The Australian summerfruit industry has greatly expanded exports in recent years, primarily to Asia markets. However, the industry has identified that domestic sales growth is impeded by low consumer satisfaction with fruit quality, leading to low prices and static consumption.

Good agronomic management can improve domestic and international demand for fruit and encourage purchase intent by consistently producing the best quality fruit.

Orchard factors such as crop load, rootstock, irrigation and canopy design govern agronomic inputs and labour costs, and affect yield, fruit maturity and fruit size.

However, there is limited published scientific information on the effects of crop load, canopy design, strategic irrigation management and rootstock on fruit quality attributes, particularly fruit sweetness for stone fruit crops under Australian conditions.

The research project ‘SF17006: Summerfruit Orchard – Phase II’ has been investigating irrigation management, canopy design, rootstock and crop load management on summerfruit (peach, nectarine, plum and apricot) in the Experimental Stonefruit Orchard at the Tatura SmartFarm.

The research contributes to improved productivity and export potential of summerfruit by providing evidenced-based local information including production protocols, industry roadshows, orchard field tours, on-line updates, videos, webinars and industry and scientific publications that guide growers to produce consistent high-quality stone fruit to meet the expectations of export and domestic markets.

Benefits to the summerfruit industry are predicted to be increased prices received from fruit sales and subsequent improved production and industry growth.

Grower production protocols for agronomic management practices (crop load, rootstock, irrigation management, canopy architecture) are available online (www.hin.com.au). The production (yield, fruit quality) data and associated key findings are summarised for each growing season (2016/17–2021/22) for the following crops and agronomic experiments:

(A) Nectarine ‘Rose Bright’ (crop load and rootstock)

(B) Peach ‘September Sun’ (crop load and rootstock)

(C) Peach ‘August Flame’ (crop load and canopy architecture)

(D) Nectarine ‘Autumn Bright’ (crop load and canopy architecture)

(E) Apricot ‘Golden May’ (crop load and canopy architecture)

(F) Plum ‘Angeleno’ (crop load and canopy architecture)

(G) Nectarine ‘September Bright’ (irrigation management).

Key findings

The Tatura stone fruit orchard systems study has increased horticultural knowledge of irrigation management, rootstocks, crop load and canopy design for Australian conditions. Overall, key findings of orchard factors on tree growth, vegetative vigour and production responses for peach, nectarine, plum and apricot have shown:

Crop Load

- High crop load resulted in high yield, small fruit size with poor fruit quality shown as delayed maturity, increased firmness and reduced sweetness and lowered packout

- Low crop load produced larger fruit, advanced maturity and sweeter fruit

- Crop load management did not affect light interception or main branch size

- High crop load reduced shoot length and pruning biomass

- In the early production years, high crop load increased suckering

Rootstock effects on scions

- Cornerstone produced large, sweet fruit and high yield with high tree vigour

- Elberta and Cornerstone showed similar tree growth and development metrics compared to Nemaguard

- Krymsk 1 compared to Nemaguard (the current industry standard for peach and nectarine) exhibited dwarfing characteristics producing less pruning biomass, smaller main branch size, a lower level of canopy light interception and reduced shoot length

- Krymsk 1 compared to Nemaguard had low yield due to reduced fruit number because of small tree size

- Krymsk 86 compared to Nemaguard showed semi-dwarfing traits: lower canopy light interception, smaller main branch cross-sectional area, shorter shoot length and less pruning biomass

- Suckering on Krymsk 86 was greater than Nemaguard, but less than Krymsk 1

- Krymsk 86 outperformed Elberta rootstock in terms of fruit size, red skin colouration and packout yield but had lower fruit sweetness

Irrigation management

- Regulated deficit irrigation (RDI) management keeps trees short of water when fruit growth is slow (known as stage 2 of fruit development) or after harvest but supplies ample water during the time of rapid growth of fruit (stages 1 and 3)

- Good RDI management did not affect fruit size, yield and fruit quality (sweetness, maturity, firmness, colour)

- Deficit irrigation levels of 30–40% of full irrigation reduced the growth of shoots.

Canopy design

• For peach and nectarine

  - Similar production (yield and fruit quality) outcomes were observed between vertical leader and Tatura trellis canopy systems

  - From a vegetative growth perspective, trunk size was not different between vertical leader and Tatura trellis canopy systems; however, greater pruning biomass (summer and winter) occurred under Tatura Trellis

  - Greater and more uniform light interception occurred under Tatura Trellis canopies despite taller trees with vertical leader trees

• For Apricot and Plum

  - Tatura trellis out-yielded vase trees in establishment years due to having larger tree size (light interception) and capacity to carry more fruit numbers

  - Tatura trellis resulted in more uniform fruit weight and maturity compared to vase canopy systems

  - Greater vegetative growth (pruning biomass, trunk growth) occurred on vase tree despite having lower tree size (light interception).

Further information on each field experiment at Tatura SmartFarm is summarised on the Profitable Stonefruit (Summerfruit) Research website.

This project is funded by Hort Innovation using the summerfruit levy and funds from the Australian Government with co-investment from Agriculture Victoria.

*Written by Mark O’Connell is a researcher at Horticulture Production Sciences, Agriculture Victoria Research, Tatura and Honorary Senior Fellow at The University of Melbourne. Contact: Mark.OConnell@agriculture.vic.gov.au