Potassium Nutrition Effects on Lint Yield and Fiber Quality of Acala Cotton

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Abstract
Although results from in vitro ovule culture studies have demonstrated a specific K requirement for fiber growth, a direct association between the K status of the cotton (Gossypium hirsutum L.) plant and fiber quality has not been established under field conditions. To evaluate this relationship, a single cultivar (1985) and two cultivars (1986 and 1987) were grown with 0, 120, 240, or 480 kg K ha‐1 in 10 blocked replicates of each K level on an irrigated, vermiculitic soil. There was a significant seed‐cotton yield response to applied K in each year. Lint yield, however, increased relatively more than seed yield, resulting in a greater lint percentage as plant K supply increased. The greater lint percentage reflected increased fiber length and secondary wall thickness (measured as a micronaire index) obtained from plants that received fertilizer K. For both cultivars, the fiber length, micronaire index, fiber strength and percent elongation, and fiber length uniformity ratio (dependent variables) were each positively related to (i) fiber K concentration at maturity, (ii) leaf K concentration at early bloom, and (iii) an index of soil K availability as independent variables in regression analyses. Comparison of cultivar regressions, however, indicated that fiber quality of ‘Acala GC510’ was higher than that of ‘Acala SJ2’ at low fiber, leaf, or soil K levels. We conclude that K supply to cotton fruit is an important determinant of fiber quality under field conditions, and that the K requirement for producing high lint yield with acceptable quality may differ among genotypes.