Within the framework of long-term experiment devoted to cereal production, the factors variety and fungicide protection were added during three years (2006, 2008 and 2010) to the factors crop rotation and soil tillage already studied since 1967. By this complement, the aim was to evaluate to what extent variety disease tolerance and fungicide protection may compensate for phytosanitary risks due to high ratio of winter wheat in rotation, and how far soil tillage interacts. Monoculture penalized grain yield from 8 to 22 q/ha, mainly because of the reduction of the grains number produced per unit of area. Two years out of three, the effect of soil tillage was significant, with a variation of 8 q/ha in favor of the ploughing. The difference between varieties reached 8 to 15 q/ha, corresponding to the known variation between the two types of wheat tested. The additional yield by fungicide protection varied between 4 and 7 q/ha. The effects of a high ratio of cereals in rotation could not be compensated. The specific contributions of each factor and many stressed interactions point out the need for better integrating the cropping techniques for a high-level production.
