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Several studies indicate links between regional occurrence of well adapted weed species and crop rotations. Monocultures or very short crop rotation, which increased in the past decades are crucial for the establishment and dispersion of problematic weed species. In this study the impact of crop rotation on the occurrence of the species Amaranthus retroflexus (L.), Anchusa arvensis (L.) M. Bieb., Echinochloa crus-galli (L.), Galium aparine (L.), Geranium pusillum (L.), Sisymbrium officinale (L.), Solanum nigrum (L.), Stellaria media (L.) Vill., Viola arvensis Murray is investigated in four crop rotations with varying potential of crop health risks. Therefore, maize (M), oilseed rape (WR) and winter wheat [early sowing (WWF) and late sowing (WWS)] are cropped in four different rotations (M, WR – WWF, WR – M – WWS and WR – WWF – M – WWS) at two study sites in Germany since year 2008 (Rostock) and 2009 (Göttingen). At the start of the project selected weed species were sown into some plots in order to simulate an artificial similar weed pressure. In all plots weed species densities were counted before spraying in a standardized observation method. Analyses of four, respectively three years give evidences of crop specific effects regarding A. arvensis, E. crus-galli, G. pusillum, S. nigrum and S. media. Moreover, first effects of crop rotations on problematic weed species indicates that expanding crop rotations is a preventive tool to reduce weed densities. |
