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- R. César Izaurralde
- Joint Global Change Research Institute
- Charles W. Rice
- Kansas State University
- 3rd USDA Symposium on Greenhouse Gases & Carbon
Sequestration in Agriculture and Forestry
Baltimore, MD
- 21-24 March 2005
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- CSiTE (Carbon Sequestration in Terrestrial
Ecosystems) Research Consortium –DOE
- http://csite.esd.ornl.gov
- CASMGS (Consortium for Agricultural Soils
Mitigation of Greenhouse GaSes) – USDA
- http://www.casmgs.colostate.edu
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- Cropland
- Reduced tillage
- Rotations
- Cover crops
- Fertility management
- Erosion control
- Irrigation management
- Rice paddies
- Irrigation
- Chemical and organic fertilizer
- Plant residue management
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- 100 samples to detect 2-3% change in SOC
- 16 samples to detect 10-15 % change in SOC
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- Use “microsites” (4 x 7 m) to reduce spatial variability
- Three to six microsites per field
- Calculate SOC storage on an equivalent mass basis
- Analyze samples taken at different times together
- Soil C changes detected in 3 yr
- 0.71 Mg C ha-1 – semiarid
- 1.25 Mg C ha-1 – subhumid
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- 64-ha fields in Nebraska: (1) irrigated continuous maize, (2) irrigated
corn-soybean rotation, and (3) a dryland corn-soybean rotation
- Sampling at about 250 locations
per field
- Geostatistical modeling: various types of kriging
- Simulate lower sampling densities to identify approaches that minimize
cost and uncertainty
- Can improved soil management justify the cost of intensive sampling?
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- Hypothesis: Field scale variability often predictable from topographic
data
- Available GIS data (remote sensing, terrain models, soil maps, precision
farming) can be used to map large areas with a minimum number of samples
- Carbon strongly predicted from terrain (wetness index) in Iowa
(glacially-derived Mollisolls)
- Relationships between C and topography are much weaker in older soils
(Ultisolls) from Ohio and Maryland
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- Wet combustion
- Soil sample treated with acid dichromate solution
- CO2 generated evaluated with titrimetric or gravimetric
methods
- Recovery is incomplete (avg. 81%)
- Dry combustion
- High temperature (1000 – 1500 C)
- CO2 generated assessed with spectrophotometric, volumetric,
titrimetric, gravimetric, or conductimetric techniques
- Very accurate, minimal variability, low operational errors
- Corrections needed when samples contain carbonates
- National and international efforts needed to cross-calibrate methods
against standard (soil) samples
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- Laser Induced Breakdown Spectroscopy (LIBS)
- Developed at Los Alamos National Laboratory
- Based on atomic emission spectroscopy
- Plasma emits light characteristic of elemental composition
- Minimal sampling volume
- Analysis time < 1 min
- Daily throughput > 200 samples
- Measurements more variable in soil low in organic matter (interference
with iron)
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- Mid Infrared / Near Infrared Spectroscopy (MIR / NIR)
- Non-destructive method measurement of C in soils based on the
reflectance spectra of illuminated soil
- Spectral regions
- NIR: 400–2500 nm
- MIR: 2500–25000 nm
- Excellent potential for assessment of spatial distribution of
belowground C
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- Inelastic Neutron Scattering (INS)
- Developed at Brookhaven National Laboratory (Wielopolski et al. 2002)
- Based on neutron emission and gamma ray detection
- C concentration proportional to C peak in gamma spectrum
- Calibration curve required
- Detection: 100 mg C m-2 with 5% precision
- Non destructive but large volume required
- How to compare against other methods?
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- Traditional sources of land cover data:
- Increased resolution being obtained with MODIS
- Good temporal resolution
- Excellent spatial detail provided by
- IKONOS and Quickbird offer excellent spatial and temporal resolution
- Two airborne sensors
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- Large scale adoption of no till practices
- Impact on soil C sequestration?
- Methods for measuring and monitoring soil C changes
- Based on best available science
- Use systems perspective
- Be verifiable and comparable
- Report uncertainty
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