Influence of long-term feedlot manure and inorganic fertilizer application on selected metal and trace elements in a clay loam soil

Long-term application of feedlot manure and inorganic fertilizer to cropland may increase metals and trace elements in soils, and negatively impact agricultural land use. We sampled a surface clay loam soil at Lethbridge in southern Alberta after 16 annual applications (2014) of feedlot manure or inorganic fertilizer, as well as an unamended control. The manure treatments were stockpiled (SM) or composted (CM) feedlot manure with barley straw (ST) or wood-chips (WD), and were applied at 13, 39, and 77 Mg ha(-1) (dry weight). The soil was analyzed for strong-acid extractable concentrations of selected metals (Al, Fe) and trace elements (As, Ba, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, Sr, Ti, V, and Zn). Manure type (SM versus CM) had little or no significant (P > 0.05) effect on the elements. Significantly greater As, Co, Cu, Fe, Li, and V were found for ST than WD at all or higher rates, and the reverse trend occurred for Cd at the highest rate. Cadmium (ST only), Cu, Sr, and Zn were increased by greater application rates, whereas most of the other elements were decreased. Concentrations were significantly increased by manure (Cu, Sr, and Zn) and inorganic fertilizer (Cd) compared with the unamended soil. Copper, Sr, and Zn were greater for manured than inorganic fertilizer treatments, and the reverse trend occurred for Al, As, Co, Cr, Fe, Li, Ni, and V. Although manure and fertilizer may increase certain elements in the soil, no concentrations exceeded the federal soil guidelines for agricultural land use.