Objective  Effects of application of combined organic and inorganic nitrogen fertilizers on dry matter accumulation, carbon and nitrogen metabolisms, economic traits, and wrapper leaf quality of cigar tobacco were studied.

Method A field experiment was conducted applying organic and inorganic nitrogen fertilizers in the ratios of 0∶1 (R1), 3∶7 (R2), 5∶5 (R3), 7∶3 (R4), and 1∶0 (R5). Dry matters, nutrient contents, carbon and nitrogen metabolism-related enzyme activities, economic traits, and wrapper leaf quality and yield of the cigar tobacco plants grown on different lots were measured.

Results As the proportion of organic fertilizer for the fertilization increased, the accumulated dry matter, total leaf yield, usable wrappers, and total output value of the tobacco plants grown on the lots rose and reached a peak followed by a decline. Of the various combinations, R2 provided significantly 30.88-60.17% higher wrapper leaf yield than the others. The more organic fertilizer was incorporated, the lower the nitrogen and potassium contents in the stems and leaves, the lower the carbon and nitrogen metabolism-related glutamine synthetase activity, and the higher but followed by declined α-amylase and neutral invertase activities. In comparison to using entirely organic fertilizer as in R5, R2 that was 30% organic produced tobacco plants with 32.32% higher in α-amylase activity and 77.22% higher in neutral invertase activity. The incorporation of organic fertilizer reduced the numbers of stems and thickness of leaves but increased the leaf area. The plants grown under R2 were rated the highest on overall appearance and had 42.14% more reducing sugar and 20.88% more total sugar in the leaves than those under R1.

Conclusion By using 3 parts of organic and 7 parts of inorganic fertilizers, R2 optimally regulated the carbon/nitrogen metabolisms of cigar tobacco plants to significantly enhance the wrapper leaf quality and yield improving the operation financial return.