Single-Row Vs Twin-Row Corn Production in the Mississippi Delta.

Twin-row corn production has been studied since 2005 in the Mississippi Delta with significant yield responses obtained with increased seeding rates and higher nitrogen (N) applications.  Producers continue to request comparisons of twin-row (TR) planting to single-row (SR) planting on wide rows (96 to 102 cm).  A multi-year project was initiated in 2007 and redesigned in 2009 to evaluate nitrogen (N) rates (157, 202, 246, and 291 kg N ha^-1) and four seeding rates (61,775 to 98,840 seeds ha^-1) for both TR and SR corn production on 102-cm beds ( lower N rate included in 2009 only).  The study was planted on Bosket very fine sandy loam, following soybean, with a MonosemJ twin-row vacuum planter and a John Deere 7300 vacuum planter.   Uniform preplant N was applied as urea-ammonium nitrate solution (32% N, 134 kg N ha^-1 in 2007 and 2008, 112 kg N ha^-1 in 2009) with N rates established at the sidedress application.  Root lodging midway through the growing season was higher as seeding rates increased especially for the SR system. Very little lodging was observed in 2008 and 2009.  For the TR system, grain yields increased from 13.9 to 15.3 Mg ha^-1 as the seeding rate increased from 71,000 plants ha^-1 to 95,900 plants ha^-1 in 2007.  The range in 2008 was 10.8 to 11.8 Mg ha^-1.  In 2009 grain yields ranged from 11.5 to 13.8 Mg ha^-1 with the lowest yield observed at the 157 kg N ha^-1 rate and the lowest seeding rate.  The highest yields were obtained with 246 kg N ha^-1 and a seeding rate of 86,500 plants ha^-1.   The yield increases from TR planting ranged from -4.4% to +16.8%.  In general, the TR system had 3% higher yields when averaged across all seeding rates and N rates in 2009.