The issue of reducing greenhouse gas emissions to address global warming is offering an opportunity to Wisconsin farmers. Farmers can now be paid a soil carbon offset (credit) by enrolling acres in a program that pays them to sequester carbon in crop residues by practicing no-tillage or strip-tillage.  Other practices such as grassland conversion, tree planting, and methane capture also offer offset opportunities. Offset payments are offered through the Chicago Climate Exchange that has entered into agreements with large companies, who in addition to agreeing to reduce CO₂ output by 6% by 2010, also provide funds to pay farmers to sequester carbon using conservation practices. 

 

What is carbon sequestration:   As soils developed in their natural state prior to agriculture, carbon accumulated and reached a steady state depending on climate, soil texture, and vegetation type. Once soils were aerated by cultivation soil carbon was lost through increased microbial respiration, eventually stabilizing at a lower soil carbon content. The current effort to sequester carbon sequestration seeks to increase soil carbon through reduced tillage management or other practices. Although research still needs to confirm the extent of carbon sequestration by these practices, most are believed to result in the net accumulation of carbon. Carbon sequestration occurs when the carbon production by plants and organisms exceed the loss as CO₂ microbial respiration of residues and soil organic matter. Specific soils will vary in their ability to sequester carbon depending on location in the U.S., the type of plants grown on the site, and the amount of soil disturbance by tillage. Practices such as no-till will sequester soil carbon by limiting the introduction of O₂ by tillage, thereby reducing microbial respiration. The idealized relationship between management and soil organic matter (soil carbon) is shown in Figure 1.

 

Carbon offset program:   The Wisconsin Farm Bureau is helping with the coordination of the carbon offset program for Wisconsin producers. Eligible fields must be contracted to remain in no-till or strip-tillage systems for five years and will be monitored annually to verify that the conservation tillage practices are maintained. A maximum of one-third of the soil area can be disturbed by tillage and two-thirds of the crop residue must be left on the surface. Currently carbon offsets are paid at a percentage of the market price for the carbon offset, which are traded in one-metric ton of CO₂ per acre per year units. Wisconsin producers in southwestern counties can receive offsets at a value of 0.6 metric ton CO₂ per acre per year or 0.4 metric ton CO₂ per acre per year for the remainder of the state. Currently CO₂ offsets are trading at a full value $4.50 per acre per year. Therefore, the actual payment to the farmer for conservation tillage will range between $1.80 and $2.70 per acre per year. Acreage that met no-till or strip-till requirements for 2007 can be included in the program. The enrolled acres will be brokered by an Iowa company – AgraGate, which pools credits from individual farmers and offers them for sale on the Chicago Climate Exchange. 

Summary: The potential benefits of contracting for carbon offsets goes beyond the financial payment for reduced tillage or other practices. No-till and strip-till are systems that are well known for reducing erosion and labor, machinery, and fuel costs. Farmers who have not practiced no-till may find a continuous no-till system challenging, especially on heavier soils. Strip-tillage is a practice that blends the benefits of full-width tillage with those of no-till. The potential for yield reduction is lower in strip-tillage and it can offer time and fuel savings. There are many more details that should be understood before enrolling acreage in the offset program. Contact the Wisconsin Farm Bureau at 800-261-3276 or wiccinfo@wfbf.com. The websites of the Chicago Climate Exchange (www.CCX.com) and AgraGate (www.agragate.com) both contain useful information that producers should review.