Influence of Early Planting On Irrigated Mid-South Corn Production.

To evaluate the impact of early planting on corn production, a multi-year field study was initiated in 2009 at the Delta Research and Extension Center, Stoneville, MS on a Bosket very fine sandy loam (Mollic Hapludalfs) and Dundee silt loam (Typic Endoaqualfs).  Two hybrids were evaluated each year 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 limited.   Hybrids were seeded at about 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 first application (134 kg n ha^-1) at planting and the remainder (67 or 134 kg N ha^-1) applied as a sidedressed band at the V5-V6 growth stage.  Grain yields in from 2009 showed no significant difference in planting dates with a range from 12.35 to 14.52 Mg ha^-1.  When averaged across hybrids and N rates, the yield was 13.25 to 13.38 Mg ha^-1.  In 2010, the last planting (April 26) resulted 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.  Greater than normal temperatures and below normal rainfall greatly impacted grain yields in 2011 even though irrigation was supplied (9.08 to 12.21 Mg ha^-1).  The last planting date (April 14) produced yields that were 11-19% lower than the earlier plantings.  Temperature and soil moisture have been the largest contributing factor to the variations between years.  Early planting generally leads to greater yields with less potential environmental stress while later planting increases plant-related stresses and decreases yield.  The study concludes in 2012 with results to be included.