Prediction of Available Zinc in Sewage Sludge‐amended Soils

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Abstract
A routine soil test would be helpful for management of agricultural soils amended with sewage sludge high in Zn. Fourteen field sites were selected in the Coastal Plain, Piedmont, and Ridge and Valley regions of Virginia to evaluate the suitability of the dilute HCl‐H2SO4 and DTPA soil extractants for prediction of Zn uptake by corn (Zea mays L.). Soil and corn tissue samples were collected from these sites where sewage sludge had been applied previously. Multiple regression analysis was used to assess the forms of soil Zn extracted by dilute HCl‐H2SO4 and DTPA. The exchangeable and specifically sorbed, organically bound and noncrystalline hydroxide and oxide bound Zn fractions were tested to develop equations. Dilute HCl‐H2SO4 extracts were related to the three Zn fractions (R2 = 0.98**), whereas organically bound Zn was the only Zn fraction related to DTPA‐extractable Zn (r = 0.96**). Earleaf Zn concentration correlated more closely with DTPA‐extractable Zn (r = 0.64*) than with dilute HCl‐H2SO4‐extractable Zn (r = 0.35). The earleaf Zn concentration was studied as a function of either DTPA‐ or dilute HCl‐H2SO4‐extractable Zn, exchangeable and specifically sorbed Zn, organically bound Zn, and noncrystalline hydroxide and oxide bound Zn. Inclusion of the above fractions in a multiple regression analysis did not improve the relationship between earleaf Zn concentration and dilute HCl‐H2SO4‐extractable Zn. A coefficient of multiple determination (R2 = 0.77**) was obtained between earleaf Zn concentration and a two variable regression equation comprised of DTPA‐extractable Zn and organically bound Zn. The negative regression coefficient for organically bound Zn indicated that a portion of this fraction, which was extracted by the DTPA, did not supply Zn to corn plants.
Funding Information
  • Virginia Water Resources Research Center