RYE RESIDUE GEOMETRY FOR FASTER CORN DEVELOPMENT

Winter cereals used as cover crops in corn (Zea mays L.) production ph ysically modify the soil-plant environment. Springtime killing of the cover crops with herbicides leaves surface residues either standing, f lat, or a combination of the two at corn planting. This study was cond ucted to verify how standing rye (Secale cereale L.) residue affected soil temperature, soil water, and corn development compared with flat rye residue in a sandy loam in Harrow, ON, in 1990, 1991, and 1992. In the 3 yr, volumetric soil water content was similar in both treatment s, but seed zone daily maximum temperatures were higher under standing than under flat residue. Corn development in standing residue was fas ter (2 to 3 d) compared with flat residue, except if seed zone maximum temperatures were regularly in the 28 to 32-degrees-C range for both treatments, such as in 1991. During vegetative stages in 1990 and 1992 , plants in the standing residue were taller than plants in the flat r esidue. Most of these height differences were related to differences i n development that were related to soil temperature. In 1991, however, which was a hot and dry year, phyllochron values indicate that develo pmental rates under both treatments were affected by a factor other th an temperature, most likely by a lack of soil water. In 2 of 3 yr, whe n seed zone temperatures were often below the optimal range for corn d evelopment, standing rye residue resulted in faster plant development than flat rye residue due to a warmer seed zone. Residue treatments di d Dot affect yield.