Site-specific strategies for cotton management

The use of site-specific data can enhance management decisions in the field. Three different uses of site-specific data were evaluated and their outcomes are promising. Historical yield data from yield monitors and height data from the HMAP (plant height mapping) system were used to select representative areas within the field, and areas of average conditions were used as sampling sites for COTMAN, a cotton management expert system. This proved to be effective, with predicted cutout dates and date of peak nodal development similar to the standard COTMAN approach. The HMAP system was combined with historical height data for variable rate application of mepiquat chloride, based on the plant growth rate. The system performance was evaluated, but weather conditions in 2004 did not allow a true evaluation of varying mepiquat chloride. A series of multi-spectral images were normalized utilizing the soil line transformation (SLT) technique and normalized difference vegetation index (NDVI) was calculated from the transformed images, from the raw image and for the true reflectance images. The SLT technique was effective in tracking the change in true reflectance NDVI in some images, but not all. Changes to the soil line extraction program are suggested so that it more effectively determines soil lines