Planting Date Effects On Grain Yield, Ear Height and Ear Characteristics of Irrigated Corn in the Mississippi Delta.

The first step in successful corn production in the Midsouth is getting the crop planted.  The window of opportunity can run from late February into June but most producers target planting from early March through April.  Early planting of corn generally has the crop reaching reproductive growth before the hottest and driest conditions are prevalent but early planting can lead to slow seedling development and delays.  A multi-year field study was conducted (2009-2012) at the Delta Research and Extension Center to hybrids, nitrogen (N) rates (202 and 269 kg ha^-1) and planting dates (early-to mid-March and continuing on 2-week intervals) as weather permitted.   The hybrids were seeded at around 80,000 seed ha^-1 on 102-cm rows in 4-row plots with six replications.  Nitrogen applications were managed for each planting date with the initial application (134 kg n ha^-1) at or near planting and the remainder (67 or 134 kg N ha^-1) applied as a sidedress at the V5-V6 growth stage.  Yield results from 2009 showed no significant difference in planting dates while 2010 and 2011 resulted in significantly lower yields with a late-April planting.  Temperature and soil moisture have been the largest contributing factor to the variations between years.  Earlier planting tends to favor greater yields with less potential environmental stress while later planting increase plant-related stresses and decrease yield.  In order to assess plant difference due to planting date, ear height and ear characteristics have been evaluated to determine what may be affected by planting dates.  Ear length, row number, nub-back, and other measurements have been made on ear samples collected at harvest.  Ear height has been shown to increase as planting date moves later into the season.  As the ear height goes up, the potential for lodging is also increased.  More irrigations can also be required.