Assessing the quality of Burley tobacco. Part 1 : Grade index and associated factors
This study determined an average yearly grade index (GID) from sales data for Burley tobacco for the years 1959-1990. This index was used as a quality measure for each crop year. Several leaf-group, leaf-color, and seasonal-crop variables were significantly correlated with GID. Within the leaf groups, the leaf and lugs categories had a positive effect on GID, while tips, nondescript, and a combined group (TNM) had negative correlations. A tradeoff existed between these leaf groups in relation to the grade index. For the color groups, the tan groups within the lugs and leaf categories (CF, BF) and the tannish-red leaf group (BFR) had significant positive correlations with GID, while green color in the leaf, tips, and flyings groups had significant negative correlations with GID. Total crop production area had a significant negative correlation with GID, while it was positively correlated with the undesirable leaf groups of tips, nondescript, and TNM. This indicated that market quality was reduced when production area increased. The significantly correlated variables were used to develop a regression equation to predict GID. The equation had a regression coefficient of 0.935, and it predicted GID reasonably well for the 32-year period.