Effect of interseeding cover crops and fertilization on weed suppression under an organic and rotational cropping system: 1. Stability of weed suppression over years and main crops of potato, maize and soybean

In organic farming, interseeding cover crops has been shown to reduce the necessity of hand-weeding and tillage. The purpose of this study is to determine the impact of interseeding the cover crops hairy vetch and winter rye with potato, soybean, and maize in an organic system following a four year rotation (2003-2006). Dry weight of weeds and number of weeds at maximum plant height of main crops, vegetative cover ratios, and yields of main crops were measured and compared among no fertilizer + no cover crop (control), no cover crop + fertilizer, winter rye cover + fertilizer, and hairy vetch cover + fertilizer. The interseeding of cover crops between three and five weeks after planting main crops significantly reduced weed number and dry weight without significantly impacting main crop yields. No significant differences were seen between hairy vetch and winter rye covers, and application of organic fertilizers had positive effects on yield and weed suppression. In organic systems, such as the one used in this study, hand-weeding and tillage can be expensive and time-consuming tasks for farmers. This study supports the use of interseeding cover crops in organic systems for the reduction of both of these practices without negatively affecting yields.