Sequestering and Measuring Soil Carbon: Prairie Soil Carbon Balance Project Brian McConkey 1 *, Chang Liang 2,, Glenn Padbury 1, Arlan Frick 3,Wayne Lindwall 1 1 Agriculture and Agri-Food Canada, 2 Environment Canada, 3 formerly University of Saskatchewan, currently Saskatchewan Crop Insurance Corporation

Soil Carbon “Soil at Risk” (1984) identified depleting soil organic matter as one of three major threats to Canada’s soils (with erosion and salinization) Programs initiated to promote practices like no-till and reduced fallow to increase soil organic matter Soil organic carbon key indicator of the soil health

Soils Sinks Practices that increase soil carbon are those that accomplish soil conservation and increase efficiency and effectiveness of using available water resources Reduced tillage and direct seeding Increasing plant production Irrigation, Improved nutrient supply, Better adapted and more productive varieties, Improved grazing strategies Reducing summerfallow Organic C additions Cover crops, Green manures, Compost, Animal manures

Soil Sinks Have Many Benefits Better environment Water quality Air quality Soil quality Biodiviersity Consistent with Adaptation for Climate Change Practices that conserve soil and make more efficient and effective use of water Thinking of the soil-plant-animal system as an ecosystem Net emission reduction until GHG cleaner technologies Sustainable development goals

Quantification and Verification Essential to reward removal of atmospheric CO 2 Reward good land stewardship Importance to acceptance

Prairie Soil Carbon Balance Project (PSCB) Objective: Quantify and verify changes in soil C due to adoption of better agricultural management practices

PSCB - Components Perennial Cropping (Forage) C change due to better management of tame and native forage stands Annual Cropping C change due to adoption of direct seeding and reduced fallow Scaling Up Technology to scale up from point estimates to regional estimates

PSCB - Who Research: AAFC (Brandon, Swift Current, Lethbridge) Universities of Manitoba, Saskatchewan, Alberta Alberta Agriculture, Food, and Rural Development Saskatchewan Soil Conservation Association Funding Support: GEMCo TransAlta Utilities AAFC Matching Investment Initiative Canadian Cattleman’s Association Ducks Unlimited

Develop estimates for rate of C sequestration Research Experiments Medium- and long-term paired farm comparisons Modelling C change (CENTURY model of C dynamics) Establish benchmark verification/auditing system on commercial farm fields Ability to detect C change over 3 yr? PSCB Annual Cropping What

C Sequestration Coefficients (tonne C/ha per yr) Prairie Climate Soil Texture SandyLoamyClayey Semiarid Subhumid

Eliminate Fallow C Gains (tonne C/ha/yr) Subhumid Semiarid Fallow 1 yr in 4Fallow 1 yr in 2Prairie Climate Crop Rotation

Soil C Model GIS Benchmarked Farm Fields Soil, Weather, & Management Databases Basic Research/ Plot Measurements Verification Soil C model Parameterization Land-Farming System-Weather Situations Large-area or National Soil C Stock Changes Auditing Outline of Prairie Soil Carbon Balance Project Remote Sensing/ Flux Measurements (Future)

NATIONAL SOILS COVERAGE SOIL LANDSCAPES OF SASKATCHEWAN SOIL LANDSCAPE POLYGONS SOIL LANDSCAPE SOIL PROFILE

Measurement of soil C gain Initial Increase with improved management Variability from completely random sampling Soil C (tonne C ha -1 ) (hypothetical example)

Dealing with Variability Account for topography Carefully deal with surface litter and large roots Account for differing soil density Return to same small area (benchmark) for repeated measurements Select benchmarks carefully Take multiple soil samples

Benchmarks Benchmarks established on 143 commercial fields that were converted to direct seeding in 1997 Change in soil C due to adoption of no-till + any associated decreases in fallow frequency Sampled in fall 1996 and 1999, greatest value if sampled again in 3 to 5 years Return to the same small benchmark to measure changes in soil C to minimize effect of inherent spatial variability. Benchmarks selected carefully within field so no atypical variation within the benchmark.

1996 sampling 1999 sampling N 2 m Buried Electromagnetic Marker 5 m Benchmark

Outline of Prairie Soil Carbon Balance Project Soil C Model GIS Benchmarked Farm Fields Soil, Weather, & Management Databases Basic Research/ Plot Measurements Verification Soil C model Parameterization Land-Farming System-Weather Situations Large-area or National Soil C Stock Changes Auditing Remote Sensing/ Flux Measurements

Results

Crop Yields from 22 PSCB Fields with Tilled Strip Retained * * * Tilled less than direct seeded at confidence of 95%

Measuring Soil Carbon

2 m 5 m Small-scale 0-10 cm SOC Variability

Surface Residue  Creates Many Sampling Problems  Additional C sink  Amount variable with time and from field to field  No-till residue sink typically from 0.1 up to 2.0 tonne C/ha more than same sink in conventionally tilled systems in Saskatchewan (usually less than 0.3 tonne C/ha more no-till)  Creates Many Sampling Problems  Additional C sink  Amount variable with time and from field to field  No-till residue sink typically from 0.1 up to 2.0 tonne C/ha more than same sink in conventionally tilled systems in Saskatchewan (usually less than 0.3 tonne C/ha more no-till)

Results for Fields Converted to Direct Seeding in 1996(t C/ha) Expected C Gains from Measured 0-20 cm C Gains from Includes decrease in fallow (occurred in majority of fields converted) Measured change significant (95% confidence)

CENTURY vs. Measured performance ( ) Prairie Climate Measured Mean (t C/ha) CENTURY Mean (t C/ha) Semiarid Subhumid All

Variability Benchmarks reduced but did not eliminate variability Measured SOC changes have to be treated statistically Results for benchmark on individual field can’t usually be meaningfully interpreted Cost-effective verification systems will probably involve benchmarked fields over large areas of similar soil-climate- management situations

Measurement Issues Careful measurement of SOC critical to verification Need for certification from unbiased party or international team of experts? 5 years practical minimum for measuring SOC change 5 yr is Kyoto commitment period for which greenhouse gas emission reduction targets apply

Sink – Asset or Liability? Sink is the verb Credit giving for the process of removing CO 2 from atmosphere Stock is the noun No credit for CO 2 already sunk into a C stock 2-3% decrease in prairie agricultural soil stock would release CO 2 equal Canada’s 1990 emissions (CO 2 equivalent) Should be liable for release from the stock regardless of whether part of the stock was used a credited sink

Full Carbon Accounting Canada obligated to report all CH 4 and N 2 O emitted from agricultural soils Also reports CO 2 emitted from agricultural soils Ecological common sense to also report removals of CO 2 into soil where occurring Ag soils will still be net emitter in CO 2 equivalents on national basis Ag soil sinks Included in national estimates whether farmer rewarded for practice or not Once reported farmer can not take it back Agriculture liable for releases of ag soil C

Soil Carbon is Part of Whole Greenhouse Gas Budget Soil C quantification and verification system will become part of comprehensive greenhouse gas farm budget of CO 2, CH 4, and N 2 O Biofuels C sequestered in building products Livestock Manure Feeds

Have to Consider Greenhouse Gas Budget in a Farming System CH 4 CO 2 Soil organic matter N2N2 Fertilizer Legumes N2ON2O

Summary Agricultural ag soil sinks have many benefits Measurement and verification is essential to acceptance and value of agricultural soil sinks Prairie Soil Carbon Balance Project demonstrated a practical and cost-effective system for quantifying and verification of SOC changes Indicated many opportunities for improvements in measurement and modeling Cost-effective verification systems will likely pool SOC changes over large areas Need to start thinking less of C sequestration alone and more about entire farm greenhouse gas budget