Spatio-Temporal Water-Fertilizer Coupling Effect On Flue-Cured Tobacco

Water-fertilizer coupling in the different growth stages and spatial position hasdifferent effect on flue-cured tobacco. Under different fertilization and water condition,two pot experiments and a field experiment were carried out to investigate effects ofdifferent top dressing stages and alternate partial root-zone irrigation (APRI) onphysiological characteristics, growth, yield, quality, water use and nutrient use offlue-cured tobacco. Pot experiment 1 had four top dressing stages, i.e. no topdressing(Z₁), topdressing during seedling resuscitating stage (Z₂), topdressing during rootspreading stage (Z₃), topdressing during vigorous growing stage (Z₄), four fertilizationlevels, i.e. no fertilization (F₁), low fertilization (F₂), mid fertilization (F₃), higherfertilization (F₄), and four irrigation levels (W₁, W₂, W₃, W₄). Pot experiment 2 had twofertilization levels, i.e. lower fertilization and higher fertilization, four water treatedstages, i.e. water treated during the root spreading stage, water treated during thevigorous growing stage, water treated during the maturing stage, and water treatedduring the combined root spreading, vigorous growing and maturing stages, and threeirrigation methods, i.e. conventional irrigation (CI), fixed partial root-zone irrigation(FPRI) and alternate partial root-zone irrigation (APRI). Field experiment had twofertilization levels, i.e. lower fertilization and higher fertilization, three irrigationmethods, i.e. conventional furrow irrigation (CF), fixed furrow irrigation (FF) andalternate furrow irrigation (AF). The main results are outlined as follows: (1) Z₂F₄W₂ was the best-combined treatment on growth (plant height, leaf number,leaf area) and yield of flue-cured tobacco. Topdressing in the seedling resuscitating stage(Z₂) and appropriate amount of water deficit (W₂) in the root spreading stage werebeneficial for the growth and yield of flue-cured tobacco. Z₄F₄ was the best-conbinedtreatment to increase tobacco leaf N, K contents, so sufficient nutrient can guaranteehigher tobacco leaf N, K contents, and top-dressing for K fertilizers at early of vigorousgrowing stage was beneficial to increase leaf K contents and improve leaf quality oftobacco.(2) Compared to CI, under two different fertilization levels, APRI greatly reducedtranspiration rate and stomatal conductance of tobacco leaf during different growthstages, reduce 12.4% and 10.9%, 18.6% and 3.1% averagely respectively in the mid andlater stage of vigorous growing stage, but changed net photosynthetic rate slightly (meanincrease or decrease less than 1.0%), thus increased leaf WUE by 12.6% and 11.3%averagely respectively. In field experiment, similar result were also obtained, comparedwith CF, under two different fertilization levels, leaf transpiration rate and stomatalconductance of tobacco in AF were reduced by 13.3% and 14.7%, 4.7% and 6.6%, Netphotosynthetic rate were changed slightly (increases 0.1% in the vigorous growing stage,reduces 10.5% in the earlier maturing stage), leaf WUE was increased by 16.0% and5.6% averagely respectively at the later vigorous and earlier maturing growth stages.Compared to CI, APRI during different growth stages of tobacco saved irrigation waterby 8.4%, but increased tobacco leaf WUE slightly under two different fertilizationlevels.(3) Compared to CI, APRI during different growth stages of tobacco not onlyincreased plant height significantly, but also increased leaf nitrogen (N), phosphorus (P)and potassium (K) contents, thus improved the inherent quality of tobacco leaf. Undertwo different fertilization levels, APRI increased mean plant height by 14.0%, meanmiddle tobacco leaf N, P, K contents by 11.1%, 21.4%, 24.7% respectively. In fieldexperiment, compared to CF, AF increased mean plant height by 6.5% under twodifferent fertilization levels, mean middle tobacco leaf N, P, K contents by 4.6%, 5.4%and 10.6%, reducing sugar and soluble protein contents by 12.9% and 4.4%, mean soluble sugar to nicotine ratio and soluble sugar to N ratio by 8.4% and 7.5%,respectively.(4) Under higher fertilization condition, APRI during the root development stageincreased middle leaf N, P, K contents by 18.8%, 69.0% and 38.6%, soluble sugar andnicotine contents by 16.4% and 3.3%, soluble sugar to nicotine ratio and soluble sugarto N ratio by 5.0 and 9.2 when compared to CI.The above-mentioned results indicate that topdressing during the seedling andvigorous growing stage, and APRI treated in the root developing are the best modes ofspatio-temporai water-fertilizer coupling for tobacco production with proper yield andhigher quality.