In addition to soil conservation and soil improvement, cover crops can be useful tools for weed suppression.
Winter cover crops compete with weeds for light, moisture, and nutrients. When cover crops are killed, they produce a soil-covering mulch, which can inhibit weed germination. In addition, some cover crops may release chemicals which further inhibit weed seed germination.
Greater cover crop biomass leads to a thicker mulch layer, and thus better weed control. Earlier cover crop planting and later cover crop termination increases cover crop biomass. In organic reduced-tillage systems, mechanically killed cover crops can suppress weeds that would otherwise be controlled with tillage and cultivation. However, the efficacy of cover crop termination also depends on termination timing.
