Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 1996
Publication Date: N/A
Technical Abstract: Concerns exist over the long-term availability of trace metals following land-application of biosolids. The objective of this study was to quantify the long-term bioavailability of heavy metals 16 years after three annual biosolids applications. During the years 1977-79, three rates of biosolids were applied to a silt loam soil. For this study, corn (Zea mays L.) was produced on these plots and analyzed for heavy metal contents in the stove and grain. The corn variety used was the same as in earlier uptake studies at this site. Soils were sampled at 15 cm increments to a depth of 90 cm and analyzed for DTPA and HNO3 extractable heavy metals. Cadmium and Zn concentrations in corn stover and grain increased linearly with biosolids application rate. Tissue concentrations of other heavy metals (Cr, Cu, Ni, and Pb) were variable and showed no consistent trend with biosolids applications. Cadmium and Zn concentrations in stover and grain were within the ranges observed 3 to 6 years after biosolids applications indicating little or no decrease in bioavailability with time. Cadmium and Zn concentrations extracted from the plow layer (0-15 cm) with DTPA and 1 M HNO3 were only slightly lower than the amounts extracted during the initial 6 years after biosolids applications suggesting little change in the extractable forms of these metals. There was no evidence of heavy metal movement to soil depths greater than 50 cm.