Off-season groundcover and runoff characteristics of perennial clover and annual grass companion crops for no-till corn fertilized with manure

Various companion crops, such as spring-interseeded or fall-seeded cover crops and herbicide-suppressed living mulches, are recommended for reducing the environmental impacts of silage corn (Zea mays L.) production. In a four-year Wisconsin study, we compared off-season dry matter yield (DMY) and nitrogen (N) accumulation in groundcover produced by five companion crop systems for glyphosate-resistant no-till corn amended yearly with spring or fall surface-banded manure. In two rotational systems, corn was grown for one year with kura clover (Trifolium ambiguum Bieb.) living mulch or spring interseeded red clover (Trifolium pratense L.) followed by one year of clover production. Three continuous corn systems utilized spring interseeded ryegrass (Lolium multiflorum Lam.), fall-seeded rye (Secale cereale L.), or no companion. Fall DMY and N accumulation in groundcover were greatest for rotationally grown clovers in forage production and interseeded ryegrass, whereas spring DMY and N accumulation were greatest for fall-seeded rye and kura clover going into corn production. Overall, the kura clover-corn rotation came the closest to providing significant DMY and N accumulation in groundcover throughout the off-season period. Shifting manure application from spring to fall mainly influenced rye by stimulating its growth under warm spring conditions. In a follow-up study, spring surface runoff and losses of phosphorus (P) and sediment with fall manure were least with rye followed by ryegrass. Shifting manure application to spring largely negated companion crop effects on spring runoff and substantially increased loading of dissolved reactive P.