Optimizing Timing of Chemical Harvest Aid Application in Cotton by Predicting Its Influence on Fiber Quality

To optimize yield and fiber quality, boll cutting is used by cotton (Gossypium hirsutum L.) managers to determine when crops are mature and ready for chemical harvest aid application. While it is accepted that the maturity of bolls is defined using seed coat color, we found no investigations of this definition on overall crop fiber quality. Three field experiments were undertaken in different seasons that systematically varied the timing of harvest aid application to vary the amount of immature, mature, and open bolls to assess (i) fiber quality of open, mature, and immature bolls; (ii) the variation that exists within and across seasons; and (iii) if quality at the time of harvest aid application of immature, mature, and open bolls is related to final micronaire. Within seasons, quality varied by up to 1.06 to 1.53 for micronaire, 0.13 to 0.14 for maturity ratio, and 28.2 to 30.7 mu g m(-1) for linear density among immature, mature, and open bolls. When data were combined across all seasons relationships were developed that predicted micronaire at harvest using micronaire (r(2) > 0.73) and its components together (maturity and linear density) (r(2) > 0.81) of the immature bolls measured at harvest aid application. Relationships were improved when percent open bolls was included as a factor in the regressions (r(2) > 0.88). The ability to estimate harvest aid timing influences on micronaire may help avoid discounts. This concept requires more testing with multiple cultivars and would be enhanced with access to reliable and simple methods to measure quality of small field samples.