| The soil C/N ratio wasimbalancein tobacco-growing area in middle of Henan Province because of itcontinuous cropping.The tobaccoquality was reduced.Two years study was try to find the optimum organic material type under C/N=25,and then validated it in field.In the first year,the optimum type of organic material,biochar,was chosen by the pot experiment with three organic material types under C/N = 25.In the second year,based on 1600 kg/hm2 boichar,four nitrogen(N)levels was set to explore the effect of biochar on N transformation and tobacco growth.Experiment 1:Effects of organic material under the same carbon/nitrogen ratio on tobaccogrowth and carbon nitrogen metabolism The results showed:(1)The agronomic traits of tobacco,such as the leaf length,leaf width,leaf number,leaf area weresignificantly improvedunder pig manure(TM)and biochar(TB)treatments.But the opposite effect on tobacco was appeared under maize straw(Ts)treatment.The activities of key enzymes related to C and N metabolism in the tobacco leaves were significantly promoted under the organic material treatments.The highest activities of nitrate reductase,amylase,and invertase were 33.3 ?g/g/h,14.42 mg/g/min,and 5.08 mg/g/h,respectively.And the activities of key enzymes were increased at first and then decreased,becoming highest in 45 and 60 days after the tobacco transplanted.The activities of key enzymes under TS was blow the control.Compared to the control treatment,the N,P,and K content in tobacco leaf was significantly elevated under the organic material treatment.(2)Compared to the control treatment,the Nand soil organic matter(SOM)was enhanced under organic material treatments.The soil Nwas significantly elevated under TM,and the SOM was significantly increased under TB.Meanwhile,the soil urease activity was significantly improved under TM,and the maximum value was 17.8 mg/kg.While the soil sucrose activity changed little among the treatments.(3)Biochar application can improve the C and N metabolism and form harmoniously tobacco chemical components,and promote the tobaccoquality;while the pig manure provided more available soil nutritionbased on the soil C/N as 25/1 in middle of Henan Province.Experiment 2: Effect of biochar on the growth and carbon nitrogen metabolism and quality of flue-cured tobacco under different nitrogen application rate The results showed:(1)Compared to the control treatment,the N application significantly improved the agronomic traits of tobacco,while,littleeffect bybiochar.The N2(52.5 N kg/hm2)and N3(67.5 N kg/hm2)treatment could elevate plant height,stem girth,leaf number and leaf area significantly.The biochar and nitrogen fertilizertreatments could improve the activities of key enzymes related to C and N metabolism in the tobacco leaves.The highest activities of nitrate reductase,amylase,and invertase were 51.19 ?g/g/h,19.98 mg/g/min,and 3.90 mg/g/h,respectively.However,there is no clearlyrelationship between the activities of key enzymes and N application.Compared to the control treatment,the N content in tobacco leaf was significantly elevated under the biochar treatment,while,the P and K content was little changed.(2)The total sugar,reducing sugar,K,sugar/alkali and K/Cl inthe upper middle tobacco leaves were significantly improved under biochar applied treatments.And the effect of N application rate on chemical components of flue-cured tobacco was the best one under N3 treatment.The neutral aroma constituents content were improved under the biochar and N application.The highest content was appeared under N0(0 N kg/hm2)treatment with 616.29 ?g/g.Biochar application can improve thetobacco C and N metabolism and regulate its chemical quality.Whilst,the growth and quality indices such as the agronomic traits,chemical components and neutral aroma componentsof flue-cured tobacco leaveswas more sensitive by the N application rate.(3)The biochar and nitrogen fertilizer treatmentscould improve the activity of the soil urease significantly in 90 days after tobacco transplanted.The soil urease activity of different treatment showed that: N2>N1>N0>CK>N3.Moreover,the biochartreatmentscould elevate the soil sucrose activity significantly in 60 days after the tobacco transplanted.Although the nitrogen fertilizer could improve the soil sucrose activity significantly in 90 days after the tobacco transplanted,there is no clearlyrelationship between the activities of soil sucrose activity and N application.Additionally,the biochar can't effect the SOM contentor the nitrogen fertilizer in 0~20 cm layer.The biochartreatmentsabated the Ncontent in the soil deep layer,which indicated the it elevated nitrogen sequestration in top layer soil.Compare with the control treatment,the decrement of total N(TN),available N(AN),nitrate nitrogen(NO3--N)and ammonium nitrogen(NH4+-N)content was 11.21%,49.07%,42.29% and 31.35% in the N0 treatment.The AN,NO3--N,NH4+-N content was mainly existed in 0~20 cm layer,and all of them increased with Napplication rate.The highest content of TN,AN,NH4+-N was happened under N3(67.5 N kg/hm2)treatment,which was 2.10 g/kg,261.86 g/kg,264.90 mg/kg,49.80 mg/kg,respectively.While the NO3--N content was concentrated in 0~20 cm layer with the highest level as 264.90 mg/kg in N3(67.5 N kg/hm2)treatment.The effect of Napplication rate on its transformation before 30 d after the tobacco transplanted.(4)It was suggested that the biochar combined with 67.5 kg/hm2 nitrogen application was the optimum practice to improve the tobacco quality and soil nutrition in central of Henan Province... |
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