Enhancing US Cotton Classing with Varietal Data

Cotton quality is determined by many fiber properties. Two properties which participate to form a good prediction of yarn quality are Maturity Ratio (MR) and Standard Fineness (H_s).  MR is derived from theta Θ (Θ/0.577).  Theta is defined as the ratio of the secondary cell wall area of the cotton fiber to the area of a circle having the same diameter. H_s is an indirect measurement closely related to the diameter of the fiber derived from gravimetric fineness (H) and MR.  These properties are not currently measured independently in a commercial setting, as the USDA standard is Micronaire (MIC).  MIC is a combined measure of MR and H_s and cannot be separated into its components without additional measurements.  In a previous study, we found that since the H_s of a fiber is largely determined by genetics and less by growing conditions, we could infer the MR of a cotton using its MIC and variety via the Lord Micronaire Eq. if we first established a varietal H_s using the Uster AFIS.  We compared AFIS measured MR to inferred MR using varietal H_s for 889 samples taken in 2016 we calculated an R² of 0.87. To apply this method to a commercial program we would need to answer two main questions: How many samples would be required to establish a varietal H_s for any given variety, and would the varietal H_s remain stable for successive growing seasons?  We found that 105 randomly selected representative samples of a given variety would likely be enough to estimate varietal H_s with a high degree of accuracy (H_s ± 1.)  However, the varietal H_s does not appear to be stable between growing seasons and could cause problems with inferring varietal H_s.  The source of this variation in H_s is not currently known and requires further investigation.