Effects Of Water Deficit During Different Growth Stages On Yield, Quality, Nutrient- And Water-Use Of Flue-Cured Tobacco

The pot experiments were conducted to investigate water deficit effect onphysiological characteristic, growth, dry matter accumulation, water use and nutrientuse of flue-cured tobacco (Nicotiana tabacum L.) under two fertilization levels. Sevenwater treatments, i.e. conventional irrigation (CK), mild (A₁) and medium water deficit(A₂) during the root developing stage, mild (B₁) and medium water deficit (B₂) duringthe root developing and vigorous growing stages, mild (C₁) and medium water deficit (C₂)during the root developing and maturing stages, and two fertilization levels, i.e. F₁ andF₂ were designed for Experiment 1. Five water treatment, i.e. mild (D₁) and mediumwater deficit (D₂) during the root developing stage, mild (E₁) and medium water deficit(E₂) during the vigorous growing stage, and two fertilization levels, i.e. F₃ and F₄, weredesigned for experiment 2. The main results are outlined as follows:(1) Transpiration rate, stomatal conductance and photosynthesis rate of flue-curedtobacco decrease with the increased water deficit, and all water deficit treatments canrestore or exceed CK after rewatering, both leaf photosynthesis rate and transpirationrate in mild water deficit treatment restore more quickly than those of the other waterdeficit treatments, so the obvious compensation effect is observed in the mild waterdeficit treatment. (2) After rewatering, plant height and leaf area in mild water deficit treatment aregreater than those of conventional irrigation treatment during the root developing andmaturing stages of flue-cured tobacco. But plant height and leaf area in the other waterdeficit treatments are generally lower than those of conventional irrigation treatment.(3) Comparing with CK, A₁ increases tobacco yield by 13.7%, B₁ and B₂respectively decrease by 1.2% and 11.8% under the condition of F₁; A₁ increases theyield by 8.7%, B₁ and B₂ respectively decrease by 6.7% and 11.2% under the conditionof F₂. The result of experiment 2 show that D₂ increase the yield by 8.5%, E₁ and E₂respectively decrease 6.1% and 14.3% under the condition of F₃; D₁ increases the yieldby 10.5%, E₁ and E₂ respectively decrease 2.2% and 4.0% under the condition of F₄.(4) Comparing with CK, water deficit treaments increase tobacco water useefficiency (WUE) by 23.7-38.4% under F₁ condition, and by 17.0-60.3% under F₂condition. And the result of experiment 2 show that except for E₁ treaments, tobaccoWUE in both D₂ and E₂ were increased under F₃ condition, and tobacco WUE in allwater deficit treaments were higher than those of CK under F₄ condition.(5) Compared to CK, nutrient contents in upper and middle leaves under waterdeficit condition during the root developing stage were increased, and N, P and Kcontents under water deficit condition during the vigorous growing stage weresignificantly lower than those of CK.(6)Comparing with CK, mean reducing sugar content in middle leaf wererespectively reduced by 33.4% and 24.9%, and mean nicotine content were respectivelyincreased by 25.1% and 40.0% for all water deficit treatments under F₁ and F₂conditions, and the range of reducing sugar/nicotine and N/nicotine ratios in A₁ and A₂during the root developing stages were 8.1-12.8 and 0.7-1.4, respcetively. The F₃, F₄ hadthe similar results.(7) Soil available contents of N, P and K in water deficit treatment during the rootdeveloping and maturing stages were lower than those of CK, but there were nodifferences during the vigorous growing stage.(8) Plant height, biggest leaf area, dry matter accumulation, reducing sugar andnicotine contents, nutrient contents, yield and water use efficiency of flue-cured tobacco under F₂, F₄ fertilization condition were consequently higher than those of F₁, F₃fertilization treatment.In summary, mild water deficit during the root developing stage is benefit forincreasing the yield and quality of flue-cured tobacco. Mild water deficit during thematuring stage can save water use, but has no significant effect on the yield and quality.In any case, it is not suitable for water deficit treated during the vigorous growing stage.