Considerable soil variation occurs within and across cotton production fields in the Southeastern United States which results in the development of cotton plants with a tremendous amount of growth variability associated with them. Blanket applications of PGR based on a constant rate often results in the application of chemical to areas of a field that may not require treatment and as a result, may decrease yields. Likewise, insufficient application may also decrease yields in excessively leafy areas. The objectives of this study were to investigate the feasibility of site-specific application of plant growth regulators (PGR) and harvest aids (HA) based on soil electrical conductivity (EC) data and plant Normalized Difference Vegetation Index (NDVI) measured utilizing airborne three-band multi-spectral imagery and sprayer-mounted GreenSeeker mapping system. An inexpensive variable-rate application delivery system for PGR and HA was developed and retrofitted to an existing spraying equipment. The production field was divided into three management zones based on EC and NDVI data. There were no differences in PGR requirements between two cotton varieties (DP 555 and DP 455). The variable-rate application required %40 less PGR compared to uniform-rate applications. There were strong correlations between the EC and NDVI measurements with the plant parameters such as plant height and internode spacing.