Fungal diseases and yield in organic and conventional wheat production

The different farming systems had no influence on the incidence of disease, except for fungal pathogens on the leaves, which were reduced by fungicide treatment in the conventional systems. The influence of the annual weather conditions was significant. The amount of fertiliser applied and the previous crop in some cases significantly affected the incidence of fusaria and Microdochium nivale on wheat grains. So the incidence of M. nivale in the organic systems was lower at the higher fertiliser input level. Moreover germination capacity deteriorated with increasing incidence of M. nivale. In 2003, when summer was very dry and hot, a high incidence of Fusarium poae on wheat grains after maize as previous crop was observed. Grain yield in the organic farming systems, where the input of mineral nitrogen was 75% lower, was significantly lower (15 %) than in the conventional farming systems. Hectolitre weight though was not influenced by the farming system. In 1999 and 2002, when part of the wheat plants lodged, and in 2003, a very dry year, the poorer growth of the plants was reflected in the lower yields and smaller, less well-formed wheat grains.