Burley Tobacco Curing Update

1. Burley Tobacco Curing Update Paul Denton, Bob Pearce and Andy Bailey

2. Factors that Control Leaf Quality • Overall Curing Season • Time of Harvest and Housing within the Season • Variety

3. Factors Affecting Quality Curing • Humidity, Temperature, Air Movement • Too a great degree, we are at the mercy of the weather • Can have some control over air movement and humidity • Fortunately, upper South/lower Midwest climates favor good curing • But in bad curing years, limited options

4. Managing for Quality -Curing • Ideal conditions • Temperature 60 to 90 F • Daily average RH 70 to 75 % • Hot, low humidity • Flash cure • K, piebald, pawpaw (yellowish and mottled) • Cool, low humidity • Green • Hot, high humidity • Barn rot (house burn) • Cool, high humidity • Barn rot and/or green cure

5. Managing for Quality -Curing • Conventional barn: tight, with doors and vents • Most opportunity for management • Normal weather • Open during day, close at night early in cure • Later, may leave open to dry stems, bring in and out of order • Dry, warm weather • Open at night, close during day to keep humidity in • May wet barn floor for more humidity • Can add fans for ventilation, possibly heat for drying • Conventional barn: no doors, no controllable vents, siding on walls • Hang to prevent barn rot in wet years • Pray for good curing weather • No management options after housing

6. Managing for Quality -Curing • Plastic covered field structure • Hang tight to keep humidity high early • Cover top as soon as possible • Normal weather • Raise plastic sides until yellow • Drop sides for rest of cure • Dry, hot weather • Drop sides during yellowing to slow cure • Wet ground under structure ??? • Monitor closely for rot • More possibility to manage cure than many conventional barns • Requires good management of covers for high quality

7. Managing for Quality -Curing • Low barns, open, one or two tiers • Hang tight to keep high humidity early • No management options after housing • Large open sided barns • No research • Open and well ventilated on sides, lower and upper tier • Limited ventilation in center • Intermediate between relatively open conventional barn and low tier • No management options after housing

8. Managing for Quality - Field • Proper fertilization • N rates • N timing • Limited or no muriate of potash or poultry litter • Consider irrigation • Keep crop growing, avoid concentrated salts in plant which cause curing problems • Avoid late harvest • Cool T or freezing promote green cure

9. Quality and Variety

10. KT 204 and KT 206 • Predominant varieties • High yield • Best black shank resistance • 204 rated 7 – 7 • 206 rated 10 - 7 • Quality ??? • Many complaints in 07 and 08

11. Factors that Control Leaf Quality 2008 • General Curing Season Quality Range of 29 Among 4 Locations • Time of Curing Quality Range of 6 (Springfield) to 23 (Greeneville) • Variety Quality Range of 5

12. Effect of Variety on Usability and Grade Index 2008

14. Effect of Harvest Time and Location on Grade Index 2008

19. Causes of Fleshy Green and Yellow Spot Curing • We don’t really know • Worse in certain years • Thought to be due to excess salts • Associated with • Dry season with rain before harvest • Late harvest with cool temperatures • High N rates • Muriate of potash or manure • Sometimes no apparent explanation

20. Curing and TSNA

21. TSNA and Curing Conditions • Ideal conditions • Good quality • Moderate TSNA • Hot, low humidity • Flash cure: K, piebald, pawpaw • Very low TSNA • Cool, low humidity • Green • Low TSNA • Hot, high humidity • Barn rot (house burn) • Very high TSNA • Cool, high humidity • Barn rot and/or green cure • Moderate to very high TSNA

22. TSNA Curing Model Study2005 PMUSA and Univ of Tennessee Lucy Joseph in cooperation with Paul Denton and the UT REC at Greeneville

23. Variables • Curing regimes • Ventilated cure • “Tight” conventional cure • Varieties • KT 204 LC : low converter • TN 90 LC: medium converter • NC 6: relatively high converter (screened) • N fertilization • 100 ppi + 100 sidedress • 200 ppi • 300 ppi + 100 sidedress • 400 ppi

24. Curing Regimes • Ventilated Cure • Ventilated with ceiling fans and exhaust fans • Goals was humidity in low optimal range • “Tight” Conventional Cure • Tight barn • Ventilation by opening doors • Goal was high humidity cure • Just short of barn rot

25. TSNA by Cure and Variety

26. TSNA by Cure and N Fertilization

27. TSNA – Variety and Cure • Variety (conversion potential) appears to be most important factor • KT 204 < TN 90 < NC 6 as expected • Ventilated cure < tight conventional • Interaction not significant

28. TSNA by Variety, Cure and N – Lamina

29. 2006 Curing Study • Dropped variety variable- used 204 LC • Added lower N rates • Added locations at Glade Spring and Springfield • Continued in 2007

30. Lamina TSNA HRREC 2006

31. Lamina TSNA GREC 2006

32. Yield and Quality HRREC 2006

33. Lamina TSNA GREC 2007

34. TSNA – Curing Studies • Ventilated cure < tight conventional • Curing barn and overall season as important as N rates and ventilation • Screened KT varieties have potential for much lower TSNA than older varieties • A dry curing season gives low TSNA regardless of other factors