Influence of Planting Date on Corn Yield In the Mississippi Delta.

Corn plantings have continued to increase in the last few years in the Mississippi Delta with nearly 380,000 ha planted in 2007.  Early planting has been shown to improve soybean yield across the Mid-south and has been a preferred practice for many corn producers when weather permits.  In order to assess the impact of planting date on grain yield and various plant and ear characteristics, a multi-year study was initiated in 2009 at the Delta Research and Extension Center near Stoneville, MS on a Bosket very fine sandy loam (Mollic hapludalfs) and Dundee silt loam (Typic Endoaqualfs).  Two corn hybrids were used at two nitrogen (N) rates (202 and 269 kg ha^-1) and four planting dates beginning in 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.  Nitrogen applications were specific for each planting date with the initial application (134 kg n ha^-1) applied at or near planting and the remainder (67 or 134 kg N ha^-1) applied as a sidedress.  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 two planting dates.  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.