Enzymatic Activity and Concentration of Trace-Elements in Soil Collected from Three Kentucky Counties.

Enzymatic measurements could be explored as a biological index of soil fertility and biological processes. Microorganisms, despite their relatively low amounts, play a significant role in keeping the main nutrients (C, N, and P) in soil through recycling from organic matter. With increasing cost and shortage of nitrogen fertilizer, there is increased emphasis on use of municipal sewage sludge (SS) for land farming. However, SS may contain trace-elements that potentially affect soil microbial growth and the enzymes they produce. Soil samples were collected from three Kentucky Counties (Adair, Meade, and Franklin) from areas where SS was applied for land farming. Hydrolysis of the fluorescein diacetate reagent revealed that the total soil enzyme activities were significantly greater in SS amended soils compared to native soils. The activities of the enzymes hydrolyzing urea (urease), sucrose (invertase), and p-nitrophenyl phosphate (acid and alkaline phosphatase) were also greater in SS amended soil compared to native soil. Cadmium, Pb, and Ni are the metals of great concern to human health, since plants could accumulate and introduce them into the food chain. The mobility of Cd, Pb, and Ni from soil into edible plants grown in soil amended with SS was also monitored. Results indicated that okra fruits and onion leaves accumulated greater concentrations of Cd (51 and 49 µg g^-1 dry weight, respectively) compared to beets and onion bulbs (21 and 13 µg g^-1dry weight, respectively).