Spatiotemporal distribution of soil nutrients within an abandoned cattle feedlot

Abstract

Purpose Nutrients from cropland and feedlot operations can move through preferential pathways into wetlands, groundwater, and surface water, which can cause adverse health and ecological problems. It is hypothesized that nitrogen (N) can cause a short-term contamination of soils and groundwater beneath feedlots, but phosphorus (P) can cause both short-and long-term contamination in well-drained soils. This paper examines the spatial and temporal distribution of nutrients within an abandoned feedlot and adjacent wetlands. Materials and methods Fifteen O-horizon, sixty-three composite O-and A-horizon, and sixty-one B-horizon composite grab samples from five different soils within a northwest Minnesota (USA) feedlot and adjacent wetlands were collected and analyzed for P, nitrate (NO 3 − ), and ammonium (NH 4 + ). Groundwater data from a deep-monitoring well were used to examine the change in nutrient concentration through time. Results and discussion Spatiotemporal distribution of nutrients indicated alignment of high concentration of P within the well-drained soil at the former feedlot pens and low concentration within the wetlands. By contrast, NO 3 − showed high concentrations in the wetland compared with the pens. The well-drained soils indicated leaching of NO 3 − in most of the area and sequestration of P. Groundwater data indicated a decline in NO 3 − concentration through time. Conclusions Results of this study suggest that NO 3 − poses short-term contamination of soil and groundwater in feedlots, but P poses both short-and long-term problems due to sequestration and immobilization, which may not impact soilquality downgradient from the feedlot unless intense erosion and runoff occur.