INFLUENCE OF NITROGEN APPLICATION RATE ON THE YIELD, QUALITY, AND CHEMICAL COMPONENTS OF FLUE-CURED TOBACCO, PART II: APPLICATION METHOD

Research was conducted in 2012 and 2013 to determine the effect of nitrogen application timing and method on the yield, quality, and leaf chemistry of flue-cured tobacco. Liquid urea–ammonium–nitrate supplied 100% of the total nitrogen and was applied in differing combinations of rates, timings, and methods. Nitrogen rates above, at, and below recommendation for specific locations were split into two, three, or four application timings depending on treatment. Nitrogen application was initiated at transplanting and concluded before or at topping. Applications of nitrogen were either soil applied at each interval or were soil applied until topping where application occurred over top to promote stalk rundown. Leaf tissue samples were collected at layby and topping to evaluate total nitrogen content throughout the growing season. Composite cured leaf tissue samples from all four stalk positions were analyzed for total alkaloid and reducing-sugar content. Yield data were collected and leaf quality was determined according to U.S. Department of Agriculture grade. Crop value per hectare was determined using a combination of yield and quality. Data were subjected to analysis of variance using the PROC GLM procedure in SAS ver. 9.4. Treatment means were separated using Fisher's Protected LSD at P ≤ 0.05. Soil-applied treatments yielded higher than stalk rundown treatments but contained lower nitrogen content at topping and chlorophyl level (SPAD) measurements. Leaf quality was similar when nitrogen was applied as a stalk rundown at above recommended rates and when soil applied at recommended rates. Leaf value and total alkaloid content were not affected by treatments; however, sugar content was highest when less nitrogen was applied early in the season. Leaf nitrogen was higher at layby when a larger percentage of nitrogen was applied earlier in the season. Rainfall played a significant role in observed results and producers should exercise similar treatments with caution.