Carbon Sequestration in Agro-Ecosystems

Transcription

1 Carbon Sequestration in Agro-Ecosystems Charles W. Rice Soil Microbiologist Department of Agronomy K-State Research and Extension

2 Atmospheric Concentrations of CO 2, Methane (CH 4 ), and Nitrous Oxide (N 2 O) from 1000 A.D. From IPCC (2001)

3 Global economic mitigation potential for different sectors at different carbon prices 7 GtCO 2 -eq <20 <50 <100 Energy supply <20 <50 <100 Transport Buildings Industry Agriculture Forestry Waste Non-OECD/EI T EIT OECD World total US$/tCO 2-eq IPCC, 2007

4 Carbon Emissions Reductions: WRE 550 with Soil Carbon Sequestration Credits Carbon Emissions (Pg C per y) Soil C Sequestration Energy Intensity Fuel Mix WRE550 BAU From: Rosenberg, N.J., R.C. Izaurralde, and E.L. Malone (eds.) Carbon Sequestration in Soils: Science, Monitoring and Beyond. Battelle Press, Columbus, OH. 201 pp.

5 Agriculture A large proportion of the mitigation potential of agriculture (excluding bioenergy) arises from soil C sequestration, which has strong synergies with sustainable agriculture and generally reduces vulnerability to climate change. Agricultural practices collectively can make a significant contribution at low cost By increasing soil carbon sinks, By reducing GHG emissions, By contributing biomass feedstocks for energy use There is no universally applicable list of mitigation practices; practices need to be evaluated for individual agricultural systems and settings IPCC Fourth Assessment Report, Working Group III

6 Agricultural management plays a major role in greenhouse gas emissions and offers many opportunities for mitigation Cropland Reduced tillage Rotations Cover crops Fertility management Erosion control Irrigation management Grasslands Grazing management Fire management Fertilization No-till seeding in USA

7 10/6/ [ERS 2004]

8 Climate Soils Management Sunlight CO 2 Harvestable Yield Soil Organic Matter (Humus) Microbial Activity

9 Soil C Sequestration with conversion to No-tillage Site Crop MT C ha -1 y -1 (Mt CO 2 /a/y) CO & KS Wheat Kansas Sorghum KS, MI, OH Maize Kansas Soybean < Brazil Global Kansas CRP

10 Carbon sequestration rate over 29y (Fabrizzi and Rice 2008) Treatment C sequestration Rate (Mg C/ha/y) No-till Reduced-till Tilled Soybean Sorghum Wheat 0.487

11 Conservation of Soil Carbon Plant characteristics H 2 O Temperature Substrate quality Clay Biological factors O 2 Disturbance Organics Mineralogy Clay Microbial composition and activity Physical Protection Chemical Organic C CO 2 Hierarchy of importance

12 Microbial community - Phospholipid fatty acid levels (0-5 cm depth) 14 Mole % Prairie Grass No-Till Sorghum Tillage Sorghum :2w6,9c 18:1w7c i15:0 i16:0 10Me17:0 16:1w7c cy19:0 i17:0 10Me18:0 Fungi Gm- Bacteria Gm+ Bacteria Actinomycetes Bars of the same color for a given PLFA biomarker are not different (p<0.10). Lines are ± 1 standard error.

13 Fungal Role (18:2w6 biomarker) Significant tillage X residue interaction (p<0.05) 0.08 a Mole Fraction c* b c 0 CT + No R CT + Residue NT + No R NT + Residue Frey et al. (1999) found greater fungal networks optically in NT as compared to CT for the same soil. White and Rice, 2007

14 From: Juca Sá 5 cm

15 Conservation of Soil Carbon Plant characteristics H 2 O Temperature Substrate quality Clay Biological factors O 2 Disturbance Organics Mineralogy Clay Microbial composition and activity Physical Protection Chemical Organic C CO 2 Hierarchy of importance

16 g aggregate 100 g -1 soil b a b a b Soil Aggregation a a a * b b Restored prairie No-tillage Sorghum Tillage Sorghum 0 < >2000 Microaggregates Macroaggregates Aggregate Size Class More macroaggregates were present in RP after 3 y, as compared to the agroecosystems. *Bars with the same letter within size class are not different (p<0.05). Lines are + 1 std error. White and Rice, 2007

17 Organic carbon 25 Organic C sand-free aggregates) hyphae root (g kg r = P< Extraradical hyphae (m g -1 ) Increases in fungal hyphae increases the amount of carbon sequestered in the soil. Formation of soil aggregates physically protects soil carbon from decomposition. Data from Wilson and Rice; Photo from Mike Miller and Julie Jastrow

18 80 Amount of macroaggregates (g 100g -1 soil) Y Vertisol = 1.56 SOC R 2 = Y Mollisol = 1.48 SOC R 2 = Y Oxisol = 0.58 SOC R 2 = SOC (g C kg -1 ) Fabrizzi, 2006

19 Tillage = Higher disturbance No-Till = Lower disturbance CO 2 Plant C CO2 Fungi Fungi SOM Microaggregates SOM Soil Macroaggregate Soil Macroaggregate White and Rice, 2007

20 Belowground interactions NO 3, N 2 O-N 2 CO 2 Bacteria N CO 2 CO 2 SAP Fungi C N C N N C N P AM Fungi C N C N C N Grazers C N C N Macroaggregates & Slowly Available C & N

21 Carbon Stocks and Depth

22 Soil C stocks after 18 years * NT CT * * 22

23 O Change in management Years of cultivation A E SOC levels (Mg C -1 ) ha

24 Soil C sequestration rates for 15 years Depth cm Fertilizer N Tilled (Mg C/ha/y) Fertilizer N No-till Manure N Tilled Manure N No-till NT > Tilled What is baseline?

25 -1 SOC levels (Mg C ha ) O Change in management E D C A Years of cultivation

26 Depth cm Net effect of NT for 15 years NT (0-15y) Till (0-15y) No N 0.5 Fertilizer N Fertilizer N Mg/ha/y 0.5 Manure N Manure N

27 Relative Yield, Economic, and Sequestration Characteristics for adopting NT continuous Corn, NE Kansas NT Mean Yield (bu/a) 86 CT 87.7 Net Return ($/a) Soil Carbon (tons/a/y) Total C Emissions (tons/a/y) Net Carbon (tons/a/y) Soil C Value ($/a/y) $4.00 value $ % additional income 27

28 Illustrative Ranking of Carbon as a Crop in U.S. Per Proposed GHG Limits in Senate Bill 280 (Lieberman-McCain) 1/12/07 Production Value ($B) dates nectarines cukes oats beans almonds lettuce Carbon at $10/MT CO 2 e, fresh tomato [Crop Source: USDA - National Agricultural Statistics Service US Crop Rankings Production Year Ranking Based on Value of Production] rice 10/6/ oranges potatoes grapes cotton wheat CARBON hay soybeans grain corn

29 Globally So What is the Potential? It is estimated that soil has the potential to offset 30% of the annual CO 2 emissions United States It is estimated that soil has the potential to offset 15% of the annual CO 2 emissions Additional options for N 2 O and CH 4 The economic potential is ~30-50% of that value

30 Measurement, Monitoring and Verification Detecting soil C changes Difficult on short time scales Amount changing small compared to total C Methods for detecting and projecting soil C changes (Post et al. 2001) Direct methods Field measurements Indirect methods Accounting Respired C Stratified accounting Remote sensingc Models Heavy fraction Soil organic C Light fraction C Litter C Root C Captured C Woodlot C Eroded C SOC t = SOC 0 + C c + C b - C h - C r - C e Harvested C Cropland C Respired C Buried C Databases / GIS Soil profile Remote sensor Simulation models Sample probe Eddy flux Post et al. (2001) Wetland C Soil inorganic C

31 Soil C sequestration Summary Available technology at low cost Significant impact on emissions: Bridge to the Future Need advancement in MMV to account for variability Agricultural soil C sequestration Keeps land in production thus providing food security and rural economic development (no leakage) Improves soil quality In many cases increases profitability for the farmer Provides other environmental benefits to society Water quality (less runoff, less erosion) Flood control Wildlife habitat May help adapt to climate change as well as mitigate Therefore a Win-Win Situation

32 Chuck Rice Phone: Cell: Websites K-State Research and Extension