Relationships between soil pH, clay, organic matter and CEC and heavy metal concentrations in soils and tobacco
Adamu, CA; Mulchi, CL; Bell, PF
The purpose of this investigation was to provide information on baseline concentrations of heavy metals in Atlantic Coastal Plain soils and to examine possible relationships between certain chemical and physical properties of soils and the metal concentrations in tobacco at flowering. Duplicate Ap soil and composite plant samples were collected in 1983 from 33 farms representing three replicates each of 11 soil series used for tobacco production across Southern Maryland. Soil characteristics examined included pH, organic matter (C), clay, cation exchange capacity (CEC), and total and DTPA (pH 7.3) extractable Zn, Cu, Mn, Fe, Pb, Nl, and Cd concentrations. Linear regression analyses were used to establish the relationships between soil physical and chemical properties and metal concentrations in plant and soil samples. Soil CEC was strongly correlated (r) with clay (0.7**), weakly associated with soil C (0.22), but not influenced by pH (-0.12). Total soil metals were significantly correlated with soil C for: Zn (0.23*), Cu (0.44**), Mn (0.53**) and Pb (0.37**); soil clay for Zn (0.25*), Cu (0.30**), Mn (0.46**), Fe (0.51**), Pb (0.40**) and Ni (0.70**); and with CEC for all metals except Cd. DTPA (pH 7.3) extractable metals were significantly correlated with soil C for Mn (0.50**), Pb (0.42**) and Cd (0.34**); soil clay for Cu (0.32) and Mn (0.31**); and CEC for Cu (0.24*), Mn (0.31**), Fe (0.26*), Ni (0.28*) and Cd (0.30**). Significant negative correlation coefficients were between soil pH and DTPA extractable Zn (-0.28*), Mn (-0.59*), Fe (-0.58**), and Ni (-0.48**); however, the relationship for Cd (0.44**) was positive. Leaf metal concentrations were significantly correlated with total soil metal for Zn (0.34**), Mn (0.5**), and Fe (0.41**) and with DTPA extractable metal for Zn (0.67**), Cu (0.23*), Mn (0.75**) and Ni (0.46**). Leaf metals were negatively correlated with soil pH for Zn (-0.35**), Mn (-0.55**), Fe (-0.34**), Ni (-0.41**) and Cd (-0.39**).