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Burley Tobacco Curing Update. Paul Denton, Bob Pearce and Andy Bailey. Factors that Control Leaf Quality. Overall Curing Season Time of Harvest and Housing within the Season Variety. Factors Affecting Quality Curing. Humidity, Temperature, Air Movement
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Burley Tobacco Curing Update Paul Denton, Bob Pearce and Andy Bailey
Factors that Control Leaf Quality • Overall Curing Season • Time of Harvest and Housing within the Season • Variety
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
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
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
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
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
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
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
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
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
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
TSNA Curing Model Study2005 PMUSA and Univ of Tennessee Lucy Joseph in cooperation with Paul Denton and the UT REC at Greeneville
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
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
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
2006 Curing Study • Dropped variety variable- used 204 LC • Added lower N rates • Added locations at Glade Spring and Springfield • Continued in 2007
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