Increased concern about global warming has created interest in sequestering carbon in the soil as a possible mechanism of mitigating increases in atmospheric greenhouse gases. Work at The Rodale Institute's Farming Systems Trial®, 2003 whitepaper, indicates significant potential for carbon sequestration in organically farmed soils. Sampling at this site in the 1990's showed significantly higher populations of arbuscular mycorrhizal [AM] fungi in organic vs. conventionally farmed soil. Given that AM fungi produce glomalin; a glycoprotein that i) plays a role in stabilizing soil aggregates, ii) is resistant to degradation, and iii) can be a significant proportion of soil organic matter; we hypothesize that AM fungi play a significant role in carbon sequestration in organically and conventionally farmed soils. A two year study was initiated in 2006. Soil samples were collected on Nov. 29 following corn (Zea mays) harvest to a depth of 80 cm from three farming systems: conventional, organic with animal manure addition, and organic with legume cover crops. Samples were segmented by soil profile depth and analyzed for AM fungi, glomalin, soil C and organic matter, and water stable soil aggregates. Though AM fungus spore populations did not follow the patterns reported earlier for farming systems comparisons, the organic rotations had more propagules of AM fungi in the top 20 cm of soil than the conventional rotation. Propagules were nearly absent at the 60-80 cm depth in all systems. Soil carbon in the top 20 cm was significantly greater in the manure (2.59%) and legume (2.41%) based organic systems than in the conventional system (1.79%), but was similar in all systems below that depth. Small aggregates in the 0.25 to 1 mm class were 55 to 91% water stable aggregate compared to 10 to 38% for 1 to 2 mm aggregates class. Water stable aggregation for the 1 to 2 mm aggregate size class was significantly greater in the both organic treatments over the conventional treatment. In all systems mean values of aggregates declined with deeper depths similar to overall declines in organic matter. There were no significant differences in treatment or in depth in the 0.25 to 1 mm aggregates.  The high moisture content of sampled soils during the growing season, collection, and prior to processing might account for some of the results we found.  We are proceeding with determination of glomalin content. From past experience, we expect glomalin data will follow the trends of the aggregate stability and soil organic matter, but greater differences are expected with treatment and depth in the 0.25 to 1 mm aggregate size class.