Soil carbon In Tasmania Dr Bill Cotching

Transcription

1 Soil carbon In Tasmania Dr Bill Cotching

2 research development extension education

3 Rachel Brown, Jamie Cooper, Ross Corkrey, Mark Downie, Richard Doyle, Darren Kidd, Chris Grose, Duncan MacDonald, Bruce McCorkell, Kerry Hawkins, Rob Moreton, Garth Oliver, Suresh Panta, Jocelyn Parry-Jones, Sam Rees, Bill Rowley, Leanne Sherriff, Leigh Sparrow, Eve White, Tasmanian farmers, many others research development extension education

4 How Does Carbon Enter The Soil? Plant residues

5 Soil organic carbon Potential Attainable Actual

6 Clay content & type Rainfall & Soil organic carbon temperature Management Actual Attainable Potential

7 Soil carbon level controlled by: Clay content Rainfall (+ irrigation) Land use / management (Topography in Tasmania)

8 Relationship between carbon and the clay + silt content for Tasmanian soils Sparrow, Belbin & Doyle

9 Relationship between soil carbon and Nov-March rainfall for Dermosols under pasture

10 All soils are NOT equal

11 Topsoil carbon in Tasmanian agricultural soils Soil health Sparrow & Cotching et al. 7 Soil carbon mm (%) g n i s a e r c n I o c y cl a t n e nt Tenosols Sodosols Ferrosols Dermosols Vertosols

12 Carbon stocks in Tasmanian soils - SCEAM Mean + range (0 30 cm) Maximum Minimum

13 Carbon stocks in Tasmanian soils - SCaRP Mean + range (0 30 cm) Carbon stock 0-30 cm depth (T/ha) pasture cropping Dermosol pasture cropping Ferrosol pasture cropping Texture Contrast pasture cropping Vertosol

14 130 sites

15 Soilquality.org.au

16 Relationship between soil carbon and Land use in Tasmania SCaRP

17 Effect of long term cropping on soil carbon in Ferrosols Sparrow, Cotching, Parry-Jones, Oliver, White, Doyle 2013

18 Cotching 1979

19 Changes in soil carbon over 13 years

20 Effect of tillage on soil carbon 0 10 cm Total organic carbon (mgc/g) 50 Minimum till Conventional till Dermosol Ferrosol Vertosol Texture Contrast

21 SCaRP findings: The potential SOC is determined by inherent soil characteristics of clay content and clay type, that are encapsulated by Soil Order. The attainable level of SOC is determined by the local climate predominantly annual rainfall. Actual SOC is determined by the type of land use and the soil management practices undertaken

22 It is not possible to increase the attainable SOC in soil, but management practices determine whether or not the attainable storage of SOC in soil is achieved. Farmers can influence SOC concentrations more by their choice of land use than their day-to-day soil management. Farmers can influence SOC by cropping less frequently and reducing the amount of tillage during soil working, as long as these practices are considered together with economic sustainability.

23 Clay content & type Rainfall & Soil organic carbon temperature Management Actual Attainable Potential

24 Duplex soil profile carbon SOC Content Proportion of profile SOC Relative response time 0 cm High 30 % Rapid Moderate 40 % Intermediate Moderate 30 % 10 cm 30 cm 100 cm Slow

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26 Soil carbon has a major role in soil health Physically Good soil structure water infiltration and retention Aeration of the soil Assists root growth Reduces erosion and compaction Chemically Contributor to soil cation exchange capacity = Reduced leaching of nutrients Increased nutrient availability to plants Binding sites for pesticides /heavy metals Biologically Food source for microbes and invertebrates Cycling of nutrients vital for soil fertility and plant growth

27 Soil health Sparrow & Cotching Microbial biomass carbon (mg/kg) Soil carbon % 6 7 8

28 How much soil carbon is enough? Targets for soil carbon Soils can become saturated with carbon

29 Tasmanian humus carbon McDonald, Baldock & Kidd humus carbon % Total soil carbon %

30 Tasmanian particulate carbon McDonald, Baldock & Kidd 2010 Particulate Organic Carbon Organic Carbon %

31 Soil carbon components Optimum Tas Range % % Particulate Humus Recalcitrant

32 Target levels of soil organic carbon in the surface 75 mm of soil. Topsoil texture Sandy loam or loamy sand Land use Annual rainfall (%) Pastures & cropping All Target Saturated (%) >2 4 Clay loam or clay Cropping > 800 < 800 >3 > Pastures > 800 < 800 >4 > >4 10 Heavy clay (cracking soil) Pastures All & cropping

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36 Organic matter Organic carbon Total soil carbon Organic matter = 1.72 X organic carbon OM = carbon + nutrients (58 %)

37 1 tonne of humus-c will lock up 50 kg N, 20 kg K, 3 kg P and 4 kg S 0.1 % carbon on your soil test = 1 T organic carbon /ha = $140 / ha of N, P, K, S

38 Biochar The carbon-rich solid product resulting from the heating of biomass in an oxygen-limited environment (pyrolysis). Biochar is chemically and biologically more stable compared with the organic matter from which it was made. Biochar can offer potential value to crop productivity through interactions with nutrients and soil mineral particles as well as offer benefits with regard to carbon sequestration.

39 Biochar

40 Emissions Reduction Fund The Government will purchase Australian Carbon Credit Units from existing Carbon Farming Initiative projects that are competitive at an auction The Government s preference is that contracts will be for 5 years. Some emissions reduction activities are likely to be most cost-effectively implemented through aggregation.

41 Carbon Credits (Carbon Farming Initiative) Act 2011 Measurement-Based Methodology for Sequestering Carbon in Soils in Grazing Systems 159 pages + 70 pages appendices Methodology proposal to the Domestic Offsets Integrity Committee (DOIC) open for public consultation until 6 May 2014

42 The management actions that comprise the project must include one or more new management actions (project management actions). Project management actions may include, but are not limited to, one or more of the following: a) Converting from cropland to pasture b) Undertaking pasture cropping c) Managing pasture through: i. Changing pasture species composition ii. Implementing or changing pasture irrigation iii. Applying organic or synthetic soil amendments to pastures iv. Rejuvenating pastures through eligible tillage activities and / or seeding d) Managing grazing through: i. Changing stocking rates ii. Altering the timing, duration, intensity and extent of grazing It should be noted that none of the management actions set out above are guaranteed to build soil carbon on any particular project site. It cannot be assumed that any one or more management actions that effectively build soil carbon in one context will have similar results for other projects.

43 7. The following types of management actions are not eligible under this methodology: a. The permanent de-stocking of grazing systems; b. Tillage, other than eligible tillage; c. Importing crop residue, hay, straw or plant material, other than compost, from outside of the project area into the project area; d. Applying crop residue, hay, straw or plant material, including in composted form, from within the project area to CEA s within the project area; and e. Application of biochar or amendments containing coal to the soil; and f. Conversion of forest to pasture or other removal of woody vegetation from within the project area other than to manage regrowth of invasive woody weeds on existing pasture.

44 Requirements: 8. Engage a qualified technician and undertake baseline soil sampling, preparation and analysis in accordance with the CFI Soil sampling and analysis method. a) Technicians must have nationally recognised qualifications in the competencies described in the CFI Soil sampling and analysis method and guidelines document. 9. Calculate baseline SOC stock as set out in section 11.1a of this methodology. 10. Implement the new management actions and erosion protection measures for the project described above. 11. Engage a qualified technician to undertake follow-up rounds of soil sampling at intervals of not less than one year and not more than 5 years after the previous sampling round. 12. Use the results of sampling rounds to calculate SOC stock change over time. 13. Calculate changes in emissions from sources and sinks set out in section 8 and use this to calculate net abatement as set out in section 11 of this methodology.

45 To reduce the risk of crediting a short-term SOC stock change that exceeds the long-term average SOC stock change, a conservative, flat discount rate of 50% is applied to the SOC stock change after 2 sampling rounds. This will reduce the risk and magnitude of potential over-crediting. A linear regression approach is used to calculate SOC stock change after three or more sampling rounds, to smooth the effects of environmental variation. The calculated average rate of SOC stock change with a defined probability of exceedance 80% is used.

46 Measuring soil carbon Photo: T Ackroyd

47 Soil sampling 1. Stratification of CEAs and identification of sampling locations Must define within the project area one or more CEA s - carbon estimation areas Each CEA must include a minimum of three evenly sized strata. 2. Collection and compositing A single soil sample from every stratum is combined to create a composite sample. A minimum of three composites must be included Sampling must occur to the minimum depth of 30cm Minimum cutting head diameter of 4 cm Bulk density samples must be taken 3. Laboratory analysis NATA accredited or ASPAC certified for organic carbon analysis High temperature dry combustion method (LECO), or

48 It is recommended to take more than ten samples. It is also suggested that at least 4 composites, but possibly more, are needed to reduce uncertainty. A GPS must be used to locate every sampling location.

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50 Bulk Density = a measure of mass in a given volume

51 What has mapping carbon at farm scale taught us?

52 Farm property map is an ideal way to summarise the overall carbon picture of the farm The Farm Carbon Story uses information which is already routinely compiled as part of a well delivered property management plan eg. farm map, soil types, land use areas (cropping, native bush, grassland). The Farm Carbon Story uses existing carbon calculators, which are all developed in accordance with the National Carbon Accounting Guidelines

53 45 Farm Carbon Stories completed Area (ha) Annual C footprint (TCO2e) Annual farm emissions equivalent to annual emissions from: Northwest cropping Midlands Mixed Dairy 400 cows Hiluxes 230 Hiluxes 530 Hiluxes

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55 Carbon millionaires Soil carbon millionaires

56 How much soil carbon have we got on farms? Clay soils Sandy soils Wet soils 200 t/ha 100 T/ha 160 T/ha in top 30 cm of soil

57 Carbon in the bank NW cropping 420 T CO2e (115 T C) soil organic carbon / ha (0-30 cm) Carbon may be priced at $23 /T CO2e = $ 9700 / ha Average farm size = 180 ha Soil organic carbon in the bank = $M 1.7 But at $5 /T CO2e = $ 378,000

58 Carbon in the bank Midlands mixed 275 T CO2e (75 T C) soil organic carbon / ha (0-30 cm) Carbon may be priced at $23 /T CO2e = $ 6300 / ha Average farm size = 850 ha Soil organic carbon in the bank = $M 5.4 But at $5 /T CO2e = $M 1.2

59 Shu Kee Lam, Deli Chen, Arvin R. Mosier & Richard Roush (2013) Meta analysis of 56 Australian studies At a carbon price of $23/tonne, all practical soil management practices lost at least $3 per hectare per year. When N fertilizer was used to increase crop growth and subsequent soil carbon, the costs of the extra fertilizer use generated a financial loss across all systems. Under normal cropping practices, farmers would need about $36 per hectare to break even on carbon payments. Carbon must remain sequestered 100 years, But drought & changing land ownership and practices limit the viability of the Carbon Farming Initiative.

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61 BlackMagic Organic carbon model for Tasmanian Cropping Soils Leigh Sparrow, Peter Rayner and Bill Cotching

62 BlackMagic Contains Tasmanian parameters from thirty major crops, fourteen soil/area combinations 60 representative sets of climatic conditions. The organic matter decomposition rates are based on the RothC model developed by Rothamsted Research, U.K.

63 Yield You may enter your expected yield (T/ha). When left blank, hidden default values are used to make this calculation. District, soil and use of irrigation determine the default values.

64 BlackMagic does : Compare crops and farming practices Demonstrate the benefits of stubble incorporation, green manure crops and pasture illustrates equilibrium helps farmers, researchers & teachers

65 Coal Valley cropping

66 Coal Valley cropping

67 Coal Valley cropping

68 Coal Valley cropping

69 Oatlands - pasture

70 Oatlands - pasture

71 Oatlands - pasture

72 Ferrosol cropping

73 Ferrosol cropping

74 Ferrosol cropping

75 Ferrosol cropping + green manure

76 Ferrosol cropping + green manure

77 Ferrosol cropping + green manure

78 So what s good? and what s not so good for soil organic matter

79 Contribution to soil organic carbon + - Perennial pastures Green manure crops Recycled amendments Stubble/crop residue retention Fertilisers No tillage Tillage Stubble burning Fallow Erosion d e s a re c In rg o il o s i n a n o rb a cc ls e lev

80 Summary of on-farm trial results Leanne Sherriff Different soils respond differently to treatments Mixed trial results from different amendments They don t all work all the time Some work some times! Adding organic matter increases microbe No s & diversity You can grow lots of organic matter

81 Tasmanian farmer trials Organic carbon increases microbial numbers & diversity Increased nutrients increases microbial activity Microbes don t like EC > 0.1 ds/m Arbuscular mycorrhizal fungi don t like increased levels of nutrients, probably associated with cultivation

82 Microbes are Magic

83 Soil health Only believe half what you see and nothing that you hear!

84 UK Govt scientific review You improve the work of soil organisms by: Feeding the soil a diverse diet. This entails increasing the variety and overall amount of organic matter added to the soil (eg. green manures) Reducing tillage, both the total amount and also intensity; Diversifying cropping systems (having a wider range of crops and/or pasture). If farmers and growers make the system changes, the soil organisms natively present will work better. If they don t make the system changes, adding a few extra microorganisms is unlikely to bring much benefit

85 Points to remember Soil organic matter levels are controlled by clay content, climate and management. Soil carbon can vary widely both spatially and over time Soils have a finite ability to build productive organic matter To increase organic carbon by 1%, approximately 40 t/ha of dry matter will need to be added to the soil. Living organisms will occur wherever there is food. Feed soil biota organic matter and they will flourish.

86 Points to remember Introducing perennial plants into crop rotations has the greatest potential to increase soil organic matter Perennial systems don t sequester soil C after equilibrium Drought often results in soil organic matter decline Difficult to measure soil carbon accurately

87 Key messages Different soils have different capacities to store soil carbon Growing more plant material is the best way to boost soil C Soil organic matter (carbon) is part of a sustainable farming operation, not a get rich quick scheme.

88 The land does not lie; it bears a record of what men write on it (WC Lowdermilk)