The relationship between nutrient uptake and root growth of cotton (Gossypium hirsutum) under field conditions has not been studied. This field study was conducted to evaluate cotton root growth and nutrient influx by cotton roots throughout the growing season. The study was conducted in 1994 on a long-term K rate study located on a Dewey silt loam (clayey, kaolinitic thermic Typic Paleudult) in North Alabama. The experiment had a randomized complete block design with 4 replications All measurements were taken from the 4 replicated field plots of a treatment that had received annual applications of 60 lb K₂O/acre since 1987. Whole plants were harvested (by plot) at approximately 10 day intervals beginning at 37 days after planting (cumulative heat units (CHU) = 211). A total of 9 samplings were collected during the 1994 growing season. Harvested plants were analyzed for dry matter production and nutrient (N, S, K, P, Ca, Mn, Cu, Fe, Mn and Zn) content. At each sampling, a total of 5 soil cores were collected per plot for the determination of root length. The first core was take directly over the plant and a second core was taken in-row half way between the next adjacent plant. Three additional cores were collected perpendicular to the row at distances of 5, 10 and 20 inches from the in-row position. Each core was subdivided into depth increments of 0-6, 6-12, 12-18 and 18-24 inches prior to the collection of roots by washing. Nutrient uptake data were combined with the root length data to calculate average nutrient influx rates (µmol/meter of root/day) for each sampling interval using the Williams equation.