Sequestering and Measuring Soil Carbon: Prairie Soil Carbon Balance Project Brian McConkey 1 *,...
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Transcript of Sequestering and Measuring Soil Carbon: Prairie Soil Carbon Balance Project Brian McConkey 1 *,...
Sequestering and Measuring Soil Carbon:
Prairie Soil Carbon Balance Project
Brian McConkey1 *, Chang Liang2,, Glenn Padbury1, Arlan Frick3 ,Wayne Lindwall1
1Agriculture and Agri-Food Canada, 2Environment Canada, 3formerly University of Saskatchewan, currently Saskatchewan Crop Insurance Corporation *[email protected]
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 CO2
Reward good land stewardship Importance to acceptance
Prairie SoilCarbon 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)
PrairieClimate
Soil Texture
Sandy Loamy Clayey
Semiarid 0.1 0.2 0.3
Subhumid
0.2 0.3 0.4
Eliminate Fallow C Gains(tonne C/ha/yr)
0.150.3Subhumid
0.10.2Semiarid
Fallow 1 yr in 4
Fallow 1 yr in 2
Prairie Climate
Crop Rotation
Soil C Model
GIS
BenchmarkedFarm Fields
Soil, Weather, & Management Databases
Basic Research/Plot Measurements
Verification
Soil C modelParameterization
Land-FarmingSystem-WeatherSituations
Large-area orNational Soil CStock Changes
Auditing
Outline ofPrairie Soil
Carbon BalanceProject
Remote Sensing/Flux Measurements
(Future)
NATIONAL SOILSCOVERAGE
SOIL LANDSCAPES OFSASKATCHEWAN
SOIL LANDSCAPE POLYGONS
SOIL LANDSCAPE
SOIL PROFILE
Measurement of soil C gain
0
10
20
30
40
50
60
70
80
Initial
Increase with improved management
Variability from completely random
sampling
Soil C
(to
nn
e 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.
Verification SitesSaskatchewan
CANADAJune, 1997
56
48
42
34
14
10
4
21226142630
2
4
6
16
18
28
58
60
Outline ofPrairie Soil
Carbon BalanceProject
Soil C Model
GIS
BenchmarkedFarm Fields
Soil, Weather, & Management Databases
Basic Research/Plot Measurements
Verification
Soil C modelParameterization
Land-FarmingSystem-WeatherSituations
Large-area orNational Soil CStock Changes
Auditing
Remote Sensing/Flux Measurements
Crop Yields from 22 PSCB Fields with Tilled Strip
Retained
0
1
2
3
4
5
6
7
Dry Matter Yield
(tonne/ha)
Above-groundBiomass
Grain Above-groundResidue
No-TillTilled
*
*
*Tilled less than direct seeded at confidence of 95%
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 1996-1999
Measured 0-20 cm C Gains from 1996-
1999
1.16 1.01
•Includes decrease in fallow (occurred in majority of fields converted)
•Measured change significant (95% confidence)
CENTURY vs. Measured performance (1997-99)
PrairieClimate
MeasuredMean (t C/ha)
CENTURYMean (t C/ha)
Semiarid 0.71 0.92
Subhumid 1.25 0.90
All 1.01 0.91
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 10-20 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 CO2 from atmosphere
Stock is the noun No credit for CO2 already sunk into a C stock 2-3% decrease in prairie agricultural soil stock
would release CO2 equal Canada’s 1990 emissions (CO2equivalent)
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 CH4 and N2O
emitted from agricultural soils Also reports CO2 emitted from agricultural soils
Ecological common sense to also report removals of CO2 into soil where occurring Ag soils will still be net emitter in CO2 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 CO2, CH4, and N2O Biofuels C sequestered in building products Livestock
Manure Feeds
Have to Consider Greenhouse Gas Budget in a Farming System
CH4
CO2
Soil organic matter
N2
Fertilizer
Legumes
N2O
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