AGRONOMY & SOILS Potassium Fertilization of Conventional- and No-Till Cotton

Potassium fertilization of the fast-fruiting cotton (Gossypium hirsutum L.) cultivars requires fertilizer information on soils with varying extractable K levels, tillage practices, and K rates. In 1991, research was established to evaluate both foliar- and soil-applied K for conventional- and no-till cotton production on three soils. After 4 yr, the initial objectives were changed, eliminating the foliar evaluations and increasing the number of soil-applied K rates to seven. The effects of soil-applied K rates on extractable leaf and petiole K concentrations and Mehlich-I extractable K levels were evaluated. Field research was conducted between 1995 and 1997 on low extractable K Memphis silt loam (Typic Hapludalfs), high extractable K Lexington silt loam (Ultic Hapludalfs), and high extractable K Loring silt loam (Oxyaquic Fragiudalfs). Both conventional-till and no-till production systems were evaluated on the Memphis silt loam, while no-till production was evaluated on the Lexington and Loring silt loam soils. Evaluations of conventional-till fertilization of the Memphis silt loam and of no-till fertilization of the Loring silt loam were discontinued after 1997. Initially the Mehlich-I extractable K levels were 90 and 80 lb K acre$1 in the 0- to 6-inch soil layer of the Memphis silt loam conventional- and no-till systems, respectively. Extractable K was 201 lb K acre$1 for the Loring silt loam and was 179 lb K acre$1 for the Lexington silt loam. The experimental design was a randomized complete block. Treatments included broadcasting potassium chloride (KCl) at 0, 30, 60