The COTMAN decision-aid system predicts crop maturity based on heat-unit accumulation after the last effective bloom stage of cotton. However, remote sensing of spectral reflectance from the crop canopy may also indicate crop condition and progress towards maturity. Research was conducted at Jackson, Tennessee in 2005 and 2006, to determine the relationship between normalized difference vegetative index (NDVI) and COTMAN heat-unit data for monitoring crop maturity. The study was conducted in long-term no-till plots of winter cover crop (wheat, vetch, and no cover) and nitrogen fertilization (ranging from 0 to 90 lb N/ac/yr), applied at cotton planting. For COTMAN, data on nodes above white flower (NAWF) were collected during flowering, and heat-unit accumulation was calculated from local weather station data. Canopy NDVI data were collected weekly, using a hand-held sensor suspended above the canopy. Maturity differences between treatments were detected in both NDVI and COTMAN data, as N deficiency reduced both NAWF and NDVI earlier than with sufficient N. Canopy NDVI closely tracked with NAWF in treatments that differed in cutout due to N and cover crop residue. Results indicate that ground-based NDVI may provide data on the progress of crop maturity that may be useful in the future development of the COTMAN decision-aid system.