Nitrogen Rate By Cultivar Interactions in Single-Row and Twin-Row Corn Production in the Midsouth.

Twin-row corn production has been used effectively in the Mid-South for corn production in a wide-row (102-cm) bedded production system.  Equipment companies have made the shift to twin-row (TR) equipment while research over the last decade has shown a yield response with increased seeding rates in the twin-row (TR) system compared to the single-row (SR) production system.  Increased nitrogen (N) rates have also been used to increase yields with varied responses depending on the cultivar selected.  Four N rates (157, 202, 246, and 291 kg N ha^-1) and four cultivars (Pioneer 1319 HR, Pioneer 1739 HR, Pioneer 1745 HR and Pioneer 2088 YHR) were evaluated in TR and SR planting systems with five replications.  Previous research at the Delta Research and Extension Center and on producer fields has shown that significant yield increases could be obtained by increased seeding rates in the TR planting system.  Therefore, for this study, the SR corn was planted at 80.3 K seed ha^-1 (32,500 seed/acre) with a John Deere Vacuum Planter while the TR was seeded at 92.6 K seed ha^-1 (37,500 seed/acre) with a Monosem Twin-row Plus, both on 102-cm beds.  In 2013, the entire field average 15.4 Mg ha^-1 (245.6 bu/acre) with yields ranging from 13.6 (216.4 bu/acre) to 16.6 Mg ha^-1 (263.9 bu/acre).  When averaged across all other treatment combinations, there was a significant yield increase with increasing N rates up to 246 Kg N ha^-1.  Some cultivar differences were observed as expected.  Both bushel test weight and seed index (seed weight) were significantly affected by treatments.  The 2014 plot data from this study will be included but were not available at writing.  On-farm evaluations of various cultivars in 2013 showed a significant response to increasing N rates across the cultivars with optimum yields achieved with 269 kg N ha^-1.