Wednesday, November 15, 2006 - 10:15 AM
282-5

Enzyme Activity in Soils Treated with Trace Element-Enriched Broiler Litter.

Osagie Idehen and K. Kpomblekou-A. Tuskegee University, 210 Campbell Hall, Tuskegee, AL 36088

Reactions involved in nutrient cycling in soils are mediated by plant roots and microorganisms. The reactions are catalyzed by soil enzymes and are dependent on pH, temperature, ionic strength, and presence or absence of activators or inhibitors such as trace elements (TEs). Even though studies have shown that broiler litter (BL) contains TEs, it remains the most widely used source of organic N in the Southeast of the United States, especially in organic farming. The objective of the present studies was to investigate the effects of trace element-enriched broiler litter (TEEBL) on arylamidase (a-aminoacyl-peptide hydrolase, EC 3.4.11.2) and L-glutaminase (L-glutamine amidohydrolase, EC 3.5.1.2) activities in three soils of a wide range of C/N ratios. Four reagent grade TE (As, Cr, Ni, and Se) solutions were mixed as single elements with a BL sample to give a concentration of 0.1 mmol g-1 BL. Batch incubation studies were carried out on surface (0-15 cm) soils mixed with the TEEBL materials to give a concentration of 300 mg N kg-1 soil and incubated for 0, 2, 4, 6, 8, and 10 weeks at 25 °C. Enzyme assays were carried out on the soil samples at each sampling time. Arylamidase activity in the BL treated soils varied from soil to soil and with incubation time but reached its maximum activity six weeks after incubation (500 mg β-naphthylamine kg-1 soil h-1) after which it declined. In the Appling soil, all the four TEs inhibited arylamidase actity (5-55%) but the inhibition decreased with increasing incubation time. In the Hartsells soil, however, the inhibition was less pronounced (< 5%). L-glutaminase activity was also inhibited by As, Cr, Ni, and Se in both soils.