MAIZE GRAIN YIELD RESPONSE TO VARIABLE ROW NITROGEN FERTILIZATION

Crop yields are affected by the rate and method of nitrogen (N) fertilizer application. This study was conducted to determine the effects of applying variable N rates by row on maize grain yields. The effects of variable rates and row application were investigated at the R.L. Westerman Irrigation Research Facility near Stillwater, Oklahoma on a Port-Oscar silt loam (fine-silty, mixed, super active, thermic Cumulic Haplustolls) and at Hennessey, Oklahoma on a Bethany silt loam (fine, mixed, thermic Pachic Paleustolls). For 2005 that was characterized by high yields, significant yield differences occurred in non-fertilized rows adjacent to N (67, 100, 134kg N ha(1)) fertilized rows, but not when adjacent to low N [34 and 67 (some cases) kg N ha(1)]. In 2006, which had a dry growing season, grain yields were significantly lower than those produced in 2005. With few exceptions, rows receiving N did not produce significantly higher yields in 2006. In 2007, trends were similar to those observed in 2005. Excluding 2006, all site-years showed a significant reduction in yield when N fertilizer was not applied to each row. In order to maximize corn grain yields, N fertilizer should be applied by row, while alternate row N application should be avoided.