EFFECTS OF DELAYED HARVEST, CULTIVAR, AND BOLL TYPE ON WEATHERING DAMAGE TO YIELD-RELATED TRAITS AND FIBER QUALITY IN UPLAND COTTON

Scope of Study. The purpose of this research was to investigate the effects of delayed harvest, cultivar, and boll type on field deterioration of (i.e., weathering damage to) yield-related traits and fiber quality in upland cotton (Gossypium hirsutum L.). Four stormproof, four storm resistant, and four open-boll cultivars were utilized in this study over 3 years at a single location. Each year when plant growth had totally ceased, random samples of 15 mature bolls were taken from each plot at approximately 2-week intervals. Seven traits associated with yield and six fiber quality characteristics were studied using analyses of variance and regression techniques.;Findings and Conclusions. In most cases, cultivars having the same boll type displayed similar trends for weathering effects on traits associated with yield and fiber quality. Interactions of boll type with duration of pre-harvest weathering were significant in approximately half the possible instances, indicating that trends were frequently different among the three boll types studied. All yield-related traits were reduced by delayed harvests in at least 2 of the 3 years. Adverse effects of weathering on most traits were more serious in open-boll cultivars than in the other two boll types, especially when compared to the stormproof cultivars. Storm resistant cultivars generally displayed intermediate responses between the open-boll and stormproof types, but did not differ significantly from the stormproof types for any yield-related trait in any year. Significant differences between storm resistant and open-boll types were occasionally detected. The three boll types did not differ in the rates at which their lint and seed indexes were reduced by weathering. All fiber quality traits were reduced by delayed harvests in at least 2 of the 3 years. Differences in weathering trends among boll types were not as consistent for fiber quality as they were for the yield-related traits. Significant differences among boll types for such trends were not detected for 2.5% span length, micronaire, or T(,1) fiber strength. In one year, storm resistant and open-boll types lost uniformity index more rapidly than did stormproof cultivars. In another year, open boll cultivars suffered 50% span length reductions more rapidly than the other two; and open-boll cultivars lost T(,0) fiber strength more quickly than did the storm resistant types. The amounts of loss in each character that can be expected for each 2-week delay in harvest are provided for each boll type in this paper.