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31 March 'The Wrap Up '
If this is the first time you have read about this project, you may like to get a refresher by going to the Introduction Page.
Stylised Graph Showing Irrigation Applied in Megalitres/Ha and also Irrigation plus rain, since the start of the Season'
Click on the links below to view graphs comparing post harvest Fruit Quality Assessments for both seasons.
Observations and conclusions:
Water:
As mentioned above, cumulative season rainfall of around 120mm made a useful contribution to the total water available to the crop over the season. This equates to around 1.2 ML/Ha overall. The soil moisture readings had remained steady in January in both the RDI and control rows until harvest. At that point both soils rapidly dried to the point where the monitoring equipment barely worked. It's difficult to determine any radical differences in the soil moisture for January until the last few days and after the rapid drying occurs. The control rows then seem to remain wetter in the 0-40 cm zone.
Fruit Size:
At harvest, no significant difference was apparent in the size of fruit. This graph (9kb.pdf) shows that the difference is less than 2 mm.
GBug reading to the end of January
Average Leaf Temperature:
Average leaf temperature may be an indication of moisture stress and the variance was 6 degrees Celsius (the highest difference experienced since the demonstration started) with the control trees showing a higher temperature. This variance graph (8kb.pdf) shows the difference in leaf temperature which, when compared to the soil moisture graph shows an increase in leaf temperature difference with drier soils. The early and post harvest RDI periods can clearly be seen as the temperature increase's under RDI. Both the RDI and control tree leaf temperature increase markedly as the soil dries post harvest. Although the control trees unexpectedly become far warmer than the RDI trees as the soils in both plots dried.
Shoot Length:
The final difference in shoot length between RDI and control rows was approximately 45mm. Trees in the RDI rows are not notably smaller, even after a second year of RDI, what difference exists will probably not be apparent at all post pruning. It remains to be seen if pruning is faster as a result of shorter shoots. Grower sentiment seems to be that even if shoots are smaller a tree will still need a similar number of cuts.
Although, the advantage of less shoot growth may indicate greater light, water and fertiliser efficiency by not growing wood that just needs to be cut off.
Average Leaf Water Potential:
Leaf water potential refers to the water status of leaves, is widely used in plant science research and can indicate tree water stress.
There was a large variance between the treatments, particularly in the latter part of the season. When comparing mean soil moisture and mean LWP line graphs (55kb.pdf) there appears to be an inverse relationship because as soil kPa declines LWP increases. | Image showing tree structure for RDI on the left and Control on the right |
Visitors and Events:
During the life of the demonstration the total number of visitors recorded was 133. Although it can't be confirmed how many of these may have changed their irrigation practices. The site was also the venue for a number of field walks where growers discussed their experiences with RDI and other irrigation management practices. A number of growers assisted collect data in a bid to demonstrate if RDI increases occurrence of doubles. An important aspect of the demonstration site was it showed growers how they could put new practices to the test on their own farm.
Fruit Quality Parameters:
Size difference was hardly a factor again this season with the RDI fruit only an average of 1.7 mm smaller than control. A slight increase in colour was apparent in the RDI and control fruit where an average of 14.7 g heavier. Flesh Firmness was 1 kg less for RDI and control fruit were 2 Brix higher in Total Soluble Solids (TSS).
Measurement | RDI (07/08) | RDI (08/09) | Control (07/08) | Control (08/09) |
Weight in grams | 161 | 144 | 162.9 | 158.7 |
Diameter in millimetres | 71 | 65 | 69.8 | 66.7 |
Colour out of 10 | 6.2 | 7.2 | 7.2 | 6.45 |
Flesh Firmness | 6.75 | 5.46 | 6.45 | 6.4 |
Brix | 16 | 14.8 | 17.4 | 16.7 |
Cost of Production:
According to an AgriGater (external site) decision support tool Cost of Production (CoP) Report (50kb.pdf) and using yield data from the farm manager showed a reduction in CoP in the RDI rows equivalent to $500/ha compared to the control rows. Most of the reduction in CoP is a result of the RDI yield being higher. An assumption could be that the energy usually used by the tree to develop extra wood is being diverted for carrying more fruit. A decrease in shoot length and a corresponding increase in light interception may result in a greater conversion of sunlight to fruit.
This is only a demonstration site and therefore doesn't prove these concepts however it does tend to support what we already know about RDI and many of the physiological responses.
Table: Orchard Measurements
For explanations of the headings and more information regarding the table, visit the 'RDI Journal Table Headings Explained' page.
Date: |
RDI H2O [total lt/Tree] |
Control H2O [total lt/Tree] |
RDI Av fruit size mm |
Control Av fruit size mm |
RDI Av Shoot Length cm |
Control Av Shoot Length cm |
RDI Av Leaf Temp C |
Control Av Leaf Temp C |
Leaf Temp Variance C |
RDI Leaf Water Potential (BAR) |
Control Leaf Water Potential (BAR) |
Total Visitors |
24-Sep |
211.8 |
227.2 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
1-Oct |
449.4 |
474.7 |
20 |
22 |
6.6 |
7.95 |
13.82 |
12.4 |
1.4 |
13 |
12.5 |
-- |
8-Oct |
707 |
561 |
24.4 |
23.6 |
7.95 |
11.55 |
17.45 |
1.1 |
1.1 |
9.7 |
9.1 |
-- |
24-Oct |
1257 |
1135 |
30.3 |
32 |
16 |
24.5 |
14.5 |
14.6 |
0.1 |
12.7 |
11.2 |
3 |
31-Oct |
1890 |
1798 |
32.9 |
33.5 |
21 |
30 |
20.79 |
16 |
4.8 |
-- |
-- |
3 |
11-Nov |
3681 |
2537 |
32.9 |
35.7 |
22.5 |
36.5 |
15.07 |
15 |
0.7 |
6.8 |
6.0 |
3 |
21-Nov |
3281 |
3407 |
36.1 |
37.9 |
26.2 |
41 |
-- |
-- |
-- |
-- |
-- |
12 |
4-Dec |
4010 |
4408 |
37.4 |
41.3 |
24.3 |
45.4 |
-- |
-- |
-- |
-- |
-- |
22 |
15-Dec |
4764 |
5614 |
43.1 |
45.4 |
27 |
45.4 |
13.21 |
12.3 |
0.9 |
9.7 |
6.3 |
23* |
31-Dec |
6083 |
7430 |
55.1 |
58.1 |
23.2 |
46.7 |
15.88 |
15.6 |
-0.3 |
16.5 |
13.8 |
23* |
28-Jan |
10095 |
11878 |
65.14 |
66.69 |
28.5 |
48 |
26.14 |
26.9 |
0.7 |
12 |
8.5 |
23* |
17-Mar |
14108 |
16328 |
-- |
-- |
29.35 |
53.6 |
42.58 |
36.6 |
-6.0 |
-- |
-- |
23* |
* Further counting wasn't possible due to a malfunction in the counter
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