Impact of Planting Date On Corn Grain Yield and Ear Characteristics in Mid-South Production.

A multi-year field study was conducted from 2009 through 2012 at the Delta Research and Extension Center, Stoneville, MS on a Bosket very fine sandy loam (Mollic Hapludalfs) and Dundee silt loam (Typic Endoaqualfs) to evaluate the impact of planting date, cultivar, and nitrogen (N) rate on grain yield, test weight, seed weight, ear height and ear characteristics.  Two hybrids were evaluated each year at two N rates (202 and 269 kg ha^-1) and four planting dates (early-to mid-March and continuing on 2-week intervals).   Hybrids were planted at around 80,000 seed ha^-1 on 102-cm rows in 4-row plots with six replications.  Nitrogen applications timing was specific each planting date and year with the initial 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.  Ear samples were collected from a 4-m section of row in each plot.  Prior to ear removal, ear height was determined from the top of the bed to the base of the ear.  The number of ears, ear weight, number of rows, kernels per row, and nub or tip length.  These characteristics were determined for each ear then averaged across all ears from the harvested section.  The ear samples were then shelled and cleaned.  Subsamples were used to again determine moisture content, bushel test weight, and seed weight to compare with machine-harvested samples.  Grain yields from machine-harvested plots showed ranged from 9.08 Mg ha^-1 (145 bu/acre) to 13.46 Mg ha^-1 (215 bu/acre) depending on treatment.  Later planting generally resulted in grain yield reductions ear height increases.  Lodging and “green snap” were a problem only in the last year with the latest planting date.  Bushel test weight and seed weight tended to decrease with later planting.