Effect of organic nitrogen source and application timing on the yield and quality of flue-cured tobacco
Mineralization rates of organic nitrogen are extremely dependent upon factors such as soil pH, temperature, and moisture. Flue-cured tobacco is extremely sensitive to nitrogen availability; therefore, many questions have been presented regarding appropriate application programs for organic tobacco systems. It has been theorized that organic nitrogen application at layby could result in late-season mineralization and uptake, thus creating management and curing issues. To address these concerns, research was conducted in North Carolina 2012 and 2013 to evaluate the impact of two organic nitrogen sources: Nature Safe (13-0-0) and Nutrimax (12-1-0) when applied at three different timings: 100% broadcast prior to bedding, 50% broadcast prior to bedding/50% sidedress at layby, or 50% sidedress after transplanting/50% sidedress at layby. Nitrogen application rate was the same for all treatments and was targeted at a rate appropriate for each environment. In addition, a single treatment of synthetic 28% Urea-Ammonium-Nitrate was included as a control and was applied 50% sidedress after transplanting and 50% sidedress at layby to reflect recommended practices employed by conventional producers. Tissue samples were collected at layby, topping, and after curing to evaluate nitrogen accumulation during the season. After curing, leaf yield, quality, and chemistry were determined as well. In general, yield was not impacted by nitrogen source or application timing; however, increases in leaf quality, nitrogen uptake, and total alkaloids were observed where nitrogen application occurred after transplanting. These results likely indicate that nitrogen use efficiency was improved when the nutrient was placed in closer proximity to the rooting zone of the plant.