Effect of long-term tillage and residue managements on weed flora and its impact on winter wheat development

In Hesbaye region (Belgium) with a loamy soil and under temperate climatic condition, winter wheat is a key component of agricultural rotations. As part of these rotations, soil management is a known driver of soil fertility and carbon storage. However, it could also influence the weed flora. In this study, the long-term effect of four soil management on the expressed and potential weed flora was examined. Soil management levers were i) the export (OUT) or restitution (IN) of crop residues and ii) the burial of residues by conventional tillage (mouldboard ploughing 25 cm depth, CT) or reduced tillage (cultivator ploughing 10 cm depth, RT). The weed seedbank and expressed flora in winter wheat were characterized. Weed diversity was assessed using the Richness and the Shannon diversity index. Then, the impact of flora and management on yield were investigated. Tillage management showed little impact on weed diversity with only a slight increase in diversity in reduced tillage. However, reduced tillage resulted in a higher weed seedling density and a higher weed density than conventional tillage, which indirectly led to yield losses. Exporting residues had no clear effect on weeds. In conclusion, within cropping systems based on the cultivation of wheat, reduced tillage can pose problems for the long-term management of the weed flora, and great attention has to be paid to its management.