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Sense and nonsense in CA: principles, pragmatism and productivity..... John Kirkegaard

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

Text of Sense and nonsense in CA: principles, pragmatism and productivity..... John Kirkegaard

  • 1. Sense and nonsense in Conservation Agriculture: principles, pragmatism and productivity...... John KirkegaardMark 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 DALBY120Mixed farms (2000 ha)0 CONDOBOLIN 0 1 crop/yr (May-Nov) 120GERALDTON120 Mean yield 2 - 3 t/ha0 MOOMBOOLDOOL 120 0 MERREDIN 0120 WAGGA WAGGA 120 1200 0 0ESPERANCEROSEWORTHYHORSHAM 4. Farming system evolution Up to 1980sley pastures grass/annual legumes (merino sheep for wool)cereals (wheat and barley)PastureWheat Barley Since 1990 - Intensification of croppingfewer , larger farmsincreased crop area per farm (3.6% pa)less pasture, fewer sheepmore crop diversityPasture Canola Wheat Wheat Lupin Wheat 5. Australian national wheat yield trends2.5herbicides, N1.1% pa break cropssemi-dwarf wheat2.0Break crops & nitrogen Milleniumdrought legume pasture Phosphorus & Yield (t ha-1)mechanisation improved pasture1.5Fallowing, PFallowing & fertilisermechanisation Organic cultivarsnew1.0 farming0.5 CA0.01860 18801900 1920 19401960 1980 2000Angus (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 adoption8073 - 96% crop area6040Mallee200 1975 1980 1985 1990 1995 2000 2005 2010 YearGRDC 2010; Llewellyn et al 2011 7. Precision agriculture - building on CAControlled traffic (CT)Variable rate technology (VRT) 8. Pragmatic adoption of principlesPrinciple 1. Minimum soil disturbance No-till adopters cultivate 24% crop area 88% use narrow tines, not discsPrinciple 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-sowingNo-till adopters use cultivation on 24% area88% use narrow points only (rather than discs)Discs used to sow ~30% cropped area(GRDC 2010; Llewellyn et al 2011) 10. Strategic tillageInfrequent tillage in an (otherwise) No-till systemDoes 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 managementMultiple 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 fallowCurrent Glyphosate-resistant weeds in summer fallowConyza EchinochloaUrochloaChloris Sonchus(at risk)No grazing (seed set control)No cultivation or burningFactors influencingLess disturbance (disc seeders)evolution under CAWide 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 fieldRhizoctonia solaniNo-till Cultivate No-till Fumigate(Simpfendorfer et al 2002)Cultivate No-till 14. Inhibitory Pseudomonas on root tips in no-till soilPseudomonasper mm root (x 103) 12 8 4 Cultivated soilNo- till soil (Fast growing roots) (Slow growing roots)0Fast growingSlow growing(Watt et al 2005, 2006)roots Roots 15. No-till root environment....not all good!Pore in no-till soil Live wheat crop rootsDead roots frompreceding crop Hard soil no roots 5 mm(Watt et al., 2005; ME McCully, images) 16. Further benefits from root-soil biology researchUnderstandingYield constraints may remain Varietal responses? Interactions of new root genetics precision placement novel inputs (formulations)Lab TilledNo-till Farming systemsFurther efficiency and productivity gains 17. Principle 2 - Stubble retention Adoption rates are highCutting height , straw spreaders, wider rows, inter-row sowingdisc openers, improved herbicides, seed collection, seed destruction High rainfall mixed farms (heavy cereal residues > 6t/ha)less erosion riskhigh in-crop rainfallwide rows reduce yieldweed, pest, disease issuespastures build soil Calternate use for residueMakes sense to manage to thresholds 18. CIMMYT: 30% retained = 100% retainedLong-term wheat yields on permanent beds (1993-2006) 100% retained = 30% retainedNone retained (burnt)Govaerts et al (2005) 19. Principle 3 Diversity (pastures)Managing livestock (and pastures) in CA systemsIntegrateSegregate EliminateDiverse 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)OutcomesSoil physical damage shallow and transientRemoval of cover more importantWater balance impacts season-dependantEffects on yield are rareSheep mouths do more damage than hoovesJames 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 paddocksVirtual 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/grazingNew 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 systemsInter-rowOn-rowTake-all18% Infection50% 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:S1000 kg C requires 83 kg N; 20 kg P; 14 kg SNutrients (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 SE10 t/ha wheat straw 2.5+ nutrients NPSCarbon (%) Carbon % 2.010 t/ha wheat straw 1.5 0 1 2 34 5 6 7 Incubation cycleRepeated 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-legume360 kg GJ-1 No-till 177 kg GJ-1 Cereal monoculture 137 kg GJ-1Impact on GHG emissions (chemicals substitute for tillage) Chemical use80 kg CO2e/ha Tillage 97 kg CO2e/ha (Maraseni & Cockfield 2011) 28. CA systems component interactionsBaseline Scenario (Kerang, Victorian Mallee)1980s - Burn/cultivate, grazed fallow, continuous wheat, sow after 25 May Cumulative improvementsNo-till/stubble retain, spray fallow, pea break crop, sow after 25 AprilCumulative improvements Wheat Yield (t/ha)Baseline (1980s) 1.60 No-till /SR 1.84No-till/SR + spray fallow2.80 No-till/SR + spray fallow + pea break crop3.45No-till/SR + spray fallow + pea break crop + sow 25/44.01Kirkegaard and Hunt (2010) Journal Experimental Botany 29. Summary of key messagesCA principles make sense - adoption is high Australian adoption is pragmatic (in system context) strategic tillage residue thresholds flexible sequencesEvidence-based innovation needs to continue 30. CSIRO Plant IndustryJohn KirkegaardPhone: 02 62465080Email: [email protected] youContact UsPhone: 1300 363 400 or +61 3 9545 2176Email: [email protected] Web: 31. Strategic tillage for multiple constraints Water-repellent sandy topsoil Herbicide resistant weeds Stratified organic matterCompact, 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/haYield 1.6 t/ha Inversion to 25 cm depthYear 2Reduced weedsReduced water-repellence Reduced soil strength Improved pH profile (+lime) Increased C in top 30cm(Steve Davies DAFWA) Yield 2.5 t/haYield 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 WAGGAYield diff (RDD-BC) (t/ha)Yield gain 0.5 0.0 -0.5 Yield loss -1.0 -1.50 100 200 300 400500 600 Growing season rainfall (mm) Insert presentation title 35. Biological constraints in Retain - DDYellow leaf spot RhizoctoniaInhibitory Pseudomonas Insert presentation title 36. Wheat productivity improvements ??Yield differences (t/ha)StateNo-till vs Cult Retain vs BurnNSW 0.01 - 0.31Victoria0.04 - 0.02Western Aust.- 0.03- 0.09 Queensland 0.06 - 0.14 South Australia - 0.02- 0.02Mean - 0.02- 0.15Review 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 v

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