Much interest has been shown by tobacco growers during recent months in fertilization and or other management practices that can be used to produce darker and redder cured leaf of burley tobacco. The purpose of this newsletter is to summarize what we know about some of the factors which affect color of cured leaf

Palmer, Gary K.

Sims, J. L.

Wells, Kenneth L.

English

University of Kentucky

University of KentuckyUKnowledgeSoil Science News and Views Plant and Soil Sciences1993Factors Affecting Color of Cured Burley LeafJ. L. SimsUniversity of KentuckyGary K. PalmerUniversity of Kentucky, gary.palmer@uky.eduKenneth L. WellsUniversity of KentuckyRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/pss_viewsPart of the Soil Science CommonsThis Report is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in Soil ScienceNews and Views by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu.Repository CitationSims, J. L.; Palmer, Gary K.; and Wells, Kenneth L., "Factors Affecting Color of Cured Burley Leaf " (1993). Soil Science News andViews. 105.https://uknowledge.uky.edu/pss_views/105UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE Lexington, KY 40546--0064 ---- - ---- --. --COOPERATIVE EXTENSION SERVICE Department of Agronomy Soil Science News & Views Vol. 14, No. 2, 1993 FACTORS AFFECTING COLOR OF CURED BURLEY LEAF J.L. Sims, G.K. Palmer and K.L. Wells Much interest has been shown by tobacco growers during re-cent months in fertilization and or other management practices that can be used to produce darker and redder cured leaf of burley tobacco. The purpose of this newsletter is to summarize what we know about some of the factors which affect color of cured leaf. Curing Season Characteristics It is our opinion that the nature of the curing season exerts the most influence on color of cured leaf. Weather patterns that are dry and cool during curing, will result in more variegated or light colored cured leaf. Also, if the curing season is dry, there will be more green coloration. In contrast, when the curing sea-son is warm and moist, colors are likely to be dark and some-what more uniform. Although weather patterns are beyond one's control, curing conditions inside the barn can be improved by managing airflow with the use of ventilators and fans to move air through the tobacco during high humidity periods, and to restrict airflow during very dry periods. Supplemental heat can be used to lower hu-midity levels, improve curing, and prevent houseburn during extremely humid periods. Nitrogen Content of the Leaf In general, tobacco containing high concentrations of nitrogen will cure a darker color. Several factors can influence leaf content of nitrogen: ·Nitrogen fertilizer rates. Research has shown a relationship between increased rates of nitrogen and increased presence of dark colors. However, use of excessive rates above those recommended will like-ly cause green tobacco at maturity and increase leaching losses of ni-trogen. ·Time of topping (early topping is likely to lead to a higher leaf content of nitrogen, and conse-quently, to darker colors). • Stalk position of the leaf (up-per leaves contain higher amounts of total nitrogen, and thereby cure darker). Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, handicap, or national origin. UNJVERSITY OF KENTUCKY, KENTUCKY STATE UNIVERSITY, U.S. DEPARTMENT OF AGRICULlURE, AND KENlUCKY COUNTIES, COOPERATING Soil Science News & Views • Use of molybdenum in setter water (molybdenum aids in nitrogen nutrition of the plant and reduces the nitrate nitrogen content of the leaf, thereby increasing the likelihood for darker leaf colors). Potassium Rates and Sources Recommended rates of potas-sium fertilizer are more likely to result in burley leaf with high Federal grades and good burn-ing characteristics. When ap-plied in the spring, sulfate of potash produces leaf of higher quality and of more uniform color than muriate of potash. Muriate of potash applied in the · spring is almost sure to lead to a high percentage ofM (mixed color as opposed to the other "M" mixed grades) and K (var-iegated) grades. If muriate of potash is used, it should be ap-plied before January 1 of the crop year. Variety Grown Varieties may differ signifi-cantly in the style, color, and appearance of tobacco that is produced. Many factors can influence the color and quality of cured leaf produced from a specific variety. However, some varieties have a tendency to pro-duce red, heavy bodied leaf and others may produce more light, thin bodied leaf. Many of the varieties that have been intro-duced recently were developed prior to the current shift in mar-ket preference for darker leaf. However, some varieties like R 610, R 141, Hybrid 403, KY 14 X Burley 64, and N 88 have a tendency to produce the type of cured leaf that is preferred by buyers. Although use ofR 610 has some other disadvantages, it is more likely to maintain higher quality than many other varieties. Many varieties have a tendency to be light colored when cured. Some may produce a "flashy" colored tobacco. The variety TN 86 is an example of a variety that often cures to produce more mixed color (M) and K grades than those mentioned above. It became popular due to superior disease resistance and a general lack of concern for quality (almost all burley leaf sold for the same price) soon after its release in 1986. Although TN 86 was used to transplant 15% of the 1992 crop, preliminary sales for 1993 indicate that its popularity has declined significantly. TN 90 has comparable disease Page2 resistance to TN 86, and preliminary evaluations indicate that the cured leaf color will be redder. Several of the new hybrid varieties have TN 86 as a parent and others have TN 86 in their breeding history. While not all of these varieties have been fully tested for quality, some do pro-duce a light colored tobacco similar to that seen in TN 86. NC BH129 tends to be bright colored, but the off-colored characteristics seen in TN 86 are not common. Some other varieties tend to possess colors that are not con-sidered favorable on the burley market. Cured leaves of Hybrid 501 tend to have light tan color, while R 7-11 leaves often have pink color. Although some do-mestic companies will buy to-bacco with a pink color, others including those buying for the export market, prefer not to buy it. The pink color has been as-sociated with high nitrosamine levels in some studies. R 7-11 is a good yielding variety, but the tendency to cure pink has hurt its popularity. A dark color after curing is not always considered good quality. Many producers changed back to old varieties in an attempt to achieve a dark Soil Science News & Views color. Varieties like KY 9, KY 10, and Burley 21 X KY 9 were selected by producers due to the dark color traditionally as-sociated with the cured leaves of these varieties. University tests which included these vari-eties confirmed that they pro-duced a dark colored tobacco. However, in the cases of KY 9 and Burley 21 X KY 9, the dark color was associated with other characteristics that resulted in a low Federal grade. In addition to poor quality, the yield and disease resistance of both vari-eties were lower than new and commonly used varieties. To achieve the desired quality, the tobacco must have a uniform tannish-red color. Timing of Topping Regardless of the variety grown, topping at the right stage of plant development can improve color. Even varieties that have a tendency to be light in color will produce a redder tobacco if topped at a 10 to 25% bloom stage. Many of the new varieties have different management requirements than older varieties for the production of high quality leaf. Late maturing varieties like TN 86 and KY 8959 respond favorably to topping when plants are in the ... - ---------~-- -----------------elongated bud stage. All other varieties should be topped when no more than 25% of the plants have one flower open. Although there are many reasons for topping at 10 to 25% bloom, topping at the proper time is essential for improving the color of varieties like TN 86, KY 8959, NC BH129, Hybrid 501, and R7-11. Growing Season Climate Cooler than normal growing seasons may result in more ammonium nitrogen in the root zone and less nitrate nitrogen than normal. This can result in a greater uptake of ammonium ni-trogen that could likely darken leaf color. Growing seasons with above normal rainfall may lead to leaching of soil nitrogen and result in leaf oflighter color. Summary There is not a lot of scientific evidence regarding factors that can be managed to predictably result in dark and red colors in cured burley leaf. Evidence available indicates that management to increase plant nitrogen content will result in darker colors, whereas excessive potassium content Page 3 may result in somewhat lighter colors. Spring applications of muriate of potash are not recommended. Variety and time of topping can both affect color. While all these factors can have effects, climatic conditions during curing are likely to have the greatest effect on cured leaf color. Growers should note that color is only one factor of leaf quality which graders and buy-ers assess. Leaf size, finish, body (thickness), stalk position, soundness, odors, and foreign matter are also taken into ac-count. Producers should at-tempt to grow high yielding varieties and manage them to produce high quality leaf in or-der to attain maximum returns. COOPERATIVE EXTENSION SERVICE U.S. DEPARTMENT OF AGRICULTURE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE LEXINGTON, KENTUCKY 40546 OFFICIAL BUSINESS . PENALTY FOR PRIVATE USE, $300 AN EQUAL OPPORTUNITY EMPLOYER BULK RATE POSTAGE & FEES PAID USDA PERMIT No. G268 

Factors Affecting Color of Cured Burley Leaf

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Factors Affecting Color of Cured Burley Leaf

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