| Medicinal materials of Andrographis paniculata is the dry aerial part of Andrographis paniculata(Burm.f.)Nees in Acanthaceae family.It is the raw material for a variety of Chinese medicine compounds and proprietary Chinese medicines.The demand has increased significantly in recent years,but the problem of continuous cropping obstacle has caused serious adverse effects on the output and quality of A.paniculata.The purpose of this research is to reveal the cause of continuous cropping obstacle of A.paniculata and provide basis for the application of continuous cropping obstacle mitigation and regulation technology.Sequencing analysis of samples from continuous cropping group(rhizosphere soil of A.paniculata with five years of continuous cropping)and control group(uncultivated natural soil with the same texture as the soil around A.paniculata with five years of continuous cropping)were performed using16 S r RNA gene high-throughput sequencing technology.The differences in richness,diversity and community structure of soil bacteria from two groups were analyzed.Field trial was conducted on a 2-year continuous cropping field of A.paniculata,and four treatment groups were set up for continuous cropping treatment(no bamboo charcoal and effective microorganisms applied),single application of bamboo charcoal,single application of effective microorganisms,and mixed application of bamboo charcoal and effective microorganisms.After application of bamboo charcoal and effective microorganisms,related indicators of A.paniculata rhizosphere soil micro-ecology and soil bacterial population structure,agronomic characters of A.paniculata,leaf nitrogen metabolism enzyme activity,seed quality during the fruiting periodare and active ingredient content were measured and analyzed to study the field application of bamboo charcoal and effective microorganisms to relieve the continuous cropping obstacle of A.paniculata.The main results are as follows:1.The bacterial chao1 index and observed＿species index in the soil of continuous cropping group were significantly lower than those of the control group(P<0.05),and the simpson index and shannon index in the soil of continuous cropping group were lower than those of the control group,but the differences were not significant.Principal coordinates analysis(PCo A)and Analysis of molecular variance(Amova)in community structure between groups showed that continuous cropping of A.paniculata significantly changed soil bacterial community structure(P<0.05).At the phylum level,compared with the control group,the relative abundance of Proteobacteria and Acidobacteria in the continuous cropping group was significantly increased by21.97% and 46.33%(P<0.05),respectively,while the relative abundance of Patescibacteria was significantly reduced by 68.99%(P<0.05).At the genus level,compared with the control group,the relative abundance of the beneficial bacteria Flavobacterium and Haliangium in the soil of the continuous cropping group was significantly reduced by 78.40% and 54.55%(P<0.05),respectively,while the relative abundance of the plant pathogenic bacterium BurkholderiaCaballeronia-Paraburkholderia in the soil of the continuous cropping group was increased significantly by 804.17%(P<0.05).2.Compared with continuous cropping treatment,both single and mixed application of bamboo charcoal and effective microorganisms significantly promoted the 6 growth indexes of continuous cropping A.paniculata,the dry weight of the underground part,the dry weight of the above-ground part,rootto-shoot ratio,plant height,leaf area and chlorophyll content.Among them,the mixed application of bamboo charcoal and effective microorganisms treatment had the most obvious promotion effect on plant height and above-ground dry weight,which increased by 21.65% and 47.03%(P<0.05),respectively,compared with continuous cropping treatment.Compared with continuous cropping treatment,both single and mixed application of bamboo charcoal and effective microorganisms increased the leaf nitrate reductase,nitrite reductase,glutamine synthetase and glutamate synthase activities to varying degrees in different growth stages of A.paniculata.And from the overall point of view,the mixed application of bamboo charcoal and effective microorganisms increased the leaf nitrogen metabolism enzyme activity more effectively than the single application.Compared with continuous cropping treatment,during the harvest period of A.paniculata,the key enzymes of nitrogen metabolism,nitrate reductase and glutamine synthetase activity of the mixed application of bamboo charcoal and effective microorganisms treatment increased by 162.50%and 37.94%(P<0.05),respectively.The mixed application of bamboo charcoal and effective microorganisms improved the seed quality of A.paniculata during the fruiting stage more effectively than the single application.Among them,compared with the continuous cropping treatment,the thousand-seed weight,germination rate,germination potential and germination index of the mixed application of bamboo charcoal and effective microorganisms treatment increased by 4.37 %,15.39%,55.37% and 35.51%(P<0.05).The mixed application of bamboo charcoal and effective microorganisms is more effective than the single application in increasing the content of andrographolide and dehydroandrographolide and the total content of the two lactones in aboveground part of A.paniculata during the harvest period.Compared with continuous cropping treatment,these three indexes of the mixed application of bamboo charcoal and effective microorganisms treatment increased by 73.35%,62.01% and 69.75%,respectively(P<0.05).3.Compared with continuous cropping treatment,soil p H value,organic matter and available potassium content were increased by 3.23%,67.77% and42.74% after mixed application of bamboo charcoal and effective microorganisms(P<0.05).Compared with the continuous cropping treatment,the mixed application of bamboo charcoal and effective microorganisms during the harvest period of A.paniculata had no significant effect on the number of soil bacteria(P>0.05),while the number of soil fungi decreased by 33.07%(P<0.05)and the number of soil actinomycetes increased by 36.45%(P<0.05).The mixed application of bamboo charcoal and effective microorganisms generally improved soil enzyme activity more effectively than the single application of bamboo charcoal and effective microorganisms.During the harvest period of A.paniculata,compared with continuous cropping treatment,the soil catalase,urease and invertase activities of the mixed application of bamboo charcoal and effective microorganisms treatment were increased by12.98%,21.78% and 39.60%(P<0.05).Compared with the single application of bamboo charcoal and effective microorganisms,the mixed application reduced the content of soil composite phenolic acid and water-soluble phenolic acid more effectively.Compared with continuous cropping treatment,the content of these two types phenolic acid of the mixed application of bamboo charcoal and effective microorganisms treatment was reduced by 20.46% and77.98%(P<0.05),respectively.4.Compared with continuous cropping treatment,both single and mixed application of bamboo charcoal and effective microorganisms increased the ace index,chao1 index,observed＿otus index and shannon index,but there was no significant difference.At the phylum level,compared with continuous cropping treatment,both single and mixed application of bamboo charcoal and effective microorganisms reduced the relative abundance of Nitrospirae.Among the top20 bacterial genera in relative abundance at the genus level,single application of bamboo charcoal treatment increased the relative abundance of the beneficial bacteria Pseudarthrobacter,and single application of effective microorganisms treatment increased the relative abundance of the beneficial bacteria Sphingobium,Bacillus and Pseudoarthrobacter.Compared with continuous cropping treatment,although mixed application of bamboo charcoal and effective microorganisms did not increase the relative abundance of the main bacterial phyla and genera,the LEf Se analysis showed that mixed application of bamboo charcoal and effective microorganisms enriched the beneficial bacteria of Nitrosomonadaceae,Enterobacter and etc.To sum up,continuous cropping of A.paniculata reduced the richness and diversity of soil bacteria,changed the bacterial community structure,and broke the original microecological balance.While the application of bamboo charcoal and effective microorganisms promoted transformation from the "fungal" soil to "bacteria" soil,improved soil enzyme activity,reduced soil phenolic acid accumulation,improved soil physical and chemical properties,increased the number of beneficial bacteria and improved soil bacterial community structure.The application of bamboo charcoal and effective microorganisms promoted the nitrogen metabolism level of A.paniculata,improved the quality of seeds during the fruiting period,and improved the yield and quality of A.paniculata.The application of bamboo charcoal and effective microorganisms could alleviate the continuous cropping obstacle of A.paniculata to a certain extent. |
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