Presentation from the WCCA 2011 event held in Brisbane, Australia.

1. Sense and nonsense in Conservation Agriculture:
principles, pragmatism and productivity......
John Kirkegaard
Mark Conyers, James Hunt, Clive Kirkby
Michelle Watt, Greg Rebetzke

2. Principles - Conservation Agriculture (FAO)
● Continuous minimum mechanical soil disturbance
● Permanent soil cover (crop or mulch)
● Diversification of crop species in sequence/association

3. Australian environment, soils and system
Dry (300-500mm), infertile soils, unsubsidised agriculture
120
0
CLERMONT
120
120
0
DALBY
120
Mixed farms (2000 ha) 0
CONDOBOLIN
0
1 crop/yr (May-Nov) 120
GERALDTON
120
Mean yield 2 - 3 t/ha 0
MOOMBOOLDOOL
120
0
MERREDIN
0
120
WAGGA WAGGA
120 120
0 0 0
ESPERANCE ROSEWORTHY HORSHAM

4. Farming system evolution
● Up to 1980s
ley pastures grass/annual legumes (merino sheep for wool)
cereals (wheat and barley)
Pasture Wheat Barley
● Since 1990 - Intensification of cropping
fewer , larger farms
increased crop area per farm (3.6% pa)
less pasture, fewer sheep
more crop diversity
Pasture Canola Wheat Wheat Lupin Wheat

5. Australian national wheat yield trends
2.5
herbicides, N
1.1% pa break crops
semi-dwarf wheat
2.0 Break crops
& nitrogen Millenium
drought
legume pasture
Phosphorus &
Yield (t ha-1)
mechanisation
improved pasture
1.5
Fallowing, PFallowing &
fertiliser
mechanisation
Organic cultivars
new
1.0
farming
0.5
CA
0.0
1860 1880 1900 1920 1940 1960 1980 2000
Angus (2009); Fischer (2009)

6. No-till adoption and use in Australia
100 Extent of Use (2009)
WA, QLD
62 - 92% use No-till
% no-till adoption
80
73 - 96% crop area
60
40
Mallee
20
0
1975 1980 1985 1990 1995 2000 2005 2010
Year
GRDC 2010; Llewellyn et al 2011

7. Precision agriculture - building on CA
Controlled traffic (CT)
Variable rate technology (VRT)

8. Pragmatic adoption of principles
Principle 1. Minimum soil disturbance
● No-till adopters cultivate 24% crop area
● 88% use narrow tines, not discs
Principle 2. Permanent soil cover
● Crop residues often reduced (graze, bale, burn)
Principle 3. Diversity in sequence
● integrating livestock and crops
● Intensive cereals (64 - 80% cereal)

9. Principle 1 – Minimum soil disturbance
High adoption, but flexible approach
< 5% practice multiple cultivation pre-sowing
No-till adopters use cultivation on 24% area
88% use narrow points only (rather than discs)
Discs used to sow ~30% cropped area
(GRDC 2010; Llewellyn et al 2011)

10. Strategic tillage
Infrequent tillage in an (otherwise) “No-till” system
Does it cause irreparable soil damage?
Case specific, but evidence is contested
Strategic tillage can resolve some issues
Weed, disease management
Lime incorporation - 23M ha acid subsoils
Subsoil amelioration
Is some soil disturbance needed?

11. Strategic tillage - integrated weed management
Multiple herbicide resistant annual ryegrass (L. rigidum)
189 cases glyphosate-resistance (50% no-till, continuous crop)
Tillage has a role in IWM approach (Preston 2010)
Resistant populations
of annual ryegrass
Harrington seed destructor

12. New threat - resistant weeds in summer fallow
Current Glyphosate-resistant weeds in summer fallow
Conyza Echinochloa Urochloa Chloris Sonchus
(at risk)
No grazing (seed set control)
No cultivation or burning
Factors influencing
Less disturbance (disc seeders)
evolution under CA
Wide rows (light for germination)
No crop competition (summer fallow)
3-4 herbicide applications/yr

13. Strategic tillage - disease and biological constraints
Intact soil cores from field
Rhizoctonia solani
No-till Cultivate No-till
Fumigate
(Simpfendorfer et al 2002)
Cultivate No-till

14. Inhibitory Pseudomonas on root tips in no-till soil
Pseudomonas
per mm root (x 103)
12
8
4
Cultivated soil No- till soil
(Fast growing roots) (Slow growing roots) 0
Fast growing Slow growing
(Watt et al 2005, 2006) roots Roots

15. No-till root environment....not all good!
Pore in no-till soil
Live wheat crop roots
Dead roots from
preceding crop
Hard soil – no roots
5 mm
(Watt et al., 2005; ME McCully, images)

16. Further benefits from root-soil biology research
Understanding
Yield constraints may remain
● Varietal responses?
● Interactions of…
new root genetics
precision placement
novel inputs (formulations)
Lab Tilled No-till
Farming systems Further efficiency and productivity gains

17. Principle 2 - Stubble retention
Adoption rates are high
Cutting height , straw spreaders, wider rows, inter-row sowing
disc openers, improved herbicides, seed collection, seed destruction
High rainfall mixed farms (heavy cereal residues > 6t/ha)
less erosion risk
high in-crop rainfall
wide rows reduce yield
weed, pest, disease issues
pastures build soil C
alternate use for residue
Makes sense to manage to thresholds

18. CIMMYT: 30% retained = 100% retained
Long-term wheat yields on permanent beds (1993-2006)
100% retained
=
30% retained
None retained (burnt)
Govaerts et al (2005)

19. Principle 3 – Diversity (pastures)
Managing livestock (and pastures) in CA systems
Integrate Segregate Eliminate
Diverse Efficient (time/labour)
Soil damage? Pasture benefits lost

20. Impact of livestock in CA systems
● Surprisingly little data for southern Australia
● Literature review (Bell et al 2011)
● Field experiments (4 sites since 2008)
Outcomes
Soil physical damage shallow and transient
Removal of cover more important
Water balance impacts season-dependant
Effects on yield are rare
Sheep mouths do more damage than hooves
James Hunt , Thursday 9.35, pg 382

21. Dual-purpose crops – graze and grain
● Cereal and canola crops grazed without yield penalty
● Increase flexibility, profitability and reduce risk
● Increase animal and crop production from mixed farms

22. Future - precision animal management....
● Efficient, safe grazing in larger crop paddocks
“Virtual” fences
● zonal crop and stubble grazing
● livestock „sweeping‟ to achieve cover targets
● patch weed control

23. Principle 3 – Diversity (broad-leaf crops)
Intensive cereals dominate (64-80%)
Why cereals?
easy to manage and market
lower risk (cost and reliable performance)
high residues for cover/grazing
New technology helps
disease resistance, soil/seed fungicides, soil DNA testing
precision inter-row sowing and residue management
new herbicide options

24. Inter-row sowing in CA systems
Inter-row On-row
Take-all
18% Infection 50%
Large stubble load
● Cereal on cereal 6-9% yield benefit
● Canola on cereal
(Matt McCallum 2008)

25. CA Systems - the carbon conundrum.....
Pastures build soil organic carbon (SOC)
CA slows SOC decline, but rarely builds (slow)
Why?
Stable organic matter (humus) has a constant ratio of C:N:P:S
1000 kg C requires 83 kg N; 20 kg P; 14 kg S
Nutrients (not C) might limit humus formation
(Kirkby et al. Geoderma 2011)

26. Nutrients and C sequestration - incubation study
Soil + stubble + supplementary nutrients Leeton
3.0 Laboratorystubble
Soil + incubation study (Leeton soil)
error bars are SE
10 t/ha wheat straw
2.5
+ nutrients NPS
Carbon (%)
Carbon %
2.0
10 t/ha wheat straw
1.5
0 1 2 3 4 5 6 7
Incubation cycle
Repeated addition of 10 t/ha wheat straw (3 monthly)
(Clive Kirkby, Poster 122, pg 538)

27. CA systems - energy efficiency?
Time, labour, fuel efficiencies undisputed (on-farm)
Overall energy efficiency (grain yield per unit energy input)
Conv. 173 kg GJ-1 Cereal-legume 360 kg GJ-1
No-till 177 kg GJ-1 Cereal monoculture 137 kg GJ-1
Impact on GHG emissions (chemicals substitute for tillage)
Chemical use 80 kg CO2e/ha
Tillage 97 kg CO2e/ha
(Maraseni & Cockfield 2011)

28. CA systems – component interactions
Baseline Scenario (Kerang, Victorian Mallee)
1980s - Burn/cultivate, grazed fallow, continuous wheat, sow after 25 May
Cumulative improvements
No-till/stubble retain, spray fallow, pea break crop, sow after 25 April
Cumulative improvements Wheat Yield (t/ha)
Baseline (1980s) 1.60
No-till /SR 1.84
No-till/SR + spray fallow 2.80
No-till/SR + spray fallow + pea break crop 3.45
No-till/SR + spray fallow + pea break crop + sow 25/4 4.01
Kirkegaard and Hunt (2010) Journal Experimental Botany

29. Summary of key messages
CA principles make sense - adoption is high
Australian adoption is pragmatic (in system context)
strategic tillage
residue thresholds
flexible sequences
Evidence-based innovation needs to continue

30. CSIRO Plant Industry
John Kirkegaard
Phone: 02 62465080
Email: john.kirkegaard@csiro.au
Thank you
Contact Us
Phone: 1300 363 400 or +61 3 9545 2176
Email: Enquiries@csiro.au Web: www.csiro.au

31. Strategic tillage for multiple constraints
Water-repellent sandy topsoil
Herbicide resistant weeds
Stratified organic matter
Compact, acid subsurface
(Steve Davies DAFWA)
Deep Yellow Sand

32. Strategic inversion tillage (1 year in 10)
Plough ($70/ha) Herbicides ($70/ha)
Year 1
Yield 2.5 t/ha Yield 1.6 t/ha
Inversion to 25 cm depth
Year 2
Reduced weeds
Reduced water-repellence
● Reduced soil strength
● Improved pH profile (+lime)
● Increased C in top 30cm
(Steve Davies DAFWA)
Yield 2.5 t/ha Yield 1.5 t/ha

33. 3. Improving productivity of modern, no-till farming
Adoption is driven by
Erosion control, water conservation
● Labour, machinery, fuel savings
● Timelines of operations
● Soil “health” benefits
● Improved productivity

34. Impact of season on response to no-till
 HARDEN
1.0
 WAGGA
Yield diff (RDD-BC) (t/ha)
Yield gain
0.5
0.0
  
 

-0.5 
Yield loss 

-1.0

-1.5
0 100 200 300 400 500 600
Growing season rainfall (mm)
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35. Biological constraints in Retain - DD
Yellow leaf spot
Rhizoctonia
Inhibitory Pseudomonas
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36. Wheat productivity improvements ??
Yield differences (t/ha)
State No-till vs Cult Retain vs Burn
NSW 0.01 - 0.31
Victoria 0.04 - 0.02
Western Aust. - 0.03 - 0.09
Queensland 0.06 - 0.14
South Australia - 0.02 - 0.02
Mean - 0.02 - 0.15
Review of 39 long-term experiments (Kirkegaard 1995)

37. Adoption of No-till

38. CSIRO long-term study, Harden NSW
(commenced 1990)
• Increased earthworms
• Higher microbial biomass
• Disease suppression (Rhizoctonia)
• Higher abundance of mites, nematodes, collembola
• Diversity shifts in mites, nematodes, collembola
• Maintain levels of organic C and N
• Improved infiltration and less runoff
• Good crop establishment in all years
• Reduced crop vigour and yield (-11%) x
• Rhizoctonia, inhibitory bacteria, yellow leaf spot x
• Herbicide resistance x
• Increased drainage x