Changes in spectral reflectance from the cotton canopy may indicate progress towards crop maturity.  Research was conducted  at Jackson, Tennessee, to determine the relationship between normalized difference vegetation index (NDVI) and crop maturity. Small plots fertilized with 0, 60, 120, and 180 lb K₂O/ac/yr were planted to cotton in 2006 and 2007.  Canopy NDVI data were collected periodically after first bloom, using an active hand-held sensor suspended above the canopy and aligned with the rows.  Values of NDVI were calculated as the difference between red and infrared reflectance, divided by the sum of red and infrared reflectance.  Earliness of maturity was measured as the percent of total yield picked at the first of two harvests.  The relationship between NDVI values and crop maturity differences is analyzed.