Topics:

Irrigation management for stonefruit

  • Water supply and delivery
  • Water application
  • Irrigation strategies linked to fruit growth and development
  • Monitoring soil moisture, weather and irrigation system performance

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

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.

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.

The experiment has three irrigation levels and four irrigation application timings as treatments.

The irrigation levels (% of tree evapotranspiration), applied using drip irrigation, are:

  • 0: extreme deficit irrigation to impose high level of water stress
  • 20 & 40: deficit irrigation to impose severe and moderate level of water stress
  • 100: control irrigation, crop water requirement to maximise yield

The experiment has four irrigation application timings and likely crop responses:

  • Stage I of fruit development: cell division (rapid fruit growth) - water stress restricts cell division, reduces fruit size and yield
  • Stage II of fruit development: pit hardening (slow fruit growth, maximum vegetative growth) - water stress reduces vegetative vigour
  • Stage IIIa of fruit development (early): cell expansion - water stress reduces fruit size and yield
  • Stage IIIb of fruit development (late): cell expansion (sugar accumulation, chlorophyll degradation) - water stress reduces fruit size and yield

Table 1: Irrigation experimental treatments

2016-2017 Irrigation Experiment table 2016/17 irrigation experiment

Regulated deficit irrigation (RDI) occurs during stage 2 of development. See Graph below.

Shoot and fruit growth graph

Video: Introduction to the Nectarine irrigation experiments. 2015

Dr Mark O'Connell introduces the Nectarine, Open Tatura trellis, irrigation experiments.
  • Nectarine cv. September Bright with Rootstock: Elberta
  • Planted winter 2014 in Open Tatura tree training at a density of 2222 trees/ha

Video transcript - introduction to experiment

In this field experiment we have September Bright, 1 year old trees, trained in an open Tatura trellis, 2 metre tree spacing per side, one meter diagonally opposite, four and a half meter row spacing, and we're going to try and train these trees in at least four leaders per tree, up to six per tree. We have a north-south row direction, and again in year three, we will commence the field experiment and in this case we're going to look at irrigation management, and irrigation strategies, and deficit irrigation at different growth stages of the crop cycle. Stage 1 growth, early growth of the fruit, we will stress some of these trees. In stage 2, we will also stress these trees, and in stage 4, post harvest, we will also stress some of these trees, and look at the interaction of water stress and fruit yield and fruit quality, in particular sweetness, Brix.

Results

2020

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)

2016-20 Yield and fruit results from deficit irrigation study on Nectarine ‘September Bright’

Tables 1– 4 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 and 2019/20, 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 was 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 (≥15.1 °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)

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). 2017
  • '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

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

September 2019 - Flowering of Nectarine September Bright

More Virtual tours more 360 degree photo tours of irrigation trees 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.

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.