Planting Date Effects for Irrigated Corn In the Mississippi Delta.

Early planting of corn generally has the crop reaching reproductive growth before the hottest and driest conditions are prevalent.  However, with cool and/or wet springs, planting and early seedling development may be delayed.  To evaluate the impact of planting date on corn production, a multi-year field study was initiated in 2009 at the Delta Research and Extension Center on a Bosket very fine sandy loam and Dundee silt loam.  Two hybrids were evaluated at two nitrogen (N) rates (202 and 269 kg ha^-1) and four 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 sidedressed application at the V5-V6 growth stage.  Yield results from 2009 showed no significant difference in planting dates with a range from 12.36 to 14.52 Mg ha^-1.  When averaged across hybrids and N rates, the yield was 13.24 to 13.38 Mg ha^-1.  In 2010, the later planting (April 26) did result in significantly lower yields when averaged across hybrid and N rate.  There was a significant response to N rate for each hybrid at each planting date.   Yields ranged from 11.35 to 13.46 Mg ha^-1 with the greatest N response occurring with the Pioneer cultivar at the earliest planting dates.  Greater than normal temperatures and below normal rainfall greatly impacted grain yields in 2011 even though irrigation was supplied.  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.