Short-term cover crop decomposition in organic and conventional soils: soil microbial and nutrient cycling indicator variables associated with different levels of soil suppressiveness to Pythium aphanidermatum
2000
Grunwald, N.J. | Hu, S. | Van Bruggen, A.H.C.
Stages of oat-vetch cover crop decomposition were characterized over time in terms of carbon and nitrogen cycling, microbial activity and community dynamics in organically and conventionally managed soils in a field experiment and a laboratory incubation experiment. We subsequently determined which variables describing soil microbial community dynamics, C and N cycling could be used as predictors of Pythium aphanidermatum damping-off incidence and relative growth. Disease incidence and relative growth of aphanidermatum were measured in growth chamber assays and in vitro growth tests. No significant differences were detected between the conventional and organic farming system with respect to either relative growth or disease incidence. Stepwise discriminant analysis on three classes of disease incidence or relative growth led to selection of qualitatively similar variables. Only one soil microbial variable, total biomass of actinomycetes, was selected. Total C and N content of debris extracted from soil as well as NH4-N content of soil were selected most consistently and show promise for assessment of potential damping-off incidence by P. aphanidermatum for young seedlings.
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