On-Farm Evaluation of Nitrogen Management for Selected Corn Cultivars in a Twin-Row Production System.

Twin-row planting has been utilized for both corn and soybean production in the Mississippi Delta for wide-row (38- and 40-in) production systems.   Increasing nitrogen (N) rates and increased seeding rates have both been effective for increasing grain yields of corn under irrigated conditions.  Increased seeding rates were found to be more cost effective than increased N rates.  Also during this time, corn production has increased in Mississippi while cotton production has decreased.  Grain yields over the last two years have reached record levels (165 bu/acre in 2012 and 180 bu/acre in 2013) as cultivars are released for the area.  With the introduction of new cultivars, N management studies are needed to determine optimum recommendations for the cultivars and specifically for the twin-row production system.  Studies were setup in 2013 on producer fields to evaluate cultivars and N management.  The cultivars included six Pioneer (P) hybrids: 0912 HR, 1319 HR, 1615 HR, 1939 HR, 1745 BVT, and 2088 YHR ranging in maturity from 109 to 120 days.  These cultivars were evaluated at six N rates (120, 150, 180, 210, 240, and 270 lb N/acre) with and without pre-tassel N (PTN) applied at 40 lb N/acre.  The standard N was applied as a split applications with 120 lb N/acre applied to all plots followed by the remainder (0 to 150 lb N/acre) applied as a sidedress application.  Urea (46-0-0) was hand-applied (simulated aerial application) as each cultivar reached the VT growth stage.  All plots were harvested after field dry-down with a subsample collected to determine harvest moisture, bushel test weight and Seed Index (100-seed weight).  Yield summaries for each cultivar showed that all responded to increased N rates up to 180 to 210 lb N/acre while only the 1319 HR had a significant response to PTN.