BORDER ROW EFFECT ON CORN GRAIN RESPONSE TO SIDEDRESSED NITROGEN-FERTILIZER

Nitrogen (N) fertilizer recommendations for corn (Zea mays L.) are nor mally developed from field experiments that determine yield response t o applied N. The objective of this study was to examine the severity o f border row competition with the harvest rows for sidedressed N in fi eld experiments measuring grain yield. This study was conducted in 199 3 and 1994 on a Sharpsburg silty clay loam (fine, montmorillonitic, mi xed, mesic argiudoll). Ammonium nitrate was broadcast to the center tw o rows of a four row plot, all four rows of a four row plot and all si x rows of a six row plot. Results showed that grain yield from four an d six row plots were similar and indicated that while grain yields wer e much less in 1993 than 1994 (7.36 versus 12.06 Mg ha(-1), respective ly), corn yield response to N was similar regardless of the number of rows fertilized. Thus, there is little reason for plots larger than fo ur rows. The results also lend credibility to sidedressing only harves t rows for soil test calibration studies where grain yield response is the primary response variable.