The humification rate depends on many factors: enzyme stability, moisture, alkalinity, oxygen availability, microbial population and the physical properties of different soils. Amonette's experiments were designed to weigh the importance of these many factors and to learn ways they might be manipulated to increase humification.

In the lab, Amonette assembled 72 elaborate plastic-tube configurations he likens to "those Russian nesting dolls," matrioshkas. The tubes allowed Amonette to control individual moisture levels and oxygen availability. Each soil sample was placed between the inner and outer walls of water-tight but gas-porous concentric cylinders. These were placed inside yet a larger "chimney" tube to control the humidity as well as the type of gas and its flow rate.

Amonette was particularly interested in identifying soil components and soil additives that might improve tyrosinase's natural ability to promote humification. He found that an alkaline, porous material called "fly ash," a byproduct of coal combustion, "speeds up the normal humification process by promoting the reaction of the quinones with the amino acids and providing small pores to protect humic polymers," he said. "Frequent cycles of wetting and drying appear to be important, too, for fostering a rich microbial community that supplies many of the humic precursors and for aiding the formation of soil aggregates."

Amonette is eager to put his results to the test where it matters most--in the field. He will get his wish in May, when he travels to a field outside of Charleston, S.C. There, he and collaborators from the U.S. Forest Service and Oak Ridge National Laboratory will plant 72 pots containing various controlled mixtures of soil and catalysts.

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Contact: Bill Cannon
cannon@pnl.gov
509-375-3732
DOE/Pacific Northwest National Laboratory
1-Apr-2004