WHEAT RESIDUE MANAGEMENT OPTIONS FOR NO-TILL CORN

Corn (Zea mays L.) yield reduction following winter wheat (Triticum ae stivum L.) in no-till systems prompted a study on the effects of tilla ge and residue management systems on corn growth and seedbed condition s. Four methods for managing wheat residue (all residue removed, straw baled after harvest, straw left on the soil surface, straw left on th e soil surface plus application of 50 kg ha(-1) N in the fall) were ev aluated at two tillage levels: fall moldboard plow (MP) and no-till (N T). No-till treatments required at least 2 more days to achieve 50% co rn emergence and 50% silking, and had the lowest corn biomass at 5 and 7 wk after planting. Grain yield was similar among MP treatments and averaged 1.1 t ha(-1) higher than NT treatments (P < 0.05). Completely removing all wheat residue from NT plots reduced the number of days r equired to achieve 50% corn emergence and increased grain yields by 0. 43 and 0.61 t ha(-1) over baling and not baling straw, respectively, b ut still resulted in 8% lower grain yields than MP treatments. Grain y ield differences among MP treatments were insignificant regardless of the amount of wheat residue left on the surface or N application in th e fall. Early in the growing season, the NT treatments where residue w as not removed had lower soil growing degree days (soil GDD) compared with MP (baled) treatment, and higher soil moisture levels in the top 15 cm compared with all other treatments. The application of 50 kg N h a(-1) in the fall to NT (not baled) plots influenced neither the amoun t of wheat residue on the soil surface, nor the soil NO3-N levels at p lanting. Our results suggest that corn response in NT systems after wh eat mostly depends on residue level.