Flue-cured tobacco cultivation method for triple cropping in two years

Abstract

The invention relates to the technical field of flue-cured tobacco planting, in particular to a two-year triple cropping flue-cured tobacco cultivation method, which adopts flue-cured tobacco-oilseed rape-corn rotation, flue-cured tobacco-oilseed rape-upland rice rotation or flue-cured tobacco-oilseed rape-buckwheat rotation. By means of the flue-cured tobacco cultivation method, the soil environment for flue-cured tobacco planting can be improved to a large extent, and the quality and yield of flue-cured tobacco are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue-cured tobacco cultivation, and specifically relates to a cultivation method for flue-cured tobacco with a three-crop rotation in two years. Background Art

[0002] Flue-cured tobacco is an important cash crop. Soil quality is an important factor for its growth, and the cropping system has an important impact on soil quality. Long-term monoculture of flue-cured tobacco will lead to nutrient imbalance in the tobacco-growing soil, a decrease in enzyme activity, and changes in microbial diversity.

[0003] The flue-cured tobacco cropping system still needs to be improved. Summary of the Invention

[0004] To solve at least one of the problems in the prior art, the present invention provides a cultivation method for flue-cured tobacco with a three-crop rotation in two years, which can greatly improve the soil environment for flue-cured tobacco cultivation and further improve the quality and yield of flue-cured tobacco.

[0005] A cultivation method for flue-cured tobacco with a three-crop rotation in two years adopts any of the following methods:

[0006] 1) Flue-cured tobacco - rapeseed - corn rotation (TRM)

[0007] After the flue-cured tobacco is harvested, rapeseed is planted. After the rapeseed is harvested, corn is planted in the following year; after the corn is harvested, flue-cured tobacco is planted. After the flue-cured tobacco is harvested, rapeseed is planted again; such a rotation is carried out, and two years is a cycle;

[0008] 2) Flue-cured tobacco - rapeseed - upland rice rotation (TRR)

[0009] After the flue-cured tobacco is harvested, rapeseed is planted. After the rapeseed is harvested, upland rice is planted in the following year; after the upland rice is harvested, flue-cured tobacco is planted. After the flue-cured tobacco is harvested, rapeseed is planted again; such a rotation is carried out, and two years is a cycle;

[0010] 3) Flue-cured tobacco - rapeseed - buckwheat rotation (TRS)

[0011] After the flue-cured tobacco is harvested, rapeseed is planted. After the rapeseed is harvested, buckwheat is planted in the following year; after the buckwheat is harvested, flue-cured tobacco is planted. After the flue-cured tobacco is harvested, rapeseed is planted again; such a rotation is carried out, and two years is a cycle.

[0012] Specifically, the planting time of flue-cured tobacco is April every year.

[0013] Specifically, the planting of flue-cured tobacco is by transplanting, the row spacing is 0.5 - 0.6 m, the plant spacing is 1 - 1.2 m, and the transplanting density is 13889 - 20000 plants / hm 2 ; preferably, the row spacing is 0.5 m, the plant spacing is 1.2 m, and the transplanting density is 15000 plants / hm 2 .

[0014] Specifically, the planting time of rapeseed is September every year, preferably the end of September.

[0015] Specifically, rapeseed is planted by broadcasting, and the seeding density is 4.5 - 8 kg / hm 2 ; preferably 7.5 kg / hm 2 .

[0016] Specifically, the planting time of corn is May of the following year.

[0017] Specifically, corn is planted by sowing, with 1 - 2 seeds per hole, and the specification is 45,000 - 75,000 plants / hm 2 ; preferably 52,500 plants / hm 2 .

[0018] Specifically, the planting time of upland rice is May of the following year.

[0019] Specifically, upland rice is planted by sowing, and the seeding density is 25 - 50 kg / hm 2 ; preferably 30 kg / hm 2 .

[0020] Specifically, the planting time of buckwheat is May of the following year.

[0021] Specifically, buckwheat is planted by drilling, and the seeding density is 40 - 60 kg / hm 2 ; preferably 45 kg / hm 2 .

[0022] Specifically, the fertilization for flue-cured tobacco planting is as follows: 60 - 90 kg / hm of special tobacco base fertilizer 2 , 30 - 45 kg / hm of potassium sulfate 2 , 30 - 60 kg / hm of biological organic fertilizer 2 , 30 - 60 kg / hm of special tobacco topdressing 2 , 5 - 15 kg / hm of special tobacco seedling-promoting fertilizer 2 ; preferably 75 kg / hm of special tobacco base fertilizer 2 , 38 kg / hm of potassium sulfate 2 , 45 kg / hm of biological organic fertilizer 2 , 45 kg / hm of special tobacco topdressing 2 , 8 kg / hm of special tobacco seedling-promoting fertilizer 2 .

[0023] Specifically, for rapeseed, corn, upland rice, and buckwheat, the base fertilizer before sowing is 140 - 160 kg / hm 2 , preferably 150 kg / hm 2 .

[0024] Specifically, 70 - 80 kg / hm of urea is applied to corn at the jointing stage 2 , preferably 75 kg / hm 2 .

[0025] Specifically, the top dressing for upland rice is 70 - 80 kg / hm of urea 2 , 75 kg / hm 2 .

[0026] Specifically, rape, corn, upland rice, and buckwheat can be fertilized according to local fertilization habits.

[0027] Specifically, the tobacco variety is Xiangyan No. 7.

[0028] Specifically, the rape variety is high glucosinolate rape.

[0029] Specifically, the corn variety is Huitian 192.

[0030] Specifically, the upland rice variety is Pioneer Upland Rice.

[0031] Specifically, the buckwheat variety is FQ10.

[0032] Specifically, the planting area is in the western part of Hunan, specifically Huayuan County, Xiangxi Autonomous Prefecture, Hunan Province, preferably the Tobacco Science and Technology Park in Daoer Township. Its altitude is 482.7 m, the climate belongs to the subtropical monsoon humid climate, and the test soil is sandy loam. The basic physical and chemical properties of the tested soil are: pH 5.65, organic matter 16.05 g / kg, available nitrogen 72.94 mg / kg, available phosphorus 26.90 mg / kg, and available potassium 640 mg / kg.

[0033] Using the two - crop - three - harvest flue - cured tobacco cultivation method (TRR and TRM) of the present invention can improve economic benefits compared with continuous cropping of flue - cured tobacco.

[0034] Using the two - crop - three - harvest flue - cured tobacco cultivation method of the present invention can improve the physical and chemical properties of the tobacco - growing soil. In this planting system, flue - cured tobacco - rape increases the pH value, organic matter, total nitrogen, available nitrogen, and available potassium content of the soil. Among them, the available nitrogen and available potassium contents in the soil of the three cultivation methods (TRM, TRR, and TRS) are higher than those of the continuously cropped flue - cured tobacco soil. The roots of rape secrete a large amount of sugars, amino acids, and organic acids, which promote the accumulation of soil organic matter, the mineralization process of organic nitrogen, and the improvement of potassium utilization efficiency. Moreover, the roots of upland rice and corn are relatively developed, which can deeply absorb potassium in the soil, reduce potassium loss, and improve potassium utilization efficiency.

[0035] The two-year triple-cropping flue-cured tobacco cultivation method of the present invention can improve the microbial diversity of tobacco-growing soil. The diversity of the microbial communities in the soils of the three cultivation methods (TRM, TRR, and TRS) of the present invention has been improved to varying degrees. Different crops can change the soil environment, provide diverse root exudates and nutrient sources, promote nutrient cycling, improve the soil microecological environment, and thus promote the improvement of soil microbial community diversity.

[0036] The two-year triple-cropping system of the present invention has changed the soil microbial species composition structure to a certain extent. Among them, in the bacterial community, the TRR and TRM treatments significantly increased the relative abundance of the phylum Planctomycetota in the soil. This phylum belongs to eco-friendly microorganisms and is beneficial to promoting nitrogen cycling in farmland. In the fungal community, the three cultivation methods of the present invention all significantly increased the relative abundance of the phylum Ascomycota in the soil. Most of these fungi are saprophytes and can participate in the carbon cycle by degrading organic matter, increasing the amount of organic matter in the soil. TRR significantly increased the relative abundance of the phylum Basidiomycota in the soil, which also has the function of degrading organic matter. However, the phylum Ascomycota mainly decomposes the unstable part of straw residues, while the phylum Basidiomycota mainly decomposes more difficult-to-decompose organic matter. The relative abundance of the phylum Chlorophyta in the TRR soil is relatively high. The photosynthesis of green algae is one of the most diverse and successful major groups among eukaryotes, and many branches of this phylum can provide oxygen and organic matter to the soil surface.

[0037] Based on linear discriminant analysis, it was found that the different microbial communities of the three tillage methods in the present invention showed significant enrichment. Among them, in the bacterial community, Actinomycetota and Burkholderiales were enriched in the soil treated with TRM, indicating their potential role in promoting soil nitrogen cycling and heavy metal remediation. Gemmata was enriched in the soil treated with TRR, and this bacterium has a positive effect on the mineralization of organic matter and nitrogen cycling. The significant enrichment of Lactiplantibacillus and Sphingomonas in the TRS treatment may promote the inhibition of the growth of pathogenic bacteria in the soil and improve the degradation efficiency of heavy metals in the soil. In the fungal community, Cladosporium was significantly enriched in the soil treated with TRM, which is involved in the degradation of organic matter and soil carbon cycling. The high abundances of Chldomonadales and Eurotiales in the TRR treatment indicate their important contributions to the decomposition of organic matter and soil carbon input. Glomerellales, which was significantly enriched in the TRS treatment, has been less studied at present, but it belongs to Glomeromycetes, and Glomeromycetes plays an important role in N uptake and host metabolism.

[0038] The physical and chemical properties of the soil have varying degrees of correlation with the microbial community. Among them, there are extremely significant correlation relationships between some indicators. In the bacterial community, Acidobacteriota, Actinomycetota, and Myxococota have extremely significant positive correlations with available nitrogen, indicating that available nitrogen may help support functional microorganisms related to the nitrogen cycle. Pseudomonadota and Nitrospirota have extremely significant positive correlations with available phosphorus. The former is known for its ability to dissolve mineral phosphorus and produce growth-promoting metabolites, reflecting that these bacterial phyla may dissolve phosphates or assist plants in absorbing phosphorus. Nitrospirota has an extremely significant positive correlation with total potassium, indicating that this bacterial phylum may play an important role in soil potassium utilization or potassium-related microbial metabolism. Gemmatimonadota and Bacillota have extremely significant negative correlations with available nitrogen, which may indicate their competitive advantages in low-nitrogen environments. Planctomycetota has an extremely significant negative correlation with available phosphorus, probably because the main functions of Planctomycetota are concentrated in the nitrogen cycle and carbon cycle, rather than directly participating in phosphorus dissolution or absorption. Therefore, when available phosphorus increases, functional bacterial groups related to the phosphorus cycle are more dominant, while the ecological niche of Planctomycetota is compressed. Bdellovibrionota has an extremely significant negative correlation with available potassium, perhaps because this bacterial phylum has more competitive advantages in low-nutrient or low-potassium environments. In the fungal community, Glomeromycota has an extremely significant positive correlation with available nitrogen, probably because it promotes nitrogen absorption through symbiosis with plants and adapts to high-nitrogen conditions. The extremely significant negative correlation between Anthophyta and available nitrogen indicates that it is more adapted to low-nitrogen environments and may face competitive disadvantages under high-nitrogen conditions.

[0039] Anthophyta was significantly positively correlated with available phosphorus, probably because it indirectly participated in the phosphorus cycle through metabolic activities. Anthophyta was significantly positively correlated with total phosphorus, indicating its adaptation to phosphorus-rich environments and its possible indirect participation in the phosphorus cycle through metabolic activities. Ascomycota and Glomeromycota were significantly negatively correlated with total phosphorus, indicating that these microbial communities were more adapted to low-phosphorus environments. The significant positive correlation between Anthophyta and total potassium might be because the high-potassium environment indirectly promoted the reproduction of Anthophyta by affecting the composition of plant root exudates. The significant negative correlation between Ascomycota and total potassium indicated that it might be more involved in the degradation of organic matter and the transformation of mineral potassium under low-potassium conditions. The significant positive correlation between Ascomycota and total nitrogen might be because Ascomycota released nitrogen by decomposing organic matter, further enhancing its functional performance in nitrogen-rich soils.

[0040] Among them, the integrated effect of the tobacco-rapeseed-corn rotation (TRM) tillage method was the best. The cycle economic benefit of the TRM tillage method was relatively high. Ascomycota was significantly positively correlated with total nitrogen in the soil and significantly positively correlated with the content of hydrolyzable nitrogen. The significantly enriched genera-level microbial communities in the soil treated by TRM were Cladosporium, Setophoma, Candolleomyces, and Spizellomyces, all of which belonged to Ascomycota, indicating that the TRM tillage method was beneficial to improving soil fertility, especially nitrogen content.

[0041] The soil environment for growing tobacco in the Xiangxi region is very different from that in other regions. The differences in natural conditions such as mountainous terrain and high precipitation in the Xiangxi region, combined with the response mechanism of yellow soil relying on organic matter buffering rather than the salt-base saturation in the north or the flooding dechlorination in the south, enable the two-crops-in-three-years tillage mode to better cope with risks such as out-of-control soil acidification, excessive chlorine content, damaged buffering performance, and degraded tillage layer in the Xiangxi region.

[0042] According to the natural conditions such as light, temperature, water, and soil in the Xiangxi region, and comprehensively considering factors such as the growth period of crops and the balanced and coordinated supply of soil nutrients in the rotation system, the present invention proposes a two-crops-in-three-years tillage method for flue-cured tobacco, which can improve the soil environment for growing tobacco, enhance the comprehensive quality of tobacco fields, and promote the sustainable development of tobacco leaf production. Aiming at the problems of nutrient imbalance, decreased enzyme activity, and changes in microbial diversity in the tobacco-growing soil caused by long-term monoculture of flue-cured tobacco, the method of the present invention can significantly improve the physical and chemical properties of the soil and the microbial community structure. Description of the Drawings

[0043] Figure 1Principal coordinate analysis diagram of soil fungal and bacterial community structures for each treatment.

[0044] Figure 2 Upset diagram (set intersection diagram) of soil microbiota for each treatment.

[0045] Figure 3 Microbial community composition diagram of soil for each treatment.

[0046] Figure 4 LEfSe analysis diagram of differential bacteria and fungi in soil for each treatment.

[0047] Figure 5 Heatmap of the correlation between bacterial and fungal phyla and soil physical and chemical properties for each treatment. Detailed implementation manners

[0048] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of the specific implementation manners of the present invention. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0049] Experiment 1

[0050] 1.1 Experimental design

[0051] 1.1.1 Test materials

[0052] This experiment was conducted at the Tobacco Science and Technology Park, Dao'er Township, Huayuan County, Xiangxi Autonomous Prefecture, Hunan Province (N28°31′30″, E 109°27′20″) from March 2023 to September 2024. The altitude is 482.7 m, and the climate is subtropical monsoon humid climate. The test soil is sandy loam. The basic physical and chemical properties of the test soil are as follows: pH 5.65, organic matter 16.05 g / kg, available nitrogen 72.94 mg / kg, available phosphorus 26.90 mg / kg, available potassium 640 mg / kg. The test tobacco variety is Xiangyan 7, the rapeseed variety is high-glucosinolate rapeseed, the corn variety is Huitian 192, the buckwheat variety is FQ10, and the upland rice variety is Upland Rice Pioneer.

[0053] 1.1.2 Experimental design and treatments

[0054] Taking continuous tobacco cropping as the control (CK), four treatments were set up: tobacco - rapeseed - corn (TRM), tobacco - rapeseed - upland rice (TRR), and tobacco - rapeseed - buckwheat (TRS). There were 3 replicates, a total of 12 plots, and the plot area was approximately 65 m 2The flue-cured tobacco was transplanted in April 2023 and 2024 respectively, with a row spacing of 0.5 m and a plant spacing of 1.2 m, and the transplanting density was about 15,000 plants / hm 2 ; Rapeseed was broadcast-sown at the end of September 2023, and the seeding density was 7.5 kg / hm 2 ; Maize was sown in May of the following year, with 1-2 seeds per hole, and the specification was 52,500 plants / hm 2 ; Buckwheat was sown in rows in May of the following year, and the seeding density was 45 kg / hm 2 ; Upland rice was broadcast-sown in May of the following year, and the seeding density was 30 kg / hm 2 . The fertilization of flue-cured tobacco was carried out according to the local fertilization habit, with 75 kg / hm of special tobacco base fertilizer 2 , 38 kg / hm of potassium sulfate 2 , 45 kg / hm of biological organic fertilizer 2 , 45 kg / hm of special tobacco topdressing 2 , 8 kg / hm of special tobacco seedling-promoting fertilizer 2 . The fertilization of other crops was carried out according to the local fertilization habit, and 150 kg / hm of base fertilizer was applied before sowing 2 , and 75 kg / hm of urea was applied to maize at the jointing stage 2 , and the topdressing of upland rice was 75 kg / hm of urea 2 .

[0055] 1.1.3 Sample collection, detection items and methods

[0056] The economic benefits of each cycle were investigated. After the harvest of each crop in the following year, the five-point sampling method was used to collect the plough layer soil of 0-15 cm around the rhizosphere of the plants by the ring knife method. The collected soil samples were put into sterile bags and immediately taken back to the laboratory. After passing through a 2-mm soil sieve and removing some impurities, they were divided into two parts. One part was placed indoors for air drying and grinding for soil physical and chemical property detection; the other part was stored in a -80 °C refrigerator for soil microbial community detection. The soil pH was measured by the potentiometric method, the soil organic matter was measured by the external heating method of potassium dichromate volumetric method, the soil available nitrogen was measured by the alkaline diffusion method, the soil available phosphorus was measured by extraction (molybdenum antimony anti-colorimetric method), the soil available potassium was measured by extraction (flame photometry method), the total phosphorus was measured by molybdenum antimony anti-colorimetric method, the total nitrogen was measured by the Kjeldahl method, and the total potassium was measured by flame photometry method. The collected soil samples were sent to Guangzhou Gene Denovo Biotechnology Co., Ltd. for the detection of 16S rRNA and ITS1 of the soil microbial community

[0057] 1.1.4 Data processing and analysis

[0058] Microsoft Excel 2003 and SPSS 26.0 were used to summarize and analyze the data

[0059] 2.1 Results and Analysis

[0060] 2.1.1 Economic Benefits of Each Treatment Cycle

[0061] The total output value of TRR and TRM increased by 2,080.05 - 3,237.15 yuan / hm compared with CK 2 . It shows that the two - crop - three - harvest system can increase the economic income of farmers. The results are shown in Table 1

[0062] Table 1 Economic Benefits of Each Treatment Cycle

[0063]

[0064] Note: Different lowercase letters after the data in the same column indicate significant differences between treatments (P < 0.05); the same applies to the following tables or figures

[0065] 2.1.2 Effects of Each Treatment on Soil Physical and Chemical Properties

[0066] The physical and chemical properties of the soil after each crop harvest are shown in Table 2. Compared with CK, the pH value of TRR increased significantly; the organic matter of TRR increased compared with CK but there was no significant difference; the total nitrogen content and available nitrogen content of each treatment increased significantly; the available potassium content of each treatment increased, and there was a significant difference in TRS compared with CK

[0067] Table 2 Physical and Chemical Properties of the Soil after Each Crop Harvest

[0068]

[0069] 2.1.3 Effects of Each Treatment on Soil Microbial Diversity

[0070] PCoA analysis (principal coordinate analysis) was carried out on the soil after each treatment harvest, and the results are shown in Figure 1 . There were significant aggregations in the bacterial and fungal community structures of each treatment and in different regions, indicating differences between samples. As can be seen from Table 3, compared with CK, the bacterial Shannon index and Chao1 index of TRM increased, the bacterial Ace index of TRM and TRR increased, and there was a significant difference in the bacterial Ace index of TRR compared with CK. The fungal Shannon index of each treatment increased significantly compared with CK, the fungal Simpson index of TRM increased significantly, and the fungal Chao1 index and Ace index of TRS and TRM increased significantly. It shows that the two - crop - three - harvest system improves the microbial diversity of tobacco - growing soil

[0071] Table 3 Microbial Diversity Indexes of Soil Bacteria and Fungi in Each Treatment

[0072]

[0073] 2.1.4 Analysis of the Impact of the Double Cropping System in Two Years on the Quantity of Soil Microflora

[0074] The soil of each treatment was subjected to microflora detection and analysis, and the results are as Figure 2 shown. 5416, 4733, 4949, and 5428 species of bacterial OUTs were detected in the soil of CK, TRR, TRS, and TRM treatments respectively. Among them, there were 1945 common species, and the specific quantities were 2058, 1587, 1832, and 2032 species respectively. Compared with CK, the soil of the TRM treatment had 12 more OTUs; 964, 993, 1191, and 1102 species of fungal OTUs were detected in the soil of CK, TRR, TRS, and TRM treatments respectively. Among them, there were 393 common species, and the specific quantities were 241, 212, 393, and 281 species respectively. Compared with CK, the soil of the TRR, TRS, and TRM treatments had 29, 227, and 138 more OTUs respectively. Thus, it can be seen that the double cropping system in two years increased the quantities of bacterial and fungal microflora in the tobacco-growing soil.

[0075] 2.1.5 Impact of the Double Cropping System in Two Years on the Composition of Soil Microbial Communities

[0076] The composition of the microbial communities in the soil of each treatment is shown in Figure 3 . Figure 3 Among them, A and B are the composition diagrams of the top ten species at the phylum and genus levels in the bacterial community, and C and D are the composition diagrams of the top ten species at the phylum and genus levels in the fungal community.

[0077] From Figure 3It can be seen that in the soil after harvesting in each treatment of the two-year triple cropping system, at the phylum level of the bacterial community, Pseudomonadota, Acidobacteriota, Actinomycetota, Planctomycetota, Chloroflexota, Gemmatimonadota, Bacteroidota, Verrucomicrobiota, Bacillota, and Patescibacteria accounted for more than 80% of the total relative abundance. Compared with CK, the relative abundance of Planctomycetota in the soil was significantly increased in the TRR treatment and the TRM treatment; at the genus level of the bacterial community, Incertae_Sedis, Sphingomonas, Lactiplantibacillus, Gemmatimonas, Ellin6067, Gemmata, Bryobacter, Ramlibacter, Gaiella, and Intrasporangium were the top ten species in relative abundance; at the phylum level of the fungal community, Ascomycota, Anthophyta, Basidiomycota, Chlorophyta, Cillophora, Chytridiomycota, Mortierellomycota, Glomeromycota, Mucoromycota, and Bryophyta accounted for more than 80% of the total relative abundance. Compared with CK, the relative abundance of Ascomycota was significantly increased in each treatment, the relative abundance of Basidiomycota in the soil was significantly increased in the TRM and TRR treatments, and the relative abundance of Chlorophyta in the soil was significantly increased in the TRR treatment;At the genus level of the fungal community, Fusarium, Rhizoctonia, Mortierella, Sida, Halteria, Podospora, Spizellomyces, Setophoma, and Humicola were the species with relatively high abundances. Compared with CK, the TRM treatment significantly increased the relative abundances of Setophoma, Halteria, and Mortierella in the soil. The TRR treatment significantly increased the relative abundances of Rhizoctonia and Podospora in the soil. The TRS treatment significantly increased the relative abundances of Sida and Fusarium in the soil.

[0078] 2.1.6 LEFSe analysis of the soil microbial community in the two-year triple-cropping system

[0079] The linear discriminant analysis effect size (LEFSe) was used to identify the differential bacterial communities in the soil of each treatment, and the results are shown as follows. Figure 4 as follows Figure 4Among them, A is the linear discriminant analysis at the bacterial genus level and above (LDA > 4); B is the linear discriminant analysis at the fungal genus level and above (LDA > 4). When the LDA value is greater than 4, the bacterial communities of 8 branches at different levels are significantly enriched in the soils treated with TRM, TRS, and TRR. Among them, there are 4 indicator taxa in the soil treated with TRM, 2 are unclassified genera (Incerta_Sedis), and the other 2 are Actinomycetota and Burkholderiales; there are 2 indicator taxa in the soil treated with TRR, one is Gemmata, and the other is Pedosphaeraceae at the genus level; there are 2 indicator taxa in the soil treated with TRS, which are Sphingomonas and Lactiplantibacillus respectively. The fungal communities of 13 branches at different levels are significantly enriched in the soils treated with TRM, TRS, and TRR. Among them, there are 4 indicator taxa in the treatment of TRR, which are Chldomonadales, Eurotiales, Chaetothyriales, and Ceratobasidium respectively; there are 4 indicator taxa in the treatment of TRS, which are Glomerellales, Trelemellales at the family level, Fagopyrum, and Didymmelaceae respectively; there are 5 indicator taxa in the treatment of TRM, which are Cladosporium, Setophoma, Candolleomyces, and Spizellomyces at the genus level of Glomeromycota.

[0080] 2.1.7 Relationship between microbial communities and soil physical and chemical properties

[0081] Furthermore, a correlation analysis was conducted on the bacteria and fungi phyla in the soil after harvest of each treatment and the soil physical and chemical properties. The results are shown in Figure 5 . Figure 5 Among them, OM is organic matter, N is total nitrogen, P is total phosphorus, K is total potassium, AN is available nitrogen, AP is available phosphorus, AK is available potassium, * indicates p < 0.05, ** indicates p < 0.01, *** indicates p < 0.001.

[0082] The results of the correlation heatmap showed that in the bacterial community, Bacillota was positively correlated with pH, Acidobacteriota, Actinomycetota, and Myxococota were extremely significantly positively correlated with the available nitrogen content, Latescibacterota and Thermodesulfobacteriota were significantly positively correlated with the available nitrogen, Gemmatimonadota and Bacillota were extremely significantly negatively correlated with the available nitrogen, Pseudomonadota and Nitrospirota were extremely significantly positively correlated with the available phosphorus, Gemmatimonadota was positively correlated with the available phosphorus, Planctomycetota was extremely significantly negatively correlated with the available phosphorus, Acidobacteriota and Verrucomicrobiota were significantly negatively correlated with the available phosphorus, Bdellovibrionota was significantly negatively correlated with the available potassium, Gemmatimonadota and Bacillota were extremely significantly positively correlated with the total phosphorus, Nitrospirota was positively correlated with the total phosphorus, Acidobacteriota, Actinomycetota, and Myxococota were significantly negatively correlated with the total phosphorus, Nitrospirota was extremely significantly positively correlated with the total potassium, Pseudomonadota and Gemmatimonadota were significantly positively correlated with the total potassium, Nitrospirota was extremely significantly negatively correlated with the total nitrogen, Chloroflexota and Gemmatimonadota were significantly negatively correlated with the total nitrogen.

[0083] In the fungal community, Basidiomycota showed a significant negative correlation with organic matter, Glomeromycota showed a highly significant positive correlation with available nitrogen, Ascomycota showed a positive correlation with available nitrogen, Anthophyta showed a highly significant negative correlation with available nitrogen, Anthophyta showed a highly significant positive correlation with available phosphorus, Mortierellomycota showed a significant positive correlation with available phosphorus, Ascomycota and Glomeromycota showed a significant negative correlation with available phosphorus, Anthophyta showed a highly significant positive correlation with total phosphorus, Ascomycota and Glomeromycota showed a highly significant negative correlation with total phosphorus, Anthophyta showed a highly significant positive correlation with total potassium, Mortierellomycota showed a significant positive correlation with total potassium, Ascomycota showed a highly significant negative correlation with total potassium, Ascomycota showed a highly significant positive correlation with total nitrogen, Glomeromycota showed a significant positive correlation with total nitrogen, and Anthophyta showed a highly significant negative correlation with total nitrogen. It can be seen that there is a certain degree of correlation between soil physical and chemical properties and soil bacterial and fungal communities.

[0084] In summary, compared with continuous tobacco cropping, the two-year three-crop tobacco cultivation method of the present invention improved soil fertility, increased the content of key nutrients such as pH value, organic matter, available nitrogen, and available potassium; improved soil microbial diversity, and to varying degrees increased the Shannon index, Chao1 index, Simpsion index, and Ace index of soil bacterial and fungal communities; changed the microbial community structure, and the dominant bacterial communities in each treatment changed compared with CK. For example, the dominant fungal community at the phylum level in each treatment became Ascomycota; each treatment promoted the significant enrichment of a variety of beneficial microorganisms, such as the enrichment of Lactiplantibacillus, further indicating the enrichment effect of the two-year three-crop rotation mode of the present invention on eco-friendly bacterial communities. There is a significant correlation between soil physical and chemical properties and microbial communities, such as the highly significant positive correlation between Acidobacteriota and available nitrogen. These results provide a reference for revealing the complex interactions between soil-microorganisms-nutrients. Among them, the comprehensive effect of flue-cured tobacco-rape-corn is the best, with the highest cycle economic benefit, and significantly increases the nitrogen element content in the soil. The present invention is particularly suitable for the western Hunan region and promotes the development of the flue-cured tobacco planting system.

[0085] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A flue-cured tobacco farming method of a two-year three-cropping system, characterized in that: Use any of the following methods: 1) Flue-cured tobacco-rapeseed-corn rotation After the flue-cured tobacco is harvested, rapeseed is planted. After the rapeseed is harvested, corn is planted the following year. After the corn is harvested, flue-cured tobacco is planted. After the flue-cured tobacco is harvested, rapeseed is planted again. This cycle of planting is repeated for two years. 2) Flue-cured tobacco-rapeseed-upland rice rotation After the flue-cured tobacco is harvested, rapeseed is planted. After the rapeseed is harvested, upland rice is planted the following year. After the upland rice is harvested, flue-cured tobacco is planted. After the flue-cured tobacco is harvested, rapeseed is planted again. This cycle of planting is repeated for two years. 3) Flue-cured tobacco-rapeseed-buckwheat rotation Rapeseed is planted after tobacco is harvested, and buckwheat is planted the following year after rapeseed is harvested; tobacco is planted after buckwheat is harvested, and rapeseed is planted again after tobacco is harvested; this cycle repeats itself, with one year as a cycle.

2. The flue-cured tobacco farming method of two-year three-cropping system according to claim 1, characterized in that: The planting period for flue-cured tobacco is April every year; and / or, The planting method of flue-cured tobacco is transplanting, with a row spacing of 0.5-0.6m, a plant spacing of 1-1.2m, and a transplanting density of 13889-20000 plants / hm2. 2 Preferably, the row spacing is 0.5m, the plant spacing is 1.2m, and the transplanting density is 15,000 plants / hm2. 2 .

3. The flue-cured tobacco farming method of two-year three-cropping system according to claim 1 or 2, characterized in that: The rapeseed is planted in September every year, preferably at the end of September; and / or, Rapeseed is planted by broadcasting with a sowing density of 4.5-8kg / hm2. 2 ; preferably 7.5kg / hm 2 .

4. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 3, characterized in that: Corn is planted in May of the following year; and / or, Corn is planted by sowing, with 1-2 seeds per hole, and the specification is 45,000-75,000 plants / hm2. 2 ; preferably 52500 plants / hm 2 .

5. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 4, characterized in that: The planting time for upland rice is May of the following year; and / or, The planting of upland rice is sowing, and the sowing density is 25-50kg / hm 2 ; preferably 30kg / hm 2 .

6. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 5, characterized in that: Buckwheat is planted in May of the following year; and / or, Buckwheat is planted in rows at a density of 40-60 kg / hm2. 2 ; preferably 45kg / hm 2 .

7. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 6, characterized in that: The fertilization for flue-cured tobacco is: 60-90kg / hm2 of tobacco-specific base fertilizer 2 , Potassium sulfate 30-45kg / hm 2 , Bio-organic fertilizer 30-60kg / hm 2 , Tobacco special topdressing 30-60kg / hm 2 , Tobacco seedling fertilizer 5-15kg / hm 2 ; preferably 75kg / hm2 of tobacco-specific basal fertilizer 2 , Potassium sulfate 38kg / hm 2 , Bio-organic fertilizer 45kg / hm 2 , Tobacco special topdressing 45kg / hm 2 , Tobacco seedling fertilizer 8kg / hm 2 and / or, Rapeseed, corn, upland rice, buckwheat should be fertilized with 140-160 kg / hm2 of base fertilizer before sowing 2 , preferably 150kg / hm 2 and / or, Apply urea 70-80kg / hm2 to corn at the jointing stage 2 , preferably 75kg / hm 2 and / or, Topdressing for upland rice is urea 70-80kg / hm 2 , 75kg / hm 2 .

8. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 7, characterized in that: The tobacco variety is Xiangyan No. 7; and / or, The rapeseed variety is high glucosinolate rapeseed; and / or, The corn variety is Huitian 192; and / or, The upland rice variety is an upland rice pioneer; and / or, The buckwheat variety was FQ10.

9. The flue-cured tobacco farming method of two-year three-cropping system according to any one of claims 1 to 8, characterized in that: The planting area is Xiangxi region, specifically Huayuan County, Xiangxi Autonomous Prefecture, Hunan Province, and preferably Daoer Township Tobacco Science and Technology Park.

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