Seedbank dynamics in conservation agriculture in southwestern Zimbabwe

The influence of conservation agriculture (CA) on weed ecology has been a concern to many researchers across the world and that has culminated into this study. The trial was a factorial experiment with two factors laid out as a split plot design with tillage as the main plot factor and residue level as subplot factor with three replicates. Species richness (P>0.001) and grass weeds (P=0.003) were however significantly higher in the 0-5cm depth compared to the other two depths. A significant interaction (P=0.048) between tillage and sampling position revealed higher number of grass weeds in ripping under inter-row position compared to in-row positions and other tillage systems. All the nine main weed species and total weeds were not significantly affected by both tillage and residue levels. Eleucine indica (P=0.02), Setaria spp (P=0.004) and total weeds (P=0.003) were however higher in the 0-5cm compared to the other two depths. Although there were no direct effects of tillage and residue level on weeds the several interactions revealed that grass weeds, Setaria spp and E indica, C tridens and weed seed bank size will increase under CA systems.