Flue-cured tobacco intercropping chive planting device and method and application thereof

Abstract

The invention relates to the technical field of flue-cured tobacco planting, in particular to a flue-cured tobacco intercropping chive planting device and method and application thereof.The flue-cured tobacco intercropping chive planting method comprises the following steps that S1, a tobacco field is prepared; s2, tobacco plant transplanting; s3, intercropping chives: intercropping chives on tobacco ridges of the flue-cured tobaccos after the tobacco plants of the flue-cured tobaccos are transplanted, and controlling the plant spacing of the chives to be a preset spacing; when the height of the chives reaches 15-20 cm, the chives are harvested for the first time, and then the chives are harvested once every 25 days; s4, harvesting and soil improvement: harvesting tobacco leaves at the upper parts of the tobacco plants in mid-to-late September; removing tobacco stems of the flue-cured tobacco in late October, and immediately preparing soil and sowing green manure; turning over the green manure plants in the soil for decomposition; s5, circular planting. The method is used for relieving tobacco field damping-off, the current situation of continuous cropping of flue-cured tobaccos in a tobacco planting area can be changed, the soil microenvironment for tobacco plant growth is improved, and the problem that soil-borne diseases are increased due to long-term continuous cropping of flue-cured tobaccos is solved.

Description

Technical Field

[0001] This invention relates to the field of flue-cured tobacco planting technology, specifically to a planting device, method, and application for intercropping flue-cured tobacco with scallions. Background Technology

[0002] Flue-cured tobacco is an important economic crop in my country. In recent years, the excessive use of fertilizers and long-term continuous cropping have caused problems such as soil nutrient imbalance, frequent occurrence of soil-borne diseases, changes in soil microbial flora and diversity, and accumulation of autotoxic substances, resulting in aggravated flue-cured tobacco diseases and a decline in yield and quality.

[0003] Rhizoctonia solani Kuhn, a blight pathogen affecting flue-cured tobacco, is widespread in soil and distributed in all tobacco-producing countries worldwide, particularly severe in continuously cropped fields and under hot and humid conditions. However, control methods still have limitations. For example, while traditional chemical fungicides offer advantages such as low cost and fewer limitations, their extensive use leads to pesticide residue problems, affecting not only tobacco quality and safety but also threatening human health. Furthermore, long-term, high-volume use of chemical pesticides increases resistance in pathogens and pests; broad-spectrum pesticides can also inadvertently kill natural enemies of pests, resulting in increasingly poor efficacy and a series of environmental pollution problems. Exogenous biocontrol agents, due to their short shelf life and high cost, are still difficult to control in the short term. Therefore, finding a safer and more effective production management approach to reduce soil-borne diseases in tobacco plants is imperative.

[0004] Compared to monoculture tobacco planting, intercropping can increase the diversity of tobacco field systems. The literature "The Influence of Intercropping on the Composition and Function of Rhizosphere Soil Bacterial Community of Flue-cured Tobacco Plants" proposes that the imbalance of the rhizosphere microecological environment of flue-cured tobacco, especially the change in the structure of the soil bacterial community, is the main biological factor causing continuous cropping obstacles. In the continuous cropping mode of flue-cured tobacco, the root exudates of the same tobacco plants may lead to a simpler soil microbial community structure, thereby affecting the soil physicochemical and biological activities, ultimately resulting in a decline in soil quality, stunted growth and development of tobacco plants, reduced tobacco yield and quality, increased number of tobacco pathogens, and aggravation of soil-borne diseases. On the other hand, the intercropping and rotation planting mode is conducive to the interspecific interaction between tobacco plants and intercropped plants to activate soil nutrients, regulate the community structure of crop rhizosphere soil microorganisms, and improve plant productivity and immunity by inhibiting pathogenic microorganisms. Moreover, the stability and dominance of the rhizosphere microbial community are stronger, which is an effective means to alleviate crop continuous cropping obstacles and improve the system's stress resistance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a planting device, method, and application for intercropping scallions with flue-cured tobacco, which can help alleviate damping-off disease in tobacco fields. This application not only changes the current situation of continuous flue-cured tobacco cropping in tobacco-growing areas and improves the soil microenvironment for tobacco plant growth, but also avoids the problem of increased soil-borne diseases caused by long-term continuous flue-cured tobacco cropping.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a method for intercropping scallions with flue-cured tobacco, comprising the following steps: S1, Tobacco field preparation: In late March, apply base fertilizer suitable for flue-cured tobacco to the flue-cured tobacco field, then form ridges and cover the soil surface with biodegradable mulch film. S2, tobacco transplanting: tobacco plants are transplanted in mid-to-late April according to the preset density. The preset density of tobacco plants corresponds to a row spacing of 120cm and a plant spacing of 50-55cm. S3, intercropping with scallions: After the tobacco plants are transplanted, scallions are intercropped on the tobacco ridges, and the spacing between the scallion plants is controlled at the preset interval; when the scallions reach a height of 15-20cm, the first harvest is carried out, and then the harvest is carried out every 25 days. S4, Harvesting and Soil Improvement: Harvest the upper tobacco leaves in mid-to-late September; after removing the tobacco stalks in late October, immediately prepare the land and sow green manure; and then plow the green manure plants into the soil to decompose. S5, Cyclic Planting: Repeat steps S1-S4 to achieve cyclical intercropping of flue-cured tobacco and scallions.

[0007] Furthermore, in S2, the preset density of tobacco plants is 1100-1200 plants / acre.

[0008] Furthermore, in S3, the intercropping time for scallions is limited to 0-7 days after the tobacco plants are transplanted.

[0009] Furthermore, in S3, the preset spacing of the scallions is 8-12cm.

[0010] Furthermore, in S3, the intercropping layout of scallions is that a row of scallions is placed on each side of each row of tobacco plants in the tobacco ridge, with every two rows of scallions symmetrically distributed about the center line of the tobacco ridge.

[0011] Furthermore, in S4, the green manure is plowed and decomposed in mid-to-late March of the following year.

[0012] The above approach has the following beneficial effects: 1. This solution systematically addresses the root cause of soil-borne diseases caused by long-term continuous cropping of flue-cured tobacco. Traditional methods for dealing with continuous cropping obstacles often focus on crop rotation, chemical pesticides, or the application of exogenous biocontrol agents, which have limitations such as long cycles, environmental pollution, unstable efficacy, or high costs. This invention introduces scallions, a specific crop, into the flue-cured tobacco production system for the first time with precise agronomical specifications. This is not a simple crop intercropping, but rather based on the ecological principle that sulfur-containing compounds in scallion root exudates have broad-spectrum antibacterial, antifungal, and nematicidal activities, selectively inhibiting bacteria, activating beneficial soil microbial communities, and recruiting specific antibacterial metabolites, thus artificially constructing a continuously effective barrier in the rhizosphere of tobacco plants. At the same time, the solution seamlessly integrates the intercropping system with soil conservation measures such as autumn sowing of green manure and spring plowing and returning to the field, forming a year-round ecological cycle model of "flue-cured tobacco growing season - scallion intercropping for disease suppression and soil nourishment" and "post-flue-cured tobacco harvest - green manure planting to activate the soil." This comprehensive solution, which combines biological intercropping effects with active soil remediation, has fundamentally changed the passive control situation in tobacco-growing areas that relied on chemical inputs, and has achieved ecological, sustainable and systematic management of continuous cropping obstacles.

[0013] 2. This scheme combines intercropping with a cyclical soil improvement system to form a closed-loop planting system of "tobacco-scallion-green manure," overcoming the limitation of single intercropping only providing short-term disease relief. Existing technologies mostly focus on single crop combinations or single soil treatments, while this scheme introduces green manure sowing and composting after tobacco harvest. Through the soil fertilization effect of green manure, it complements the initial improvement effect of scallions on the soil microenvironment, further repairing problems such as nutrient imbalance and microbial flora disorder in continuously cropped soils. This cyclical design achieves an organic connection between "disease control - soil improvement - sustainable production," fundamentally breaking the vicious cycle of continuous tobacco cropping obstacles, rather than a short-term intervention that only treats the symptoms. It provides a systematic solution for sustainable tobacco production.

[0014] 3. This solution creatively balances the safety, practicality, and economic benefits of disease control, resolving the inherent contradictions of existing control methods. Traditional chemical control poses risks such as pesticide residues, resistance, and environmental pollution, while exogenous biocontrol bacteria face problems of high cost and short shelf life. This solution completely abandons chemical pesticides and expensive biocontrol agents, relying on intercropping interactions and the natural remediation capacity of the soil to achieve disease control, ensuring tobacco quality and ecological safety. Furthermore, the technical process is simple and easy to operate, with all steps adapted to existing field management models for flue-cured tobacco cultivation. No additional complex equipment or special technical training is required. Moreover, the harvesting of scallions and the application of green manure can increase the multiple cropping index in tobacco fields, increasing economic benefits while controlling diseases. This achieves a triple unity of ecological, social, and economic benefits, overcoming the shortcomings of existing technologies that struggle to balance control effectiveness with safety and cost.

[0015] 4. In addition to the highly efficient and broad-spectrum pathogen-inhibiting ability provided by the unique sulfur-containing secretions of scallion roots, this solution also benefits from the fact that scallion plants are short and do not compete with tobacco for sunlight, allowing the tobacco to maintain apical dominance. Furthermore, the shallow root system of scallions primarily absorbs nutrients and water from the topsoil, creating a complementary spatial niche with the deeper taproot system of tobacco, resulting in minimal competition. Moreover, scallions grow quickly, have a short harvest cycle, and can be harvested multiple times. Their vigorous growth period overlaps with the early and middle stages of tobacco's susceptibility to disease, providing continuous protection during the most critical periods.

[0016] Furthermore, a planting device for intercropping scallions with flue-cured tobacco, used to implement the aforementioned method of intercropping scallions with flue-cured tobacco, includes a positioning frame. The hollow part of the positioning frame is adapted to the structure of the tobacco ridge. The positioning frame spans above the tobacco ridge. Adjustment components are provided on both sides of the positioning frame. Several positioning components are fixedly connected to the adjustment components. The adjustment components are used to adjust the spacing between adjacent planting points on the positioning components on the same side of the positioning frame. The positioning components are used to mark the planting points of scallions. Each positioning component includes a positioning rod. The bottom of each positioning rod is fixedly connected to a spike. The side wall of each positioning rod is provided with a scale line for marking the insertion depth of the positioning rod.

[0017] Beneficial effects: By setting up a positioning frame adapted to the tobacco ridge structure, the stability and row alignment of the device in the field are ensured. The crucial and time-consuming operation of symmetrically and equidistantly marking points on both sides of the tobacco ridge, which originally relied on manual experience, has been transformed into a standardized process that can be completed quickly and in batches with mechanical assistance. This fundamentally solves the problem of consistency in technology implementation and ensures that during large-scale field operations, the planting position of each scallion strictly conforms to the accurate spatial layout of the tobacco ridge on both sides and in the row.

[0018] Furthermore, each adjustment component includes a slide rail fixedly connected to one side of the positioning frame. Several sliding seats are slidably fitted inside the slide rail. Each sliding seat corresponds to a positioning rod, and the positioning rod is fixedly connected to the sliding seat.

[0019] Beneficial effects: The sliding fit structure between the slide rail and the sliding seat is simple and flexible to adjust. The sliding seat and the positioning rod correspond one-to-one, and the distance between adjacent positioning rods can be directly adjusted by sliding. Precise positioning of the plant spacing of "8-12cm" can be achieved without additional measuring tools. It can not only meet the optimal plant spacing standard preset by this invention, but also fine-tune the spacing according to factors such as tobacco plant growth and soil fertility, thus improving the versatility of the device.

[0020] Furthermore, each slide rail is provided with several locking grooves, and each side of the sliding seat is hinged with a locking buckle, which corresponds to the locking groove.

[0021] Beneficial effects: The corresponding locking structure of the locking buckle and locking groove can fix the sliding seat in the preset position, avoiding the spacing deviation caused by device shaking or operation touch when marking the planting point, ensuring that the plant spacing accuracy always meets the requirements, ensuring the balance of nutrient competition between scallions and tobacco plants, and avoiding the impact of improper density on soil nutrient distribution and microbial community stability.

[0022] One of the methods for intercropping scallions with flue-cured tobacco is used to reduce damping-off disease in flue-cured tobacco fields.

[0023] Beneficial effects: By precisely controlling the intercropping layout, plant spacing and planting depth through the planting device, the optimal interspecific interaction between scallions and tobacco plants can be ensured. This can effectively improve the nutrient composition of the rhizosphere soil of tobacco plants, promote the accumulation of beneficial nutrients such as organic carbon, nitrate nitrogen and available phosphorus, reduce the content of ammonium nitrogen related to the reproduction of damping-off pathogens, and inhibit the growth of pathogens from the perspective of nutrient competition. Precision planting can ensure the stable growth of scallions, thereby increasing the diversity of fungal communities in the rhizosphere soil of tobacco plants, optimizing the composition of fungal communities, increasing the abundance of beneficial bacteria, reducing the proportion of harmful bacteria, and strengthening the role of the disease-resistant functional layer, thereby enhancing the soil's ability to inhibit pathogens. It helps to recruit antimicrobial metabolites, reduce the accumulation of harmful metabolites, and directly inhibit the activity of damping-off pathogens through biochemical action, significantly reducing the incidence of disease; It avoids the problems of pesticide residues, drug resistance and environmental pollution caused by traditional chemical fungicides, and does not rely on expensive and short-shelf-life exogenous biocontrol bacteria. It achieves disease control through ecological regulation, ensures the quality and safety of tobacco leaves, increases the multiple cropping index of tobacco fields, improves economic benefits, and provides technical support for the sustainable production of flue-cured tobacco. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the method steps in an embodiment of the method for intercropping scallions with flue-cured tobacco according to the present invention. Figure 2 This is an isometric schematic diagram of an embodiment of the planting device for intercropping flue-cured tobacco and scallions according to the present invention. Figure 3 A frontal schematic diagram of the positioning component in an embodiment of the planting device for intercropping flue-cured tobacco and scallions according to the present invention; Figure 4 The effects of different intercropping plants on the incidence and pathogen quantity of damping-off disease in tobacco fields; Figure 5 The effects of different intercropping plants on soil nutrients in tobacco fields; Figure 6 The effects of different intercropping plants on the diversity of rhizosphere soil fungal communities in flue-cured tobacco; Figure 7 The effects of different intercropping plants on the composition and function of the rhizosphere soil fungal community of tobacco plants; Figure 8 The effects of different intercropping plants on rhizosphere soil metabolites in flue-cured tobacco; Figure 9 The effects of different timing of scallion planting on the incidence and pathogen count of damping-off disease in tobacco fields; Figure 10 The effects of different timing of scallion planting on soil nutrients in tobacco fields; Figure 11 The effects of different intercropping plants on the composition and function of the rhizosphere soil fungal community of tobacco plants; Figure 12 The effects of different intercropping plants on rhizosphere soil metabolites in flue-cured tobacco; Figure 13 The effects of different densities of scallions intercropped with flue-cured tobacco on the incidence and pathogen count of damping-off disease in tobacco fields; Figure 14 The effects of different densities of scallions intercropped with flue-cured tobacco on soil nutrients in tobacco fields; Figure 15 The effects of different densities of scallions intercropped with flue-cured tobacco on the rhizosphere soil fungal community and its function; Figure 16 The impact of different densities of scallions intercropped with flue-cured tobacco on the microclimate of the tobacco field; Figure 17 Experimental group T1 was set up at the location where scallions were planted in the intercropping of flue-cured tobacco. Figure 18 The control group T2 was set up to specify the location for intercropping scallions with flue-cured tobacco. Figure 19 The effects of intercropping scallions at different locations in flue-cured tobacco fields on the incidence and pathogen count of damping-off disease in tobacco fields; Figure 20 The impact of intercropping scallions in different locations on the economic benefits of tobacco fields.

[0025] The reference numerals in the accompanying drawings include: 1. positioning frame; 2. slide rail; 3. positioning rod; 4. spike; 5. sliding seat; 6. locking buckle; 7. locking groove. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] The following detailed description illustrates the specific implementation method: Example 1: As attached Figure 1 The following is a method for intercropping scallions with flue-cured tobacco, comprising the following steps: S1, Tobacco field preparation: In late March, apply base fertilizer suitable for flue-cured tobacco to the flue-cured tobacco field, then form ridges and cover the soil surface with biodegradable mulch film. S2, tobacco transplanting: In mid-to-late April, flue-cured tobacco will be transplanted at a preset density of 1100-1200 plants / mu. The preset density of flue-cured tobacco plants corresponds to a row spacing of 120cm and a plant spacing of 50-55cm. S3, Intercropping with Scallions: After the tobacco plants are transplanted, scallions are intercropped on the tobacco rows within 0-7 days after transplanting. The spacing between scallion plants is controlled at the preset interval, which is 8-12cm. The intercropping layout is that a row of scallions is placed on each side of each row of tobacco plants, with every two rows of scallions symmetrically distributed about the center line of the tobacco row. The first harvest is carried out when the scallions reach a height of 15-20cm, and then harvested every 25 days thereafter. S4, Harvesting and Soil Improvement: Harvest the upper tobacco leaves of the tobacco plants in mid-to-late September; immediately after removing the tobacco stalks in late October, prepare the land and sow green manure; and then plow the green manure plants into the soil to decompose, with the green manure decomposing in mid-to-late March of the following year. S5, Cyclic Planting: Repeat steps S1-S4 to achieve cyclical intercropping of flue-cured tobacco and scallions.

[0030] Example 2: As attached Figure 2 As shown, the difference from Embodiment 1 is that a planting device for intercropping scallions with flue-cured tobacco is used to implement the planting method for intercropping scallions with flue-cured tobacco as described in Embodiment 1. It includes a positioning frame 1, the hollow part of the positioning frame 1 is adapted to the structure of the tobacco ridge. Within 0-7 days after the tobacco plants are transplanted, the positioning frame 1 is straddled above the tobacco ridge. Adjustment components are provided on both sides of the positioning frame 1. Several positioning components are fixedly connected to the adjustment components. The adjustment components are used to adjust the spacing between adjacent planting points on the same side of the positioning components of the positioning frame 1. The positioning components are used to mark the planting points of scallions. The positioning components include positioning rods 3. The bottom of the positioning rods 3 is fixedly connected to spikes 4. The side wall of the positioning rods 3 is provided with scale lines for marking the insertion depth of the positioning rods 3.

[0031] Each adjustment component includes a slide rail 2 fixedly connected to one side of the positioning frame 1. Several sliding seats 5 are slidably fitted within each slide rail 2. Each sliding seat 5 corresponds one-to-one with a positioning rod 3, and the positioning rod 3 is fixedly connected to the sliding seat 5, as shown in the attached diagram. Figure 3 As shown, each slide rail 2 is provided with several locking grooves 7, and each side of the sliding seat 5 is hinged with a locking buckle 6, which corresponds to the locking groove 7.

[0032] Based on the intercropping requirement of 8-12cm spacing between scallion plants, the sliding seat 5 is adjusted by sliding along the slide rails 2 on both sides of the positioning frame 1 to achieve the preset scallion plant spacing between adjacent positioning rods 3 on the same side. After the sliding seat 5 moves to the target position, the locking holes on both sides of the sliding seat 5 are engaged with the corresponding locking grooves 7 in the slide rail 2 to fix the sliding seat 5. The operator holds the top of the positioning rod 3 and presses it vertically downwards, causing the spike 4 at the bottom of the positioning rod 3 to pierce the mulch and insert into the soil, forming a planting hole, which is the positioning point for scallion seedling transplanting. During the insertion of the positioning rod 3, the insertion depth can be controlled according to the scale lines on the side wall of the positioning rod 3. After completing the point marking of a single tobacco ridge, the positioning frame 1 is removed and transferred to the next tobacco ridge for reuse, solving the problem of uneven spacing or depth in manual planting and ensuring the stability of scallion and flue-cured tobacco intercropping.

[0033] Example 3: The difference from Example 2 is that the planting method of intercropping scallions with flue-cured tobacco as described in Example 1 is applied to reduce damping-off disease in flue-cured tobacco fields.

[0034] Intercropping scallions (T1) and amaranth (T2) in flue-cured tobacco fields was used as a treatment, with monoculture tobacco as a control (CK). The effects of the three treatments on the occurrence of damping-off disease in tobacco fields were compared. The planting process for monoculture tobacco was as follows: applying basal fertilizer, ridging, and mulching the tobacco field around late March → transplanting tobacco plants in mid-to-late April → harvesting the lower, middle, and upper tobacco leaves in June, July, and August-September, respectively. The planting process for intercropping tobacco was as follows: applying basal fertilizer, ridging, and mulching the tobacco field around late March → transplanting tobacco plants in mid-to-late April → intercropping scallions and amaranth within 7 days → harvesting the lower and middle tobacco leaves in June and July, respectively → harvesting the upper tobacco leaves in August-September.

[0035] Compared with the control (CK) treatment, the T1 treatment reduced the incidence of damping-off and the number of pathogens by 36.36% and 61.54%, respectively, while the T2 treatment increased the incidence of damping-off and the number of pathogens by 9.09% and 27.27%, respectively. Figure 4 A- Figure 4 B). Correlation analysis showed that the correlation coefficient between the number of pathogens and the incidence of damping-off disease reached 0.92 (B). Figure 4 C) indicates that the incidence of damping-off disease increases with the increase in the number of pathogens.

[0036] The results above indicate that the T1 treatment (intercropping scallions with flue-cured tobacco) was the most effective in reducing damping-off disease in tobacco plants.

[0037] Furthermore, compared to the control (CK) treatment, the organic carbon in the T1 and T2 treatments increased by 34.41% and 17.2%, respectively; ammonium nitrogen decreased by 28.87% and 11.98%, respectively; nitrate nitrogen increased by 84.61% and 22.43%, respectively; and available phosphorus increased by 21.38% and 12.44%, respectively. Figure 5 A- Figure 5 D).

[0038] In addition, the contents of organic matter, available phosphorus, and nitrate nitrogen were negatively correlated with the incidence of damping-off disease and the number of pathogens, while ammonium nitrogen showed a significant positive correlation. Figure 5 E) indicates that nitrogen form transformation under the flue-cured tobacco intercropping model may inhibit pathogens through nitrogen source competition (i.e., reduce the ammonium nitrogen content in the soil), thereby inhibiting the reproduction of damping-off pathogens to a certain extent and ultimately reducing the occurrence of the disease.

[0039] Intercropping with flue-cured tobacco significantly increased the diversity of soil fungi in tobacco plants, and the fungal diversity increased with the number of years of intercropping. Compared with the control treatment, the diversity indices of Shannon, Chao, and Ace in the T1 and T2 treatments increased by 10.11% and 2.25%, 6.69% and 0.53%, and 20.62% and 4.83%, respectively. Figure 6 A- Figure 6C). Furthermore, the diversity index of the fungal community showed significant and highly significant positive correlations with both disease incidence and pathogen abundance. Figure 6 (D) This indicates that the diversity of fungal communities is closely related to disease resistance; the higher the community diversity, the stronger the tobacco plant's ability to resist disease invasion.

[0040] Metagenomic testing results showed that the dominant fungal communities in all three treatments were Ascomycota, Basidiomycota, Chytridiomycota, and Mortierellomycota. Figure 7 A). Compared with the CK treatment, the abundance of *Chytridiomycota* decreased by 65.24% and 26.91% in the T1 and T2 treatments, respectively, while the abundance of *Ascomycota*, *Basidiomycota*, and *Mortierellomycota* increased by 30.27% and 15.16%, 70.46% and 52.93%, and 68.46% and 31.35%, respectively. Further Pearson correlation analysis showed that at the phylum level, *Chytridiomycota* and *Ascomycota*, *Basidiomycota*, and *Mortierellomycota* were significantly negatively and positively correlated with the incidence and abundance of each pathogen of damping-off disease, respectively. Figure 7 B). Further analysis revealed that the main functions of the fungi *Ascomycota*, *Basidiomycota*, and *Mortierellomycota* are: 1) improving soil structure by regulating soil nutrient cycling and organic matter decomposition; 2) helping plants absorb nutrients such as nitrogen and phosphorus, enhancing water use efficiency, and thus improving stress resistance; 3) inhibiting pathogens and reducing soil-borne diseases by competing for nutrients and producing antimicrobial substances (such as lipopeptide antibiotics); and 4) decomposing organic matter and releasing nutrients for other organisms. However, excessive proliferation of *Chytridiomycota* can lead to plant diseases.

[0041] Effects on fungal community function: The fungal communities of each treatment were located in the Plant_Pathogen-Soil_Saprotroph-Wood_Saprotroph functional layer with an abundance greater than 0.1 in the secondary functional layer. Figure 7C), the abundance of the three treatments showed that T1 (0.64) > T2 (0.38) > CK (0.35). The main function of this functional layer is that Soil_Saprotroph promotes nutrient cycling by decomposing organic matter and converting complex organic matter into inorganic nutrients for plant absorption; and inhibits pathogens and reduces disease occurrence by competing for resources or producing antimicrobial substances. Wood_Saprotroph reduces the relative abundance of soil pathogens by changing the composition of the fungal community, promoting the formation of beneficial bacteria, and ultimately reducing the incidence of soil-borne diseases caused by Plant_Pathogen (including damping-off disease).

[0042] The results above indicate that intercropping with flue-cured tobacco improved the diversity of the fungal community, optimized the composition of the fungal community, and enhanced the stress resistance of the fungal community, with the T1 treatment (intercropping flue-cured tobacco with scallions) showing the best effect.

[0043] Compared with the control (CK), the levels of Lipopeptide, Isoquinoline alkaloids, Naringenin, and Phenolic acids increased by 2.35% and 1.47%, 10.62% and 7.36%, 16.74% and 11.85%, and 18.25% and 14.26% in the T1 and T2 treatments, respectively, while the levels of Aminopenicillanic acid, Ylbenzenesulfonic acid, and Garcinia acid decreased by 6.47% and 3.26%, 5.37% and 3.49%, and 4.66% and 3.25%, respectively. Figure 8 A). Among them, the first four metabolites showed a highly significant negative correlation with both the incidence and pathogen quantity of damping-off disease, while the latter three metabolites showed the opposite correlation. Figure 8 B).

[0044] The study further revealed that the first four metabolites all originated from the phenylpropane metabolic pathway, and the compounds produced by this pathway possess antioxidant, defense, and signal transduction activities in plants. These metabolic pathways are interconnected and work together to maintain metabolic homeostasis and physiological processes within organisms, thereby significantly affecting the growth and metabolism of pathogens. The increase in the first four metabolites was greater in the T1 treatment than in the T2 treatment.

[0045] In conclusion, this invention suggests that intercropping scallions with flue-cured tobacco is the most effective way to reduce damping-off disease.

[0046] To verify the effect of intercropping scallions at different times on damping-off disease in tobacco fields, the following experiment was designed: scallions were intercropped within <7 days (T1) and >8 days (T2) after tobacco transplanting, respectively, to compare their effect on reducing damping-off disease and to explore the mechanism of the difference in effect.

[0047] I. Impact on the incidence and pathogen quantity of damping-off disease in tobacco fields Compared with the T1 treatment, the T2 treatment increased the incidence of damping-off disease and the number of pathogens by 26.24% and 29.35%, respectively. Figure 9 This indicates that the T1 treatment (intercropping with scallions within 0-7 days after tobacco transplanting) is the most effective way to reduce damping-off disease in tobacco plants.

[0048] II. Impact on the rhizosphere soil of tobacco plants The results of Example 1 show that the soil nutrients, fungal community composition and metabolites in the rhizosphere of flue-cured tobacco plants under the intercropping model are highly correlated with the incidence of damping-off disease in tobacco plants. Therefore, this invention further studies the effects of intercropping scallions at different times on flue-cured tobacco plants on these three factors, in order to reveal the mechanism by which scallions reduce the differences in damping-off disease in tobacco plants.

[0049] Effects on nutrients: Compared with treatment T1, treatment T2 reduced organic carbon, nitrate nitrogen, and available phosphorus by 14.35%, 28.38%, and 2.57%, respectively, while increasing ammonium nitrogen by 18.68%. Figure 10 ).

[0050] Effects on fungal community composition: Although the dominant fungi in the T1 and T2 treatments were the same in terms of phylum ( Figure 11 A), but the difference in abundance was significant. Compared with the T2 treatment, the T1 treatment increased the abundance of Ascomycota, Basidiomycota, and Mortierellomycota by 22.54%, 11.11%, and 22.38%, respectively, while reducing Chytridiomycota by 72.58%. Figure 11 A).

[0051] Impact on fungal community function: The abundance of fungal communities in each treatment at the Plant_Pathogen-Soil_Saprotroph-Wood_Saprotroph functional layer (abundance greater than 0.1) showed a significant difference between treatments: T1 (0.23) > T2 (0.14). Figure 11 B).

[0052] Effects on tobacco rhizosphere soil metabolites: Compared with treatment T1, treatment T2 showed a 5.18% decrease in Lipopeptide, 10.60% in Isoquinoline alkaloids, 9.28% in Naringenin, and 3.32% in Phenolic acids, while an increase in Aminopenicillanic acid, Ylbenzenesulfonic acid, and Garcinia acid was 2.79%, 1.46%, and 1.19%, respectively. Figure 12 This indicates that the T1 treatment had a higher content of metabolites in the phenylpropanoid metabolic pathway with stress resistance than the T2 treatment.

[0053] In summary, this invention suggests that planting scallions within 0-7 days (T1) after tobacco transplanting is the most effective way to reduce damping-off disease in the intercropping of flue-cured tobacco with scallions. This may be because the earlier the scallions are planted, the earlier the microorganisms and metabolites released by their roots act on the soil, thus degrading the number of damping-off pathogens very early.

[0054] To verify the effect of intercropping scallions at different densities (plant spacing) on ​​damping-off disease in tobacco fields, the following experiment was designed: scallions were intercropped within 0-7 days after tobacco transplanting, with a row spacing of 120cm, but plant spacing was set at < 8cm (T1), 8-12cm (T2), and >13cm (T3) to compare the effect on reducing damping-off disease and to explore the mechanism of the difference in effect.

[0055] I. Impact on the incidence and pathogen quantity of damping-off disease in tobacco fields The three treatments showed a trend in morbidity rate: T1 (18.4%) > T3 (16.2%) > T2 (15.6%). In terms of pathogen count, T1 showed a trend of [missing data - likely a number of treatments]. 6 cfu / g)>T3(2.89×10 6 cfu / g)>T2(2.73×10 6 The trend of CFU / g showed that the differences between T1 and T2 and T3 were significant, while the differences between the latter two were not significant. Figure 13 ).

[0056] The results above indicate that the T2 treatment was the most effective in reducing damping-off disease in tobacco plants.

[0057] II. Impact on the rhizosphere soil of tobacco plants Effects on nutrients: All three treatments showed a trend of T2>T3>T1 for organic carbon, nitrate nitrogen, and available phosphorus, while showing a trend of T1>T2>T3 for ammonium nitrogen. Figure 14 The reason for these trends is speculated to be that scallions also need to absorb nutrients for growth. When the intercropping spacing is too small (high planting density), they absorb more nutrients from the soil, and the competition with tobacco plants becomes more intense, resulting in a decrease in organic carbon, nitrate nitrogen, and available phosphorus in the rhizosphere soil of the tobacco plants. Similarly, because scallions with higher planting density release more harmful substances (ammonium nitrogen), the damping-off disease becomes more severe. This result is consistent with the conclusion in Example 1 that "the content of organic matter, available phosphorus, and nitrate nitrogen is negatively correlated with the incidence of damping-off disease and the number of pathogens, while ammonium nitrogen is the opposite."

[0058] All three treatments showed a trend of T2>T3>T1 in relative abundance of Ascomycota, Basidiomycota, and Mortierellomycota, but a trend of T1>T3>T2 in relative abundance of Chytridiomycota. Figure 15 A- Figure 15 D).

[0059] Effects on fungal community function: The abundance of fungal communities in each treatment at the Plant_Pathogen-Soil_Saprotroph-Wood_Saprotroph functional layer (abundance greater than 0.1) showed the following order of abundance across the three treatments: T2 (0.41) > T3 (0.36) > T1 (0.27). Figure 15 E).

[0060] The results above indicate that the T2 treatment was most effective in reducing damping-off disease in tobacco plants because it was closely related to the relative abundance of nutrients in the rhizosphere soil, the composition of the fungal community, and the function of the fungal community.

[0061] III. Impact on the microclimate of tobacco fields In terms of temperature, humidity, and CO2 concentration in the tobacco field, the three treatments showed a trend of T1>T2>T3, with significant differences between T1 and both T2 and T3, while the differences between the latter two were not significant. Figure 16 This indicates that the smaller the plant spacing of intercropped scallions (the denser the scallions), the higher the temperature and CO2 concentration in the tobacco field, which is not conducive to the circulation of O2. This results in slow water evaporation and excessive humidity in the tobacco field, ultimately increasing the incidence of damping-off disease.

[0062] In conclusion, this invention suggests that the T2 treatment (with an intercropping spacing of 8-12 cm for scallions) is the most effective in reducing damping-off disease.

[0063] To verify the effect of intercropping scallions in flue-cured tobacco on damping-off disease in tobacco fields, the following experiment was designed for verification and comparison: Scallions were intercropped within 0-7 days after tobacco transplanting, with a row spacing of 120cm and a plant spacing of 8-12cm. Two planting positions were used for the scallions (the first being the planting method of this invention, as shown in the attached diagram). Figure 17 As shown, two rows of scallions are planted between each row of tobacco plants in the tobacco ridge, as treatment T1; the second method involves planting scallions between two tobacco plants, as shown in the attached diagram. Figure 18 As shown, (as T2 treatment), to compare its effect on reducing damping-off disease and to explore the mechanism of the difference in effect.

[0064] I. Impact on the incidence and pathogen quantity of damping-off disease in tobacco fields The two treatments showed a clear trend in morbidity and pathogen count: T2 (17.84%) > T1 (13.56%) and T2 (1.15 × 10⁻⁶%) > T1 (13.56%). 6 cfu / g)> T1(0.66×10 6 The trend of CFU / G ( Figure 19 This indicates that treatment T1 was more effective than treatment T2 in reducing damping-off disease in tobacco plants.

[0065] II. Impact on the economic benefits of tobacco fields Compared to single-crop tobacco processing, the costs of T1 and T2 processing increased by RMB 133 and RMB 107 respectively, while the profits (tobacco + scallions) increased by RMB 301 and RMB 243 respectively, and the net profits increased by RMB 168 and RMB 136 respectively. Figure 20 Although the T2 and T3 treatments showed little difference in reducing bacterial wilt disease in tobacco plants, the T2 treatment was superior to the T3 treatment in improving the economic benefits of tobacco fields.

[0066] In conclusion, this invention suggests that treatment T1 is superior to treatment T2 in reducing damping-off disease and improving the economic benefits of tobacco fields.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for intercropping scallions with flue-cured tobacco, characterized in that, Includes the following steps: S1, Tobacco field preparation: In late March, apply base fertilizer suitable for flue-cured tobacco to the flue-cured tobacco field, then form ridges and cover the soil surface with biodegradable mulch film. S2, tobacco transplanting: tobacco plants are transplanted in mid-to-late April according to the preset density. The preset density of tobacco plants corresponds to a row spacing of 120cm and a plant spacing of 50-55cm. S3, intercropping with scallions: After the tobacco plants are transplanted, scallions are intercropped on the tobacco ridges, and the spacing between the scallion plants is controlled at the preset interval; when the scallions reach a height of 15-20cm, the first harvest is carried out, and then the harvest is carried out every 25 days. S4, Harvesting and Soil Improvement: Harvest the upper tobacco leaves in mid-to-late September; after removing the tobacco stalks in late October, immediately prepare the land and sow green manure; and then plow the green manure plants into the soil to decompose. S5, Cyclic Planting: Repeat steps S1-S4 to achieve cyclical intercropping of flue-cured tobacco and scallions.

2. The method for intercropping scallions with flue-cured tobacco according to claim 1, characterized in that, In S2, the preset tobacco plant density is 1100-1200 plants / acre.

3. The method for intercropping scallions with flue-cured tobacco according to claim 2, characterized in that, In S3, the intercropping time for scallions is limited to 0-7 days after the tobacco plants are transplanted.

4. The method for intercropping scallions with flue-cured tobacco according to claim 3, characterized in that, In S3, the preset spacing of the scallions is 8-12cm.

5. The method for intercropping scallions with flue-cured tobacco according to claim 4, characterized in that, In S3, the intercropping layout of scallions is that a row of scallions is placed on each side of each row of tobacco plants in the tobacco ridge, with every two rows of scallions symmetrically distributed about the center line of the tobacco ridge.

6. The method for intercropping scallions with flue-cured tobacco according to claim 5, characterized in that, In S4, the green manure is plowed and decomposed in mid-to-late March of the following year.

7. A planting apparatus for intercropping flue-cured tobacco with scallions, used to implement the planting method for intercropping flue-cured tobacco with scallions as described in any one of claims 1-6, characterized in that, The positioning frame (1) is adapted to the tobacco ridge structure. The positioning frame (1) is straddling the tobacco ridge. Adjustment components are provided on both sides of the positioning frame (1). Several positioning components are fixedly connected to the adjustment components. The adjustment components are used to adjust the spacing between adjacent planting points on the same side of the positioning components of the positioning frame (1). The positioning components are used to mark the planting points of scallions. The positioning components include positioning rods (3). Spikes (4) are fixedly connected to the bottom of the positioning rods (3). The side walls of the positioning rods (3) are provided with scale lines for marking the insertion depth of the positioning rods (3).

8. The planting device for intercropping flue-cured tobacco with scallions according to claim 7, characterized in that, The adjustment components all include a slide rail (2) fixedly connected to one side of the positioning frame (1). Several sliding seats (5) are slidably fitted inside the slide rail (2). Each sliding seat (5) corresponds to a positioning rod (3), and the positioning rod (3) is fixedly connected to the sliding seat (5).

9. The planting device for intercropping flue-cured tobacco with scallions according to claim 8, characterized in that, The slide rail (2) is provided with several locking grooves (7), and the sliding seat (5) is hinged with locking buckles (6) on both sides. The locking buckles (6) correspond to the locking grooves (7).

10. A method for intercropping scallions with flue-cured tobacco as described in any one of claims 1-6, applied to reduce damping-off disease in flue-cured tobacco fields.

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