Interaction of Seeding Rates and Cultivars for Twin-Row Corn Production in Mississippi.

Twin-row corn production has gained acceptance for wide-row (96 to 102 cm) production in the Mississippi Delta.  A 4-yr research project was established in 2005 on a production field to evaluate the interaction of nitrogen (N) rates (202, 246, and 291 kg N ha^-1) and seeding rates (60,000 to 100,000 seeds ha^-1) for twin-row (20-25 cm apart) corn production.  There was a significant response to increasing N rates and seeding rates in both 2006 and 2007 where corn followed cotton.  Each increase in seeding rate resulted in an additional increase in grain yield both years.  While the response to increasing N rates was significant, the cost of the fertilizer N could not be recovered.  In 2008 following corn, there was no significant N response above 246 kg N ha^-1 and no increase in yield with seeding rates above 90,000 seeds ha^-1.  Cultivars differed throughout the study and a question surfaced as to the potential for cultivar effects in twin-row systems.  To address this concern, a large-scale on-farm study was initiated in 2009 to evaluate three seeding rates (74,130, 86,485, and 98,840 seeds ha^-1) and six different cultivars.  All cultural practices and field operations were managed by the producer.  Grain yields ranged from 13.43 Mg ha^-1 to 15.50 Mg ha^-1 (214.2 to 247.2 bu/acre).  Responses to increasing seeding rates were different for the different cultivars.  The largest response came with Pioneer ‘31P42’ (1.81 Mg ha^-1, 28.9 bu/acre) followed by Pioneer ‘31G96’ (1.56 Mg ha^-1, 24.9 bu/acre).  The lowest response was observed for DeKalb ‘DKC 67-23’ (0.42 Mg ha^-1, 6.7 bu/acre).  This cultivar had higher yields at the lowest seeding rate compared to the other cultivars.  Averaged across the three seeding rates, Pioneer 31P42 yielded 14.74 Mg ha^-1 (235.0 bu/acre) and had the highest average yield of the six cultivars.