1 / 16

Ploughing through soil carbon: – science foundations and directions

Ploughing through soil carbon: – science foundations and directions. Brian Keating, Jeff Baldock and Jon Sanderman Business Leaders Forum on Sustainable Development: 27 th May 2010. Australia’s terrestrial carbon sinks are large!.

janina
Télécharger la présentation

Ploughing through soil carbon: – science foundations and directions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ploughing through soil carbon: – science foundations and directions Brian Keating, Jeff Baldock and Jon Sanderman Business Leaders Forum on Sustainable Development: 27th May 2010

  2. Australia’s terrestrial carbon sinks are large! (Source: R Waterworth, National Carbon Assessment System, DCC and Australia’s State of the Forest Report, DAFF). (Soil depth used = 30 cm) • Australian vegetation and surface soils: approx 100 Gt CO2-e • Annual total emissions: approx 0.6 Gt CO2-e

  3. Soil Carbon has often run-down under past agriculture • The potential does exist to sequester carbon in Australian soils

  4. Soil organic carbon content Inputs of organic carbon Losses of organic carbon f = , Inputs Losses • Conversion of organic C to CO2 • Protection offered by soil minerals • Extent of cultivation • Plant biomass and residue return to the soil • Addition of waste organic materials What determines soil organic carbon content?

  5. Soil C has been a focus for research for a long time ! Hoosfield Continuous Barley Experiment, Rothamsted, UK 1852 – present day Continuous Manure Initial Manure, then no additions (0 - 23cm) No additions 1980 1860 Petersen et al 2005 Soil Biol Biochem 37 359

  6. Soil C storage capacity is finite Soil C changes take place over long time periods Management changes that build soil C must be maintained to maintain soil C Useful models available with predictive skill Some soil C principles

  7. Turnover Rates 100 – 1000’s years 1-10 years 10 - 100 years Not all soil carbon is made the same! • Need to combine carbon measurement with carbon modelling to predict likely rates and directions of change

  8. Where is the evidence we can change agricultural practices to build soil C – from Australia ? • Reviewed available trial data on soil C change in response to management • Reports data for 96 trials and/or treatments across Australia • Rates of soil C change with “C friendly” management • Within cropping or grazing management in range 0.1 to 0.3 Mg C ha-1 yr-1 • Conversion of cultivation to permanent pasture in range 0.5 to 0.6 Mg C ha-1 yr-1 • Many current systems are still running soil C down so some “C friendly” practices simply reduce this rundown rate • Net sequestration vs emissions avoidance Available at http://www.csiro.au/resources/Soil-Carbon-Sequestration-Potential-Key-Findings.html

  9. Where is the evidence we can change agricultural practices to build soil C – internationally ? Improved grassland mgnt. * * Reduced fallow * No-till adoption * Conservation tillage * * Forages in rotations * * Cultivation conversion * Manure inputs * * Altered fertiliser inputs * Source: Hutchinson et. al. (2007) Some perspectives on carbon sequestration in agriculture. Agric. For. Meteorol. 142, 288-302. (adapted from Table 4)

  10. What practices favour higher soil carbon levels ? • Anything that increase carbon additions or reduces carbon losses • Improved crop or pasture nutrition (including fertiliser, manures, legume fixation) • Reduced fallow periods • Including pasture phases in the crop rotation • Retaining crop residues • Reduced tillage • Reducing overgrazing that damages pastures and soils • Eliminating soil losses through wind or water erosion • Converting from cultivation to permanent pasture or forest • Adding carbon from off-site sources (e.g. biochar from waste streams) • All actions need to be subject to “whole of life cycle” caveats • No value in reducing emissions in one place and increasing them in another • No value in reducing C loss but increasing emissions of other greenhouse gases such as methane or nitrous oxide

  11. National Soil Carbon Research Program NT DPI* Qld rangelands Extra sampling - with additional partners Qld cropping WA rangeland Soils* C3/C4 Panic/Rhodes NSW MER samples (500 soil profiles) NSW Soils 14C labelling sites Murray CMA C3/C4 Kikuyu SA soils Victorian sampling sites WA Soils CfOC 0 350 700 Tasmania soils Kilometres * proposed Expanding our soil carbon knowledge-base

  12. Potential costs and benefits of building soil carbon • Potential benefits • Enhanced water holding capacity and soil structure • Reduced erosion risk • Enhanced soil fertility and nutrient cycling • Potentially, a soil carbon offset with financial value • subject to due diligence on long term obligations • at 0.1 to 0.5 Mg C ha-1 yr-1 and a carbon price of $20 t-1 CO2-e, gross returns in the order of $7-35 ha-1 yr-1. • Potential costs • Management changes need to make sense in terms of farm finances • Increased input costs or reduced output income • Any costs associated with measurement and verification of soil carbon offsets • Likely to be conditional on nature of the offset system

  13. Summing up ….. • Soil C is part of the solution • But not the solution …. • Rapid and cost effective measurement is a research priority • Enables responses in both practice and policy • Big step-up in soil carbon assessment now underway across the country (2000 plus locations) • Limited time-series sampling (not possible in 3 years) • Can’t sample everywhere so models still important • Long-term soil C monitoring is also important • We’re talking about processes that can take 30-50 years plus to unfold.

  14. Brian Keating Director Sustainable Agriculture Flagship Phone: +61 7 32142373 Email: Brian.Keating@csiro.au Contact details Contact UsPhone: 1300 363 400 or +61 3 9545 2176Email: Enquiries@csiro.au Web: www.csiro.au

  15. Relative difference Improved management Traditional management Factors influencing rate of change of soil carbon Drawn from 48 observations / trials around Australia Rate of change (Mg C ha-1 yr-1) -1.0 -0.5 0.0 0.5 1.0 0 • Soil C changes in response to a management change greatest in top 20 cms of soil depth 10 20 Depth (cm) 30 40 50

  16. 1.0 0.5 0.0 Rate of change (Mg C ha-1 yr-1) -0.5 -1.0 0 10 20 30 40 Trial duration (years) Relative difference Improved management Traditional management Factors influencing rate of change of soil carbon Drawn from 48 observations / trials around Australia • Soil C changes in response to a management change greatest over first 10 - 20 years

More Related