Impact of tillage on the incidence ofFusarium spp. in soil

The influence of several long-term conventional and conservation tillage treatments on the incidence and the diversity ofFusarium spp. in soil was studied. Soil samples were randomly collected from naturally contaminated field trials and Fusarium species were isolated by using the dilution plate method. The identification of the species was done by direct microscopic observation onFusarium-specific media. The isolation frequency ofFusarium species and the total number of colony forming units was affected by the sampling year and the cultivated crop and showed significant differences between the tillage treatments. Moldboard plough-treatments resulted in a lower diversity of Fusarium species than the chisel plough and rotary tiller treatments. Besides the tillage system the tillage depth also appeared to affect theFusarium populations. The deeper the tillage the lower was the number of isolatedFusarium spp. TwentyFusarium species were identified over both years of investigation. In conservation tillage plots a higher diversity ofFusarium species was found than in the moldboard plough-based tillage plots. A correlation betweenFusarium species producing the mycotoxin deoxynivalenol (DON) isolated from soil and the DON-content of grain could not be observed. However, these investigations indicate that conservation soil tillage results in conditions which increase the incidence ofFusarium species in soil.