Effects of Topsoil Thickness and Nitrogen Fertilizer on the Revegetation of Coal Mine Spoils

Abstract

AbstractA field study was established at a coal mine site in northwest Colorado to measure the effects of 0‐, 10‐, 20‐, 30‐, and 46‐cm depths of topsoil (a fine, montmorillonitic Typic Argiboroll) on establishment, percent stand, and species composition of a seeded stand. Percentage stand increased linearly from 16.4% on the 0‐cm topsoil treatment to 49.1% on the 46‐cm treatment by the second growing season. A greenhouse study using topsoil and spoil from the same area evaluated the same topsoil depths with respect to their effects on herbage and root production of intermediate wheatgrass (Agropyron intermedium) and wheat (Triticum aestivum). Herbage and root production of both species increased linearly with increasing topsoil thickness. Herbage production of wheat was, on the average, 32% greater than that of intermediate wheatgrass; however, root production of intermediate wheatgrass was 78% greater than wheat when grown in topsoil and 145% greater when grown without topsoil in spoil alone. A 112 kg N/ha fertilizer treatment increased biomass (herbage and roots) of intermediate wheatgrass by 74% over similar unfertilized treatments. When 15 cm of topsoil was mixed with 15 cm of spoil (total thickness of the topsoil mixture was 30 cm) in the greenhouse, herbage and root production of intermediate wheatgrass were the same as when grown in 15 cm of topsoil alone.