Kearney Foundation of Soil Science

Soil Carbon and California

Terrestrial EcosystemsDirector: Kate Scow

UC Davis

Martin Theodore Kearney’s endowment

•Kearney Foundation of SoilScience established 1951.

•5-year missions address public concerns in CA and support research in soils, plant nutrition and water science

SOIL CARBON CYCLE

2001-2006: Soil Carbon and California Terrestrial Ecosystems

•Understand mechanisms and processes governing storage and flow of carbon in soils of CA's diverse ecosystems;

•Quantify impacts of inputs of water, nutrients, and pollutants, as well as physical disturbance, on storage, transformations and transport of carbon in soils;

•Assess roles of soils in emissions and consumption of greenhouse gases,

•Identify and analyze strategies and policy options for soil carbon management

Projects Funded:• 25 “traditional” research projects across UC campuses

•3 projects funded in special call for research on soil carbon in joint California Dept of Food & Agriculture Specialty Crops/Kearney Foundation

•9 graduate fellowships in soil carbon

Kearney Sponsored Workshop on Soil Carbon Sequestration: Interface Between Science and

Policy (Sept 22, 23, 2003)

1. What are on-going efforts in the science and policy of C sequestration in Europe, Canada and US?How does soil science, resource economics and policy analysis interact in developing policy on C sequestration?2. What are on-going efforts in climate change assessment and mitigation in the State of California? Estimation of C sequestration potential in CA soils and other reservoirs. 3. Presentation of Kearney-funded research on soil carbon in California terrestrial ecosystems.

Soil Carbon Sequestration; history and projections

REDUCE C LOSSBY REDUCED TILLAGE

GROW CROPS THAT SEQUESTER MORE C, GROW COVER CROPS, LEAVE MORE STUBBLE

INCREASE CROP INPUTS OF C BY HIGHER YIELDS OR LESS FALLOW PERIODS

INCREASE PRODUCTIVITY OF MARGINAL LANDS

PROMOTE MICROBIAL COMMUNITIES WITH HIGHER C CONTENT

MECHANISMS FOR ENHANCING SOIL CARBON SEQUESTRATION

Estimated rates of C sequestration in soil within US:

75-200 Tg C in croplands (Lal et al. 1998)

30-90 Tg C in grazing lands (Follett et al. 2001)•Assumes widespread adoption of improved management practices. •Does not account for changes in other biogenic greenhouse gases (nitrous oxide and methane) that may be by-products of management changes.  

THUS C sequestration in terrestrial ecosystems can account for about 6.4% of emissions (based on 5000 Tg C per yr in 1990). Management-induced C sequestration in soil is only a temporary and partial solution to the greenhouse gas problem.  

Other benefits of increased soil carbon

Projects on soil carbon sequestration

•Scoping study in joint CEC/Kearney/ CDFA project.

•Upcoming call for proposals from joint CEC/Kearney/CDFA to conduct pilot study to estimate carbon sequestration potential study in CA agricultural county.

SCOPING STUDY: County scale assessment of carbon

sequestration and trace gas emission from California

croplandsWilliam Salas1, Marc Los Huertos2 and

Changsheng Li3

1Applied GeoSolutions, LLC, 10 Newmarket Road, Durham, NH, 038242Center for Agroecology and Sustainable Food Systems, University of California Santa Cruz3 Complex Systems Research Center, University of New Hampshire, Durham, NH 03824

Labile humads

NH4

NO3-

CO2

NO2 -

N2O

N2

Water uptakeby roots

Daily water demand

Daily N uptake by roots

Daily biomassaccumulation ( LAI )

N demand Grain

Stalks

Roots

Very labilelitter

Labilelitter

Resistantlitter

Labile microbes Resistant microbes

DOC

DOC

Nitratedenitrifier

Nitritedenitrifier

N2Odenitrifier

NO

Water stress

The DNDC Model

Passive humus

Resistent humads

Annual averagetemperature

Daily potentialET

EvaporationWater flowbetween layers

LAI-regulated albedo

Soil temperatureprofile

Soil moistureprofile

Transpiration

Soil Eh profile

Oxygendiffusion

Oxygenconsumption

NH4+DOC Nitrifiers

Clay-NH4+NH3NO3-

NH3NON2O

Root respiration

Soilenvironmental variables

Ecological drivers

Substrates (NH4+, NO3- and DOC)

Effect of temperature and moisture on decomposition

pHMoistureTemperature

Climate Soil Vegetation Anthropogenic activity

Soil climate

Plant growth

Decomposition

NitrificationDenitrification

Eh

CH4NH4+ Soil Eh

Aerenchyma

DOC

CH4 production

CH4 oxidation

CH4 transport

Fermentation

Figure 2

Soil carbon content

Scaling Up from Site to RegionsApproaches

Modeling with DNDC

Model development: predictingbiochemical &geochemical processes at sitescale

GIS databaseconstruction:providing climate, soil, vegetation, and managementdata at regional scale

Field & labexperiments

Statistical datacollection

Remote sensinganalysis:improving crop acreage data & providing phenology data

Soil fertility determined by soil organic matter storage

Crop yield

Emissions of CO2, CH4,N2O, NO, N2, and NH3

Leaching of nitrateRemote sensingdata acquisition

Soil carbon content

Soils• NRCS STATSGO Soils data

DWR crop area mask Derived area weighted statistics of range (min,

max) in SOC, pH,

texture (%clay),

and bulk density

by county

County Agricultural Data• Various Sources of

California data: County Commissioners Reports, FRAP (Fire Resource & Assessment Program, CDF), NASS, DWR

• Used DWR mid-1990s data: – Sub-county spatial resolution– Based on Aerial Photos

coupled with field surveys– Total crop area: 38,344km2

GIS Database

Next Steps• Fertilizer: use different application rates across

regions• Soils: Use crop class specific soils data at the county

scale. Merge DWR and STATSGO• Validation analyses for California. Need to collect existing

data. – Long-term SOC changes. – N2O data– CH4 from rice

• Evaluate scenarios for C sequestration: cover crops, conservation tillage, no till, climate change, …

• Run 20 and 40 year scenarios to examine C sequestration capacity and net GWP (N2O offsets)

EXAMPLE OF OTHER KEARNEY FUNDED RESEARCH

1. Stabilization of organic matter in soils*Litter quality (e.g., C/N, tannins, lignin, etc.) in regulating organic matter turnover*Litter diversity in affecting microbial function and soil C dynamic*Pedogenic factors in regulating soil carbon storage*Carbonate chemistry as a source/sink of carbon in soils

2. Transformation of trace gas in soils*Microbial processes on the dynamics of trace gas formation*Factors affecting trace gas fluxes between the atmosphere and soil

3. Impacts of management*Effect of management practices (N fertilization, irrigation, minimum tillage, wetland drainage) on carbon storage and trace gas dynamics*Soil carbon sequestration effects on fertilizer use efficiency*Role of soil carbon in maintaining surface and subsurface water quality*Development of water storage strategies through enhanced soil structure and water penetration

4. Scaling of research results to regional and global scales

*Soil carbon and trace gas dynamics on the small watershed scale (5 - 100 hectares)*Hydrologic conditions on soil carbon and trace gas dynamics*Landscape scale evaluation of global climate change and it relationship to soil organic matter storage and trace gases dynamics

5. Policy and Economics

*Regional and global policy considerations to maintain environmental quality*Economic and policy analysis of agricultural productivity and sustainability