Influence of Poultry Litter on Dark Tobacco Growth and Soil Nutrient Availability

Due to the relatively high value of dark tobacco compared with fertilizer costs, nitrogen is recommended at levels as high as 338 kg ha 1. Such rates of inorganic fertilizers increase the osmotic pressure of the soil solution and soil acidity, often causing reduced stands, Mn toxicity, Mo and Ca deficiencies, and reduced yield and quality of the cured leaf (Sims et al., 1984). Poultry litter utilized as a nutrient source is an inexpensive alternative to this dilemma due to its relatively neutral or alkaline composition. However, due the amount of chloride present in poultry litter, the University of Kentucky advises that application be limited to a maximum of 9 Mg ha 1 (Wells, 1996). Environmental concerns such as nitrate contamination of groundwater, P runoff into surface water, and accumulation of heavy metals in the soil are often related to excessive application of poultry litter. Studies were conducted at Western Kentucky University\u27s Agricultural Research and Education Complex in Bowling Green, Kentucky and a farm in Owensboro, Kentucky to evaluate the influence of poultry litter on dark tobacco growth and soil nutrient concentrations. Results from these studies indicate that when applied at recommended rates, poultry litter in most cases can alleviate soil acidification often associated with the use of inorganic fertilizer sources. In general, poultry litter amendments increased soil pH, while inorganic fertilizers had the opposite effect. Data from the Rate Study suggests that rate of inorganic fertilizer and soil pH are negatively correlated. Due to the high nutrient content of poultry litter, its utilization could possibly lead to an accumulation of P2O5 and certain heavy metals, such as Cu and Zn. Data from the Bowling Green Timing Study indicated that poultry litter amendments increased postharvest soil P availability compared to inorganic fertilizer amendments. At the Owensboro location there were no differences in soil P availability among treatments. Results from the Rate Study suggest that soil P availability and poultry litter rate were positively correlated. Data from all studies indicate that in some cases, soil Cu availability was greater in poultry litter treated plots than in plots treated with inorganic fertilizers. With one exception, plots receiving poultry litter were higher in soil Zn availability than inorganic fertilizer plots at the Bowling Green Timing Study. Data from the Rate Study suggests that increasing the poultry litter rate increased soil Zn availability in poultry litter plots receiving a sidedress application. Data from the Owensboro Timing Study indicated that regardless of application timing, cured lamina tissue chloride concentration in poultry litter amended plots were greater than the tobacco industry standard of 1%. Chloride concentrations in the lamina and stem were higher in plots receiving poultry litter than plots treated with inorganic fertilizers. Despite these concentrations there were no noticeable differences in curing and USDA quality rating. Data from the Timing Studies indicated that total yields were equivalent in poultry litter and inorganic fertilizer treated plots, however yields of certain grades did vary. Plots receiving a source of fertilizer had higher total yields than the untreated control. Results from the Rate Study showed that total yields were quite variable, which may be attributed to poor water drainage from the study area. In the Rate Study, a general trend emerged in which increasing the rate of poultry litter in combination with a sidedress application increased trash, lug, and total yield, but decreased tip yield