Comparison of Twin-row and Single-row Planting Patterns for Optimum Corn Production in the Mississippi Delta.

On-farm evaluations of twin-row production systems have been studied since 2005 in the Mississippi Delta with significant yield responses achieved with increasing nitrogen (N) rates and seeding rates.  Producers continue to question the comparison 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 to evaluate nitrogen (N) rates (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.  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) with N rates established at the sidedress application.  In 2007, root lodging was evident midway through the growing season and increased as seeding rates increased especially for the SR system. Little lodging was observed in 2008.  With the SR system, yields were not significantly increased with the increased seeding rates in 2007 but did increase up to 74,000 seed ha^-1 in 2008.  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.  Yield response to increasing N rate was not significant in 2007 (related to early root lodging) but was significant in 2008 up to 246 kg N ha^-1.  Irrigation plays a significant role in seeding rate response for both SR and TR corn.  Yields in 2007 and 2008 were below the potential for these soils in the Mississippi Delta.  On farm studies have shown higher yield potential for the same soils.