Trace element concentrations in soils under different land uses in Mpumalanga Province, South Africa

Abstract

Trace element deficiencies and toxicities have become important aspects of land quality and are affected by the increased pressure on land from industrialisation and agricultural practices. The objective of the study was to determine if differences occur in trace element concentrations in soils under different land uses in the Mpumalanga province of South Africa. Land uses were divided into four groups, namely rangeland, irrigation, dryland, and resource-poor. Two extraction methods were used, i.e. ammonium-EDTA and EPA 3050 acid digestion. The extracted solutions were analysed using an Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) or Atomic Adsorption Spectrophotometry (AAS). The trace element concentrations followed the trend: irrigated > > dryland > rangeland resource-poor for B, As, Co, Cr, Cu, I, Mn, Ni and Zn, with few exceptions. There appeared to be additions of trace elements to irrigated land and dryland areas, and depletion from resource-poor farm lands. Trace elements that were exceeded suggested threshold concentrations and/or were raised in irrigated lands are B, As, Co, Cu, Hg, Mn, Ni, Se, V and Zn. Trace elements that were lower than suggested deficiency threshold, especially for the resource-poor farm lands, are B, Co, Cr, Cu, Fe, I, Mn, Mo, Se and Zn.