Macadamia irrigation
past present and future
Chris Searle
Grower Liaison Officer
Suncoast Gold Macadamias
Gympie Qld
Background
• Macadamias one the few Australian plants
brought into cultivation
• Native to coastal rainforests of SE Qld- NNSW
• Warm wet summers, cool winters, dry springs
• Have a range of drought adapted traits surface roots + sinker roots - low resistance
• Industry only started in Australia in mid 1960s
• Cultivars are almost wild – little plant breeding
Industry
• Majority of production from NNSW/SE Qld
• Largely rainfed - increasing use of
supplemental irrigation in SE Qld
• Major expansion in Bundaberg/central Qld
since 1990s – irrigation is essential
• Over 6,000 ha of irrigated production in Qld
• Central Queensland where future expansion is
likely to occur – all will require irrigation
• Irrigation second biggest cost of production
Knowledge
• Limited information on water requirements of
macadamia
• Most sensitive periods to water stress
1. Oil accumulation (December/Jan)
2. Flowering – September
3. Nut set – October/November
• Difficult to measure water stress in
macadamia
• Some varieties require more than others
D aily w ater u se (L /tree/d ay)
65
60
H A ES 741
55
H A ES 344
50
45
40
35
30
m ax
m in
25
20
15
J
A
S
O
N
D
J
F
M
A
M
J
T im e
Fig.1 Range in daily transpiration (water use in L/tree/day) for two
cultivars 741 and 344, averaged over two seasons (1999/2000 and
2000/2001), growing at Bundaberg under well watered conditions.
Water use measured using Grainier sap flow. Trees 6m in height,
312 trees/ha.
Actual water application
• Grown successfully on 4ML/ha irrigation in
Bundaberg (around 1,000mm/yr rainfall)
• 8-10 ML at Emerald one line of drip tube
(around 640mm rainfall)
• Supplemental irrigation of 1.4ML/ha at
Amamoor, SE Qld (around 1100mm rain/yr)
significant impact on yield.
• Little use of monitoring equipment – though
use is increasing - mainly capacitance probes
Sprinkler V Drip
continuing debate
Sprinklers
•
•
•
•
•
•
•
More expensive to install
More expensive to maintain
Easier to apply
Allows use of solid fertliser
Less efficient water use
Easier to monitor
Allows for breakdown of
organic matter (mulch,
compost, manures)
• Wets nuts during harvest
period (possibly detrimental)
Drip
• Cheaper to install – except
higher filtration costs
• Cheaper to maintain/run
• Need to think ahead
• Mostly fertigation
• More efficient water use
• Where do you place soil water
monitoring equipment ?
• Does not assist with organic
matter breakdown
• Nuts remain dry during
harvest period
‘Others factors’
• Need to consider other factors besides water
requirements of tree when designing a mac system
• Maintenance of inter-row ground covers
• Bare earth to facilitate harvesting creates problems
• Long term soil degradation (no organic matter)
• Reduced infiltration rates
• Sprinklers allow for organic matter breakdown
• Use of manures as fertiliser (cheap alternative)
• Unlike avocados no major disease problems created by
irrigation – still needs to be considered
• Supplemental irrigation – maintenance of tree health
Long term decline in ‘soil health’
Under-tree
infiltration rate
4.8mm/hr
Grassed inter-row
Infiltration rate
29mm/hr
Current systems
• Many older systems designed in 90s have
problems - uneven pressures – ageing systems
• GPS planting from 2005 better contour mapping –
better systems?
• Around 10% of plantings since 2004 on drip
• Economics forcing macadamias onto more
marginal soils – use of drip tube
• Irrigation seen by many as a ‘chore ‘ rather than a
vital component of their business
• Need better systems tailored to coastal soils and
rainfall patterns – better monitoring
Future system
Sub-surface drip in macadamia
• First of its kind
• System designed around soil type and cultivar
• Concerns about long term viability
• Root intrusion- clamping off – aggressive roots
Potential benefits
• Ability to harvest while irrigating
• Keep under-tree ground covers growing
• WU efficient – labour efficient
Soils map information
Infiltration rate >120mm/hr
Infiltration rate <5mm/hr
Need to define soils boundaries due to large differences in infiltration rate
Defined soil boundaries by
sampling on 50m grid
Low infiltration rate <5mm/hr
High infiltration rate
>120mm/hr
Matched cultivars to
soil type
The system
• Pressurized system - self flushing
• Use of highly accurate satellite guidance
• Initially two lines drip tube (2.3l/hr at 40cm
spacing - 1.28mm/hr)
• Four lines when tree mature (2.58mm/hr)
• Open field hydroponics
• Rest of development 90l hr sprinklers
(2.86mm/hr)
• Several pumps - manifold
Sub-surface drip low infiltration
rate
Gully
90 l hr sprinklers
High
infiltration
rate
The future of irrigation in Macs
• Macadamia industry likely to expand - all irrigated
• Expansion onto more marginal soils
• Systems tailored to coastal soils and rainfall
patterns – better monitoring
• Need for system designers to work more closely
with agronomists, soils scientists, growers
• Awareness of factors other than just water
requirements of crop