Populations of microorganisms from soil treated with guanidine thiocyanate,
guanylurea sulfate, thiourea, or furfural were compared with those of untreated soil.
The materials affected quantitative and/or qualitative changes in composition of the
soil microflora depending on the compound used. Guanidine thiocyanate (Gt)
significantly increased total fungal populations relative to populations of other
treatments. Populations of Penicillium purpurogenum were markedly higher in Gt-
treated soil. Gt also increased total bacterial populations, and was the only compound
that increased actinomycetes populations. The percentage of Trichoderma harzianum
was significantly higher in soil treated with thiourea more than in the other treatments.
Furfural increased the percentage of P. purpurogenum with respect to total fungi, and
was as effective as guanylurea sulfate in increasing chitinolytic bacteria and those in
the Pseudomonas cepacia-group. Thiourea most effectively promoted proliferation of
coryneform bacteria. Chitinobyotic fungi increased synergistically when Gt and
guanylurea sulfate were applied in combination.