Emergence timing and persistence of kochia (Kochia scoparia) in Manitoba fields

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Schwinghamer, Timothy Damian
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This research addresses the ecological niche of Kochia scoparia (L,) Schrader (family: Chenopodiaceae), and how growers can close the ecological niche of K. scoparia in prairie cropland. The predictability of the spring emergence period of K. scoparia is a potentially exploitable attribute that may be applied to weed management. The emergence timing of K. scoparia was monitored, during the spring and summer of 2005 and 2006, in 12 fields (including high and low disturbance fields, a no-till alfalfa field and fields seeded to barley, beans, canola, corn, and wheat) in southern Manitoba, Canada. K. scoparia begins to emerge prolifically at only 50 cumulative growing degree days (GDD T base 0 C) and K. scoparia continues to emerge throughout the growing season into late summer. Soil samples taken in the fall from quadrats in which emergence was monitored reveal a very limited K. scoparia seedbank. This data supports other research which shows that K. scoparia seeds have little or no dormancy and a limited ability to persist in a seedbank. The effects of seeding depth (2, 10, 20, 40, and 80 mm) on emergence was observed, under controlled growth room conditions. K. scoparia seeds placed at the soil surface (2 mm) had the greatest emergence. Seeding depth reduced K. scoparia emergence significantly. The results from this study show that K. scoparia is a very early emerging seed-limited weed species with seed that cannot emerge from great depths. This information will facilitate K. scoparia control timing decisions and management for farmers and the data from this study can be used to create an emergence model for K. scoparia.