1. Macadamia irrigation past present and future
Chris Searle
Grower Liaison Officer
Suncoast Gold Macadamias
Gympie Qld

2. 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

3. 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

5. 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

6. 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.

7. 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

8. Sprinkler V Drip continuing debate
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
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)

9. ‘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

10. Long term decline in ‘soil health’
Under-tree
infiltration rate 4.8mm/hr
Grassed inter-row Infiltration rate 29mm/hr

11. 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

12. 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

13. Soils map information Infiltration rate >120mm/hr
Need to define soils boundaries due to large differences in infiltration rate

14. Defined soil boundaries by sampling on 50m grid
Low infiltration rate <5mm/hr
High infiltration rate >120mm/hr
Matched cultivars to soil type

15. The system Pressurized system - self flushing
Use of highly accurate satellite guidance
Initially two lines drip tube (2.3l/hr at 40cm spacing mm/hr)
Four lines when tree mature (2.58mm/hr)
Open field hydroponics
Rest of development 90l hr sprinklers (2.86mm/hr)
Several pumps - manifold

16. Sub-surface drip low infiltration rate
High infiltration rate
Gully
90 l hr sprinklers

17. 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