First Year Results from Evaluation of ZINC Rates and Nitrogen Rates for Cotton and Corn in Rotation.

Over the last tens years, the Mississippi Delta has shifted from a cotton-based production system to a grain-based production system.  Grain bins replaced cotton gins and grain trucks have replaced cotton module haulers.  Greater demand has been placed on the nutrient supplying ability of the soil with greater nutrient removal in the grain crops.  Deficiency symptoms have become more evident with a much stronger need for soil testing.  The emphasis has always been placed on nitrogen (N), phosphorus (P) and potassium (K) but sulfur (S) and zinc (Zn) deficiency symptoms are starting to emerge.  Limited research results on either zinc or sulfur has been presented for the Mid-South.  The objective of this research was to evaluate N rates and Zn rates for both corn and cotton being grown in a 1:1 corn/cotton rotation.  The N rates on corn were 120, 160, 200, and 240 lb N/acre (134, 179, 224, and 269 kg N/ha) and cotton were 30, 60, 90, and 120 lb N/acre (34, 67, 101, and 134 kg N/ha).  A uniform N rate (120 lb N/acre) was applied at planting for corn with the remaining N applied as a sidedress at V5-V6.  For cotton, 30 or 60 lb N/acre was applied at planting with either 30 or 60 lb N/acre applied as a side dress application depending upon the treatment.  Zinc sulfate was dissolved in hot water and applied at rates of 0, 5, 10, or 15 lb Zn/acre (0, 5.6, 11.2, or 16.8 kg Zn/ha) with the same applicator used for N application.  The 4x4 factorial treatment arrangement placed in a RCB (5 reps) for each crop.  Plot were harvested and samples collected to determine harvest moisture, test weight, and Seed Index for corn and lint percentage in cotton.  First year results will be presented.