The unique capacity of fungi to efficiently sequester carbon in aerobic conditions, presents a way to maximize OC gain in agricultural systems. Oat ( Avena sativa) was planted in the temperate climate of southern Ontario, Canada to study factors affecting soil organic carbon (OC). The plots varied with initial OC from 25 to 68 g kg -1 or with ground cover of differing decomposability (alfalfa ( Medicago sativa) growing from seed, dried oat straw, dried hay and compost) on high OC soil (60-70 g kg -1). The soil was analysed for correlation of changes in soil aggregation, moisture, OC, fungal hyphal number and length and distribution of organic matter by mass and OC in density fractions within the growing season. At harvest, soil OC and moisture were increased only in plots with ground cover. Total hyphal length was not significantly different with ground cover treatment at harvest, and did not correlate with soil aggregation and soil OC. However, the number of hyphae with >5 m diameter (primarily mycorrhizal fungi) correlated with % OC in ground cover plots while the number of hyphae
