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Macadamia irrigation past present and future

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

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  1. Macadamia irrigationpast 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

  4. 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

  5. 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.

  6. 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

  7. 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

  8. ‘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

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

  10. 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

  11. 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

  12. Soils map information Infiltration rate >120mm/hr Infiltration rate <5mm/hr Need to define soils boundaries due to large differences in infiltration rate

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

  14. 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

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

  16. 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

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