Continuous corn silage production can result in large losses of P and N in surface runoff because of the lack of residue cover. Manure application and the incorporation of different companion or cover crops into a corn silage system may lead to reduced sediment and nutrient losses by increasing residue cover and infiltration or increased nutrient losses due to the release of P and N from manure and vegetation. We examined the effects of four years of different manure/cover crop combinations in no-till corn silage production on runoff volume and on concentration and loads of P, N, and sediment generated by 60 minutes of simulated rain. The crop management treatments evaluated were fall- or spring-applied dairy manure in combination with no cover, interseeded Italian ryegrass, interseeded red clover, or a winter rye cover crop.  N fertilized plots without manure or cover crop were used as a control. Recent (spring-applied) manure increased total and, especially, dissolved P concentration in runoff. Runoff quantity and sediment load were reduced with cover crops, but recent surface-applied manure had similar effects, presumably due to a mulching effect.