Land and water condition for agriculture: constraints and opportunities - Dr Richard George, Principal Research Scientist Department of Primary ...
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Land and water condition for agriculture:
constraints and opportunities
Dr Richard George, Principal Research Scientist
Department of Primary Industries & Regional Development, Bunbury
The context talk…
• Emphasis – water balance
• Start dryland and end irrigation –
• system constraints (broad acre) – land degradation
• opportunities (irrigation) - water
• Context sustaining south & growing north…
examples…
• Key message – manage water, manage degradation
and improve productivity & resilience
1993
The South: “Wheatbelt”
Region 25.115 M ha
Native Veg – 7.601 M ha
Cleared - 17.514 M ha cleared
Majority 2400mm evaporation
Rapid and extensive clearing
1950s to 1983.
Roots to bedrock… used water
365 days… resilient to aridity
Wheatbelt ~ 15 M ha
3
WA 2016/17 agriculture = production
& exports
$7 billion GVAP
*2.47 multiplier
$17 B to WA economy
https://www.agric.wa.gov.au/food-export-investment/western-
australia’s-agrifood-fibre-fisheries-and-forestry-industries-2018
17.9 mt
1994 2007 2014
Farm size (ha) 2500 4000 6000
Yield (t/ha) 1.8 2.1 2.6
Total net asset $3m $6.5m $12m
Annual rainfall WA Production 8mt 12mt 17mt
changes < 1975 No. Growers producing 85% of 1200 800 600
and after 2000 WA crop
GVAP WA crop $1.4b $2.8b $5.5b
1994 2007 2014 2025
Farm size (ha) 2500 4000 6000 12000
Yield (t/ha) 1.8 2.1 2.6 3.0
Total net asset $3m $6.5m $12m $20m
Growing season WA Production 8mt 12mt 17mt 22mt
rainfall changes No. Growers producing 85% of 1200 800 600 300
< 1975 and after 2000 WA crop
GVAP WA crop $1.4b $2.8b $5.5b $9b
But… annual systems…
•
Eventually consequences under ~150 day
agriculture system Salinity & Waterlogging
Summer 2008
….Visible
Salinity, water and wind erosion, acidification,
eutrophication
Invisible… soil/subsoil acidity, non-wetting, Community: water quality, biodiversity,
compaction, soil decline…. GRDC infrastructure…. 8
Extent and Risk - Mapping
ABS Census 1955-2002
Satellite maps 1998-2000
New planned 2019-2021
1 M ha severe
+ 1 M ha moderate/transient?
Interactive tools
2018 OAG Report
2019 Salinity Consultative Review
9
Extent and Risk - Mapping
ABS Census 1955-2002
Satellite maps 1998-2000
New planned 2019-2021
1 M ha severe
+ 2.8 M ha valley hazard
Interactive tools
2018 OAG Report
2019 Salinity Consultative Review
102013
GRDC 2018 – main 5 soil constraints costing $330 ha or
$4.3 billion year (ROSA tool) with treatment enabling an
increase of 1 T/ha…
Salinity Chapter
First full review 2013
11Landcare, Regenerative Ag….
…adaptation to use more water … to create resilience
& regional development
New needs – e.g. GHGs like CO2
#ClimateSmartAg…wetter North …drier South…
1600
Perth dams -1% rain -3% 1400
runoff 1200
Rainfall (mm)
1000
~11,000 GL 800
600
(865 GL/a) 400
~200 TDS 200
0
1880 1900 1920 1940 1960 1980 2000 2020
Year
Annual rainfall 10 yr Mean Long-term Mean
186 GL
(68 GL/a)
2030
1300 TDS2016 – use ~ 300 GL/a $400m GVAP • Food & fibre crops • Cattle • Horticulture • Tree crops • Bush tucker
…Growing in the North (La Grange)…
…catalyst to respectful Broome
Before project 3 GL used of
irrigated agricultural 50 GL available.
development…
After project 100% applied
for….
3 TOs & 7 Stations
2 Hort businesses• Soils, chemistry, risks
• Regolith depths, aquifers, salinity, chemistry
• Aquifer use – modelling, saltwater interface
• Aquifer ages, recharge and hydrodynamics with
strong cultural recognition.Myalup
Grow
Stable
Less
$877 m GVAP
18
~350 GL40 T/ML 5-9 T / ML
Opportunities for growth and
sustainability – to 2040 ?
• Water & food planning –
• Major international drivers in food supply and demand (quality): eg wheat.
• Changing food culture (vegan, paleo, ….)
• Increasing pressure on finite resources
• Recognising resource impacts & costs (energy) & market advantage
• Dryland - Better manage landscapes soil and water – RegenAg...
• Irrigation – growth – then unconventional water supplies
• Brackish water sources – and desalinisation
• Stormwater & wastewater - WWTP & MAR
• Mining & post mine closure – legacy opportunities
• Horticulture - protected cropping**Contact
Work - PO Box 1231, Bunbury 6230.
Questions ? richard.george@dpird.wa.gov.au
M 0404 819 532
21/18Report Cards
https://www.agric.wa.gov.au/climate-land-water/resource-
assessment/report-card-conditions-and-trends
Salinity interactive model
https://www.agric.wa.gov.au/resource-
assessment/interactive-groundwater-and-salinity-map-
south-west-agricultural-region
La Grange case study
https://www.agric.wa.gov.au/assessment-agricultural-
expansion/la-grange-interactive-soil-and-groundwater-map
Myalup case study
https://www.agric.wa.gov.au/assessment-agricultural-
expansion/myalup%E2%80%93wellington-assessment-
expanded-irrigation
What www searchers are downloading - from Climate Land
and Water DPIRD website (August)
22Wheatbelt ‘average crop’ water balance – 400mm rainfall (1mm = litre/m2)
180 mm (transpiration to grain)
20
100 mm (Evaporation)
1mx1m
10 10 Minimum 10 + 10 mm (runoff & recharge)
100 mm (summer)
231963 Farm cleared Drilled 1993 Bluegums 1995 Harvest 2014-16
Highest t CO2-e/ha sequestration areas
Water Balance
- ve (leaching)
-ve (dry/runoff)
-ve (water use)
-ve (runoff/recharge)
-ve excess runoff
-ve store/runoff
-ve - all above
-ve lost water storage
-ve runoff
-ve groundwater26riseWhat do we do with 60,000 GL… (aka 400mm) in wheatbelt agriculture………
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