RYE RESIDUE GEOMETRY FOR FASTER CORN DEVELOPMENT

Winter cereals used as cover crops in corn (Zea mays L.) production physically modify the soil-plant environment. Springtime killing of the cover crops with herbicides leaves surface residues either standing, flat, or a combination of the two at corn planting. This study was conducted 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 treatments, but seed zone daily maximum temperatures were higher under standing than under flat residue. Corn development in standing residue was faster (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 residue. Most of these height differences were related to differences in development that were related to soil temperature. In 1991, however, which was a hot and dry year, phyllochron values indicate that developmental rates under both treatments were affected by a factor other than temperature, most likely by a lack of soil water. In 2 of 3 yr, when seed zone temperatures were often below the optimal range for corn development, standing rye residue resulted in faster plant development than flat rye residue due to a warmer seed zone. Residue treatments did Dot affect yield.