OVERSEEDING RYE INTO CORN REDUCES NO3 LEACHING AND INCREASES YIELDS

Non-irrigated corn (Zea mays L.) produced on coarse-textured soils dur ing droughty years can result in excess NO3 available for leaching. To evaluate the effect of overseeding cereal rye (Secale cereale L.) int o corn on yields, NO3 leaching ansa pre-sidedress nitrate test (PSNT), we broadcast rye seed(Aug. 1993, 1994 and 1995) into conventional til lage (CT) and no-tillage (NT) corn receiving six fertilizer N rates. T here 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 depe nded 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 NO3- N L-1 (fall 1995) foll owing 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 gr owing season (average of CT and NT). improved PS availability with the rye was detected by a PSNT under CT, but not under NT. Therefore side dress N rates can be adjusted for release of rye residue-N under CT, a nd potential NO3 contamination of groundwater can be reduced by overse eding winter rye into both CT and NT corn systems.