Cover crops improve weed management in South Africa's Mediterranean climate region

Abstract

Cover crops offer an alternative weed management strategy that could contribute to addressing herbicide resistance. In South Africa's Swartland region, integrating cover crops into crop rotations is increasingly popular due to their multiple benefits for cropping systems. However, there is a paucity of information on how to manage cover crops for weed suppression, in particular for herbicide-resistant ryegrass (Lolium spp.), which is a major challenge to crop production in the region. This knowledge gap leaves farmers without the necessary insights to formulate effective weed management decisions. This study tested two cover crop mixtures (cereal-based and legume-based) and three termination methods (grazed, cut and utilized as hay, and rolled). Weed seedbank counts taken before sowing the cover crop and before sowing the subsequent crop (1 year later) were used to evaluate treatment effects. Neither cover crop selection, termination method, nor their interaction affected the overall weed seed abundance. A cereal-based cover crop mixture was better at suppressing Lolium spp. abundance than a legume-based cover crop mixture (p < 0.05). There was no interaction between the cover crop mixture and termination method (p > 0.05). We found some evidence that using grazing as a termination method could result in a lower Lolium spp. abundance. However, using cover crops as hay or grazing has the additional benefit of improving fodder flow to support income from livestock.