The number of multiple herbicide resistant weed biotypes has been increasing due to heavy use of synthetic herbicides. Herbicide application is threatening our environment and food security. This issue raises the need for alternative tools in weed management. Our goal is to develop long-term ecologically based weed management strategies to support our agricultural communities in the Northern Great Plains (NGP). The field experiment was conducted for two consecutive years (2018-19) with randomized complete block design at the Montana State University Central Agricultural Research Center in Moccasin, Montana. Treatments included two heights of spring wheat (short and tall) with each height seeded at either 67 or 101 kg/ha. Other treatments included lentils, tilled fallow, a mixture of spring barley and pea forage crop, and a mixture of winter triticale and Austrian winter pea forage crop; forage crops were either grazed by sheep or hayed. We assessed how well these ecologically based tactics suppressed the growth and seed production of wild oat (Avena fatua L.) and kochia (Bassia scoparia L.), which are the current most problematic weeds in the NGP.
Results/Conclusions
Biomass and densities of wild oat and kochia were different between years. Our results show that spring-seeded and winter-seeded forage crop mixtures have a higher suppression of wild oat and kochia’s growth when compared to spring wheat and lentils. Wheat seeding rate and height did not make any differences on wild oat and kochia performances. Our research suggests that integrating forage crops in the cropping systems reduces the target weed populations. Additionally, the target weeds will have less chance to produce seeds before forage crops are terminated. Understanding how wild oat and kochia perform (biomass and density) across different cropping systems and management practices is important because it will help us to construct population dynamic models. We will use the model to build better crop rotations and develop effective weed management plans. We hope these tactics can be adapted to manage other weeds in agroecosystems in the NGP.