Soil microbial biomass C (SMBC) was determined
by the chloroform fumigation/incubation method proposed
by Jenkinson and Powlson (1976) with modi-
®cations (Franzluebbers et al., 1994), using kC 0.41
(Voroney and Paul, 1984). This constant represents the
fraction of microbial C mineralized in the 10-day
incubation following fumigation. Soil samples were
rewetted and pre-incubated for seven days prior to
fumigation. Franzluebbers et al. (1996) demonstrated
that air-dried samples that were rewetted and preincubated
for seven days prior to fumigation resulted
in similar SMBC values as samples that were continuously
®eld moist.