessibility by the string thinner can be improved by pruning to eliminate excessively long or short fruiting laterals, removal of shoots in less accessible regions of the canopy, and by tree training to maintain straight scaffold.

The recommended time for mechanical flower thinning is prior to full bloom (i.e. 60 – 80 % bloom) to allow for possible fruit losses due to frost damage. Mechanical flowering thinning aims to remove approximately 30 % of flowers. The speed of rotation (RPM) of the string thinner and the tractor speed can be set to upscale or downscale the number of flowers removed. Similarly, handheld sting-type blossom thinning equipment has a variable speed option.

Recommend time for precision hand thinning of fruit is 30 – 45 days after full bloom when fruit size is 19 – 25 mm. Precision hand thinning is undertaken by the initial removal of fruit from end of branches, ‘doubles’, small, disfigured and damaged fruit followed by even thinning of remaining fruitlets to the desired crop load target.

Optimal fruiting levels or ‘crop load targets’ are aimed at maximising fruit size and fruit sweetness. Crop load targets depend on crop type, spring pollination conditions and tree size.

Plums and apricots, having smaller fruit are thinned differently to peaches and nectarines. Heavy flowering in spring (i.e. minimal frost incidence, high bee activity, optimal vegetative growth conditions) may require greater thinning. Larger trees (canopy size) have capacity to grow and yield more high-quality fruit.

For plum and apricot, a cropping level of ~ 1 fruit per 5 – 8 cm of fruiting lateral is recommended to maximise cell number and final fruit size and sweetness.

For peach and nectarine, a cropping level of ~ 1 fruit per 10 cm of fruiting lateral is recommended to maximise cell number and final fruit size and sweetness.

For peach and nectarine, a target vertical spacing of fruiting laterals of approximately 20 cm is recommended to avoid the deleterious effects of internal shading and limb rub of fruit. For plum and apricot, approximately 10 cm lateral spacing is recommended.

Consideration should be given to varying crop load within a tree. Better quality fruit is produced where more light (interception) occurs in the canopy. Larger fruit size, sweeter fruit and increased in colour intensity and coverage are produced on the upper canopy zones that are exposed to high light regimes.

Overall, crop load studies at Tatura on peach, nectarine, plum and apricot have shown excessive crop load results in high yield but low marketable yield due to small fruit size and poor fruit quality (i.e. low sugar). High crop load has also been shown to delay fruit maturity.

On an early-season nectarine and a late-season peach under vase canopy architecture (1,111 trees/ha), high crop loads delayed fruit maturity and lowered marketable yield due to small size fruit with reduced sweetness.

For high-density (2,222 trees/ha) blocks of mid-season peach and nectarine, under Tatura Trellis and Vertical Leader planting systems, high fruit loads produced poor fruit quality; reduced fruit weight and lowered sweetness (°Brix).

Similarly, for plum and apricot, irrespective of canopy architecture (vase, Tatura Trellis), low fruiting levels produced large sweet fruit while excessive crop loads reduced fruit weight, decreased sweetness and delayed fruit maturity.

Tree growth and vegetative vigour responses under different crop load regimes have been measured at Tatura on peach, nectarine, plum and apricot.

On an early-season nectarine under vase canopy architecture, excessive crop loads resulted in lower main branch size, reduced shoot length, less pruning biomass and increased suckering. Similarly, on a late-season peach under vase canopy architecture, high crop loads reduced main branch size.

For both peach and nectarine under high-density Tatura Trellis and Vertical Leader systems, crop load management did not impact vegetative growth.

For plum, irrespective of canopy architecture (vase, Tatura Trellis), low fruiting levels partitioned more assimilates into vegetative growth and produced higher levels of pruning biomass and grew larger trunks. For apricot (vase, Tatura Trellis), trunk size was not impacted by crop load; however, increased pruning weight occurred under low fruiting levels.

Table 1 presents production results (yield, fruit quality) for nectarine ‘Autumn Bright’ under crop load treatments (high, medium, low) for Vertical Leader and Tatura Trellis canopy systems for 7 consecutive seasons: 2015/16, 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

Overall, low crop load reduced final fruit number, increased fruit weight, reduced yield, and increased fruit sweetness (°Brix). The converse effect on yield and fruit quality occurred in the high crop load treatments. No consistent trends were noted for fruit flesh firmness (kgf), fruit maturity (I_AD) or skin redness coverage (%) under crop load treatments on either canopy system (Table 1). Notably, high fruit sweetness (≥ 12.9 °Brix) occurred throughout the study period (seasons 1 – 6), irrespective of crop load and canopy system combination.

Table 1 Download PDF in new window (Note: this document does not meet WCAG 2.0 accessibility guidelines)

Table 2 presents production results (yield, fruit quality) for peach ‘August Flame’ under crop load treatments (high, medium, low) for Vertical Leader and Tatura Trellis canopy systems for 7 consecutive seasons: 2015/16, 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

Overall, low crop load reduced final fruit number, increased fruit weight, reduced yield, increased fruit sweetness (°Brix) and advanced fruit maturity (I_AD). The converse effect on yield and fruit quality occurred in the high crop load treatments. No consistent trends were noted for fruit flesh firmness (kgf) or skin redness coverage (%) under crop loads treatments on either canopy system (Table 2). Notably, high fruit sweetness (≥ 13.3 °Brix) occurred throughout the study period (seasons 1 – 7), irrespective of crop load and canopy system combination.

Table 2 Download PDF in new window (Note: this document does not meet WCAG 2.0 accessibility guidelines)

Table 3 presents production results (yield, fruit quality) for apricot ‘Golden May’ under crop load treatments (high, medium, low) for Vase and Tatura Trellis canopy systems for 6 consecutive seasons: 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

Overall, low crop load reduced final fruit number, increased fruit weight, reduced yield, increased fruit sweetness (°Brix), lowered flesh firmness (kgf), advanced fruit maturity (I_AD), and decreased fruit skin redness coverage (%). The converse effect on yield and fruit quality occurred in the high crop load treatments.

Characterisation of each individual fruit quality (sample size per season, n ≈ 17,000 fruit) was determined from a combination of fruit weight, maturity and sweetness. Fruit was classified as ‘premium’ grade when weight ≥ 36 g, sweetness ≥ 12 °Brix, maturity < 1.2 I_AD. Typically, results showed high crop load reduced fruit weight, lowered sweetness and delayed fruit maturation and therefore failed to meet the premium grade classification (i.e. poor ‘pack-out’ performance) compared to medium and low crop load treatments irrespective of canopy system (Table 3).

Table 3 (Note: this document does not meet WCAG 2.0 accessibility guidelines)

Science paper: Crop load and canopy architecture affect yield and fruit quality of ‘Golden May’ apricot

Abstract

Fruit quality is a high priority for growers to achieve high prices and improve consumer satisfaction and consumption. This study examined the effect of crop load and canopy architecture (Tatura Trellis, free-standing Vase) on apricot yield and fruit quality in a modern high-density orchard at Tatura, Australia, during four consecutive growing seasons. Crop load treatments (high, medium, low) were applied by fruit thinning to induce a range of sink strengths for the available source of assimilates. Tatura Trellis produced a larger canopy size (light interception, fPAR) compared to Vase trees, providing the capacity to support greater fruiting levels and high yields. Vase trees produced greater pruning biomass and larger trunk cross-sectional area. For a given canopy architecture, crop load did not affect flowering date, leaf drop, suckering, trunk circumference, leaf nitrogen content, or fPAR. For seasons 1, 3, and 4, low crop load resulted in larger fruit weight at the expense of yield under both planting systems. In season 2, frost damage and low bee activity at bloom dramatically affected fruitlet development and masked crop load effects on yield and fruit quality. Overall, low crop load reduced final fruit number, increased fruit weight, reduced yield, and in most circumstances, increased fruit sweetness (°Brix) and maturity (IAD), and reduced flesh firmness (kg) and fruit skin redness coverage (%). Under high crop load regimes, the converse effect on yield and fruit quality occurred. Fruit sweetness averaged 9.4-12.4 and 9.4-13.7 °Brix under Vase and Tatura Trellis, respectively. The data suggest the need to manage fruit number to tree fPAR for high fruit quality and maximum marketable yield in ‘Golden May’ apricot.

O‘Connell, M.G. (2022). Crop load and canopy architecture affect yield and fruit quality of ‘Golden May’ apricot. Acta Hortic. 1346, 287-294
DOI: 10.17660/ActaHortic.2022.1346.36
https://doi.org/10.17660/ActaHortic.2022.1346.36

Table 4 presents production results (yield, fruit quality) for plum ‘Angeleno’ under crop load treatments (high, medium, low) for Vase and Tatura Trellis canopy systems for six consecutive seasons: 2016/17, 2017/18, 2018/19, 2019/20, 2020/21 and 2021/22, respectively at Tatura, Victoria, Australia.

Notably, high fruit sweetness (≥ 17.2 °Brix) occurred across all seasons, canopy systems and crop load treatments. Overall, low crop load reduced final fruit number, increased fruit weight, reduced yield, increased fruit sweetness (°Brix) and decreased fruit skin redness coverage (%). The converse effect on yield and fruit quality occurred in the high crop load treatments. No consistent trends were evident in fruit flesh firmness (kgf) and fruit maturity (I_AD) among crop load or canopy system. In season 4, low fruiting levels per se under both canopy systems was a consequence of frost damage during flowering.

Characterisation of each individual fruit quality (sample size per season, n ≈ 30,000 – 50,000 fruit) was determined from a combination of fruit weight, maturity and sweetness. Fruit was classified as ‘premium’ grade when weight ≥ 70 g, sweetness ≥ 12 °Brix, maturity < 1.3 I_AD. Typically, results showed despite high sweetness, high crop load reduced fruit weight and therefore failed to meet the premium grade classification (i.e. poor ‘pack-out’ performance) compared to medium and low crop load treatments irrespective of canopy system (Table 4).

Table 4 (Note: this document does not meet WCAG 2.0 accessibility guidelines)