Tillage and fertilization may reduce the abundance of indigenous arbuscular mycorrhizal (AM) fungi in agricultural field soils. The dynamics of hyphal abundance in soil were studied over two growing seasons at a site in eastern Canada in a corn crop grown in a sandy loam soil and over one growing season in a corn crop grown in a clay soil. Experimental plots in a long-term tillage experiment, had been managed under no-tillage (NT), reduced tillage (RT) and conventional tillage (CT) for 11 years. Soil receiving each of these tillage treatments also received either inorganic (N and K) or organic (liquid dairy manure) fertilizer. Soil samples were collected from different places within each plot: on the plant row, at 18.75 cm from the row (quarter of the inter-row distance) and in between two rows (mid-row, i.e., 37.5 cm from the adjacent rows). Plant and soil samples were taken at the 12-14 leaf stage of corn (June), at silking stage (August) and at harvest (October), in order to measure the fluctuation in soil hyphal densities and plant nutrients concentrations during the season. Densities of total and viable AM hyphae were greatest in the row and lowest in the mid-row. Hyphal density on the row increased steeply from 12-14 leaf stage to silking stage and decreased thereafter. No significant fluctuation of hyphal abundance was observed in the mid-row, suggesting a prevalence of AM hyphae on the row. Hyphal densities were higher in NT soil than in CT soil, while RT soil contained intermediate hyphal densities. The highest corn P, Zn and Cu concentrations were observed in NT and RT treatments concurrently with the highest hyphal densities. Concentrations of K, Ca and Mg did not change with tillage or fertilization type. Manure application significantly increased the densities of total and viable hyphae in the clay soil.