Soil Fungi Isolated from Fields under Different Tillage and Weed-Control Regimes

Abstract

A qualitative and quantitative survey of soil microfungi isolated from fields under 2 tillage regimes and 3 levels of atrazine application was undertaken. Using the soil-plate method, 1658 colonies representing 15 genera of Fungi Imperfecti, 6 genera of Zygomycetes, and 3 genera of Ascomycetes were identified. Most frequently isolated genera were Trichoderma, Fusarium, Penicillium, Gliocladium and Rhizopus. Species most prevalent (3% frequency or more of isolates identified per treatment) for each atrazine-application level and both tillage regimes were Fusarium oxysporum, Gliocladium roseum, Humicola fuscoatra, Trichoderma koningi, T. lignorum and Rhizopus oligosporus. Comparing the response of fungi to atrazine between and within tillage regimes resulted in high coefficients of similarity both in species present (65.0-84.5%) and frequencies of species present (83.1-94.5%). Analyses of variances in fungal populations in response to herbicide treatment, tillage method, and herbicide by tillage interactions showed few statistically significant results. Populations of Rhizopus oligosporus were significantly higher and populations of Penicillum velutinum were significantly lower in plowed plots.