| It is important to consider that Flue-cured tobacco holds immense economic value as a cash crop,and can help alleviate poverty and promote prosperity in southern Shaanxi region.However,due to overreliance on chemical fertilizers and insufficient use of organic fertilizers,the quality of soil has deteriorated,becoming a major obstacle to the high-quality development of the flue-cured tobacco industry in the region.To improve the yield and quality of tobacco,it is crucial to increase the application of organic fertilizers and microbial agents.Currently,most organic fertilizers and microbial agents are applied separately in this field,and there are limited studies on their synergistic regulations.This study focuses on the use of Yunyan 99 as experimental material and selected Bacillus paralicheniformis Q96 and Bacillus velezensis Q161 as microbial agents,with vermicompost as the base fertilizer.Two application methods,root application and leaf spraying were used to assess the effects of single and combined applications of vermicompost and microbial agents on the soil microbial community,growth of flue-cured tobacco,fertilizer utilization rate,and quality of flue-cured tobacco.The results are as follows:1.The combination of microbial agents and vermicompost can significantly enhance the diversity of soil bacterial communities.At the phylum level,the combination of microbial agents and vermicompost had a noteworthy impact on on improving the abundance of Mycobacteria.The T1 treatment(Q96 + vermicompost)had the largest abundance,which was 3.14 times greater than the control group(CK).At the genus level,the abundance of Bacillus was highest in T2 treatment,which was 2.86 times more than the CK,followed by T1,which increased by 69.93%.Both the single and combined application of vermicompost and microbial agents were found to be beneficial in improving the diversity and richness of bacterial microbial species.T1(Q96 + vermicompost)treatment showed the best chao index and ace index,which were 2.21 times and 2.81 times greater than the CK,respectively.The FAPROTAX function prediction revealed that the application of two kinds of microbial agents and organic fertilizer had varied effects on the ecological function of the bacterial community.The heterotrophic ability of T2(Q161 + vermicompost)treatment was improved,and the nitrate reduction ability of T4(Q161)treatment was found to be the best among all treatments.This suggests that the combined application of vermicompost and microbial agents can regulate community function and improve the carbon and nitrogen cycle of flue-cured tobacco by altering the distribution and richness of the bacterial microbial community.2.In comparison,to using chemical fertilizers alone,the application of a bacterial agent and vermicompost,either alone or combined,can enhance the growth of flue-cured tobacco.In fact,the combined application of these two agents produces better results than using either one alone.The application of organic fertilizer and a microbial agent led to significant improvements in plant height,leaf area,and root weight.The best results for plant height and leaf area in potted flue-cured tobacco were observed in Y1(Q96 leaf spraying +vermicompost),with an increase of 22.24% and 25%,respectively,compared to CK.The application of microbial agents to the roots had a stronger impact on root traits in flue-cured tobacco.The average weight gain for T1(Q96 root application + vermicompost)and T2(Q161 root application + vermicompost)was 34.58%.The combined application of organic fertilizer and microbial agents could increase the activity of catalase(CAT)and superoxide dismutase(SOD),reduce the content of malondialdehyde(MDA),and improve the disease resistance of tobacco plants.The use of a bacterial agent and vermicompost together can also reduce the disease index of brown spot,with the lowest disease index observed in Y2(Q161leaf spray + vermicompost),which was 70.73% lower than CK.Microscopic observations of paraffin sections of flue-cured tobacco leaves showed that leaf spraying with the Q161 agent had a better effect on improving leaf quality than root application.The tissue of tobacco leaves treated with Y2(Q161 leaf spraying + vermicompost)increased by 25% compared to CK,and the tissue ratio of T2(Q161 root application + vermicompost)decreased.3.Compared to CK,the utilization rate of chemical fertilizers in flue-cured tobacco can be improved to varying degrees through the single or combined application of microbial agents and vermicompost.The combined application of these agents yields better results than their individual application.Y1,which involves leaf spraying with Q96 and vermicompost,showed the highest nitrogen and potassium fertilizer utilization rates,which were 59.59% and 75.47% higher than CK.The utilization rate of phosphate fertilizer in T2(Q161 root application + vermicompost)and T3(Q96 root application)was significantly higher than that in CK,increasing by 62.48 % and 67.47 %,respectively.4.Field experiments showed that the combination of microbial agents and vermicompost effectively improved the yield and quality of tobacco.A2(leaf spraying with Q96,Q161 + vermicompost)treatment significantly increased the maximum leaf area of flue-cured tobacco by 23.66% compared to CK.A1(root application of Q96 + Q161 +vermicompost)greatly improved the yield and output value of tobacco,which were 36.86%and 43.41% higher than CK.T2 also increased the potassium content by 21.43 %,and the total amount of aroma components increased by 0.9 times compared to CK.The best control effect on field brown spot was achieved by Y2(Q161 leaf spray + vermicompost),with a control effect of 69.75%.To summarize,the use of microbial agents and vermicompost together can enhance the diversity of bacterial communities in soil,boost the efficiency of nitrogen,phosphorus,and potassium fertilizers,stimulate plant growth and development,and improve the chemical composition and aroma quality of tobacco.Specifically,among the various treatment methods tested,T2(root application of Q161 + vermicompost)and Y1(leaf spraying of Q96+ vermicompost)demonstrated particularly positive outcomes and could be employed as a viable formula to enhance the soil microbial characteristics and the yield,quality of tobacco in southern Shaanxi. |
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