Single-Row Vs Twin-Row Corn Production - Seeding Rates and Nitrogen Rates.

Twin-row corn production has been utilized by grain producers in the Mississippi Delta for several years with significant yield responses obtained with increased seeding rates and higher nitrogen (N) applications.  Twin-row (TR) planting and single-row (SR) planting on wide rows (102 cm) have been evaluated in a multi-year project that was initiated in 2009 to evaluate four N rates (157, 202, 246, and 291 kg N ha^-1) and four seeding rates (61,775 to 98,840 seeds ha^-1).  The study was planted on Bosket very fine sandy loam (Mollic hapludalfs), following soybean, with a MonosemJ twin-row vacuum planter and a John Deere 7300 vacuum planter.   Uniform preplant N (112 kg N ha^-1) was applied as urea-ammonium nitrate solution (32% N) with the actual N rates established at the time of sidedress N application.   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.  The study was rotated to an adjacent field and followed soybean in 2010.  There was no difference between the SR and TR systems when averaged across N rates and seeding rates.  The optimum planting rate was around 85,000 plants ha^-1 with no response to N rates above 202 kg N ha^-1.  The study was rotated to the original location and again followed soybean in 2011 with similar results as previous years.  One limiting factor appears to be irrigation and/or rainfall.  With the TR system, irrigation is required for each row with initiation early enough to insure good pollination.