Contributions of Pinus Ponderosa Charcoal to Soil Chemical and Physical Properties

Tom Miles

Contributions of Pinus Ponderosa Charcoal to Soil Chemical and Physical Properties
Christopher M. Briggs in Briggs, Breiner, Graham Pinus Ponderosa Charcoal 9 May 2005

Charcoal results from the incomplete burning of plant material and is found in most
soil surface horizons, but little is known about its effects on soil properties. The objectives of this
study were (1) to determine the chemical and physical properties of ponderosa pine charcoal
produced under controlled conditions, (2) to compare the properties of the laboratory-produced
charcoal to those of wildfire-produced charcoal after it had resided in the soil for a number of
years, and (3) to determine how charcoal additions to soil affect soil properties. We collected our
samples from a pine forest in the San Bernardino Mountains of southern California. We found
that laboratory-produced ponderosa pine charcoal has a cation exchange capacity on the order of
20-30 cmol kg-1 and field-collected samples accumulate native cations on their exchange sites.
Field-collected charcoal samples from immediately below the litter layer were much less water
repellent (water drop penetration time samples (water drop penetration time >2 h). The laboratory-produced charcoal C/N
ratio (644) was about three times larger than the field-collected charcoal ratio (196-263).
Addition of finely divided charcoal to mineral soil significantly increased the available water
capacity and darkened the soil. We conclude that charcoal is not simply an inert compound in
soils. It may play an important role in determining the properties and behavior of some surface horizons.

The ASA-CSSA-SSSA International Annual Meetings (November 6-10, 2005)
Salt Lake City, UT