Effects Of γ-poly Glutamic Acid Concentration On Nutrient Absorption,Yield And Quality Of Flue-cured Tobacco

As a new type of fertilizer synergist,y-polyglutamic acid(y-PGA)has achieved good effects on most vegetables,but there is still a lack of strong data support in flue-cured tobacco production.In order to explore the effect and mechanism of y-PGA on growth,nutrient absorption,yield and quality of flue-cured tobacco,0 mg·L-1(CK),50 mg·L-1(T1),100 mg·L-1(T2),150 mg·L-1(T3),200 mg·L-1(T4)and 250 mg·L-1(T5)y-PGA solution was used for root irrigation through field experiment.The effects of different concentrations of y-PGA on the physical and chemical properties of rhizosphere soil,root development,contents and accumulation of nitrogen,phosphorus and potassium in different organs of flue-cured tobacco,physiological metabolism of flue-cured tobacco,economic characters and chemical components of flue-cured tobacco were studied.The main findings were as follows:1.The application of y-PGA could significantly increase the soil volumetric water content in 0～30 cm plough layer,which was 8.94～36.31%,14.05～65.41%and 3.69～32.26%higher than that of CK,respectively.In the early growth stage,the concentration of y-PGA in 50～150 mg·L-1 could significantly increase the soil volumetric water content,while in the middle and late growth stage,the concentration of γ-PGA in 150～250 mg-L-1 was better.γ-PGA can reduce the water leakage to the soil layer below 20 cm,and increase the water content of 0～20 cm soil layers.The increasing effect of y-PGA on soil moisture content could continue to the late growth stage of flue-cured tobacco,and increased with the increase of concentration.Application of γ-PGA could increase the contents of available N,P and K in the rhizosphere soil of flue-cured tobacco in the whole growth period,and the best concentration of γ-PGA was 150～200 mg·L-1.2.The application of γ-PGA significantly promoted the growth and dry matter accumulation of flue-cured tobacco.During the whole growth period,the root volume,maximum root length and root activity of flue-cured tobacco were significantly higher when the concentration of γ-PGA was in the range of 100～200 mg·L-1 than those of CK,especially when the concentration of γ-PGA was 150 mg·L-1.When the concentration of y-PGA was more than 50 mg·L-1,the dry matter accumulation of stem and leaf was significantly increased,and 150 mg L-1 was the highest.3.The application of γ-PGA promoted the absorption and accumulation of nitrogen,phosphorus and potassium,and significantly improved the nitrogen use efficiency.Compared with CK,the accumulation of N,P and K increased by 66.84%,128.04%and 103.73%,respectively,when the concentration of γ-PGA was 150 mg·L-1.When the concentration of γ-PGA was in the range of 100～250 mg·L-1,the nitrogen use efficiency of flue-cured tobacco increased by 16.05～30.03%,and the treatment of 150 mg·L-1 with γ-PGA had the largest increase in nitrogen use efficiency.4.The application of different concentrations of γ-PGA increased the activities of SOD,POD and CAT,and decreased the content of MDA in flue-cured tobacco leaves at different growth stages.The application of γ-PGA in the range of 100～200 mg·L-1 increased the activities of antioxidant enzymes in leaves,which was conducive to improving the stress resistance of tobacco plants.The results showed that γ-PGA increased the activities of NR,GS and INV,especially in 40～80 days after transplanting.The activities of three enzymes were the highest when the concentration of γ-PGA was 150 mg·L-1,too high concentration led to high NR and GS activities and slow chlorophyll degradation at 100 days after transplanting,which was not conducive to the normal maturity of tobacco.Different concentrations of γ-PGA improved the photosynthetic characteristics and net photosynthetic rate of flue-cured tobacco,and the overall performance was T3>T4>T2>T5>T1>CK.5.All treatments with γ-PGA application improved the yield,proportion of upper and medium class of tobacco,average price and production value of flue-cured tobacco,and the economic indexes of γ-PGA treatment at 150 mg·L-1 improved significantly compared with CK.y-PGA concentration in the range of 100～200 mg·L-1 significantly improved the potassium content,potassium-chloride ratio and combustibility of post-baking tobacco.The γ-PGA concentration in the range of 150～200 mg·L-1 harmonized the sugar and alkali ratio of tobacco leaves,which was conducive to improving the intrinsic quality of tobacco leaves.In summary,γ-PGA concentration of 150 mg·L-1 had the best effect on promoting the growth and development of flue-cured tobacco,nutrient absorption,nitrogen use efficiency,tobacco yield and quality.