Long‐term farming systems and last crop sown shape the species and functional composition of the arable weed seedbank

Abstract

Questions The assembly of arable weed communities is the result of local filtering by agricultural management and crop competition. Therefore, soil seedbanks can reflect the effects of long‐term cumulative field management and crop sequences on weed communities. Moreover, soil seedbanks provide strong estimates of future weed problems but also of potential arable plant diversity and associated ecological functions. For this, we evaluated the effects of different long‐term farming systems under the same crop rotation sequence on the abundance, diversity and community assembly of weed seedbank, as well as on the functional diversity and composition. Location DOK (biodynamic (D), bioorganic (O), conventional (K)) long‐term trial, Therwil, Switzerland. Methods The effects of long‐term contrasted farming systems (i.e., biodynamic, organic, conventional, mineral and unfertilised systems) and last crop sown (i.e., wheat and maize) were evaluated on different indicators of species and functional diversity and composition of the weed soil seedbank. Results The results showed significant influences of 40‐years of contrasted farming systems on the diversity and composition of the seedbank, with higher diversities being found in unfertilised and organic farming systems, but also higher abundances than those found under conventional systems. Organic farming also allowed higher functional richness, dispersion and redundancy. Different farming systems triggered shifts in species and functional assemblies. Conclusions The results highlight the importance of organic management for the maintenance of a diverse arable plant community and its functions. However, such results emphasize the need for appropriate yearly management to reduce the abundance of settled weediness and prevent affecting crop production. The farm management filtered community composition based on functional traits. Although the soil seedbank buffers the long‐term farming and crop sequence, the last crop sown and, thus, the yearly management were important determinants of seedbank composition.