Metal concentrations in three Montana soils following 20 years of fertilization and cropping

Abstract

The presence of metals in some agricultural fertilizers has raised the concern that fertilized soils may be accumulating potentially toxic metals. A number of studies have been undertaken to determine the extent and significance of this potential problem, yet results have been mixed and the studies were not conducted in the Northern Great Plains. Therefore, a study was undertaken to determine if fertilization has increased metal concentrations in selected Northern Great Plain soils. Two irrigated sites and one non-irrigated site were selected; each had at least 20 years of fertilization and cropping history. Paired (fertilized and non-fertilized) soils from three depths (0–15 cm, 15–30 cm, and 30–45 cm) were sampled in replicate (n=10) and analyzed for a range of plant available and total metals, pH, organic matter, and phosphorus. In general, fertilized soils were found to have significantly lower levels of available and total metals than those of non-fertilized soils, indicating that long-term fertilization has not increased metal concentrations in the soils studied.