Production research

Stonefruit irrigation experiments

Introduction

The Irrigation experiment at Tatura's Stonefruit Field Laboratory aims to Identify the combinations of irrigation levels and timing that will enable the late season nectarine variety September Bright to achieve maximum uniformity in fruit quality attributes.

About the irrigation experiments

Irrigation Protocols

Current recommendations and guidelines

Researcher: Mark O'Connell, Agriculture Victoria, Tatura (https://www.researchgate.net/profile/Mark-Oconnell-9)

Irrigation protocols: Irrigation scheduling for regulated deficit irrigation (RDI) in stonefruit. Download PDF in new window (Note: this document does not meet WCAG 2.0 accessibility guidelines)

Irrigation is generally associated with minimising moisture stress. Under such conditions trees grow quickly and are very vigorous. Until a tree has reached its desired size it should not be stressed for water. Once the tree has grown to its desired size, however, vigorous growth not only increases the need for pruning but can reduce yield. Irrigation needs to be managed in such a way as to control the growth of shoots. Such management is known as regulated deficit irrigation (RDI) and in experimental plots has maintained yields of peaches and nectarines, and reduced irrigation by about 30 - 40 %.

The RDI technique

With RDI, trees are kept short of water when fruit growth is slow or after harvest but are given ample water during the time of rapid growth of fruit. This reduces the growth of shoots. If RDI is properly managed, there is no reduction in the size of fruit or yield and fruit quality (sweetness, maturity, firmness, colour) is maintained. The reason why the above technique works relates to the growth pattern of shoots and fruit. On most deciduous fruit trees, the shoots grow rapidly early in the season and their growth slows down as the fruit begins to grow rapidly. In contrast, early in the season the fruit grows slowly. Water stress at this time will reduce the growth of shoots without markedly affecting the growth of fruit.

With RDI, the irrigation season can be divided into four periods. The duration of these periods is determined by both weather and the relationship between vegetative growth and the growth of fruit.

Scheduling RDI from ETo

In all three periods, reference crop evapotranspiration (ETo) readings, which are readily available in most districts, can be used to schedule irrigation. However, it is strongly recommended that soil moisture monitoring be integrated into an irrigation schedule to avoid over- or under-irrigating trees.

In Table 1, examples of how to use ETo to schedule RDI in a peach/nectarine orchard are shown for drip, microjet and sprinkler irrigation. The table is divided vertically into three sections; each section refers to a different form of irrigation - drip, microjet and sprinkler.

To show the influence that the spacing between trees has on the calculations for scheduling of irrigation, different spacings between trees are used for each of the three systems of irrigation. As previously mentioned, the irrigation season is divided into three periods, and the calculations needed during each of these periods are set out below the appropriate period. These calculations are divided into various sub-headings shown on the left side of Table 1. The following explains these sub-headings and should be read in conjunction with a perusal of the table.

RDI with flood and furrow irrigations

With surface irrigations, such as flood or furrow, it is difficult to control the amount of water applied per irrigation. Nevertheless, the principles discussed above apply; the initial irrigation can be delayed and the interval between irrigations can be increased in period 2. . . . . After 12 years of experimenting with RDI it became obvious that in the past, much water was wasted on early irrigation. Our results at Tatura indicate that mature trees would have cropped better with less water.

Table 1. Example calculations of irrigation interval and run time for RDI under drip, microjet and sprinkler irrigation.

 

Drip

4.5 m x 1.5 m planting

Microjet

4.5 m x 1.5 m planting

Sprinkler

5 m x 3 m planting

 

Period 1

Period 2

Period 3

Period 1

Period 2

Period 3

Period 1

Period 2

Period 3

Weekly ETo (mm)

20

35

45

20

35

45

20

35

45

Effective area of shade (%)

30

60

60

30

60

60

20

50

50

Understorey coefficient (Ke)

0.1

0.1

0.1

0.2

0.2

0.2

0.8

0.5

0.5

Stress coefficient (Ks)

1

0.3

1

1

0.3

1

1

0.3

1

Weekly orchard irrigation (mm)

8.6

8.0

34.2

10.6

9.0

38.7

20.4

11.0

47.3

Area of plantingsquare (m2)

6.75

6.75

6.75

6.75

6.75

6.75

15

15

15

Weekly tree irrigation (litre/tree)

58

54

231

72

61

261

306

165

710

Recommended interval between irrigation (day)

2

2

1

10

10

3

5

21

5

Water required at each irrigaton (litre/tree)

17

15

33

103

87

112

219

495

507

Application rate (litre/h/tree)

8

8

8

40

40

40

120

120

120

Run time

(hour)

≈2

2

≈4

≈2

≈3

≈2

≈4

4⅓

Video: Dr Mark O'Connell discusses Regulated Deficit Irrigation (RDI) for stonefruit to maintain yield, fruit size, and fruit quality. August 2019

Recommendations: In water scarcity years you can use RDI in stage 2 of fruit growth at 30-40% levels of full irrigation. The same RDI treatment can be applied post harvest.

Dr Mark O'Connell from Agriculture Victoria discusses RDI for stonefruit

Presentation from Stonefruit Research Roadshow August 2019

Video Transcript: Regulated Derficit Irrigation (RDI) for stonefruit to maintain yeild, fruit size, and fruit quality.

I'm here in the stone fruit experimental orchard at Tatura, and beside me we have an irrigation field experiment where we've been looking at different timings and intervals of water management, deficit irrigation on a nectarine, late season nectarine, September Bright. And for the last three consecutive seasons we've been deficit irrigating certain trees in this orchard, comparing them with well watered, full irrigation trees. And we're looking at yeild, fruit outcomes and tree performance e.g. light interception, pruning, biomass etc. What we're finding is basically we've reconfirmed the earlier work back in the 70s and 80s that RDI deficit irrigation, regulated deficit irrigation in stage 2 of fruit growth - which is the slow period of fruit growth and the maximum vegetated growth window - if we could deficit irrigate in that window, at the 30-40 percent levels of deficit irrigation, we can maintain yeild, fruit size and fruit quality, the fruit sweetness, maturity etc. Anything below that sort of level of deficit irrigation, so the 20 percent and also zero percent watering (so just rain fed only) in stage 2, we have reduced fruit size and yield outcomes. We deficit irrigate outside those windows at stage 1, which is the cell division rapid fruit growth stage, and we have big yield penalties and fruit so as penalties. If we deficit irrigate in the late stage, stage 3, just before harvest, the month or two before harvest, again we have major penalties in yield and fruit size. So the recommendations are, in water scarcity years you can RDI in stage 2 at the 30-40 percent level of full irrigation and maintain yield and quality outcomes. Post harvest deficit irrigation is also recommended around the 30-40 percent again to help save water without any long term effects on production.

2021

Yield and fruit results from deficit irrigation study on Nectarine ‘September Bright’

Tables 1- 5 present production results (yield, fruit quality) for nectarine ‘September Bright’ in response to irrigation treatments under an Open Tatura canopy system for seasons 2016/17, 2017/18, 2018/19, 2019/20 and 2020/21, respectively at Tatura, Victoria, Australia.

During fruit growth stage I, II and III, discrete irrigation levels were applied: 0, 20, 40 and 100% of crop evapotranspiration (ETc).

The results showed that deficit irrigation had a significant effect on fruit quality and yield. Overall, yield and fruit quality were maintained at 40% ETc during stage II; however, yield and fruit size were reduced in both stage I and III under 40% ETc regimes. More severe irrigation deficits (0% ETc and 20% ETc) penalised yield and fruit size, irrespective of fruit growth stage timing.

Notably, high fruit sweetness (≥ 14.4 °Brix) occurred across all seasons and irrigation management treatments. Nevertheless, increased fruit sweetness (°Brix), delayed fruit maturity (IAD), greater flesh firmness (kgf) and higher skin redness coverage (%) occurred under late season (stage IIIb) deficit regimes (0, 20 % ETc). Whereas, early season (stage I) deficit regimes reduced fruit skin redness coverage (%).

In summary, deficit irrigation management during either stage I or stage III reduced fruit weight and penalised yield compared to the fully watered control. However, a moderate level of water stress afforded by deficit irrigation during stage II (40% ETc) maintained fruit weight, yield and fruit quality (sweetness, firmness, maturity, colour).

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

2021

Sensing fruit and tree performance under deficit irrigation in ‘September Bright’ nectarine

This study aims to determine yield and fruit quality responses under deficit irrigation of nectarine in a modern high-density orchard.

Effect of drought stress and recovery on stonefruit production varies with severity, duration and timing of water deficit.

  • Typically, fruit size was reduced under water deficit. Water deficit also lowered yield, decreased canopy size (light interception), lowered stomatal conductance, reduced leaf chlorophyll, increased photo-inhibition, increased fruit soluble solids, increased firmness, decreased maturity and increased red skin colour coverage.
  • However, moderate water deficit (40% ETc) during the traditional RDI period (Stage II of fruit growth) showed no effect on yield or fruit quality.

Fruit & tree performance under deficit irrigation

2018

Plant Water Status Trial

This study aims to test plant-based sensors for their efficiency in determining nectarine water status in a modern high-density orchard.

Continuous detection of plant water status

2017

Video: Dr Mark O'Connell discusses some of the findings from the irrigation experiment in the following video (9 min, 37 sec).

  • 'To maximize fruit size, we need to have well watered trees in phase one'
  • 'Phase 2 (the RDI period), we saw no effect on fruit size or fruit sweetness, suggesting that there is potential for water savings using RDI in stage two of fruit growth.'
  • 'In stage 3, we found big differences in fruit size and fruit sweetness when we set deficit irrigation close to harvest, and so withholding water did increase fruit sweetness, but it also penalized fruit size'
Results from the Irrigation Experiment

Irrigation management: Water supply, delivery, application and strategies

  • This covers topics on:
    • Water supply and delivery
    • Water application
    • Irrigation strategies linked to fruit growth and development
    • Monitoring soil moisture, weather and irrigation system performance
    • Irrigation management for stonefruit

Virtual Orchard Tour - A look at tree structures in the irrigation experiments

September 2019 - Flowering of Nectarine September Bright

How to navigate virtual tours

View earlier virtual tours 2018-2020

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.

Video: Photos of Nectarine, September Bright, on Open Tatura trellis, from 2015 to 2020

Video: Irrigation experiment -Time series photos of Nectarine September Bright on Open Tatura trellis 2015-2020

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.

These publications may be of assistance to you but the State of Victoria and its officers do not guarantee that these publications are without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in these publications.