Row Width and Plant Population Effect On Corn Yield in Kentucky.

Field plots were placed across the state of Kentucky in 2011 and 2012 to study the interaction between hybrid, row width, and population for corn yield.  The primary objectives were to test if 1) narrower rows increase grain yield, 2) higher plant populations increase yield in narrow and twin rows, and 3) the interactions among all factors.  Three hybrids (A6533VT3, DKC62-97, P1480HR) were randomized in a split-split plot design with row widths (76, 38 cm or twin) as the split and plant density (75000, 87500, 100000, 112500 plants ha^-1) as the split-split plot.  Three replications of the main plot (hybrid) were seeded at three locations in Kentucky (Princeton, Elizabethtown, and Lexington) in 2011 and 2012.  Intercepted photosynthetically active radiation (IPAR) measurements were taken at growth stages V8 and VT/R1.  Grain yields were machine-harvested (Wintersteiger) from the center rows and yields were adjusted to 15% grain moisture.  Grain samples were also collected from each plot to measure differences in seed size across treatments.  In 2011, grain yield and IPAR did not differ between row widths.  However, plant density within individual hybrids affected yield at Elizabethtown and Lexington with higher populations being the most productive regardless of row width.