Agriculture, Carbon & the climate CO 2 & climate change Moberg et al Source of C emissions Change in temperature & rainfall Extreme weather: drought, flood, storms Food & resource insecurity March 20, 20131

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

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

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

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

SOC trends at WICST March 20, 20136

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

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

Group Systemdescription Estimated Annual C Input c Above GroundBelow GroundRoot / Shoot (kg ha -1 ) Grain CS1continuous corn CS2corn-soybean CS3organic grain Forage CS4conventional forage CS5organic forage CS6pasture Soil C inputs on WICST March 20, 20139

,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

WICST SOC trends Δ g kg -1 Sign. NT vs. Tilled2.8† Forage vs. Grain3.2* Estimated C inputs TillageManureAbovegroundBelowground r *0.13** ** 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,

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,

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

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,

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 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 Notill

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,

Embedded components at ARL (kg CO2 eq/ha/yr), March 20,

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

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,