ABSTRACT

The new fast fruiting cotton (Gossypium hirsutumn L.)cultivars may have a higher nutrient requirement than the older cultivars. When planting these cultivars, many growers apply additional K and micronutrients to ensure a good crop, even when the soil test does not indicate the need for supplemental fertilization. A two-year field study was conducted to evaluate the effects of rate and timing of K fertilizer, alone or in combination with Cu, Zn, and Mn, on cotton yield, fiber quality, and petiole nutrients on a Calloway silt loam with high levels of Mehlich-3 (M-3) extractable K, Zn, Mn, and a medium level of extractable Cu. The effects of K and micronutrients on soil properties were also investigated after one cropping season. Treatments consisted of 100-400 lb/A of K₂O alone or in combination with 2, 2, or 5 lb/A of Cu, Mn, or Zn respectively. The experimental treatments were applied in spring 2002 only. Their immediate effect on cotton growth and fiber quality was evaluated in 2002 and their residual effects were evaluated in 2003. Application of K and micronutrients did not have any significant effect on cotton lint yield in either year. Concentrations of K in petiole samples collected during the 5^th week of flowering in both years was above the critical K levels regardless of K application. Lint quality was not affected by K or micronutrient application. Application of K fertilizer significantly increased M-3 extractable K in the 0-6” but not in the 6-12” depth. However Cu, Zn, and Mn in the 0-6” and 6-12” depth increments were not affected by application of these micronutrients.