Field experiments were conducted at Princeton, KY in 2004 and 2005 to evaluate various herbicides for weed control in no-till dark tobacco. No-till dark tobacco was transplanted into burned-down fescue in 2004 and into burned-down wheat in 2005. All plots received sulfentrazone plus clomazone pretransplant (PRETR) at 0.42 and 0.84 kg ai/ha, respectively, prior to transplanting. Experimental herbicide treatments made after transplanting included trifloxysulfuron at 5.3 g ai/ha or halosulfuron at 53 g ai/ha applied early postemergence over-the-top (EPOT) or late post-directed (LPD). Other experimental treatments included carfentrazone at 17.5 g ai/ha LPD and paraquat at 420 g ai/ha LPD. Significant injury was observed from EPOT applications of trifloxysulfuron or halosulfuron and from LPD applications of carfentrazone or paraquat. Weed species evaluated included horsenettle and honeyvine milkweed in 2004, Eastern black nightshade and smooth pigweed in 2005, and entireleaf morningglory in both years. Paraquat LPD generally provided the most effective control of most weed species evaluated, but also resulted in the most crop injury. Halosulfuron EPOT caused significant reduction in yield of cured leaves from the middle stalk position (seconds), total yield, and gross revenue of dark fire-cured tobacco in 2004 compared to tobacco that only received sulfentrazone plus clomazone PRETR. Paraquat LPD caused extensive lower plant injury and reduced lower stalk position (lug) yield compared to other treatments in both years. Herbicide treatment did not influence yield of seconds, upper stalk position (leaf), total yield, or gross revenue in 2005. Quality grade index was reduced in leaf of tobacco receiving halosulfuron EPOT or LPD and 2004, and in seconds of tobacco receiving trifloxysulfuron EPOT or halosulfuron EPOT in 2005. Of the herbicides and application methods tested in these experiments, LPD applications of trifloxysulfuron or halosulfuron may have the most potential for use in no-till dark tobacco.

Many burley tobacco (Nicotiana tabacum L.) producers are convinced that additions of nitrogen (N) rates greater than those recommended by university Extension services will result in increased yield and income. Some producers apply foliar fertilizer with other management operations to increase yield and quality of burley tobacco, but these results have not been confirmed by research. Concerns with excessive N additions include improper curing, elevated levels of tobacco-specific nitrosamines, undesirable burning characteristics of the cured leaf, unnecessary fertilizer costs, and negative impacts to environmental quality. A field study was conducted at Lexington, KY and Springfield, TN from 2000 to 2002 to determine the effects of 3 N rates (200, 250, and 300 lb/acre) and 3 foliar fertilizer products on yield and quality on burley tobacco leaf. Nitrogenous leaf compounds were measured only at the Kentucky location. Results from this study indicate that there was no significant yield or quality advantage in applying more than 200 lb N/acre for burley tobacco production, but rather, these parameters were influenced by year and location. Yield was also not influenced by foliar fertilizer application at either location; however, in 2001 the foliar products did result in a higher grade index than the untreated check. Results from this experiment do not indicate that the use of a foliar product or N rates >200 lb/acre will result in consistently higher yields or quality of burley tobacco.

To evaluate response of dark fire-cured and dark air-cured tobacco to nitrogen application rate, field experiments were conducted at 4 locations in Kentucky and Tennessee over 4 years. Locations were the University of Kentucky Research and Education Center near Princeton, KY; the West Farm of Murray State University near Murray, KY; the University of Tennessee Highland Rim Research and Education Center near Springfield, TN; and 3 private grower fields near Crofton, KY. Experiments were conducted at all 4 locations in 2003 and 2004, Crofton in 2005, and Springfield in 2006, for a total of 10 experiments. Six experiments were with dark fire-cured tobacco, and the other 4 were with dark air-cured tobacco. Phosphorus and potassium were applied at each location according to University of Kentucky soil test recommendations. Nitrogen applications were made as 2 equal side-dress applications at 2 and 4 weeks after transplanting. Total nitrogen rates applied included 2 rates at the low and high end of University of Kentucky recommendations (168 and 336 kg N/ha) and 2 excessive rates (560 and 1,120 kg N/ha) that some growers commonly used at the time this research was conducted. Excessive nitrogen applications above University of Kentucky recommendations commonly increased leaf chlorophyll index but did not increase crop vigor or leaf area. Excessive nitrogen applications did not increase total yield of dark fire-cured or dark air-cured tobacco, but did sometimes cause substantial reductions in quality grade index in dark air-cured tobacco. Nitrogen rate did not affect nicotine content in dark fire-cured tobacco, had minimal effects on nicotine in dark air-cured tobacco, and had minimal effects on nornicotine and percent conversion of nicotine to nornicotine in both tobacco types. Excessive nitrogen did result in increased total tobacco-specific nitrosamines in 2 of 6 dark fire-cured experiments and 2 of 3 dark air-cured experiments.

As part of a continuous effort at North Carolina State University, research was conducted from 2007–2009 to establish the maximum expected pesticide residue on flue-cured tobacco that would result from a maximum labeled application rate and minimum preharvest interval of specific crop protection agents (CPAs). Residues of azoxystrobin, butralin, and flumetralin were measured on flue-cured tobacco over 6 environments in North Carolina during the research cycle. Butralin and flumetralin were applied via broadcast (BC) and downstalk (DS) application. Treatments were applied to tobacco grown on research stations near Clayton and Kinston, NC. Tobacco was managed according to NC Cooperative Extension Service recommendations and harvested 4 times by stalk position. Residues on cured leaf were quantified by Global Laboratory Services, Inc., in Wilson, NC. Data were analyzed and reported by individual year, location, CPA, and stalk position; with primings 1 and 2 represented in the lower stalk position, priming 3 in the middle stalk position, and priming 4 in the upper stalk position. Generally all CPAs had residues that decrease from the lower stalk to the middle and upper stalk positions. Many results for butralin and flumetralin were below quantifiable limits, regardless of application method. Alternatively, the results for azoxystrobin were relatively high when compared to these compounds. Across all stalk positions and all locations, the highest mean residues observed for azoxystrobin, butralin-BC, butralin-DS, flumetralin-BC, and flumetralin-DS were 13.74, 13.87, 1.55, 3.75, and 2.03 mg/kg, respectively. For those CPAs that have established residue guidelines or tolerances set by CORESTA or USDA (butralin and flumetralin), the threshold was exceeded in at least 1 observation at 1 location when a broadcast application was used. The objective of this work was to determine what a maximum residue might be, not what a residue is expected to be consistently in a given environment.