Microflora of soil and wheat rhizosphere in a field following fumigation

Abstract

Light sand and heavier sandy loam wheat-growing soils at Wongan Hills, W.A. were fumigated (2: 1 mixture of chloropicrin and methyl bromide) to study its effect on the soil microflora. In fumigated soil, numbers of bacteria and fungi, after an initial reduction, remained high and low, respectively, in comparison to untreated soil, throughout the period of study. In the fumigated soil Trichoderma species rapidly recolonized the soil, becoming the dominant fungus by 15 days and remaining so to the end of the experiment (145 days after fumigation). There was no difference in the total numbers of bacteria, actinomycetes or fungi in the rhizosphere of wheat grown in fumigated and non-fumigated soils. The numbers of some fungal species were lower in the rhizosphere of wheat grown in the fumigated soil, these included Aspergillus glaucus, A. fumigatus, Beauveria bassiana, Cladosporium cladosporoides, Embellisia tumida, Fusarium oxysporum, Penicillium patulum, P. tardum, Phialophora mutabilis and Trichoderma saturnisporurn. The only fungi found to be significantly higher in the rhizosphere of plants in fumigated soil were F. merismoides, T. koningii and T. viride.