A study was initiated in 2001at four locations in western Canada toinvestigate an integrated approach to managing wild oat, the region's worstweed. The study examined the effects of combining semidwarf or tall barleycultivars with normal or twice-normal barley seeding rates in eithercontinuous barley or a barley–canola–barley–field pea–barley rotation.Herbicides were applied at 25, 50, and 100% of recommended rates. The firstphase of the study was completed in 2005. This paper reports on the secondphase, which was continued for four more years at two of the locations,Beaverlodge and Fort Vermilion, AB, Canada. The objective was to determinethe long-term impact of the treatments on wild oat seed in the soil seedbank. In 2009 (final year), the diverse rotation combined with the higherbarley seeding rate (optimal cultural practice) resulted in higher barleyyields and reduced wild oat biomass compared to continuous barley and lowerbarley seeding rate (suboptimal cultural practice). In contrast to the firstphase, barley yield was higher with the semidwarf cultivar, and cultivar hadno effect on wild oat management. Wild oat seed in the soil seed bankdecreased with increasing herbicide rate, but amounts were often lower withthe optimal cultural practice. For example, at the recommended herbiciderate at Beaverlodge, an approximate 40-fold reduction in wild oat seedoccurred with the optimal compared to the suboptimal cultural practice. Theresults indicate that combining optimal cultural practices with herbicideswill reduce the amount of wild oat seed in the soil seed bank, and result inhigher barley yields. Optimal cultural practices may also compensate forreduced herbicidal effects in terms of reducing wild oat seed accumulationin the soil seed bank and increasing barley yield. The results haveimplications for mitigating the evolution of herbicide resistance in wildoat.
