Foliar applications of KNO ₃ following Mepiquat Chloride were evaluated in 1998-2000 for effect on cotton yield and fiber quality to test the hypothesis that earlier maturing cotton with a shorter fruiting window should have a higher demand for K. Treatments were (1) an untreated control, (2) foliar KNO ₃ (11.2 kg/ha) at 1,2,3, and 4 weeks after first flower, (3) Mepiquat Chloride at pinhead square (0.438 L/ha) and first flower (0.876 L/ha), and (4) foliar KNO ₃ + Mepiquat Chloride (treatments 2 and 3 combined). Lint yield tended to respond best to PIX used in combination with foliar KNO ₃ in two out of three years. Mepiquat Chloride used alone or in combination with K generally decreased plant height. In two out of three seasons, uniformity and strength were slightly improved by use of PIX in combination with KNO ₃ as compared to KNO3 alone. High soil K levels and extreme hot, dry conditions during the peak boll development stage appeared to reduce contributions to lint yield and quality by the use of foliar KNO ₃ following PIX in these studies. Therefore, growers of irrigated cotton should closely monitor soil fertility levels and weather conditions during the growing season in order to insure discriminate use of PIX in combination with KNO ₃ for maximum lint yield and fiber quality.