A method for reducing chemical sensing substances and increasing polysaccharide content in polygonatum sibiricum planting

Abstract

The present application provides a kind of planting method of reducing allelochemicals and improving polysaccharide content of Rhizoma Polygonati, belongs to plant cultivation technical field.The planting method is planted in acidic sandy loam soil, and "biochar C" is applied to the soil 1-2 times in September-October of the second and third years, and the fruits mature, the stems are laid down after the third year, and then it can be harvested."Biochar C" is a modified, loaded with salicylic acid and UDP-D-galactose biochar.The present application not only helps to improve the physicochemical properties and bacterial community diversity of Rhizoma Polygonati planting soil, thereby reducing the allelochemicals content of Rhizoma Polygonati rhizome, but also can improve the polysaccharide content of rhizome, which helps to improve the quality of Rhizoma Polygonati and enhance its efficacy.

Description

Technical Field

[0001] This invention belongs to the field of plant cultivation technology and relates to a method for cultivating Polygonatum sibiricum by using biochar loaded with salicylic acid and uridine diphosphate galactose (UDP-D-galactose) to reduce allelopathic substances in rhizomes and increase polysaccharide content. Specifically, it relates to a method for preparing biochar using rice husks, tea stalks, and corn stalks, and then loading it with salicylic acid and UDP-D-galactose to form modified biochar that reduces the allelopathic substance content in Polygonatum sibiricum rhizomes and increases the polysaccharide content in rhizomes. Background Technology

[0002] Polygonatum multiflorum ( Polygonatum cyrtonema Polygonatum (Huang.) is an important plant used for both food and medicine. It is also considered a promising new high-quality coarse grain that doesn't require much farmland. Polysaccharides are the main active ingredient in Polygonatum, possessing pharmacological effects such as immune regulation, antioxidation, antitumor activity, and lowering blood sugar and lipids. With increasing market demand, the artificial cultivation area of ​​Polygonatum is constantly expanding. However, as a perennial medicinal plant, Polygonatum easily accumulates allelochemicals in its rhizomes during cultivation. These substances are released into the rhizosphere soil, affecting plant growth, leading to decreased yield and quality, deterioration of the rhizosphere soil microenvironment, and problems such as continuous cropping obstacles. Currently, there is a lack of economical and efficient agronomic control measures to effectively alleviate the allelopathic effects of Polygonatum.

[0003] Biochar is a carbon-rich material produced by the pyrolysis of biomass under high temperature and limited oxygen conditions. It possesses abundant pore structure, a large specific surface area, and good stability. It has been proven to alleviate the allelopathic effects of various medicinal plants such as ginseng, American ginseng, and Panax notoginseng, and promote the growth of these plants. It can also improve rhizosphere soil nutrient levels, optimize soil structure, and regulate soil pH. Furthermore, it increases the number of functional groups in plant root cell walls, enhancing root adsorption capacity and thus altering secondary metabolism in rhizomes. However, biochar prepared from different raw materials often exhibits different physicochemical properties. For example, biochar prepared from agricultural waste such as rice husks, tea stalks, and corn stalks differs in indicators such as pH and nutrient composition. Therefore, applying different types of biochar may have differentiated effects on the quality of Polygonatum odoratum rhizomes and the accumulation of allelopathic substances. However, how to select suitable biochar raw materials and application methods to reduce the accumulation of allelopathic substances in rhizomes while simultaneously increasing polysaccharide content has not yet been publicly reported. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for cultivating Polygonatum sibiricum that reduces allelochemicals and increases polysaccharide content. Biochar can improve the rhizosphere soil microenvironment, thereby promoting the growth of Polygonatum sibiricum. Biochar can also load salicylic acid and UDP-D-galactose through its excellent surface structure, thereby inhibiting the biosynthesis of terpenoid allelochemicals in the rhizomes and simultaneously providing more precursors for polysaccharide synthesis. Therefore, by adding modified biochar exogenously, not only can the abundance of allelochemicals in the rhizomes be reduced, but the polysaccharide content can also be increased, thus enhancing its medicinal value.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for cultivating Polygonatum sibiricum to reduce allelochemicals and increase polysaccharide content, wherein the method involves planting Polygonatum sibiricum in acidic sandy loam soil, applying "biochar C" to the soil 1-2 times in September-October of the second and third years, and harvesting after the fruit matures and the stems fall over in the third year; wherein the "biochar C" is modified biochar loaded with salicylic acid and UDP-D-galactose.

[0007] Furthermore, the "biochar C" includes one or more of rice husk biochar, tea stalk biochar, and corn stalk biochar loaded with salicylic acid and UDP-D-galactose.

[0008] Considering the excellent surface structure of biochar, by loading salicylic acid and UDP-D-galactose onto its surface, it is possible not only to interfere with the jasmonic acid signaling pathway through the signal transduction of salicylic acid, thereby inhibiting the biosynthesis of allelochemicals such as terpenes; but also to make full use of UDP-D-galactose as a galactosyl donor in the polysaccharide synthesis process, providing more precursor substances for the synthesis of Polygonatum rhizome polysaccharides, thereby increasing its polysaccharide content and improving the quality of Polygonatum.

[0009] Furthermore, the planting method steps are as follows:

[0010] (1) Site selection: The soil should be acidic sandy loam with a pH of 4.0-5.0. The total nitrogen, total potassium, total phosphorus and organic matter content of the soil should be in the range of 0.1-1.5g / kg, 0.2-1.5g / kg, 10-25g / kg and 10-100g / kg, respectively.

[0011] (2) Biochar preparation:

[0012] ① Preparation of “Biochar A”: Rice husks, tea stalks, and corn stalks were respectively loaded into the furnace of a carbonization furnace and purged with high-purity nitrogen for 1-20 min; then heated at 10-30℃·min -1The heating rate was increased to 500℃-700℃, and the temperature was kept constant for 2-4 hours for pyrolysis. The carbonization furnace was then closed, and the biochar inside the furnace was allowed to cool naturally to room temperature before being removed, pulverized, and passed through an 80-120 mesh sieve to obtain rice husk biochar, tea stalk biochar, and corn stalk biochar. The rice husk biochar, tea stalk biochar, and corn stalk biochar were mixed in a mass ratio of (1-2):(0.5-1):(1-2) to obtain "Biochar A".

[0013] ② Preparation of “Biochar B”: At room temperature (18℃-25℃), solution A and “Biochar A” were mixed at a volume-to-mass ratio of (10-15):1 and reacted at a constant temperature of 50℃-70℃ for 10-18 h. After the reaction was completed, the mixture was filtered and the filter residue was washed repeatedly with anhydrous ethanol and distilled water. The washed residue was placed in a vacuum drying oven and dried to constant weight at 50℃-70℃ to obtain “Biochar B”.

[0014] ③ Preparation of “Biochar C”: At room temperature (18℃-25℃), solution B and “Biochar B” are mixed at a volume-to-mass ratio of (20-30):1 and dried in an oven at 60℃-80℃ for 48-60 hours until constant weight is obtained to obtain “Biochar C”.

[0015] Rice husk biochar (RB), tea stalk biochar (TB), and corn stalk biochar (MB), all made from the above three types of agricultural waste, possess porous structures, abundant micropores, high specific surface areas, and various functional groups. RB and MB, in particular, contain unique C≡N and CO₃²⁻ compounds, respectively. 2- Functional groups, and TB contains O=C=O bonds. C≡N is a strongly polar covalent triple bond, with the N-terminus carrying a partial negative charge and the C-terminus carrying a partial positive charge; CO3 2- Can be used with Ca 2+ Fe 3+ Zn 2+ Mn 2+ The presence of metal ion complexes enhances the soil's water retention and nutrient adsorption capacity. Furthermore, the presence of O=C=O strengthens the surface polarity and ion exchange capacity of biochar, improving its loading efficiency for salicylic acid and UDP-D-galactose, while also promoting the adsorption and slow release of nutrients in the soil, thus contributing to the growth and quality improvement of Polygonatum rhizomes.

[0016] Simultaneously, after the biochar is rationally formulated, it is further loaded with salicylic acid and UDP-D-galactose. After absorption by the rhizomes, salicylic acid can inhibit the jasmonic acid signaling pathway, thereby suppressing the biosynthesis of terpenoid allelochemicals and reducing the abundance of allelochemicals in the rhizomes. UDP-D-galactose, as the activated form of galactosyl groups, is the only galactose donor that can be directly utilized by polysaccharide synthases during polysaccharide chain elongation, providing more raw materials for the synthesis of Polygonatum sibiricum polysaccharides. The application of these substances will contribute to reducing the abundance of allelochemicals and increasing the polysaccharide content in Polygonatum sibiricum rhizomes.

[0017] (3) Application of biochar: In September and October of the second and third years of Polygonatum planting, apply “Biochar C” to the soil of Polygonatum planting 1-2 times by root application.

[0018] (4) Harvesting: In the third year of planting, after the fruit is ripe and the stems have fallen over, dig up the underground rhizomes.

[0019] Furthermore, the method for preparing solution A is as follows: using anhydrous ethanol as a solvent, completely dissolve salicylic acid to form a salicylic acid solution with a concentration of 500-5000 mg / L.

[0020] Furthermore, the method for preparing solution B is as follows: using water as a solvent, completely dissolve UDP-D-galactose to form a UDP-D-galactose solution with a concentration of 50-2000 mg / L.

[0021] Furthermore, the root application method is as follows: within a range of 10-20cm from the rhizome of Polygonatum odoratum, scrape off 2-5cm of the topsoil, evenly sprinkle "biochar C", and then backfill the original topsoil.

[0022] Furthermore, the amount of "biochar C" added is 1% to 5% of the soil mass or 1-7 tons per acre.

[0023] The beneficial effects of this invention are:

[0024] (1) By scientifically and rationally determining the ratio of biochar, a biochar mixture with stable surface structure and rich functional groups is formed, which is conducive to improving the pH of acidic soil, increasing the soil's water retention and nutrient adsorption capacity, and thus improving the rhizosphere soil microecology.

[0025] (2) By scientifically and rationally determining the modification method of biochar, modified biochar with surface-loaded salicylic acid and UDP-D-galactose is formed, and then the content of allelochemicals and polysaccharides is reduced and increased by regulating the jasmonic acid pathway and polysaccharide synthesis pathway of Polygonatum rhizome.

[0026] (3) By scientifically and rationally determining the dosage and application method of biochar, it is possible to ensure that the modified biochar plays its full role and achieve the dual effect of reducing allelochemicals and increasing polysaccharide content. It can also avoid the problems of soil compaction and increased costs caused by excessive dosage, or poor effect caused by excessive dosage. At the same time, the root application method can accurately act on the rhizosphere of Polygonatum, reduce nutrient loss, improve raw material utilization, and is simple to operate and low in cost. The biochar raw material used is agricultural waste, which realizes the resource utilization of waste, conforms to the concept of green agricultural development, and is easy to promote and apply on a large scale. Attached Figure Description

[0027] Figure 1 The surface physical properties and pore structure characteristics of the biochar described in the specific embodiments are shown. Adsorption-desorption isotherms (a–c); pore size distribution curves (d–f).

[0028] Figure 2 X-ray photoelectron spectroscopy (XPS) of the biochar described in the specific embodiment. Full spectrum (ac); high-resolution C 1s spectrum (df); high-resolution N 1s spectrum (gi); high-resolution S 2p spectrum (jl).

[0029] Figure 3 Scanning electron microscope (SEM) images (a) of different biochars described in the specific embodiments; Fourier transform infrared (FTIR) spectra (b); and information on the changes in functional groups corresponding to characteristic peaks (c).

[0030] Figure 4 The image shows the energy dispersive spectroscopy (EDS) spectrum of the biochar as described in the specific embodiment.

[0031] Figure 5 The biodiversity index of the rhizosphere soil microorganisms of Polygonatum odoratum before and after the application of "biochar C" as described in the specific implementation method.

[0032] Figure 6 The changes in the physicochemical properties of the rhizosphere soil of Polygonatum odoratum before and after the application of "biochar C" as described in the specific implementation method.

[0033] Figure 7 The abundance of allelochemicals in the rhizomes of Polygonatum odoratum before and after the application of "biochar C" as described in the specific implementation method.

[0034] Figure 8 The changes in biomass and quality indicators such as polysaccharides of Polygonatum rhizome before and after the application of "biochar C" as described in the specific implementation method are shown. Detailed Implementation

[0035] To explain in detail the technical content, objectives, and effects of the technical solution, the following detailed description is provided in conjunction with specific embodiments.

[0036] Example 1

[0037] 1. Test Methods

[0038] (1) Site selection

[0039] The selected soil area has acidic sandy loam soil with a pH of 4.2. The total nitrogen, total potassium, total phosphorus, and organic matter content of the soil are 0.82 g / kg, 0.76 g / kg, 14.53 g / kg, and 12.29 g / kg, respectively.

[0040] (2) Planting: Select healthy rhizomes of Polygonatum odoratum that are free from pests and diseases. Cut rhizome segments with 2-3 buds. Soak them in a 500-fold dilution of 50% carbendazim wettable powder for 15 minutes to disinfect them. After drying, plant them in furrows with a row spacing of 30cm and a plant spacing of 25cm. The furrows should be 10cm deep. Place the plants with the buds facing upwards, cover them with 6cm of topsoil, water them thoroughly, and cover them with straw to retain moisture.

[0041] (3) Biochar preparation:

[0042] ① After crushing rice husks, tea stalks, and corn stalks, respectively, they were loaded into the furnace of a carbonization furnace and purged with high-purity nitrogen for 5 minutes; then, the furnace was heated at 20℃·min. -1 The heating rate was increased to 500℃ and kept constant for 3 hours. The carbonization furnace was then closed, and the biochar inside the furnace was allowed to cool naturally to room temperature before being removed, pulverized, and passed through a 100-mesh sieve to obtain rice husk biochar (RB), tea stalk biochar (TB), and corn stalk biochar (MB).

[0043] The physicochemical properties of rice husk biochar (RB), tea stalk biochar (TB), and corn stalk biochar (MB) are shown in Table 1. The BET specific surface area, pore volume, and pore size of the materials were determined using a fully automated specific surface area and porosity analyzer (Table 2), along with nitrogen adsorption-desorption isotherms and pore size distribution curves. Figure 1 X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition, chemical valence state, and functional group information of the material surface. Figure 2 The surface morphology was observed using a scanning electron microscope (SEM). Figure 3 a) The types and structures of functional groups on the material surface are detected using Fourier transform infrared spectroscopy (FTIR). Figure 3 b, 3c). Elemental composition was analyzed using energy-dispersive X-ray spectroscopy (EDS). Figure 4 ).

[0044] Table 1 shows that corn stalk biochar (MB), rice husk biochar (RB), and tea stalk biochar (TB) are all alkaline, with pH values ​​between 9.72 and 9.85. TB has higher CEC and TN contents, MB has the highest EC, while RB has significantly lower nutrient content and CEC than MB and TB.

[0045] Table 1 Physicochemical properties of biochar

[0046]

[0047] Note: MB, RB, and TB represent biochar derived from corn stalks, rice husks, and tea stems, respectively, and the same applies below. Data are expressed as mean ± standard deviation (n = 3). Different lowercase letters in the same row indicate significant differences between different biochars. p <0.05).

[0048] Table 2 shows that corn straw biochar (MB) has the highest BET specific surface area, indicating that it has a well-developed pore structure and abundant active sites. RB has the largest average pore size, indicating that its pore structure is more open, which is conducive to material transport.

[0049] Table 2 Surface thermophysical properties of biochar

[0050]

[0051] The adsorption and desorption curves of the three biochars showed obvious hysteresis loops, with MB exhibiting the most pronounced hysteresis loop. Figure 1 a) indicates that it is rich in mesopores of 2–50 nm and has a complex pore structure. The hysteresis loops of RB and TB are relatively weak ( Figure 1 (b, 1c) indicates a lower number of mesopores and less structural complexity. Among the three types of biochar, MB had the highest N2 adsorption capacity, while TB had the lowest. Figure 1 (a–1c). The adsorption capacity of MB increases slowly in the low P / P0 region, indicating that it contains a microporous structure and has abundant N2 adsorption sites; while the adsorption capacity of RB and TB is low and the rate of increase is slow, indicating that they have smaller specific surface areas and fewer adsorption sites.

[0052] Pore ​​volume distribution analysis showed that the pore volume (dV / dD) of MB decreased rapidly in the small pore range (less than 50 nm). Figure 1 d) indicates that it is mainly composed of micropores and small mesopores, with fewer macropores (>50 nm). In contrast, RB and TB have irregular pore volume distribution in the range of less than 50 nm, and the pore volume decreases when it is greater than 50 nm. Figure 1 (e, 1f) indicates that, compared to MB, RB and TB have more uneven pore size distribution and a higher proportion of macropores.

[0053] XPS analysis showed that ( Figure 2 The elemental composition and surface chemical bonds of the three biochar types (MB, RB, and TB) differ significantly: Elementally, TB contains F and K, RB contains Si, and MB contains Fe; in terms of chemical bonds, TB and MB both contain C–F bonds, while RB is mainly composed of C=C, C–C / C–H, and C–H / C–O bonds; among nitrogen-containing functional groups, TB contains C–N=O structures, and RB contains –NH3. + While TB contains –N–OH, MB contains –NO2 and Fe–N bonds; the sulfur-containing functional groups differ significantly, with TB containing FeS and –SH, and RB containing S. 0 While S–S, MB is characterized by FeS2 and a high proportion of C–S–C bonds, and the sulfur oxidation state distributions of the three are also different.

[0054] SEM analysis showed that ( Figure 3 a) The microstructures of the three biochars are significantly different: MB is loosely aggregated with a rough surface and irregular pores, and broken fibers and sheet-like structures are visible; RB is mainly a uniform honeycomb porous structure with good pore connectivity and smooth pore walls; TB is a continuous layered or honeycomb dense structure with uniform pore arrangement and high density.

[0055] FTIR analysis shows that ( Figure 3 (b) All three contain C–O, C=C, and O–H bonds, but their functional groups have distinct characteristics: MB and RB contain Si–O–Si bonds, while MB additionally contains CO32-. 2- RB contains C–H and C≡N bonds, while TB does not contain Si–O–Si bonds, but does contain specific C–H bonds, O=C=O bonds, and hydroxyl groups (3450, 3762 cm⁻¹) not found in MB and RB. -1 These morphological and functional group differences can affect the surface chemical properties and adsorption performance.

[0056] EDS analysis showed that carbon (C) and oxygen (O) were the main elements on the surface of the three types of biochar. Figure 4 However, there are significant differences in element content: TB has the lowest carbon content (78.64%) and the highest oxygen content (18.88%), which is significantly different from MB (C: 90.98%, O: 7.85%) and RB (C: 90.38%, O: 8.42%). Among the trace elements, TB has the highest potassium (K: 1.94%) and sulfur (S: 0.28%) content, while MB and RB have similar silicon (Si) contents (0.65% and 0.53%, respectively) and are much higher than TB (0.03%).

[0057] Based on the physicochemical and surface properties of the three biochars MB, RB, and TB, they were mixed in a mass ratio of 1:0.8:1.5 to balance their nitrogen, phosphorus, and potassium nutrient content, surface element composition, microporous structure, specific surface area, and surface functional groups, thus obtaining "Biochar A".

[0058] ② Prepare a 600 mg / L salicylic acid solution, i.e., "Solution A", using anhydrous ethanol as a solvent. At room temperature (20℃), mix Solution A and "Biochar A" at a volume-to-mass ratio of 10:1 and react at 50℃ for 10 hours. After the reaction, filter the mixture and wash the filter residue three times with anhydrous ethanol and distilled water. Place the washed residue in a vacuum drying oven and dry it to constant weight at 50℃ to obtain "Biochar B".

[0059] ③ Using water as a solvent, prepare a UDP-D-galactose solution with a concentration of 100 mg / L, i.e., "solution B". At room temperature (20℃), mix solution B and "biochar B" at a volume-to-mass ratio of 20:1, and dry in an oven at 60℃ for 48 h until constant weight to obtain "biochar C".

[0060] (4) Application of biochar: In September of the second and third years after the planting of Polygonatum, scrape off 2cm of the topsoil at a distance of 10cm from the rhizome of Polygonatum and evenly sprinkle "Biochar C" at a ratio of 0%, 1%, 3% and 5% by mass, respectively, and then backfill the original topsoil.

[0061] (4) Harvesting: In the third year of planting, after the fruit is ripe and the stems have fallen over, dig up the underground rhizomes.

[0062] 2. Experimental Results

[0063] The effects of applying the above-mentioned biochar were compared before and after application.

[0064] The bacterial diversity of the soil used for growing Polygonatum was determined by Shanghai Meiji Biomedical Technology Co., Ltd., and the results are shown below. Figure 5 The rhizosphere soil physicochemical properties were determined according to the methods described in "Soil Agrochemical Analysis," and the results are shown below. Figure 6 The abundance of allelochemicals in rhizomes was determined using non-targeted metabolomics, commissioned to Shanghai Meiji Biopharmaceutical Technology Co., Ltd. The results are shown below. Figure 7 Rhizome biomass was determined by the drying and weighing method, and the results are shown in [see figure]. Figure 8 a, 8b; Among the quality indicators of rhizomes, the polysaccharide content was determined by the H2SO4-anthrone method, and the results are shown in […]. Figure 8 c; The total brass content was determined by the NaNO2-Al(NO3)3-NaOH colorimetric method, and the results are shown below. Figure 8 d; The total saponin content was determined by the vanillin-glacial acetic acid colorimetric method, and the results are shown in [the table below]. Figure 8 e.

[0065] By scientifically and rationally determining the configuration, modification method, usage, and dosage of biochar, the application of "Biochar C" significantly increased the Shannon index and significantly decreased the Simpson index of the rhizosphere soil bacterial community of Polygonatum odoratum. Figure 5 This indicates that the α diversity of the rhizosphere soil bacterial community was significantly enhanced, and the evenness of species composition within the community was greatly improved, resulting in a better soil microecological structure and stronger stability.

[0066] Meanwhile, the physicochemical properties of the rhizosphere soil of Polygonatum were significantly improved, with a significant increase in cation exchange capacity, total nitrogen, total phosphorus, and total potassium content. Figure 6 Therefore, "biochar C" significantly improved the rhizosphere soil microecology and physicochemical properties, which created favorable conditions for the healthy growth of Polygonatum rhizomes and the regulation of secondary metabolism.

[0067] Based on this, the abundance of all seven allelochemicals in the rhizome of Polygonatum sibiricum was significantly reduced under treatment with 5% biochar C. Among them, the abundance of 5-Hydroxy-L-tryptophan, 3-Coumaric acid, and Sclareol was significantly reduced under all dosages. Figure 7 The fresh and dry weights of Polygonatum rhizomes were significantly increased. Figure 8 a, 8b), polysaccharide content significantly increased ( Figure 8 c), and at the same time increased the content of total flavonoids and total saponins (c) Figure 8 (d, 8e), the quality of Polygonatum rhizome was significantly improved.

[0068] Example 2

[0069] (1) Site selection: Select an acidic sandy loam soil zone with a soil pH of 4.7. The total nitrogen, total potassium, total phosphorus and organic matter content of the soil are 0.71g / kg, 1.23g / kg, 22.51g / kg and 32.16g / kg, respectively.

[0070] (2) Planting of Polygonatum: Select healthy one-year-old Polygonatum seedlings, retain the complete root system, soak the roots in rooting powder solution for 10 minutes before planting, plant them with a row spacing of 35cm and a plant spacing of 22cm, compact the soil, water them thoroughly, and cover them with straw to keep them warm and moist.

[0071] (3) Biochar preparation:

[0072] ① After crushing rice husks, tea stalks, and corn stalks, respectively, they were loaded into the furnace of a carbonization furnace and purged with high-purity nitrogen for 10 minutes; then, the furnace was heated at 10℃·min. -1The heating rate was adjusted to 600℃, and the temperature was maintained at this level for 4 hours. The carbonization furnace was then shut off, and the biochar inside was allowed to cool naturally to room temperature before being removed, pulverized, and passed through a 100-mesh sieve. MB, RB, and TB were mixed in a mass ratio of 1.5:1:1 to balance their nitrogen, phosphorus, and potassium nutrient content, surface element composition, microporous structure, specific surface area, and surface functional groups, thus obtaining "biochar A".

[0073] ② Prepare a 2000 mg / L salicylic acid solution, i.e., "Solution A", using anhydrous ethanol as the solvent. Mix Solution A and "Biochar A" at a volume-to-mass ratio of 12.5:1 at room temperature (25℃), and react at 60℃ for 15 hours. After the reaction, filter the mixture and wash the filter residue four times with anhydrous ethanol and distilled water. Place the washed residue in a vacuum drying oven and dry it to constant weight at 60℃ to obtain "Biochar B".

[0074] ③ Using water as a solvent, prepare a UDP-D-galactose solution with a concentration of 1000 mg / L, i.e., "solution B". At room temperature (20℃), mix solution B and "biochar B" at a volume-to-mass ratio of 25:1, and dry in an oven at 70℃ for 60 h to constant weight to obtain "biochar C".

[0075] (4) Application of biochar: In September of the second and third years after the planting of Polygonatum, scrape off 5cm of the topsoil at a distance of 10cm from the rhizome of Polygonatum and evenly sprinkle "Biochar A", "Biochar B" or "Biochar C" at a ratio of 2% by weight, and then backfill the original topsoil. The control group was not treated with biochar.

[0076] (5) Harvesting: In the third year of planting, after the fruit is ripe and the stems have fallen over, dig up the underground rhizomes.

[0077] The effects of this method on the cultivation of Polygonatum were compared. The experimental results of the abundance of allelochemicals and polysaccharide content in the rhizomes are shown in Table 3.

[0078] Table 3 Comparison of fresh weight, allelochemicals and polysaccharide content of Polygonatum rhizome

[0079]

[0080] Compared with the untreated biochar, the application of 2% biochar A, B and C significantly reduced the abundance of three allelochemicals, 5-Hydroxy-L-tryptophan, 3-Coumaric acid and Sclareol, in the rhizomes of Polygonatum sibiricum, while significantly increasing the polysaccharide content. Among them, biochar C had the best regulatory effect.

[0081] Example 3

[0082] 1. Experimental Methods

[0083] (1) Site selection: Select an acidic sandy loam soil zone with a soil pH of 4.7. The total nitrogen, total potassium, total phosphorus and organic matter content of the soil are 0.71g / kg, 1.23g / kg, 22.51g / kg and 32.16g / kg, respectively.

[0084] (2) Planting of Polygonatum: Select Polygonatum without damage and with plump buds, cut it into 10cm long rhizome segments, and after sun drying for 3 hours, plant it in shallow furrows with a row spacing of 32cm and a plant spacing of 24cm. After placing it, cover it with a 6cm thick mixture of decomposed organic fertilizer and topsoil, water it thoroughly, and keep the soil moist without water accumulation in the later stage.

[0085] (3) Biochar preparation:

[0086] ① After crushing rice husks, tea stalks, and corn stalks, respectively, they were loaded into the furnace of a carbonization furnace and purged with high-purity nitrogen for 10 minutes; then, the furnace was heated at 10℃·min. -1 The heating rate was adjusted to 600℃ and pyrolyzed at a constant temperature for 4 hours. The carbonization furnace was then shut off, and the biochar inside was allowed to cool naturally to room temperature before being removed, pulverized, and passed through a 100-mesh sieve. MB, RB, and TB were mixed in a mass ratio of 1.5:1:1 to balance their nitrogen, phosphorus, and potassium nutrient content, surface element composition, microporous structure, specific surface area, and surface functional groups, thus obtaining "biochar A".

[0087] ② Prepare a 2000 mg / L salicylic acid solution, i.e., "Solution A", using anhydrous ethanol as the solvent. Mix Solution A and "Biochar A" at a volume-to-mass ratio of 12.5:1 at room temperature (25℃), and react at 60℃ for 15 hours. After the reaction, filter the mixture and wash the filter residue four times with anhydrous ethanol and distilled water. Place the washed residue in a vacuum drying oven and dry it to constant weight at 60℃ to obtain "Biochar B".

[0088] ③ Using water as a solvent, prepare a UDP-D-galactose solution with a concentration of 1000 mg / L, i.e., "solution B". At room temperature (20℃), mix solution B and "biochar B" at a volume-to-mass ratio of 25:1, and dry in an oven at 70℃ for 60 h to constant weight to obtain "biochar C".

[0089] (4) Application of biochar: Biochar shall be applied in accordance with the following methods.

[0090] Application method 1: In September of the second and third years after planting Polygonatum, scrape off 5cm of the topsoil at a distance of 15cm from the rhizome of Polygonatum and evenly sprinkle "Biochard C" at a ratio of 2 tons / acre, and then backfill the original topsoil.

[0091] Application Method 2: In September of the second and third years after planting Polygonatum, scrape off 5cm of the topsoil at a distance of 20cm from the rhizome of Polygonatum and evenly sprinkle "Biochard C" at a ratio of 2 tons / acre, and then backfill the original topsoil.

[0092] Application method 3: In September of the second and third years after planting Polygonatum, scrape off 4cm of the topsoil at a distance of 15cm from the rhizome of Polygonatum and evenly sprinkle "Biochard C" at a ratio of 2 tons / acre, and then backfill the original topsoil.

[0093] (5) Harvesting: In the third year of planting, after the fruit is ripe and the stems have fallen over, dig up the underground rhizomes.

[0094] 2. Experimental Results

[0095] The effects of the above three application methods on the cultivation of Polygonatum were compared. The experimental results of fresh weight of Polygonatum rhizomes, abundance of allelochemicals 5-Hydroxy-L-tryptophan, 3-Coumaric acid and Sclareol in rhizomes, and content of polysaccharides in rhizomes are shown in Table 4.

[0096] Table 4. Comparison of fresh weight, allelochemicals, and polysaccharide content of Polygonatum rhizomes under different application methods.

[0097]

[0098] By scientifically and rationally determining the application method of biochar, all three application methods can significantly affect the growth and quality of Polygonatum sibiricum, increasing the fresh weight of Polygonatum sibiricum rhizomes by 16.00-41.60%, increasing the content of rhizomes polysaccharides by 28.09-59.47%, and decreasing the abundance of allelochemicals 5-Hydroxy-L-tryptophan by 19.58-36.01%, 3-Coumaric acid by 48.73-60.91%, and Sclareol by 49.66-58.16%.

[0099] In summary, through years of multi-location field trials, the rational application of biochar significantly increased the polysaccharide content of Polygonatum rhizomes and significantly reduced the abundance of allelochemicals. This not only improved the medicinal quality and commercial value of Polygonatum rhizome, but also alleviated the inhibitory effect of allelopathic effects on its growth, improved the soil microenvironment, and promoted robust rhizome growth. This is conducive to the large-scale cultivation of high-quality and high-yield Polygonatum rhizome, and provides scientific and feasible technical support for improving the quality and efficiency of artificial cultivation of Polygonatum rhizome.

[0100] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or any equivalent structural or procedural transformations made using the content of this specification, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this invention.

Claims

1. A method for cultivating Polygonatum sibiricum that reduces allelochemicals and increases polysaccharide content, characterized in that: The planting method involves planting Polygonatum in acidic sandy loam soil. In the second and third years, "Biochar C" is applied to the soil 1-2 times in September and October. The fruit can be harvested after the stems have matured and fallen over in the third year. The "Biochar C" is modified biochar loaded with salicylic acid and uridine diphosphate galactose.

2. The method for cultivating Polygonatum sibiricum according to claim 1, characterized in that: The application method of "Biochar C" is as follows: scrape off 2-5cm of the topsoil within a range of 10-20cm from the rhizome of Polygonatum odoratum, evenly sprinkle "Biochar C" in, and then backfill the original topsoil.

3. The method for cultivating Polygonatum sibiricum according to claim 1 or 2, characterized in that: The amount of "biochar C" added is 1%-5% of the soil mass or 1-7 tons / acre.

4. The method for cultivating Polygonatum sibiricum according to any one of claims 1-3, characterized in that: The "Biochar C" mentioned above includes one or more of rice husk biochar, tea stalk biochar, and corn stalk biochar loaded with salicylic acid and uridine diphosphate galactose.

5. The method for cultivating Polygonatum sibiricum according to any one of claims 1-3, characterized in that: The method for preparing "biochar C" includes the following steps: Preparation of "Biochar A": Rice husks, tea stalks, and corn stalks were respectively loaded into the furnace of a carbonization furnace and purged with high-purity nitrogen for 1-20 min; then heated at 10-30℃·min. -1 The heating rate was increased to 500℃-700℃ and pyrolyzed at a constant temperature for 2-4 hours. The carbonization furnace was then closed, and the biochar inside the furnace was allowed to cool naturally to room temperature before being removed, pulverized, and passed through an 80-120 mesh sieve to obtain rice husk biochar, tea stalk biochar, and corn stalk biochar, respectively. The rice husk biochar, tea stalk biochar, and corn stalk biochar were mixed in a mass ratio of (1-2):(0.5-1):(1-2) to obtain "Biochar A". Preparation of "Biochar B": At room temperature (18℃-25℃), solution A and "Biochar A" were mixed at a volume-to-mass ratio of (10-15):1 and reacted at a constant temperature of 50℃-70℃ for 10-18 h. After the reaction, the mixture was filtered and the filter residue was washed repeatedly with anhydrous ethanol and distilled water. The washed residue was placed in a vacuum drying oven and dried to constant weight at 50℃-70℃ to obtain "Biochar B". Preparation of "Biochar C": At room temperature (18℃-25℃), solution B and "Biochar B" are mixed at a volume-mass ratio of (20-30):1 and dried in an oven at 60℃-80℃ for 48-60 hours until constant weight is obtained to obtain "Biochar C".

6. The method for cultivating Polygonatum sibiricum according to claim 1, characterized in that: The soil in question is acidic sandy loam with a pH of 4.0-5.0, and the total nitrogen, total potassium, total phosphorus, and organic matter content should be in the range of 0.1-1.5 g / kg, 0.2-1.5 g / kg, 10-25 g / kg, and 10-100 g / kg, respectively.

7. The method for cultivating Polygonatum sibiricum according to claim 5, characterized in that: The preparation method of "solution A" is as follows: salicylic acid is completely dissolved in anhydrous ethanol to form a salicylic acid solution with a concentration of 500-5000 mg / L.

8. The method for cultivating Polygonatum sibiricum according to claim 5, characterized in that: The method for preparing solution B is as follows: using water as a solvent, uridine diphosphate galactose is completely dissolved to form a uridine diphosphate galactose solution with a concentration of 50-2000 mg / L.

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