Weeds can affect the establishment of any perennial system, especially forages. For example Hoy et al. (2002) found alfalfa fields with high densities of weeds resulted in reduced alfalfa plant densities > 50%, and others have documented similar results (Lanini et al., 1991; Simmons et al. 1995). Researchers attributed the loss in establishment from competition for soil moisture and light (Lanini et al., 1991; Simmons et al., 1995). Fortunately Wisconsin’s climate during typical establishment periods is favorable and typically soil moisture is adequate to prevent reductions in establishment. While light can be limiting, mowing/harvesting the first cutting at the appropriate timing can limit this effect. So why do we still manage weeds in establishing forages? These weeds can result in reductions in establishment in abnormally dry years and lower forage quality in the first and sometime second cutting.
Soil Science Extension
University of Wisconsin Madison