Effects of Rate and Time of Potassium Application on Cotton Yield and Quality in Turkey

Studies were conducted at Adana, in the Cukurova region of southern Turkey, to evaluate the effects of the rate and timing of application of soil-applied potassium (K) on cotton (Gossypium hirsutum L.) in 1999 and 2000. Potassium rates of 0, 80, 160 and 240 kg K 2 O ha -1 were soil-applied in single treatments (all at early boll development) or in split treatments (1/2 at first square and 1/2 at first white flower; 1/4 at first square. 1/4 at first white flower and 1/2 at early boll development). Data collected in the two years indicated that application of 160 kg K 2 O ha -1 produced significant differences in seed-cotton yield. lint yield and boll weight compared with the untreated control. The best combination producing the greatest yield was application of 160 kg K 2 O ha -1 with all of the K soil-applied at early boll development. Cotton yields did not respond to K fertilization above the rate of 160 kg K 2 O -ha -1 under the production practices typically found in the region. For application of K at a rate of 240 kg K 2 O ha -1 there was a marked difference in fibre strength between years in this study, but micronaire and uniformity ratio were not different amongst K rates within each year. When the total amount of K was applied at early boll development, higher yields, boll weights and lint turnouts were obtained compared with split applications, but the single application did not have a large impact on fibre properties.