Intensity of soil preparation and incidence of harmful organisms in a sugarbeet-wheat-wheat rotation

The effects of different intensities of soil preparation on harmful organis ms in a sugarbeet-wheal-wheat rotation were investigated at several locatio ns. In comparison with ploughing, minimum tillage systems tended to yield a weed flora with a higher population of monocotyledonous weeds. In contrast , higher densities of dicotyledonous weeds were found with soil-turning til lage, particularly in the sugar beet phase of the rotation. While few weeds remain after mini mum tillage, the weed infestation is likely to leap in t he succeeding crop. This is especially important in respect of harmful weed thresholds. The method of soil preparation does not inevitably lead to differences in t he incidence of fungal diseases. However, in wheat following wheat, the ris k of the appearance of leaf and ear diseases, in particular, increases with declining intensities of soil preparation. This is due to fungi which can survive in straw residues (among others, DTR, Septoria spp. and Fusarium sp p.). Particularly in the case of a DTR attack, the deployment of fungicides is to be adjusted to the causal organism. With optimized and, in part, increased deployment of plant protection agent s, comparable yields and qualities can be achieved in both crops.