Overseeding rye into corn reduces NO3 leaching and increases yields

Abstract

Non-irrigated corn (Zea mays L.) produced on coarse-textured soils during droughty years can result in excess NO3 available for leaching. To evaluate the effect of overseeding cereal rye (Secale cereale L.) into corn on yields, NO3 leaching and a pre-sidedress nitrate test (PSNT), we broadcast rye seed (Aug. 1993, 1994 and 1995) into conventional tillage (CT) and no-tillage (NT) corn receiving six fertilizer N rates. There was no corn yield penalty with the cover crop. Corn grain yields and the extent to which NO3 leaching was reduced by the rye cover depended on rainfall. With the rye (compared with no rye) subsoil solution NO3 concentrations were: unchanged (fall 1994) following above normal rainfall and corn yields; reduced by 8 mg NO3N L−1 (fall 1995) following intermediate rainfall and yields; and reduced by 28 mg NO3-N L−1 (fall 1993) and 11 mg NO3-N L−1 (spring 1994) following the driest growing season (average of CT and NT). Improved N availability with the rye was detected by a PSNT under CT, but not under NT. Therefore sidedress N rates can be adjusted for release of rye residue-N under CT, and potential NO3 contamination of groundwater can be reduced by overseeding winter rye into both CT and NT corn systems. Key words:Zea mays, Secale cereale, pre-sidedress nitrate test, tillage, nitrogen fertilization