Variable Rate Cotton Fertilization Development in the Coastal Plain.

Previous research has shown that cotton yields can vary across the landscape based on the management system utilized; however, typical N fertilizer rates for cotton are applied uniformly across the field.  The relationship is complicated by how cotton responds to different amounts of N, particularly excess N.  Sensor technology previously utilized in other crops can potentially quantify the N status of cotton and relate sensor output to an N recommendation that will vary across the field and simultaneously improve cotton yields and profitability.  An experimental site was established in a 9 ha. field in the Coastal Plain consisting of Typic and Aquic Paleudults that had management systems in place for 9 years.  A split plot design was utilized with main plots consisting of two soil management systems (conventional-CT and conservation-NT) and split plots of 4 N rates (0, 44, 90, 134 kg/ha) with six replications of 3.7-m. strip-transects (4-row widths) across the field that intersect management zones.  At pre-determined sampling points (3.7 x 18.3 m grids stratified within each management zone) 25 upper most mature leaves will be collected along with SPAD meter readings, plant heights, sensor measurements, and 1 m of whole plant biomass from the same pre-determined locations across landscape positions around 1^st square and mid-bloom.  Seed cotton yield will be determined across the field with a combine equipped with GPS and yield monitor.