1. Agriculture, Carbon & the climate CO 2 & climate change Moberg et al. 2005 Source of C emissions http://www.prism.gatech.edu/ Change in temperature & rainfall Extreme weather: drought, flood, storms Food & resource insecurity March 20, 20131

2. Agriculture & the global C budget CO 2 mitigation via agriculture Agricultural land as a C sink Reverse historic losses of SOC Immediately implementable Cost-effective Attractive mitigation option Cap & Trade – Chicago Climate Exchange (CCX) Ecosystem service subsidies Policy & rural economy March 20, 20132

3. How is carbon sequestered? Photosynthesis - plants fix carbon from atmosphere (CO2) Carbon that remains as plant tissue can be added to the soil as litter or residue plants die and decompose Stored in the soil is as soil organic matter (SOM) SOM is a complex mixture of carbon compounds, consisting of decomposing plant and animal tissue, microbes (protozoa, nematodes, fungi, and bacteria) Carbon can remain stored in soils for millennia, or be quickly released back into the atmosphere through respiration by soil microbes Climatic conditions, natural vegetation, soil texture, drainage, and human land use all affect the amount and length of time carbon is stored in soil. March 20, 20133

4. complexity Corn Soybean Corn Soy Clover Grain Wheat Corn alfalfa Alfalfa Oats/ alfalfa Corn Rotational Grazing Forage WICST SOC trends Cropping systems March 20, 20134

5. Activity from Reading: From the top bubble on page 1624 – can you predict which of the WICST treatments might be more successful in sequestering carbon? Why? March 20, 20135

6. SOC trends at WICST March 20, 20136

7. WICST SOC trends Bars represent ±1 standard error; Pr>|t|, † p<0.1, * p<0.05, ** p<0.01 ** 0 to 15 cm 15 to 30 cm 30 to 60 cm 60 to 90 cm Δ SOC mass Δ Mg ha -1 Grain systems Forage systems * † † * * * † † 7

8. Soil C inputs on WICST ARL (‘92-’09)LAC (‘92-’02) Systemlbs C/acre -1 Cont. corn53903301 Min-till corn-sb40813324 Org grain (c-sb-w)30382297 Conv. Forage60756353 Organic Forage63777145 Pasture with managed grazing 53805548 8eOrganic Webinar

9. Group Systemdescription Estimated Annual C Input c Above GroundBelow GroundRoot / Shoot ------------ (kg ha -1 ) ------------ Grain CS1continuous corn380022400.58 CS2corn-soybean294016700.56 CS3organic grain224012000.54 Forage CS4conventional forage305038401.25 CS5organic forage322040101.24 CS6pasture159045702.87 Soil C inputs on WICST March 20, 20139

10. 184018401850185018601870188018901900191019201930194019501960197019801990 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 YearSimulatedFieldYearSimulatedField S o i l C, k g C / h a Simulated Simulated controlfertilized manuredmanuredcontrol fertilized FieldField Field manured Fallow year Presented at Soil Carbon Sequestration Workshop, Kearney Foundation Soil Science, September 2003 ©Applied GeoSolutions, LLC Winter wheat field 150-Year Simulation for Soil C Dynamics in A Winter Wheat Field with Different Cropping Practices at Rothamsted Station, UK

11. WICST SOC trends Δ g kg -1 Sign. NT vs. Tilled2.8† Forage vs. Grain3.2* ------ Estimated C inputs------ TillageManureAbovegroundBelowground ------------------------------------ r ------------------------------------ -0.10*0.13**-0.050.11** SOC (g kg -1 ) correlations Pr>|t|, ns=not significant, † p<0.1, * p<0.05, ** p<0.01 General SOC (g kg -1 ) trends March 20, 201311

12. SOC decreases with tillage – NT: 2.8 g kg -1 > SOC than tilled – Negative correlation: tillage & SOC Forage systems > grain systems – Forage: 3.2 g kg -1 > SOC than tilled – Positive correlation: manure & SOC Pasture sequestered the most SOC – Sequestration only in pasture, but limited WICST SOC trends March 20, 201312

13. Presented at Soil Carbon Sequestration Workshop, Kearney Foundation Soil Science, September 2003 ©Applied GeoSolutions, LLC

14. http://ngm.typepad.com/photos/uncategorized/2008/01/02/0103_os.jpg

17. Relationship between N2O and Carbon Six et al. – N2O fluxes under NT higher than CT in drier environments – opposite trends in humid environments Other researchers have found opposite trends – Illustrate situation-specific nature of cropping systems impacts on SOC storage and N2O emissions – Show it is important to closely evaluate conditions under which conclusions are drawn March 20, 201317

18. DNDC-modeled C sequestration, N2O emissions and their global warming potentials (GWP) for a corn-soybean rotation system with different tillage approaches in Adair County, Iowa from 1994-2014 Critical need for models to assess long-term impacts of management decisions! C sequestrationN 2 O fluxSOC-GWPN 2 O-GWPNet GWP kg C/ha/yrkg N/ha/yrkg CO 2 equivalent/ha/yr Intensive tillage 12511.5-45956155156 Notill 46821.1-1716103018585

19. WICST LCA: Embedded Emissions Data from the GaBi databases – Seed – Diesel – Fertilizer – Pesticides – Grain Drying – Supplemental heifer feed while on pasture N2O, CH4, CO2 computed and converted to CO2 eq in kg/ha/yr March 20, 201319

20. Embedded components at ARL (kg CO2 eq/ha/yr), 1993-2008 March 20, 201320

21. RUSLE2 Soil loss estimates † (18-yr avg, ARL) March 20, 201321

22. Conclusions & Implications Agricultural NT, manure, forage crops – beneficial Perennial grasses in crop rotations – Grass ley Perennial functionality – Cover crops, intercropping Organic trends toward greater use of: manure, forage crops, perennial crops, cover cropping, and intercropping Overall reduction of tillage and inputs across systems is beneficial March 20, 201322