Topsoil reapplication on barren fill slopes in northern California significantly improved plant growth by 250% after three years compared to slopes without topsoil. The stockpiled topsoil did not degrade and had similar nutrient content and biological activity as fresh topsoil. Grasses dominated topsoiled plots, while clovers covered fill slopes. A topsoil fraction exceeding 20% of soil volume was needed for significant improvements in plant growth and soil characteristics. Moderate fertilization enhanced plant growth without reducing mycorrhizal root production. Stockpiling topsoil had little to no negative impact on its quality.