Sense and nonsense in Conservation Agriculture:

principles, pragmatism and productivity......

John Kirkegaard

Mark Conyers, James Hunt, Clive KirkbyMichelle Watt, Greg Rebetzke

Principles - Conservation Agriculture (FAO)

● Continuous minimum mechanical soil disturbance

● Permanent soil cover (crop or mulch)

● Diversification of crop species in sequence/association

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H O R SH A M

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0R O SE W O R TH Y

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E S P E R AN C E

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M E R R E D IN

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Mixed farms (2000 ha)

1 crop/yr (May-Nov)

Mean yield 2 - 3 t/ha

Australian environment, soils and system

Dry (300-500mm), infertile soils, unsubsidised agriculture

Farming system evolution

● Since 1990 - Intensification of cropping

fewer , larger farms

increased crop area per farm (3.6% pa)

less pasture, fewer sheep

more crop diversity

● Up to 1980s

ley pastures grass/annual legumes (merino sheep for wool)

cereals (wheat and barley)

Pasture Wheat Barley

Pasture WheatCanola Wheat Lupin Wheat

Australian national wheat yield trends

1860 1880 1900 1920 1940 1960 1980 2000

Yie

ld (

t h

a-1

)

0.0

0.5

1.0

1.5

2.0

2.5

Organicfarming

Fallowing &mechanisation

Milleniumdrought

Break crops& nitrogen

Phosphorus &improved pasture

1.1% pa

Fallowing, P fertilisernew cultivars

legume pasturemechanisation

herbicides, Nbreak crops

semi-dwarf wheat

Angus (2009); Fischer (2009)

CA

No-till adoption and use in Australia

Year

1975 1980 1985 1990 1995 2000 2005 2010

% n

o-t

ill

ad

op

tio

n

0

20

40

60

80

100

year vs upper year vs lower year vs mean

GRDC 2010; Llewellyn et al 2011

Extent of Use (2009)

62 - 92% use No-till

73 - 96% crop area

WA, QLD

Mallee

Precision agriculture - building on CA

Controlled traffic (CT)

Variable rate technology (VRT)

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)

Principle 1 – Minimum soil disturbance

< 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)

High adoption, but flexible approach

Strategic tillage

Case specific, but evidence is contested

Strategic tillage can resolve some issuesWeed, disease management

Lime incorporation - 23M ha acid subsoils

Subsoil amelioration

Is some soil disturbance needed?

Does it cause irreparable soil damage?

Infrequent tillage in an (otherwise) “No-till” system

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)

Harrington seed destructor

Resistant populations of annual ryegrass

New threat - resistant weeds in summer fallow

Current Glyphosate-resistant weeds in summer fallow

No grazing (seed set control)

No cultivation or burning

Less disturbance (disc seeders)

Wide rows (light for germination)

No crop competition (summer fallow)

3-4 herbicide applications/yr

Factors influencingevolution under CA

Conyza Echinochloa Urochloa Chloris Sonchus(at risk)

Strategic tillage - disease and biological constraints

Rhizoctonia solani

No-till Cultivate No-tillFumigate

(Simpfendorfer et al 2002)

No-tillCultivate

Intact soil cores from field

0

4

8

12

Fast growingroots

Slow growing Roots

Pseudomonas per mm root (x 103)

Cultivated soil(Fast growing roots)

No- till soil(Slow growing roots)

Inhibitory Pseudomonas on root tips in no-till soil

(Watt et al 2005, 2006)

5 mm

Live wheat crop roots

Dead roots frompreceding crop

Pore in no-till soil

(Watt et al., 2005; ME McCully, images)

No-till root environment....not all good!

Hard soil – no roots

Further benefits from root-soil biology research

● Yield constraints may remain

● Varietal responses?

● Interactions of…new root geneticsprecision placement novel inputs (formulations)

Understanding

Farming systems

Lab Tilled No-till

Further efficiency and productivity gains

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

CIMMYT: 30% retained = 100% retained

None retained (burnt)

100% retained=

30% retained

Govaerts et al (2005)

● Long-term wheat yields on permanent beds (1993-2006)

Principle 3 – Diversity (pastures)

Integrate Segregate Eliminate

Pasture benefits lostSoil damage?

Efficient (time/labour)Diverse

Managing livestock (and pastures) in CA systems

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

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

● zonal crop and stubble grazing

● livestock ‘sweeping’ to achieve cover targets

● patch weed control

Future - precision animal management....

● Efficient, safe grazing in larger crop paddocks

“Virtual” fences

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

● Large stubble load

● Cereal on cereal

● Canola on cereal

Inter-row sowing in CA systems

6-9% yield benefit

Take-all

18% Infection 50%

(Matt McCallum 2008)

Inter-row On-row

CA Systems - the carbon conundrum.....

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

Pastures build soil organic carbon (SOC)

CA slows SOC decline, but rarely builds (slow)

Why?

(Kirkby et al. Geoderma 2011)

Nutrients and C sequestration - incubation study

(Clive Kirkby, Poster 122, pg 538)

Leeton

Incubation cycle0 1 2 3 4 5 6 7

Ca

rbo

n (

%)

1.5

2.0

2.5

3.0

Soil + stubble + supplementary nutrientsSoil + stubble

error bars are SE

Repeated addition of 10 t/ha wheat straw (3 monthly)

Car

bon

%

10 t/ha wheat straw

+ nutrients NPS

10 t/ha wheat straw

Laboratory incubation study (Leeton soil)

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)

CA systems – component interactions

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

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

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

Thank you

CSIRO Plant IndustryJohn Kirkegaard

Phone: 02 62465080Email: john.kirkegaard@csiro.au

Contact UsPhone: 1300 363 400 or +61 3 9545 2176Email: Enquiries@csiro.au Web: www.csiro.au

Strategic tillage for multiple constraints

Compact, acid subsurface

Water-repellent sandy topsoil

Herbicide resistant weeds

Stratified organic matter

Deep Yellow Sand

(Steve Davies DAFWA)

Strategic inversion tillage (1 year in 10)

Plough ($70/ha) Herbicides ($70/ha)

Yield 1.6 t/haYield 2.5 t/ha

● Reduced weeds

● Reduced water-repellence

● Reduced soil strength

● Improved pH profile (+lime)

● Increased C in top 30cm

Yield 1.5 t/haYield 2.5 t/ha(Steve Davies DAFWA)

Year 2

Year 1

Inversion to 25 cm depth

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

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Impact of season on response to no-till

Growing season rainfall (mm)

0 100 200 300 400 500 600

Yie

ld d

iff (

RD

D-B

C)

(t/h

a)

-1.5

-1.0

-0.5

0.0

0.5

1.0Yield gain

Yield loss

HARDEN

WAGGA

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Biological constraints in Retain - DD

Yellow leaf spot

Rhizoctonia

Inhibitory Pseudomonas

Wheat productivity improvements ??

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)

Yield differences (t/ha)

Adoption of No-till

CSIRO long-term study, Harden NSW

• 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

(commenced 1990)