Yield and water use efficiency
Background colour, blush and maturity all contribute to the marketability and grade assigned to Pink LadyTM 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.
| Block | Average fruit diameter (mm) | Average single fruit weight (g) | Average fruit number per tree | Extrapolated yield (t/ha) |
| Black net | 71.7 | 170.2 | 156 | 66.3 |
| White net | 72 | 162.6 | 143 | 58.2 |
| No net DAFWA | 71.2 | 161.0 | 219 | 88.1 |
| No net grower | 71.7 | 171.1 | 137 | 58.6 |
| Drip | 70.7 | 160.5 | 162 | 65.1 |
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.
| Block | Yield (t/ha) | Irrigation applied (ML/ha) | Water use efficiency (t/ML) |
| Black net | 54 | 5 | 10.8 |
| White net | 69.8 | 5.3 | 13.2 |
| No net DAFWA | 65.3 | 6.4 | 10.2 |
| No net Grower | 45 | 5.8 | 7.7 |
| Drip* | 54-69 | 3 | 18-23 |
*no commercial yield data available. Strip pick data indicates yield within commercial range of black and white net.