Long-term effects of topsoil removal on soil productivity factors, wheat yield and protein content

Quantifying long-term effects of soil erosion on plant production and soil quality can aid in restoring degraded soils. The objectives of this study were to determine the long-term effects of topsoil removal on spring wheat (Triticum aestivum L.) yield and soil productivity factors. In 1982, the surface 0, 6, 12, and 18 cm of topsoil was mechanically removed from a Williams loam (fine-loamy, mixed, superactive, frigid Typic Argiustoll) and subsequently cropped. Soil samples were collected in 1998. There was no difference in soil organic matter (SOM), particulate organic matter (POM), mineralizable N, or water stable soil aggregates (WSA) in the surface 15 cm. Though not significant, there was an average increase of 1.2 g SOM kg-1 soil from the surface 15 cm since 1982, but fungal and bacterial biomass was reduced. The SOM and POM increased in the surface 15 cm of soil where grass was planted in strips between plots. Topsoil removal did not affect soil water at planting nor wheat yields from 1998-2001. The use of commercial fertilizer maintained crop yields, but SOM remained unchanged indicating that, restoring erosion damage is unlikely with a conventionally tilled wheat-fallow rotation in semi-arid regions.