Effects of irrigation, nitrogen forms and topping on sun cured tobacco

Tobacco yield and quality is largely designated by genetic potential, ecological conditions and cultural practices. Therefore, inefficient use of resources poses serious risks on quality-type oriental tobaccos. In the present study, effects of irrigation, N forms and topping stages on agronomic and chemical characteristics of oriental tobacco (Nicotiana tabacum L. cv. Xanthi 81) were evaluated. In two growing seasons (2017 and 2018), 5 nitrogen forms, 4 irrigation levels and 3 topping levels were experimented in strip-strip plot experimental design with 3 replicates. Besides yield and quality grade index, single and interactive effects of experimental treatments on chemical composition were also focused on. Recommendations were provided along with the grower and market demands. Quality grade index values were within the acceptable levels (60.8–99.7 %) and plants exhibited positive response to topping and increasing water stress. Present findings revealed that high nicotine demand of the market could be met with topping treatments. Additionally, greater nicotine content could be achieved with ammonium nitrate treatments applied at irrigation level of 33 % of the field capacity (1.48 %). Reducing sugar content and phenolics increased with topping treatments and similar responds were exhibited to irrigation and N forms. The greatest total sugar content (12.92 %) was obtained from I₂ N₂ T₃ treatments and the greatest total phenolics (1099.1 g kg⁻¹) was obtained from I₁ N₂ T₂ treatments. If there aren’t any specific demands directing nitrogen, irrigation and topping levels, I₄ N₄ T₂ treatment was identified as the most advantageous one in terms of net return in tobacco farming. In other words, together use of ammonium and nitrate forms, 3 irrigations, the first about 1 month after planting, as to bring the deficit moisture to field capacity and a surficial topping at the beginning of flowering is recommended. In this case, 17.4 % greater yield and thus 1250 $ ha⁻¹ greater gross return could be achieved.