Climate change and horticulture in Western Australia

Page last updated: Tuesday, 14 September 2021 - 5:51pm

Climate change will affect horticultural production in Western Australia (WA) in a number of ways, and the effects will depend on location, soil type, crop type and management. Reduced rainfall and increased temperatures in the south-west will increase risk for horticultural enterprises, particularly in areas at the margins of enterprise suitability.

The Department of Primary Industries and Regional Development provides this information to support farm business managers and industry managers in their response to a changing climate in Western Australia.

How will climate change affect horticultural production?

Projections for climate change effects on horticultural regions are presented by region.

Southern Western Australia

Increased temperatures will make matching crop type to climatic areas increasingly important, particularly for long-lived perennial crops and those requiring a high degree of chilling.

Projected changes are:

  • Annual rainfall will decrease in most areas, with several reductions in water availability:
    • there will be less soil moisture from rainfall available for plant growth
    • groundwater recharge and run-off into dams will decrease by a larger proportion that the decrease in rainfall.
  • Temperatures will increase in most areas, leading to:
    • greater risk of crop damage during hot spells
    • a possible expansion of the area suitable for growing tropical and subtropical crops
    • a possible contraction of the area suitable for temperate crops
    • the Manjimup area being able to grow more heat-tolerant crops, such as capsicum
    • the Manjimup growing season being extended for some crops
    • the Manjimup area not being able to grow heat-sensitive varieties in summer
    • the Gingin area needing more heat-tolerant lettuce cultivars, if summer production of lettuces is to continue after 2030
    • increased energy costs for activities such as post-harvest chilling.
  • Extreme weather events will increase the risk of crop and infrastructure damage.
  • The south-west will remain suited to producing high quality grapes and wine, though it may be necessary to change varieties in some areas.

Carnarvon

Projected changes are:

  • Annual rainfall will decrease and become more variable:
    • there will be less soil moisture from rainfall available for plant growth
    • groundwater recharge and run-off will decrease.
  • Temperatures will increase, leading to:
    • increased importance of matching crop type to appropriate climatic areas, particularly for long-lived perennial crops
    • greater risk of crop damage during hot spells
    • a possible increase in area suitable for growing tropical and subtropical crops
    • a possible decline in suitability for growing temperate crops
    • increased energy costs as temperatures increase energy requirements for activities such as post-harvest chilling.
  • Carnarvon will remain suited to producing bananas until at least 2030.
  • Increased tropical cyclone intensity will increase the risk of storm damage to horticultural crops and infrastructure and the risk of soil erosion.

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Northern Western Australia

Projected changes are:

  • Annual rainfall will remain largely unchanged.
  • Temperatures will increase, leading to:
    • increased importance of matching crop type to appropriate climatic areas, particularly for long-lived perennial crops
    • greater risk crop damage during hot spells
    • a possible increase in area suitable for growing tropical and subtropical crops
    • increased crop water requirements as a result of increased evaporative demand
    • conditions in Kununurra becoming too warm for banana production by 2030
    • increased energy costs as rising temperatures increase energy requirements for activities such as post-harvest chilling.
  • Attracting investment in long-term, climate-dependent agricultural assets, such as irrigation infrastructure and orchard development, may become more challenging.
  • Increased tropical cyclone intensity will increase the risk of storm damage to horticultural crops and infrastructure and the risk of soil erosion.

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How can horticultural businesses adapt to climate change?

A drier climate will reduce the availability of water and increase cost of water for horticulture. To successfully adapt to climate change, managers will need to improve irrigation practices. Where the cost of water increases, it may be possible to change the crop or enterprise type, and improve the financial return per unit of water used.

Changes in water availability may be less of an issue for new and expanding irrigation areas in the north of WA, but temperature changes in absolute terms are expected to be greater in the north compared to the south. Matching crop type to climatic area will be increasingly important, particularly for long-lived perennial crops.

There are many ways for horticulture to adapt to the climate changes described above.

Use best-adapted crop species and varieties

Options include:

  • crop varieties, species or rootstocks with increased physiological tolerance of hot conditions
  • varieties with reduced chill requirements
  • varieties or species which are better able to exploit the fertilisation effect of increased atmospheric carbon dioxide to improve water use efficiency
  • changed crop rotations and schedules
  • crop varieties or species bred to resist current pest and disease risks and new risks presented by changing climate
  • crop rotations with break-crops for disease management.

Improve water harvesting and storage

Technology and infrastructure for harvesting and storing water need to be improved in a drying climate. There are many options:

  • design dams and catchments to cope with projected rainfall and evaporation rates
  • treat roaded catchments with chemical sealants to reduce the rainfall run-off threshold to 4–6mm
  • reduce evaporation loss from dams by using:
    • suspended and floating covers and mono-layer films applied to the water surface
    • windbreaks to reduce air movement over the water surface
  • if available, use treated sewage or grey water for crop irrigation
  • use in-row water harvesting for grapes and tree crops
  • harvest water run-off from greenhouses
  • use desalination and reverse osmosis to recover otherwise poor quality or saline water
  • increase investment in tanks and dam storages.

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Improve irrigation efficiency

Technology and management improvements to gain the best production per unit of irrigation water include:

  • watering at night
  • drip irrigation
  • subsurface drip irrigation
  • improved irrigation scheduling based on monitoring soil water content, soil type, crop factors and evaporation timing and volume of irrigation
  • regulated deficit irrigation
  • partial root zone drying
  • improved water distribution systems
  • reduced evaporation of soil water through:
    • mulching with organic materials
    • mulching with plastic
  • rapid crop canopy development/closure
  • increased speed and depth of infiltration by using:
    • claying
    • application of surfactants (wetting agents)
  • reducing run-off by using:
    • appropriate irrigation rates
    • mulches
    • contour sowing
    • minimum tillage
    • claying.

Grow crops under shelters or greenhouses

Shelters or greenhouses can ameliorate the affect of higher temperatures and provide better water management. There are several options:

  • use netting to provide shade (reduced canopy temperature and evaporation) and reduce risk of hail and bird damage
  • grow crops in greenhouses to increase productivity by using:
    • plastic tunnels
    • plastic structures with computerised temperature control and shading systems
    • glass structures with computerised temperature control and shading systems
    • hydroponics to increase water use efficiency.

Manage higher temperatures

There are chemical and management options, including:

  • chemical dormancy breakers, such as application of hydrogen cyanamide, as a method to promote budburst
  • crop regulation and canopy management, such as using temperature dataloggers to optimise bunch-zone temperatures
  • using irrigation to ameliorate temperature extremes; sprinkler irrigation can reduce canopy temperatures.

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Improve plant water use efficiency

Increase plant ability to access soil water

Remove physical constraints to root growth with:

  • gypsum to improve soil structure
  • increased soil organic carbon content, using organic mulches and manure
  • deep-ripping to remove hard pans
  • drainage, such as deep drains, raised beds and surface drainage, to reduce waterlogging.

Remove chemical constraints to root growth by:

Use crop varieties, species or rootstocks with:

  • increased ability to explore soil profile
  • the right root morphology (deep versus lateral roots)
  • tolerance of chemical soil constraints, such as pH, boron, aluminium, transient sodicity
  • tolerance of saline irrigation water
  • ability to grow through soil physical constraints, such as a hard pan or transient waterlogging.

Increase volume of plant available soil water

Improve soil water-holding capacity by using:

  • increased soil organic carbon content
  • reduced tillage
  • deep-ripping
  • gypsum to improve soil structure
  • claying (surface application/delving/spading) to reduce non-wetting.

Use decision support tools

There are many apps, services and calculators that help improve management decisions:

  • use seasonal and long-range weather forecasts to determine rotations and cropping area
  • save inputs by using variable rate seeding, spraying and fertiliser application based on yield potential and soil testing
  • use tools, such as crop models, flowering calculators, climate data and soil water calculators, to support decisions about:

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Consider your business management

  • Change species mix if the cost of water increases to achieve maximum financial return per unit of water.
  • Relocate production of heat- or water-sensitive crops to cooler or wetter areas.
  • Use all risk insurance policies.
  • Have risk management strategies in place to manage productivity variability within and between seasons.
  • Diversify farm income by using:
    • carbon farming (reduce nitrous oxide emissions from soil, sequester carbon in the soil or improving energy efficiency)
    • other novel income streams.
  • Improve energy use efficiency in the business by:
    • improving energy efficiency for irrigation
    • reducing post-harvest chilling costs and energy use by:
      • harvesting at night or early morning
      • reducing produce temperatures by the right amount at the right speed after harvest
    • generating renewable energy on-farm.
  • Obtain training in business management.
  • Maintain information and innovation via sharing networks and links.

Manage increased soil erosion risk in a drier, more-variable climate

Reduce wind erosion risk by using:

  • reduced tillage
  • stubble retention
  • windbreaks on very erosion prone sites
  • claying.

Reduce water erosion risk by using:

  • reduced tillage
  • stubble retention
  • contour farming, including drainage in high rainfall regions
  • claying.

Use vegetated buffers along waterways to trap silt before it enters the water.

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Change public policy

Policy options to help adapt to climate change:

  • identify and protect priority horticultural land
  • move to water pricing that reflects the true cost of water
  • remove uncertainty related to water allocation and low water availability, including restricted water allocations to limit irrigation of poor returning crops
  • reduce barriers and distortions to water trading
  • optimise the environmental water allocation and seek synergies between environmental and irrigation water allocations
  • facilitate water allocation carryover and capacity-sharing at larger scales.

Note

Managers need to assess these adaptations at each site – for their technical efficacy and environmental and economic impacts – before investing.

Incremental adaptations to climate change can work in the short to medium term. In the longer term, horticulturalists might need to make transformational investment in irrigation infrastructure and suitable crops.

For more information

Download Bulletin 4870 Climate change: impacts and adaptation for agriculture in Western Australia or use the contact details below.

Contact information

Rob Sudmeyer
+61 (0)8 9083 1129