The plant protection carried out in the Danish crop rotation experiment is described. These measures can be quite different in the different systems. While mechanical weed control can be carried out in systems without catch crops, it is not possible to do so in systems with catch crops without affecting the establishment of the catch crop.
The occurrence of weeds, pests and diseases is recorded, and the results are described. Since the results are only from the two first years of the experiments, it is not possible to conclude anything about the crop rotations as such. There are however differences related to the other experimental treatments in the experiment: the presence or absence of catch crops and manure. Only in very few cases are the differences statistically significant
