Competition from weeds and an interplanted sudangrass [Sorghum bicolor (L.) Moensch, formerly S. sudanense (Piper) Stapf.] cover crop was allowed to occur in newly-planted strawberries (Fragaria ×ananassa Duch.) for varying lengths of time, and at different times during the growing season. Newly planted strawberries were most susceptible to weed and cover crop competition during the first 2 months after planting, as both runnering (stolon formation) and subsequent yield were impacted. In 1994-95, 1 month of weed competition in June reduced yield by 20%, whereas 2 months of weed competition reduced yield by 65%. However, 1 month of uncontrolled weed growth later in the growing season had little to no impact on yield, although weed biomass was much less then. Herbicide (napropamide) use alone was insufficient to prevent weed competition and yield reduction. In our study, yield was reduced 0.67 t·ha-1 or 5.5% for each 100 g·m-2 of weed biomass. The data suggest that it is critical for growers to minimize weed competition early in the planting year when weed growth is greatest. Since an interplanted sudangrass cover crop displaced a portion of the weeds, it could be seeded later in the year to provide some weed suppression without a negative impact on yield. Chemical names used: N, N, Diethyl-2-(1-naphthalenyloxy)-propionamide (napropamide); N-(phosphonomethyl)glycine (glyphosate).
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