Corn response to row spacing and seeding rate varies by hybrid and environment in Kentucky

There has been recent interest in growing corn in narrow rows (<30 inches wide) and at dense plant populations to increase grain yields. The purpose of this study was to evaluate three corn hybrids adapted to the midsouthern United States at multiple row spacings and seeding rates. Studies were established at Lexington and Hodgenville, KY during the 2011 and 2012 growing season. The corn hybrids were planted in 15-inch rows, twin 8-inch rows on 30-inch centers, and 30-inch rows at seeding rates of 30,000; 35,000; 40,000; and 45,000 seeds/acre. Plant stands, stalk diameter, intercepted photosynthetically active radiation, and grain yield were evaluated for all hybrid × row spacing × seeding rate combinations. Stalk diameter decreased with increasing seeding rates, but no lodging was observed. At Hodgenville in 2011, corn planted in twin rows yielded 6.7% more than corn in 30-inch rows, but row spacing did not affect yield in the other site-years. Under favorable growing conditions at Lexington in 2011, grain yield increased by 1.5 bu/acre per 1000 seed increase in seeding rate; however, under hot and dry conditions in 2012, grain yield decreased 0.87 bu/acre for every 1000 seed increase in seeding rate. At Hodgenville in 2012, a hybrid × seeding rate interaction was observed in which one hybrid responded positively, one responded negatively, and one was unresponsive to seeding rate. Corn producers considering decreasing row widths or increasing plant population density should ensure that they choose hybrids appropriate for their management systems and environmental conditions.