Effects of conservation tillage on harmful organisms and yield of oilseed rape

In a long-term field trial, the effects of three different tillage systems on harmful organisms and yield were investigated. The focus was on fungal diseases, weeds and slugs. With the ploughing system as the standard, a non-inversion/ conservation tillage and a direct drilling/no till system were compared with one another. The crop rotation oilseed rape-wheat-barley, which was established in 1995, was reconverted into a crop rotation oilseed rape-wheat-wheat in 1998 due to problems with volunteer wheat in the following barley in the two ploughless tillage systems. The occurrence of Phoma root-collar and stem disease, the most important in Germany, was not affected in comparison over the years by the intensity of the cultivation. For Sclerotinia stem rot, a correlation could only be determined with the tillage systems in one year of the trial series. The infection became more severe with decreasing intensity of soil cultivation. Whether this result can be reproduced in future growing seasons remains to be seen. Effects on the incidence of Verticillium longisporum could not be determined. Other diseases arose only sporadically at very low levels. However, in comparison, the occurrence of weeds was affected significantly. The amount of grass weed species (Alopecurus myosuroides, Apera spica-venti, volunteer barley) increased in the systems without ploughing. The effect on dicotyledonous weed species was dependent on the particular species. In individual years, heavy slug damage could be correlated with direct drilling system.