While cotton remains the crop of choice on the sandier soils of the Mississippi Delta, corn has increased significantly in the last ten years. Production from the areas harvested has exceeded 8.3 Mg ha-1 each of the last three years. Most corn has been rotated with cotton to enhance cotton production potential. In an effort to optimize corn production, nitrogen (N) and potassium (K) rate studies were initiated on different soil types.. In one series of studies, a 5x4 factorial arrangement of N rates (134, 179, 224, 269, and 314 kg N ha-1) and K rates (0, 45, 90, and 134 kg K ha-1) have been evaluated for six years with corn following two years of cotton. An additional study was initiated in 2004 to examine higher N rates (up to 336 kg N ha-1) with varying K rates. The first studies were located on a Bosket very fine sandy loam (Mollic Hapludalfs) at the Delta Research and Extension Center (DREC) and on a Forestdale/Dundee silty clay loam (Typic Ochraqualfs/Aeric Ochraqualfs). No significant N x K interaction has found at either location and no significant response to K additions in most years. A significant N response has been measured across the years with optimum yields achieved with varying N rates. At DREC yield response was significant up to 224 kg N ha-1 in most years, with 314 kg N ha-1 needed in 2004 to optimize yield. In five of six years, 269 kg N ha-1 was needed to produce optimum yields. In the second study, corn yields were optimized with 235 to 269 kg N ha-1 the first year with yields ranging from 9.6 to 10.4 Mg ha-1. The 2005 yields were much higher ranging from 12.3 to 13.0 Mg ha-1, but little response to increasing N rates.