1. Department of Agriculture, Fisheries and Forestry, Queensland
Macadamia crop load and
productivity, and lessons from the
apple industry
John Wilkie
Department of Agriculture, Fisheries and Forestry Queensland

2. My vision for macadamia orchard systems of the future:
• Vigour managing rootstocks
• High plant densities
• Optimising light interception and
distribution
• Understanding and management of
crop load
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 2

3. Crop load experimental design
Racemes per canopy volume (racemes/m3)
70
60 'A203' spring 2006
50
40
30
20
10
0
0 20 40 60 80 100
Treatment (Percentage of racemes removed)
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 3

4. Crop load – the vegetative/reproductive balance of the tree
• High crop load  low vegetative
growth 1400 5/01/2007 A
1200
• Low crop load  high vegetative y = 2.72 + 40.91 . 0.907 x
Mean total shoot growth per branch (mm)
1000 r2 = 0.46
growth 800
• Apple growers use this 600
understanding to manage their 400
canopies 200
0
1400 22/03/2007 B
1200
x
1000 y = 39.28 + 79.29 . 0.905
r2 = 0.40
800
600
400
200
0
0 10 20 30 40 50 60
-3
Raceme density (racemes m )
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 4

5. Crop load - fruit size relationships 12
High crop load  small fruit/nuts
Nut weight (g)
• 11
10
• Low crop load  large fruit/nuts
9
• Fruit size is extremely important in
8
apple production and growers use
7
these crop load/fruit size
6
relationships to manipulate fruit 0.0 0.2 0.4 0.6
size. Yield efficiency (kg NIS m-3)
45
Kernel recovery (%)
40
35
30
25
0.0 0.2 0.4 0.6
© The State of Queensland, Department of Agriculture, Fisheries and Forestry Yield efficiency (kg NIS m-3) 5

6. Crop load – flowering in the following season
Raceme density 2007 (racemes m )
-3
'A203' (a)
• Crop load in one season affects 100
y = 13.94 - 139.90 . 0.772 x
flowering in the following season. 80
P < 0.0001
r2 = 0.70
• This is consistent with the alternate 60
bearing cycles in crops such as 40
apples.
20
• Apple growers manage their crop
0
loads to ensure flowering in the
0 10 20 30 40 50 60
following season. Raceme density 2006 (racemes m ) -3
Raceme density 2007 (racemes m )
(b)
-3
100
y = 13.92 - 252.19 . 4.28e-6 . x
P < 0.0001
80 r2 = 0.71
60
40
20
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7
-3
Yield efficiency 2007 (kg NIS m )
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 6

7. Crop load - Raceme density and yield
• Yield increases with
raceme density up to a
NIS per canopy volume (NIS/m3)
'A203' 2006-07
point, after which there
is no further increase in 0.6
yield.
• The tree has some ability 0.4
to compensate for low '849' 2007-08 'A203' 2007-08
raceme densities.
0.2
0.0
0 20 40 60 80 100
Racemes per canopy volume (racemes/m3)
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 7

8. Crop load - Summary
• Crop load affects a range of physiological processes within the tree.
• In apple, there are a range of methods that growers can use to manage
crop loads to achieve the optimum balance between productivity and
quality for their canopies.
• In macadamia, I think we need to improve our understand of the effect
of crop load on the system, and then develop methods to manage it.
© The State of Queensland, Department of Agriculture, Fisheries and Forestry 8