Effects on plant growth of inoculation of stored stripmining topsoil in North Dakota with mycorrhizal fungi contained in native soils

Stored topsoil from stripmining operations in western North Dakota was inoculated with mycorrhizal fungi contained in native prairie soil. The effects on plant mycorrhizal infection percentage, growth as shoot dry weight, and phosphorus uptake were determined. The studied topsoil piles were found to contain little or no vesicular arbuscular mycorrhizal (VAM) fungal inoculum at a depth of 120 cm. The inoculum soil was mixed into the stored soil at rates of 10% and 1%, or surface-applied at 1%. In control pots, sterilized inoculum soil was used. Corn plant (Zea mays) bioassays were used. After 30 days growth the percent VAM fungal infection of the test plants increased with both the 10% and 1% soil inocula. Phosphorus concentrations were generally increased by inoculation with 10% soil mixtures but not 1%. Shoot dry weights of the plants were not measurably different between 10% and 1% inoculation. However, when the plant growth period was increased to 60 days, all three parameters were increased over the check plants. When the inoculum was not mixed into the soil, but layered on the surface, there were no differences in any of the parameters.