Assessment of land-use effect on trace elements concentrations in soil solution from Ultisols in North Florida

Pasture-applied manure, including excreta from grazing animals, contain considerable amount of trace elements such as Zn and Cu that could potentially pollute groundwater. The objective of this study was to assess the potential for leaching of trace elements by monitoring soil solution at different depths below the root zone of cattle- and goat-grazed bahiagrass pastures in comparison with arable/fallow land. On an Ultisol at Quincy, Florida, 27 suction cup lysimeters were randomly installed in bahiagrass pasture (Paspalum notatum Flugge) and arable/fallow plots at the depths of 61, 122, and 183 cm. Soil solution samples were collected monthly from November 2002 through August 2003 and analyzed for pH, electrical conductivity (EC), Al, Cd, Cu, Fe, Mn, Ni, Pb, and Zn. To evaluate trace elements in atmospheric deposition, surface, and ground waters, samples from rain, nearby stream and three wells on the farm were collected and analyzed over the testing period. Overall, soil solutions were low in salts (below 1 g L−1) and had near neutral pH. Zinc concentrations in soil solution were low, ranging from 0.048 to 0.222 mg L−1. The Zn concentration increased significantly (P < 0.05) in pasture plots with the highest value being recorded beneath continuously stocked cattle pasture. A significant decrease in Zn with depth was observed; the mean concentration at 183 cm was about 3 times lower than at 61 cm. Concentrations of Zn in soil solutions tended to be higher than those in rain, surface and ground waters. Concentrations of Al, Cu, Mn, and Zn in soil solutions were below the US drinking water quality standards, although Pb concentration from continuously stocked cattle pasture were higher than from rotationally grazed goat pasture and arable land. No Cd, Fe, or Ni was detected in any of the analyzed water samples.