ABSTRACT

Potassium requirements for high yielding early season cotton varieties are not well established. With the adoption of early maturing cotton cultivars, efficiency of rates and methods of K fertilization should be reevaluated. Field experiments were conducted on an alluvial Morganfield silt loam soil to determine the effect of K rate and methods of application on cotton lint yield, nutrition, and soil test levels. Treatments were 0, 60, 120, and 180 lb K/acre broadcast with 0 banded; 30, 60, and 90 lb K/acre banded with 0 broadcast; and 60-30, 60-60, 120-30, and 120-60 broadcast-band combinations. All fertilizer treatments were applied prior to planting and the source was KCl. Lint yield, leaf and petiole K concentration (at early bloom), and extractable soil K were measured. Overall, lint yield responded quadratically to K rate with a predicted maximum yield of 1179 lb lint/acre at 156 lb K/acre. Due to what appears to be a synergistic response, the highest average yield was 1280 lb lint/acre with the 120-30 broadcast-band combination treatment. Potassium concentration in leaves and petioles was significantly influenced by K application in all years. Although petiole K had a stronger relationship than leaf blade K with soil test K, the relationship between lint yield and leaf blade K was stronger than for petiole K. Soil extractable K significantly increased in a linear fashion to broadcast K rates.