Pre-Tasseling Nitrogen Applications In Mid-South Corn Production Systems.

Most nitrogen (N) applications for corn production in the Mid-south occur from up to 3-4 weeks prior to planting through the V4 to V5 stage of growth.  In some instances, the N is applied in a single application but more often, N is applied just prior to planting with a second application prior to the V5 growth stage.    It is important to have adequate moisture and nutrient supplies for rapid plant growth that would indicate the need for early application of nutrients.  Many producers continue to question the possibility of additional N applications over the top of the crop using aircraft for application and irrigation or rainfall for incorporation.  A study was established in 2009 to evaluate the use of pre-tassel N (PTN) as a means of increasing corn yields.  Five N rates were established (134 to 314 kg ha^-1 in 34-kg ha^-1 increments) with 134 kg N ha-1 applied prior to planting and the remaining N applied at the V4 to V5 stage.  The PTN treatments were applied at rates of 0, 22, or 45 kg N ha^-1.  Urea was hand-applied followed by irrigation to assure incorporation.  In both 2009 and 2010, there was significant response to N rates and to PTN.  In 2009, corn yields ranged from 3.78 to 11.06 Mg ha-1 with the highest yields observed where the highest N rates were applied.  The PTN applications increased grain yields by 1.60 to 2.16 Mg ha^-1 when averaged across the five N rates initially established.  In 2010, the highest yield was obtained with 269 kg N ha^-1 when average across the PTN rates.  Actual yields ranged from 8.58 to 14.18 Mg ha^-1.  When averaged across all N rates, adding 22 to 45 kg N ha^-1 significantly increased grain yields by 0.75 to 1.13 Mg ha^-1.