Nitrogen Transformation and Enzymes Activity As Affected by Broiler Litter Enriched with Trace Elements.

In Southeastern United States, broiler litter (BL) is produced in large amounts and added to soils. The BL, however, contains enzymes inhibitors—trace elements (TEs) that may accumulate over time with negative impacts on soil biochemical processes. A BL sample was enriched with reagent grade TEs  (As, Cr, Cu, Mn, Ni, Se, and Zn) to give concentrations of 10 or 100 mmol TE kg^-1 BL and applied to an Appling soil at 0, 50, 100, 150, 200, 250, and 300 mg N kg^-1 soil. The soil-trace element-enriched BL (TEEBL) material was incubated for five weeks at 25 ^oC. The inorganic nitrogen (N) released was used to determine threshold of N inhibition in the soil. Based on these results, a subsequent experiment was initiated to study the effect of TEEBL containing As, Cr, Ni, and Se (100 mmol TE kg^-1 BL) applied to Appling, Cecil, and Hartsells surface soils at 300 mg N kg^-1 soil and incubated for 12 weeks at 25 ^oC. Activities of arylamidase (a-aminoacyl-peptide hydrolase,EC 3.4.11.2) and L-glutaminase amidohydrolase, EC 3.5.1.2) were assayed every two weeks. Results showed that the most effective inhibitor of inorganic N was As (19.8%) and Cu the least (<1%). At the end of the 12-week incubation time, Ni inhibited nitrification by 20% in Cecil soil, while As inhibited nitrification by 43% in Appling soil. All the four TEs inhibited arylamidase and L-glutaminase activities (5-55%) in the soils. Thus, long-term application of BL containing high levels of TEs may affect soil biochemical reactions.