Modified no-till systems for corn following wheat on clay soils

Concerns about corn (Zea mays L.) grain yield reduction with no-till following winter wheat (Triticum aestivum L.) in rotation oil clay soils has been a major factor in slowing the rate of adoption of no-till systems in Ontario. Our objective was to determine conservation tillage and wheat residue management systems that provide favorable seedbed conditions for emergence, growth, and yield of corn following winter wheat on clay soils. Seven tillage and residue management systems (fall moldboard plow, chisel plow, tandem disk, and zone-till, and no-till bare and with straw baled and not baled) were evaluated in 1994 and 1995 at two locations in Ontario. Fall zone-till reduced the amount of wheat residues on the soil surface. Wheat residues remaining in late fall with zone-till, no-till (baled), and no-till (not baled) treatments were 3.1, 4.0, and 7.1 Mg ha(-1). Volumetric soil moisture levels in the top 15 cm early in the season did not differ among fall tillage treatments, but were all lower than for no-till with wheat residue. Modifying the no-till system by adopting fall zone-till or fall tandem disk produced grain yields no different front fall moldboard plow or fall chisel plow treatments, and greater by 5 to 10% than for no-till with wheat residue. No-till yield potential was affected by the level of wheat residue present. Completely removing all wheat residue increased no-till corn grain yields by 0.5 and 0.9 Mg ha(-1) compared with baling and not baling straw, respectively. The baled and not-baled no-till treatments had the lowest proportion of finer soil aggregates in the seedbed, greatest penetrometer resistance up to the 20-cm soil depth, slowest corn growth, and lowest grain yield. We recommend zone-till or tandem disk in the fall for corn production on clay soils following wheat.