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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

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macadamia irrigation past present and future

Macadamia irrigationpast present and future

Chris Searle

Grower Liaison Officer

Suncoast Gold Macadamias

Gympie Qld

background
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
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
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
slide6

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
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
Sprinkler V Dripcontinuing 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
‘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
Long term decline in ‘soil health’

Under-tree

infiltration rate 4.8mm/hr

Grassed inter-row Infiltration rate 29mm/hr

current systems
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
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 – labourefficient
slide13

Soils map information

Infiltration rate >120mm/hr

Infiltration rate <5mm/hr

Need to define soils boundaries due to large differences in infiltration rate

slide14

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
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
slide16

Sub-surface drip low infiltration rate

High infiltration rate

Gully

90 l hr sprinklers

the future of irrigation in macs
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