A 4-year field experiment examined how monoculture and biculture winter cover crops were affected by prior inorganic nitrogen (N) fertilization of sweet corn (Zea mays) and by kill dates associated with tillage methods. Hairy vetch (Vicia villosa) biomass production and N content remained relatively constant with (N+) or without (N0) prior N application. In N+ treatments, biomass production of winter rye (Secale cereale) and a vetch-rye biculture were significantly greater than vetch biomass production. Rye responded to prior N fertilization and recovered N from residual inorganic N fertilizer at an average annual rate of 30 kg·ha-1 (27 lb/acre), excluding contributions of roots. Nitrogen contents of vetch and biculture cover crops were similar in most years and were significantly greater than those of rye. Nitrogen contents in vetch and biculture treatments were not increased by the residual inorganic N fertilizer addition of the N+ treatment. In the biculture treatment prior N application increased total biomass production but decreased the percentage of vetch biomass. Monoculture vetch biomass production was significantly increased by delaying cover crop kill dates for 8 days in mid-May. However, such delays also significantly lowered vetch foliar N concentrations and consequently did not significantly affect vetch N content. No significant effects of delays on rye or biculture cover crops were detected. It was concluded that prior fertilization of sweet corn with inorganic N affected various cover crops differently and that delaying vetch kill dates 8 days increased biomass production but did not affect N content.