Micronutrient Availability As Affected by Long-Term Biosolids Amendments.

Micronutrient availability is important to crop production and may be affected by long-term application of biosolids and other amendments. This study was conducted to assess the effects of long-term application of anaerobic digested biosolids on soil   B, Cu, Fe, Mn, Mo and Zn availability, and the relationship between diethylenetriaminepentaacetic acid- sorbitol (DTPA-sorbitol) extractable micronutrients and concentrations of those micronutrients in winter wheat tissue and grain. The concentrations of soil B, Cu, Mn, Mo and Zn in DTPA-sorbitol extract were determined from a site received 12 annual applications of biosolids. Plant tissue and wheat grain samples were also collected and digested with nitric acid and analyzed for micronutrient contents by an ICP-AES.  Long-term application of biosolids significantly increased DTPA-extractable B, Cu, Fe, Mo, and Zn as compared to the control plot that did not receive biosolids. Biosolids application significantly increased (p < 0.001) Zn concentrations in wheat grain compared with grain from unamended plot, but had no significant effect on grain B and Mn. Biosolids application significantly decreased (p < 0.001) wheat grain Cu. Biosolids increased (p < 0.001) Zn and Mo concentrations in wheat tissue compared with unamended, but had no significant effect on wheat tissue Cu, B and Fe concentration. The concentrations of Zn, and Mo in wheat tissue and grain samples were significantly correlated with soil extractable Zn, and Mo, respectively. Long-term application of biosolids increased the soil concentration of B, Fe and Cu micronutrients while their bioavailability remained low, since there was no significant effect on the concentrations of these elements in winter wheat tissue.