Netted apple orchard 2014 - 2015 season results and update

Introduction

Established in October 2013, the netted apple demonstration at the Lyster’s Orchard near Manjimup is aimed at showing the value of netting to improve water use efficiency and productivity in high density orchard production systems.

The 1.2 hectare site has 0.5ha of permanent net constructed over an established Cripps Pink and Fuji orchard. Sections of black and white 16mm quad netting were installed, each covering 0.25ha. The remaining area contains two comparison blocks, a DAFWA-managed no netted area, and a grower practice no netted area as a control treatment.

Particular attention has been given to assessing the impact of netting on fruit quality parameters such as sunburn, windburn, colour, firmness and sugars, while in-field data is being collected to compare tree development and chill accrual under the nets compared with outside the nets.

Demonstration treatments

A further treatment using drip irrigation under the netting was added to address the high tree vigour observed in the first season.  It is widely accepted that vigour negatively impacts the production of good quality fruit on Cripps Pink trees, affecting fruit size  and colour development, very important quality and marketing criteria.

Drip irrigation lines were installed either side of four rows of trees under the changeover from black and white net. The addition of drip irrigation brings the treatments being tested to five;

1. Black net, under tree sprinkler
2. White net, under tree sprinkler
3. DAFWA no net, under tree sprinkler
4. Grower no net, under tree sprinkler and
5. Drip irrigation under netting

Ten Cripps Pink trees within each area were tagged, intensively monitored during the season then harvested separately from the remaining crop. All thinning, pruning and tree management was done as per normal practice by the Lyster’s.  An independent irrigation system controlled remotely allowed for different irrigation scheduling for treatments as required.

The drip area was in between the buffer area of the netted treatments and comprised one row each of Cripps Pink and Fuji under black net and one row each under white.

The ten tagged trees from each treatment block were strip picked by DAFWA staff based on maturity (starch conversion tests) but not colour development, starting the 27 April 2015. The remainder of each treatment block (390 trees) were picked to commercial standards based on colour and maturity by the Lyster’s. The commercial harvest continued through May. The fruit in the commercial harvest were allowed slightly longer to develop colour and only fruit suitable for packing was picked by the Lyster’s.  The drip section has data only from the DAFWA strip pick harvest.

Average fruit numbers, from the 10 trees picked, varied between treatments with the no net grower treatment averaging 167 apples/tree. The black and white net and drip treatments all had similar fruit number of 198, 202 and 209 fruit per tree respectively.  The no net DAFWA treatment had significantly more fruit with an average of 301 fruit per tree.

All strip picked fruit from individual trees was manually graded as marketable and non-marketable based on the incidence of damage (bird damaged, sun damaged, bruising, marks, insects and disease). Fruit considered marketable was assessed against the Pink Lady standards. A subset was weighed, measured for diameter and tested for maturity (table 1). Non marketable fruit ranged between 18% in the no net grower treatment and 29% in the white net treatment.  The most common reason for non-marketable fruit was small fruit and dents, which increased as fruit numbers per tree increased, as expected.

# sunburn is a subset of non-marketable fruit.

Yield and water use efficiency

Background colour, blush and maturity all contribute to the marketability and grade assigned to Pink Lady^TM apples. While the results are presented separately it is important to consider them together.

Both the strip picked data (table 2) and the commercial pick data (table 3) have been included to demonstrate the difference in the assessment and importance of working on a commercial property. Only marketable fruit from the strip picking was assessed for size and quality.

Encouragingly, average fruit diameters from the strip pick were all very similar between treatments.  There was a slight difference in average fruit weight, which when multiplied with the difference in average number of fruit per tree, contributed to the difference in extrapolated yield per hectare.

The data from the Lyster’s harvest (table 3) based on bins picked from the remaining 390 trees per treatment shows a slightly different story.  The commercial yield was lower for the black net and both DAFWA and grower no net treatments, and higher under the white net. This may be due to the increased number of trees being assessed per treatment, averaging out differences in fruit numbers between trees and staggered picking over several weeks,  allowing for colour to guide the timing of harvest.  Several harvests apposed to a strip pick meant fruit with less blush than desired may have increased in size and weight before being picked by the Lysters, with some fruit left on the trees that were already over mature or not considered marketable.

As the drip irrigation was part of the black and white net treatments, there was not separate grower harvest data for those rows. Based on the strip pick data and discussion with the Lyster’s on their observation during harvest, it is assumed those rows had a commercial yield similar to that of the black and white netted areas.

As expected, water applied to the drip area was much lower. Only three mega litres/ha (ML/ha) was applied using the drip irrigation compared to 5ML/ha and 5.3ML/ha under the black and white net respectively.  The drip area used 45% less water but had no difference in yield.

Water use efficiency is the tonnes of fruit picked per mega litre of water used (t/ML).  The DAFWA no net treatment had 32% increase in water use efficiency compared to the grower no net treatment.

The increase in water use efficiency from the DAFWA no net treatment to the white net treatment is 30%.  This is an encouraging result, with an increase in yield using less water for both netted areas; reducing pumping costs and potentially increasing returns from the block.

When water use efficiency for drip irrigation is compared to the best of the sprinkler irrigation treatments under the net, there is a significant improvement. A yield of 18-23 t/ML compared with 13.2 t/ML, with a 36% to 74% greater water use efficiency achieved using drip irrigation compared to under tree sprinklers under netting.

*no commercial yield data available.  Strip pick data indicates yield within commercial range of black and white net.

Colour

Colour was assessed using the Pink Lady^TM Europe Ctifl colour charts (Centre technique interprofessionnel des fruits et legumes (Ctifl) Pink Lady^TM Eurofru colour charts) on the 40 apples sampled from each of the 10 trees.  Each apple was given a score for background colour (F1-F7), a score for blush intensity (R1-R8) and a percentage of blush intensity when the blush was over R3.

At the time of strip picking the majority of apples had reached the ideal background colour.  78% of fruit in both the no net DAFWA and black net blocks were between F3 to F4.   68% of white net apples and only 47% of apples in the no net grower treatments were between F3 to F4 (table 4).

Background colour greater than F4 is undesirable for long term storage, as the green background begins to move toward yellow. Between 22% (DAFWA no net) and 53% (no net grower) of fruit were beyond the ideal background storage colour.

F score from Ctifl standards for Pink LadyTM.  Optimum for long term storage F 3-4.

While optimum Blush is between R4 and R5 for long term storage, blush greater than R4 is preferred in all fruit. Colour under the black and white net sprinkler irrigated treatments was lower than desired at strip picking with the majority of fruit lower than R4.  The fruit on the trees irrigated using drip irrigation had better colour with 72% of fruit above R score 4 (table 5). The no net grower treatment had 81% of fruit at greater than R4.

R score for background colour from Ctifl standards for Pink Lady. Optimum for long term storage R4-5.

Conclusions and plans for the coming season

There was greater vigour in the sprinkler irrigated trees under net.  The greater leaf cover hinders light penetration and reduces colour development under the lower light situation of netting.  This is likely to have caused the difference in colour between the sprinkler irrigated crop and the drip irrigated crop under the net.

Under tree sprinkler irrigation will sustain significant grass cover that requires maintenance during the season, an added cost.   It also may reduce the amount of reflected light from the surface, potentially affecting the colour development.  Under drip irrigation, less grass cover persists between the rows, a direct result of limiting water to a narrow band around the trees as shown in the images.

While colour was better this season, we hope to improve in the coming season.  Due to the reduced water use and vigour and increased colour development under the net using drip irrigation, it is planned to convert the entire netted area to drip for the coming season.

There are benefits to be made from using drip irrigation under the net and possibly outside the netted area, based on this year’s observations.   The Lysters, Pomewest and the DAFWA team have also decided that the entire outside netted area will be converted to drip for comparison with under net, with the benefit of still having the under tree sprinklers in extreme heat events and to maintain some ground cover if required.

This work is supported through funding from Royalties for Regions Department of Regional Development, Horticulture Innovation Australia and The Commonwealth Department of Agriculture, Fisheries and Forestry.