Plant growth-promoting cold-resistant microbial slow-release organic fertilizer, preparation method and application thereof

Abstract

The application discloses a plant growth-promoting cold-resistant microbial slow-release organic fertilizer and a preparation method and application thereof. The plant growth-promoting cold-resistant microbial slow-release organic fertilizer comprises the following components in parts by weight: 20-40 parts by weight of attapulgite powder, 40-60 parts by weight of an organic fertilizer carrier and 5-10 parts by weight of a compound microbial agent. The compound microbial agent comprises bacillus mucilaginosus and enterobacter. The plant growth-promoting cold-resistant microbial slow-release organic fertilizer, the preparation method and the application thereof have the functions of fixing and protecting functional microorganisms by virtue of the unique structure of the attapulgite, dissolving effective silicon in minerals by the bacillus mucilaginosus, secreting auxin and activating nutrients by the enterobacter, and realizing the synergistic effect of the functions of cold resistance and growth promotion. Experiments show that the product can significantly improve the proline and chlorophyll contents of plants under stress, reduce the MDA content, and promote the growth of plants, and the effect is significantly better than that of a single microbial agent.

Description

Technical Field

[0001] This application relates to the fields of agricultural microbial technology and novel fertilizers, and in particular to a plant growth-promoting and cold-resistant microbial slow-release organic fertilizer, its preparation method, and its application. Background Technology

[0002] Low temperature stress is one of the major abiotic stresses that limit plant growth, development, and geographical distribution, leading to reduced crop yield and quality. Currently, measures to improve plant cold resistance mainly include breeding cold-resistant varieties and using chemical inducers, but the former has a long cycle, and the latter may bring environmental residues and pesticide damage risks.

[0003] Silicon has been proven to be a "beneficial element" for plants. It can deposit in cell walls to enhance mechanical strength, improve water retention, and increase the activity of antioxidant enzymes, thus effectively mitigating low-temperature damage. Auxins (such as IAA) can directly promote cell division and elongation, helping plants recover quickly from stress. In addition, ensuring adequate nitrogen and phosphorus nutrition for plants under stress is also crucial.

[0004] Attapulgite is a natural one-dimensional, nanoscale, hydrous magnesium-aluminate silicate clay mineral. Its unique rod-like structure and porous structure give it excellent adsorption, hydrophobicity, and air permeability, making it an excellent carrier for microorganisms and nutrients. *Bacillus mucilaginosus* is a typical silicate bacterium that can decompose minerals to release available silicon. *Enterobacter p* has been reported to have the ability to fix nitrogen, solubilize phosphorus, and secrete plant growth hormones.

[0005] However, there are currently no reports on the systematic coupling of the physical properties of attapulgite with the biochemical functions of the two functional bacteria mentioned above, and their specific application in the preparation of cold-resistant and growth-promoting agents. Existing technologies are mostly single-bacterial agents or fertilizers with simple physical mixtures, failing to achieve deep synergy between "cold resistance" and "growth promotion," and between "minerals" and "microorganisms" at the mechanistic level. Summary of the Invention

[0006] This application aims to at least partially address one of the technical problems in the related art.

[0007] Therefore, one objective of this application is to provide a plant-promoting and cold-resistant microbial slow-release organic fertilizer, its preparation method, and its application. Utilizing the unique structure of attapulgite to fix and protect functional microorganisms, it achieves synergistic effects of "cold resistance" and "growth promotion" by leaching effective silicon from the mineral through Bacillus subtilis and simultaneously utilizing Enterobacteriaceae to secrete auxins and activate nutrients. Experiments show that this product can significantly increase the proline and chlorophyll content of plants under stress, reduce MDA content, and promote plant growth, with effects significantly superior to single microbial agents. This provides a highly efficient and environmentally friendly new solution to address the problem of low-temperature stress in plants.

[0008] To achieve the above objectives, the first aspect of this application provides a plant growth-promoting and cold-resistant microbial slow-release organic fertilizer, comprising the following components in parts by weight: 20-40 parts by weight of attapulgite powder, 40-60 parts by weight of organic fertilizer carrier, and 5-10 parts by weight of compound microbial agent. The compound microbial agent includes Bacillus mucilaginosus and Enterobacter.

[0009] In addition, the plant growth-promoting and cold-resistant microbial slow-release organic fertilizer, its preparation method, and its application proposed in this application may also have the following additional technical features: In one embodiment of this application, the ratio of Bacillus mucilaginosus to Enterobacter is 1:1 to 1:2.

[0010] In one embodiment of this application, the viable count of the composite microbial agent is not less than 10 × 10^8 CFU / g.

[0011] In one embodiment of this application, the attapulgite powder is a hydrous magnesium aluminosilicate clay mineral powder that has been pre-treated by crushing and passed through a 100-200 mesh sieve. The organic fertilizer carrier is a decomposed plant-derived organic material with a particle size that matches the attapulgite powder.

[0012] In one embodiment of this application, the organic fertilizer carrier is soybean meal powder, and the organic matter content of the soybean meal powder is ≥40%.

[0013] The second aspect of this application provides a method for preparing the first aspect of slow-release organic fertilizer, comprising the following steps: S1 prepares high-concentration bacterial suspensions of Bacillus mucilaginosus and Enterobacter spp., respectively; S2 involves crushing and pre-treating the attapulgite powder; S3 After mixing the two bacterial suspensions from step S1, it is thoroughly stirred and mixed with the attapulgite powder from step S2, and allowed to stand for adsorption to obtain a mineral-carrying bacterial premix. S4. The mineral-carrying bacterial premix is ​​mixed with the organic fertilizer carrier, granulated, and dried in a ventilated manner to obtain the finished product.

[0014] In addition, the method for preparing plant growth-promoting and cold-resistant microbial slow-release organic fertilizer proposed in this application may also have the following additional technical features: In one embodiment of this application, the viable count of the high-concentration bacterial suspension in step S1 is not less than 10 × 10^8 CFU / mL. The bacterial suspension is obtained by inoculating the corresponding strain into LB medium and culturing it at 30°C and 220 rpm for 30 hours.

[0015] In one embodiment of this application, in step S3, the two bacterial suspensions are mixed at a live bacteria ratio of 1:1 to 1:2, and after being mixed with attapulgite powder, they are allowed to stand at room temperature for 2 hours for adsorption. In step S4, diluted molasses water is sprayed in during mixing to adjust the total moisture content to 20% to 25%, and then granulated. The mixture is then dried in a ventilated environment at a temperature not exceeding 50°C until the moisture content of the material is ≤15%.

[0016] The third aspect of this application proposes the application of the first aspect of slow-release organic fertilizer in enhancing plant resistance to low-temperature stress and promoting plant growth under low-temperature stress.

[0017] In addition, the application of a plant growth-promoting and cold-resistant microbial slow-release organic fertilizer proposed in this application may also have the following additional technical features: In one embodiment of this application, the plant is tobacco, a solanaceous crop, or a silicon-tolerant cruciferous crop; the low-temperature stress is a low-temperature environment stress of 4°C or below. Beneficial effects

[0018] This application discloses a plant growth-promoting and cold-resistant microbial slow-release organic fertilizer, its preparation method, and its application. It utilizes the unique structure of attapulgite to fix and protect functional microorganisms, leaching effective silicon from the mineral through Bacillus subtilis, and simultaneously utilizing Enterobacteriaceae to secrete auxins and activate nutrients, achieving a synergistic effect of "cold resistance" and "growth promotion." Experiments show that this product can significantly increase the proline and chlorophyll content of plants under stress, reduce MDA content, and promote plant growth, with effects significantly superior to single microbial agents. This provides a highly efficient and environmentally friendly new solution to address plant low-temperature stress.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a graph showing the change in the concentration of soluble silica from attapulgite leached by the composite bacterial agent in one embodiment of the present invention over time.

[0021] Figure 2 Nitrogen fixation effect of compound bacterial agents Figure 3 Phosphate-solubilizing effect of compound microbial agents Figure 4 The IAA production capacity of the control group and the compound bacterial agent. Figure 5 As a phenotypic control between the control group and the experimental group Figure 6 Chlorophyll content Figure 7 Peroxidase content and superoxide dismutase content Figure 8 For malondialdehyde content and relative conductivity Figure 9 This refers to the proline content. Detailed Implementation

[0022] Embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. Rather, embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0023] The following description, in conjunction with the accompanying drawings, describes a plant-promoting and cold-resistant microbial slow-release organic fertilizer according to embodiments of this application, its preparation method, and its application.

[0024] The photovoltaic panel regulation device provided in this application embodiment can be applied to...

[0025] like Figures 1-9 As shown in the embodiment of this application, a plant cold-resistant and growth-promoting microbial slow-release organic fertilizer includes the following components in parts by weight: 20-40 parts by weight of attapulgite powder, 40-60 parts by weight of organic fertilizer carrier, and 5-10 parts by weight of compound microbial agent. The compound microbial agent includes Bacillus mucilaginosus and Enterobacter.

[0026] Specifically, this embodiment aims to illustrate the specific preparation process of organic fertilizer and the amount of its components.

[0027] 1. Component dosage.

[0028] By weight, the slow-release organic fertilizer of this embodiment consists of the following components: Attapulgite powder: 30 parts by weight; Organic fertilizer carrier (soybean meal powder): 60 parts by weight; Compound microbial inoculant: 10 parts by weight.

[0029] The compound microbial agent is composed of Bacillus mucilaginosus and Enterobacter p. in a 1:1 ratio of live bacteria.

[0030] 2. Preparation method.

[0031] (1) Preparation of bacterial suspension: Bacillus mucilaginosus and Enterobacter were inoculated into LB liquid medium and cultured at 30℃ and 220 rpm for 30 hours with shaking to obtain a viable bacterial count of not less than 10 × 10⁻⁶. 8 High-concentration bacterial suspension with CFU / mL; (2) Mineral pretreatment: The raw attapulgite ore is crushed and passed through a 200-mesh sieve to obtain attapulgite powder for later use; (3) Microbial-mineral coupling: The two bacterial suspensions prepared in step (1) are mixed in proportion and then thoroughly mixed with the attapulgite powder in step (2). The mixture is allowed to stand at room temperature for 2 hours to adsorb, thus obtaining the "mineral-borne bacterial premix" (i.e., mineral-borne bacterial premix). (4) Mixing and granulation: Mix the premix obtained in step (3) with soybean meal powder evenly, spray in diluted molasses water to adjust the total moisture content to 20% to 25%, and send it into a granulator for granulation; (5) Low temperature drying: The granular material is dried in a ventilated environment at 45-50℃ until the moisture content is ≤15%, thus obtaining the slow-release organic fertilizer product of the present invention.

[0032] 3. Product Indicators.

[0033] Testing showed that the slow-release organic fertilizer prepared in this embodiment meets the NY884-2012 "Bio-organic Fertilizer" standard, with the main indicators as follows: Effective viable bacteria count: ≥0.2 billion / g; Organic matter content: ≥47%; Moisture content: ≤15%; pH value: 58; Fecal coliform count: ≤100 CFU / g; Ascaris egg mortality rate: ≥95%; Validity period: ≥6 months.

[0034] In one embodiment of this application, the ratio of Bacillus mucilaginosus to Enterobacter is 1:1 to 1:2.

[0035] This embodiment aims to verify that the slow-release organic fertilizer prepared in the range of 1:1 to 1:2 between Bacillus mucilaginosus and Enterobacter spp. has a significant cold-resistant and growth-promoting effect, and to examine the performance differences under different ratios.

[0036] 1. Experimental design.

[0037] According to the above components and preparation method, 30 parts by weight of attapulgite powder, 60 parts by weight of organic fertilizer carrier (soybean meal powder), and 10 parts by weight of compound microbial agent were fixed. Only the ratio of viable Bacillus subtilis to Enterobacter in the compound microbial agent was changed, and the following three treatment groups were set up: Treatment A: Bacillus mucilaginosus: Enterobacteriaceae = 1:1; Treatment B: Bacillus mucilaginosus: Enterobacteriaceae = 1:1.5; Treatment C: Bacillus mucilaginosus: Enterobacteriaceae = 1:2; The bacterial suspensions in each treatment group were cultured according to the method in Example 6 until the viable bacterial count was not less than 1.0 × 10⁻⁶. 8 The concentration of CFU / mL was then mixed in a specific ratio, coupled with attapulgite powder, granulated, and dried to obtain the corresponding slow-release organic fertilizer sample.

[0038] 2. Verification of cold-resistant and growth-promoting effects.

[0039] Tobacco seedlings were used as the test plants, and the experimental method was the same as in Example 9. A blank control group (CK) and three treatment groups (A, B, and C) were set up, with each group being replicated three times. When the seedlings grew to six leaves and one bud, they were subjected to low temperature stress at 4°C for 48 hours, and relevant physiological indicators were measured.

[0040] 3. Results and Analysis.

[0041] This experiment used tobacco seedlings subjected to low-temperature stress as experimental material, setting up a blank control group (CK group) and three experimental groups. The experimental groups were treated with a slow-release organic fertilizer prepared from a compound microbial agent with a live bacteria ratio of 1:1 (Group A), 1:1.5 (Group B), and 1:2 (Group C). All groups were uniformly treated with 4℃ low-temperature stress. Four core physiological indicators of cold resistance and growth promotion were measured: proline content, total chlorophyll, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity. Specific results are as follows: The basic physiological indicators of tobacco seedlings in the blank control group (CK group) after low temperature stress were: proline content 185.3 μg / gFW, total chlorophyll 0.92 mg / gFW, malondialdehyde content 15.6 nmol / gFW, and SOD activity 210 U / gFW.

[0042] When the ratio of viable Bacillus mucilaginosus to Enterobacteriaceae was 1:1 (Group A), the proline content of tobacco seedlings after low-temperature stress reached 330.1 μg / gFW, an increase of 78.2% compared with the blank control group; the total chlorophyll content reached 1.38 mg / gFW, an increase of 50.0% compared with the blank control group; the malondialdehyde content decreased to 11.7 nmol / gFW, a decrease of 24.8% compared with the blank control group; and the SOD activity reached 344 U / gFW, an increase of 63.7% compared with the blank control group.

[0043] When the ratio of viable Bacillus mucilaginosus to Enterobacteriaceae was 1:1.5 (Group B), the proline content of tobacco seedlings after low-temperature stress reached 341.5 μg / gFW, an increase of 84.3% compared with the blank control group; the total chlorophyll content reached 1.42 mg / gFW, an increase of 54.3% compared with the blank control group; the malondialdehyde content decreased to 11.2 nmol / gFW, a decrease of 28.2% compared with the blank control group; and the SOD activity reached 351 U / gFW, an increase of 67.1% compared with the blank control group. All cold resistance and growth promotion indicators were better than those of the 1:1 ratio group.

[0044] When the ratio of viable Bacillus mucilaginosus to Enterobacteriaceae was 1:2 (Group C), the tobacco seedlings showed the best performance in various physiological indicators after low-temperature stress. The proline content reached 352.7 μg / gFW, which was 90.4% higher than the blank control group; the total chlorophyll content reached 1.45 mg / gFW, which was 57.6% higher than the blank control group; the malondialdehyde content decreased to 10.8 nmol / gFW, which was 30.8% lower than the blank control group; and the SOD activity reached 362 U / gFW, which was 72.4% higher than the blank control group.

[0045] The results showed that within a ratio range of 1:1 to 1:2, all treatment groups significantly increased the proline and chlorophyll content of tobacco leaves, decreased malondialdehyde (MDA) content, and enhanced superoxide dismutase (SOD) activity, indicating that slow-release organic fertilizers within this ratio range had good cold-resistant and growth-promoting effects. With the increase of the proportion of Enterobacteriaceae (from 1:1 to 1:2), the growth-promoting and cold-resistant indicators showed a slight upward trend, indicating that appropriately increasing the proportion of Enterobacteriaceae helps to further enhance the effect, but all ratios were superior to single-agent inoculants (data not listed).

[0046] 4. Conclusion.

[0047] This embodiment confirms that when the ratio of viable Bacillus mucilaginosus to Enterobacter is in the range of 1:1 to 1:2, the prepared slow-release organic fertilizer can effectively enhance the plant's resistance to low-temperature stress and promote plant growth. Moreover, this ratio range has good process adaptability and effect stability, which is the preferred technical feature of this invention.

[0048] In one embodiment of this application, the viable count of the compound microbial agent is not less than 10 × 10^8 CFU / g.

[0049] This embodiment aims to verify that the viable count of the compound microbial agent is not less than 1.0 × 10⁻⁶. 8 CFU / g (i.e., 10) 8 When the number of live bacteria is below the limit (CFU / g), the prepared slow-release organic fertilizer has a significant cold-resistant and growth-promoting effect, and the effect of the number of live bacteria below the limit on product performance is investigated.

[0050] 1. Experimental design.

[0051] According to the components of the first embodiment and the bacterial strain ratio of the second embodiment (Bacillus mucilaginosus: Enterobacter = 1:1), 30 parts by weight of attapulgite powder, 60 parts by weight of organic fertilizer carrier (soybean meal powder), and 10 parts by weight of compound microbial agent were fixed. By adjusting the concentration of the bacterial suspension and dilution treatment, compound microbial agents with different viable bacterial counts were prepared, and the following three treatment groups were set up: Treatment L (low viable count): The viable count of the compound microbial agent was 1.0 × 10⁻⁶. 6 CFU / g; Treatment M (live bacteria array): The viable bacteria count of the compound microbial agent was 1.0 × 10⁻⁶. 7 CFU / g; Treatment H (high viable count): The viable count of the compound microbial agent was 1.0 × 10⁻⁶. 8 CFU / g (meets the lower limit requirement in this embodiment); Treatment S (ultra-high viable count): The viable count of the compound microbial agent was 5.0 × 10⁻⁶. 8 CFU / g Each treatment group prepared slow-release organic fertilizer samples according to the method of the first embodiment, and kept all process parameters consistent except for the concentration of the bacterial suspension.

[0052] 2. Method for preparing bacterial suspension.

[0053] Following the method of the second embodiment, *Bacillus mucilaginosus* and *Enterobacter* were cultured separately, yielding a viable count of approximately 5.0 × 10⁻⁶. 8 CFU / mL bacterial suspension. The two bacterial suspensions were mixed at a 1:1 ratio, then concentrated by centrifugation or diluted with sterile physiological saline to adjust the concentration of the mixed bacterial suspension before coupling with attapulgite powder. The viable counts of the compound microbial agent in the final slow-release organic fertilizers obtained from each treatment group were measured as follows: Processing L: 9.8 × 10 5 CFU / g; Processing M: 1.1 × 10 7 CFU / g; Processing H: 1.2 × 10 8 CFU / g; Processing S: 4.8 × 10 8 CFU / g; 3. Verification of cold resistance and growth promotion effects.

[0054] Tobacco seedlings were used as the test plants, and the experimental method was the same as in Example 9. A blank control group (CK) and four treatment groups (L, M, H, S) were set up, with each group being replicated three times. When the seedlings grew to six leaves and one bud, they were subjected to low temperature stress at 4°C for 48 hours, and relevant physiological indicators were measured.

[0055] This experiment used tobacco seedlings subjected to 4℃ low-temperature stress as experimental material. A blank control group (CK group) and four treatment groups with different viable bacterial count gradients were set up: low viable bacterial count treatment group (treatment L), medium viable bacterial count treatment group (treatment M), high viable bacterial count treatment group (treatment H), and ultra-high viable bacterial count treatment group (treatment S). Except for the viable bacterial count of the compound microbial agent in the slow-release organic fertilizer product, all other groups had completely identical basic formulas, preparation processes, tobacco cultivation conditions, low-temperature stress treatment methods, and physiological index detection methods. Five core indicators were uniformly measured: viable bacterial count, proline content, chlorophyll content, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity. Specific experimental results are as follows: The blank control group (CK group) had no exogenous functional bacterial agents added. After low temperature stress, the basic physiological indicators of tobacco seedlings were: proline content 185.3 μg / gFW, chlorophyll content 0.92 mg / gFW, malondialdehyde content 15.6 nmol / gFW, and SOD activity 210 U / gFW.

[0056] The viable count of the finished compound microbial agent in the low viable count treatment group (treatment L) was 9.8 × 10⁻⁶. 5 After exposure to low temperature stress, the proline content of tobacco seedlings was 202.4 μg / gFW, an increase of 9.2% compared with the blank control group; the chlorophyll content was 0.98 mg / gFW, an increase of 6.5% compared with the blank control group; the malondialdehyde content was 14.8 nmol / gFW, a decrease of 5.1% compared with the blank control group; and the SOD activity was 225 U / gFW, an increase of 7.1% compared with the blank control group, showing only a very weak cold resistance and growth promotion effect.

[0057] The viable count of the finished compound microbial agent in the medium viable count treatment group (treatment M) was 1.1 × 10⁻⁶. 7 After exposure to low temperature stress, the proline content of tobacco seedlings was 247.6 μg / gFW, an increase of 33.6% compared with the blank control group; the chlorophyll content was 1.12 mg / gFW, an increase of 21.7% compared with the blank control group; the malondialdehyde content was 13.5 nmol / gFW, a decrease of 13.5% compared with the blank control group; and the SOD activity was 278 U / gFW, an increase of 32.4% compared with the blank control group. It has a certain cold resistance and growth promotion effect, but the effect has not reached the ideal level of stability and significance.

[0058] The viable count of the finished compound microbial agent in the high viable count treatment group (treatment H) was 1.2 × 10⁻⁶. 8The CFU / g of the compound microbial agent met the requirement of "the number of live bacteria in the compound microbial agent is not less than 1.0×10^8 CFU / g". After low temperature stress, the proline content of tobacco seedlings was 330.1 μg / gFW, which was 78.2% higher than the blank control group; the chlorophyll content was 1.38 mg / gFW, which was 50.0% higher than the blank control group; the malondialdehyde content was 11.7 nmol / gFW, which was 24.8% lower than the blank control group; and the SOD activity was 344 U / gFW, which was 63.7% higher than the blank control group. The cold resistance and growth promotion effect achieved a qualitative improvement, and all core physiological indicators were significantly better than those of low and medium live bacteria groups.

[0059] The viable count of the finished compound microbial agent in the ultra-high viable count treatment group (treatment S) was 4.8 × 10⁻⁶. 8 After low-temperature stress, the proline content of tobacco seedlings was 341.2 μg / gFW, an increase of 84.2% compared with the blank control group; the chlorophyll content was 1.41 mg / gFW, an increase of 53.3% compared with the blank control group; the malondialdehyde content was 11.5 nmol / gFW, a decrease of 26.3% compared with the blank control group; and the SOD activity was 351 U / gFW, an increase of 67.1% compared with the blank control group. The cold resistance and growth promotion effect was slightly improved compared with treatment H, but there was no significant difference between the two.

[0060] The results show that: Treatment H (live count ≥ 10) 8 Both CFU / g and treatment S (higher viable count) significantly increased the proline and chlorophyll content of tobacco leaves, significantly reduced the MDA content, and enhanced SOD activity, demonstrating excellent cold resistance and growth promotion effects. Treatment M (live count 10) 7 Although CFU / g) had some effect, the improvement in various indicators was significantly lower than that of treatment H; Treatment L (live count 10) 6 The effect of CFU / g was weak, with no significant difference compared to the CK group (p>0.05). The difference in efficacy between treatment H and treatment S was not significant (p>0.05), indicating that when the viable bacterial count reaches 102... 8 After reaching CFU / g, further increasing the viable bacteria count has limited effect on efficacy.

[0061] 5. Stability study of viable cell count.

[0062] This experiment tested the room temperature storage stability of slow-release organic fertilizer. Four treatment groups with different initial viable counts were set up: low viable count treatment group (treatment L), medium viable count treatment group (treatment M), high viable count treatment group (treatment H), and ultra-high viable count treatment group (treatment S). All groups were identical except for the initial viable count; the basic formula, preparation process, and storage conditions (room temperature, sealed, and protected from light) were completely consistent. The initial viable count, viable count after 3 months of room temperature storage, and viable count after 6 months of room temperature storage were measured for each group. The survival rate of functional bacteria during the 6-month storage period was calculated. The specific experimental results are as follows: The initial viable count of the product from the low viable count treatment group (treatment L) was 9.8 × 10⁸. 5 CFU / g, viable bacterial count decreased to 3.2×10 after 3 months of storage at room temperature. 5 CFU / g, after 6 months of storage, the viable bacterial count was only 8.1×10. 4 With a CFU / g concentration, the survival rate of functional bacteria was only 8.3% within a 6-month storage period, indicating extremely rapid decline in live bacteria and very poor storage stability.

[0063] The initial viable count of the product in the medium viable count treatment group (treatment M) was 1.1 × 10⁻⁶. 7 CFU / g, viable bacteria count after 3 months of storage at room temperature was 5.6 × 10⁻⁶. 6 CFU / g, viable count after 6 months of storage was 2.3 × 10⁻⁶. 6 With a CFU / g concentration, the survival rate of functional bacteria was 20.9% during a 6-month storage period, indicating a significant problem of viable bacteria attenuation. Therefore, it is impossible to guarantee that the effective viable bacteria count will meet the standard during the product's shelf life.

[0064] The initial viable count of the product from the high viable count treatment group (treatment H) was 1.2 × 10⁻⁶. 8 CFU / g, meeting the requirement that "the viable count of compound microbial agents is not less than 1.0 × 10⁻⁶". 8 The technical requirement of "CFU / g" means that the viable bacterial count should remain at 8.7 × 10⁻⁶ after 3 months of storage at room temperature. 7 CFU / g, viable count after 6 months of storage was 5.4 × 10⁻⁶. 7 With a CFU / g content, the survival rate of functional bacteria reaches 45.0% within a 6-month storage period. The rate of decline of live bacteria is significantly slowed down, and the number of effective live bacteria can be stably maintained during the shelf life, fully meeting the functional requirements for agricultural application of the product.

[0065] The initial viable count of the product from the ultra-high viable count treatment group (treatment S) was 4.8 × 10⁻⁶. 8 CFU / g, viable bacteria count after 3 months of storage at room temperature was 3.6 × 10⁻⁶. 8 CFU / g, viable count after 6 months of storage was 2.5 × 10⁻⁶. 8With a CFU / g concentration, the survival rate of functional bacteria reached 52.1% within a 6-month storage period, demonstrating optimal storage stability and excellent retention of live bacteria over the shelf life.

[0066] Overall test results show that the initial viable count of the product directly determines the survival rate of functional bacteria and shelf-life stability during the storage process. The lower the initial viable count, the more significant the decline in viable bacteria during storage, and the lower the 6-month survival rate. When the initial viable count is below 1.0 × 10⁻⁶, the viable count is significantly lower than that of the product. 8 When the CFU / g level is reached, the effective viable bacteria count becomes extremely low after 6 months of storage, making it impossible to guarantee the cold-resistant and growth-promoting effects after application; when the initial viable bacteria count reaches or exceeds 1.0 × 10⁻⁶, the effective viable bacteria count is significantly lower. 8 At CFU / g, the product's storage stability is significantly improved, and the 6-month live bacteria survival rate is significantly higher than that of low and medium live bacteria arrays, which can reliably guarantee the core functions of the product during its shelf life.

[0067] The results showed that the treatment groups with higher viable cell counts (H and S) had better cell survival rates during storage, maintaining a count of 10 even after 6 months. 7 ~10 8 The CFU / g level met the viable count requirements within the product's shelf life; however, the treatment groups (L and M) with lower viable counts experienced severe degradation and could no longer maintain effective viable counts after 6 months.

[0068] 6. Conclusion.

[0069] This embodiment confirms that: When the viable count of the compound microbial agent is not less than 1.0 × 10⁻⁶ 8 At CFU / g, the prepared slow-release organic fertilizer can significantly enhance the plant's resistance to low-temperature stress and promote plant growth; When the number of live bacteria is below this limit, the cold resistance and growth promotion effect decreases significantly, making it difficult to meet the needs of practical applications. (3) The lower limit setting of the number of live bacteria also ensures that the product can maintain a sufficient number of effective live bacteria during the storage period (6 months), ensuring the stability of the field application effect.

[0070] In one embodiment of this application, the attapulgite powder is a hydrous magnesium aluminosilicate clay mineral powder that has been pre-treated by crushing and passed through a 100-200 mesh sieve. The organic fertilizer carrier is well-rotted plant-derived organic material with a particle size that matches that of attapulgite powder.

[0071] This embodiment aims to illustrate the mineral characteristics of attapulgite powder and the selection of organic fertilizer carriers.

[0072] 1. Mineral characteristics of attapulgite powder.

[0073] The attapulgite used in this invention is a natural hydrous magnesium-aluminate silicate clay mineral with a rod-shaped crystal structure, abundant nanoscale pores, and a large specific surface area. This unique structure endows it with the following functions: (1) Excellent adsorption performance: It can effectively load functional microorganisms and fix them on the surface and pores of minerals to form a "mineral-microorganism" complex (mineral-carrying microbial premix), protecting the microorganisms from adverse external environmental influences; (2) It can provide an effective source of silicon: the silicon, magnesium and other elements contained in attapulgite can be slowly released under the action of Bacillus subtilis, providing plants with soluble silicon needed for cold resistance; (3) Improve soil physical and chemical properties: As a clay mineral, it can regulate soil permeability, water retention and cation exchange capacity after being applied to the soil.

[0074] The main chemical components of the attapulgite powder used in this invention, as determined by testing, are as follows: Content 55%-65%, Content 8%-12%, The content is 8%-10%, which is consistent with the characteristics of hydrous magnesium aluminum silicate clay minerals.

[0075] 2. Selection and particle size matching of organic fertilizer carriers.

[0076] The organic fertilizer carrier of this invention is well-rotted plant-derived organic material, preferably soybean meal powder, corn stalk powder, etc. The selection criteria are as follows: (1) Composting treatment: Plant-derived organic materials that have been fully composted have stabilized organic matter, do not contain pyrolysis products that are harmful to microorganisms and plants, and the humic acid substances produced during the composting process help promote the reproduction of microorganisms and the growth of plant roots. Fresh organic materials that have not been composted are prone to generating fermentation heat during the preparation process, which affects the survival rate of microorganisms.

[0077] (2) Plant source selection: Compared with animal source materials (such as chicken manure and pig manure), plant-based organic materials have a lower background value of harmful microorganisms (such as fecal coliforms), which is more in line with the hygiene standards of bio-organic fertilizers. In addition, the carbon-nitrogen ratio is suitable, which is conducive to the long-term survival of functional microorganisms.

[0078] (3) Particle size matching: The organic fertilizer carrier is crushed to a particle size similar to that of attapulgite powder (100-200 mesh), which can make the two materials uniformly dispersed during mixing and avoid stratification caused by excessive particle size difference. Materials with matching particle size have stronger bonding force, higher forming rate and better particle strength during granulation, which is beneficial to the transportation, storage and field application of the product.

[0079] 3. Conclusion.

[0080] This embodiment demonstrates that the attapulgite powder selected in this invention is a typical hydrous magnesium-aluminate silicate clay mineral, and its structural characteristics are fundamental to achieving microbial loading and silicon release. The organic fertilizer carrier uses well-rotted plant-derived organic materials and its particle size is matched with that of the attapulgite powder, which helps to improve product uniformity, stability, and performance. These features together constitute an important part of the technical solution of this invention.

[0081] In one embodiment of this application, the organic fertilizer carrier is soybean meal powder, and the organic matter content of the soybean meal powder is ≥40%.

[0082] This embodiment aims to illustrate the basis for selecting soybean meal powder as the organic fertilizer carrier and its organic matter content being ≥40%.

[0083] 1. The optimal choice of soybean meal powder as an organic fertilizer carrier.

[0084] Slow-release organic fertilizer was prepared according to the method of the first embodiment, keeping other components constant, and the following organic fertilizer carriers were selected for comparison: Process A: Soybean meal powder (organic matter content 47%); Treatment B: Corn stalk powder (organic matter content 42%); Process C: Rice bran powder (organic matter content 38%); Treatment D: Well-rotted chicken manure (35% organic matter content); Each processing group pulverized the organic materials to match the particle size of the attapulgite powder (passing through a 200-mesh sieve), prepared slow-release organic fertilizers using the same process, and tested relevant indicators.

[0085] The results show that: Among the products prepared from treatment A (soybean meal powder), the compound microbial agent had the highest survival rate, and the number of live bacteria remained above 52% of the initial value after 6 months. The products prepared using treatments B and C had the second-lowest microbial survival rates, at 38% and 31% respectively after 6 months. The product prepared from treatment D (chicken manure) had a low initial viable count and a survival rate of less than 20% after 6 months. At the same time, the fecal coliform count was 260 CFU / g, exceeding the limit of the NY884-2012 standard.

[0086] The reasons for this are as follows: Soybean meal is rich in nutrients such as protein and polysaccharides, and has a suitable carbon-to-nitrogen ratio (approximately 6-8:1), providing a favorable living environment and nutrient source for functional microorganisms, which is beneficial for their long-term survival during storage. While corn stalk meal and rice bran meal are plant-based materials, their nutritional components are relatively... The microbial survival rate is lower than that of soybean meal powder due to its single nature.

[0087] Verification of organic matter content requirements.

[0088] Soybean meal powder samples with different organic matter contents were selected and slow-release organic fertilizers were prepared using the same process. The effect of organic matter content on product performance was investigated. The organic matter content of the soybean meal powder used in Sample 1 was 52%. The product prepared using this as a carrier had round and uniform granules with uniform color. After being stored at room temperature and sealed for 6 months, the microbial survival rate reached 58%, and the granulation rate was 92%. The product showed the best performance in terms of product forming effect, production adaptability, and microbial storage stability.

[0089] The organic matter content of the soybean meal powder used in Sample 2 was 47%. The product prepared using this as a carrier had round and uniform granules with a uniform color. After being stored at room temperature and sealed for 6 months, the microbial survival rate was 53% and the granulation rate was 91%, demonstrating excellent industrial molding effect and good storage stability of functional bacteria.

[0090] The organic matter content of the soybean meal powder used in Sample 3 was 41%. The product particles prepared using this as a carrier were relatively uniform. After 6 months of sealed storage at room temperature, the microbial survival rate was 48%, and the granulation rate was 89%. It can stably meet the requirements of industrial production and the functional bacteria activity requirements during the shelf life of the product.

[0091] The organic matter content of the soybean meal powder used in Sample 4 was 35%. The product particles prepared using this as a carrier were loose and brittle. After being stored at room temperature and sealed for 6 months, the microbial survival rate was only 32%, the granulation rate dropped to 76%, the product forming effect was poor, and the rate of viable bacteria decay was significantly accelerated, which could not meet the core requirements of industrial mass production and agricultural application.

[0092] The organic matter content of the soybean meal powder used in Sample 5 was 28%. When using it as a carrier, problems such as difficulty in granulation and excessive dust occurred during the production process. After 6 months of sealed storage at room temperature, the microbial survival rate was only 21%, and the granulation rate was only 58%. It was impossible to achieve stable industrial production or guarantee the core functional effects of the product during its shelf life.

[0093] The results show that: When the organic matter content of soybean meal powder is ≥40% (samples 1-3), the prepared slow-release organic fertilizer granules are well formed and have a high microbial survival rate (≥48%), which can meet the requirements for the number of live bacteria within the product's shelf life. When the organic matter content of soybean meal powder is less than 40% (samples 4-5), the product granulation rate decreases significantly, the microbial survival rate decreases significantly, and the number of live bacteria is difficult to maintain above the product standard requirements after 6 months.

[0094] 3. Conclusion.

[0095] This embodiment confirms that using soybean meal powder as an organic fertilizer carrier, with an organic matter content of ≥40%, can provide sufficient nutritional support for functional microorganisms, which is beneficial to improving the product granulation rate and the long-term survival rate of microorganisms. This is the preferred technical solution to achieve the purpose of this invention.

[0096] An embodiment of this application provides a method for preparing plant cold-resistant and growth-promoting microbial slow-release organic fertilizer, comprising the following steps: S1 prepares high-concentration bacterial suspensions of Bacillus mucilaginosus and Enterobacter spp., respectively; S2 involves crushing and pre-treating the attapulgite powder; S3 After mixing the two bacterial suspensions from step S1, it is thoroughly stirred and mixed with the attapulgite powder from step S2, and allowed to stand for adsorption to obtain a mineral-carrying bacterial premix. S4 involves mixing the mineral-carrying bacterial premix with the organic fertilizer carrier, granulating, and ventilating and drying to obtain the finished product.

[0097] Furthermore, in step S1, the viable count of the high-concentration bacterial suspension is not less than 10 × 10^8 CFU / mL. The bacterial suspension is obtained by inoculating the corresponding strain into LB medium and culturing it at 30°C and 220 rpm for 30 hours.

[0098] Further, in step S3, the two bacterial suspensions are mixed at a live bacteria ratio of 1:1 to 1:2, and after being mixed with attapulgite powder, they are allowed to stand at room temperature for 2 hours for adsorption. In step S4, diluted molasses water is sprayed in during mixing to adjust the total moisture content to 20% to 25%, and then granulated. The mixture is then dried in a ventilated environment at a temperature not exceeding 50°C until the moisture content of the material is ≤15%.

[0099] Specifically, Sixth embodiment: Functional verification of compound microbial agents.

[0100] (1) Verification of effective silicon leaching capability.

[0101] Prepare LB liquid medium (10 g / L tryptone, 5 g / L yeast extract, 10 g / L sodium chloride) and dispense 200 mL into 500 mL Erlenmeyer flasks. Add 4.0 g (2%, w / v) of attapulgite powder that has passed through a 200-mesh sieve to each flask, and adjust the initial pH of the medium to 7.2 using 0.5 M hydrochloric acid solution. Autoclave the medium at 121 °C for 20 minutes and allow it to cool before use.

[0102] Experimental group: Inoculated with 5% (v / v) compound microbial agent (Bacillus mucilaginosus and Enterobacter p. mixed at a live count ratio of 1:1).

[0103] Control group: A blank control group without bacterial inoculation was set up.

[0104] All conical flasks were placed in a shaker at 30℃ and 220 rpm for incubation. Samples were taken on days 0, 1, 2, 3, and 4 of incubation. After centrifugation at 12,000 rpm for 10 minutes, the supernatant was collected, and the concentration of soluble silicon was determined using the molybdenum blue method. The determination method is briefly described as follows: An appropriate amount of supernatant was diluted to the linear range, and 0.6 mol / L sulfuric acid solution and 5% ammonium molybdate solution were added. The mixture was reacted in a water bath at 30-35℃ for 15 minutes. Then, 5% oxalic acid solution and 1.5% ascorbic acid solution were added to eliminate phosphate interference and develop the color. After making up to volume, the mixture was allowed to stand for 20 minutes, and the absorbance was measured at a wavelength of 700 nm. The silicon concentration was calculated using a standard curve.

[0105] Results: The concentration of soluble silicon in the leachate of the experimental group reached 69.8 mg / L, while that of the control group was below 6.0 mg / L. This demonstrates that the compound bacterial agent can efficiently leach the available silicon from attapulgite.

[0106] (2) Verification of the ability to produce plant growth hormone (IAA).

[0107] The compound microbial agent was inoculated into LB liquid medium containing 200 μg / mL tryptophan and cultured at 28℃ and 180 rpm for 48 hours. After the culture was completed, the fermentation broth was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was collected. The colorimetric reaction was performed using the Salkowski method, and the quantification was performed using ultraviolet spectrophotometry.

[0108] Results: The IAA concentration in the fermentation broth of this compound microbial agent reached 192.99 μg / mL, proving that it has a significant ability to produce plant growth hormones.

[0109] Following the same standardized microbiological testing, the compound bacterial agent grew well and formed clear zones on both nitrogen-fixing and inorganic phosphorus-free bacterial culture media, confirming its simultaneous nitrogen-fixing and phosphorus-solubilizing capabilities. Figure 1 As shown.

[0110] Seventh Example: Preparation of high-concentration bacterial suspension of compound microbial agent.

[0111] The compound microbial agent from the sixth embodiment was inoculated into fresh LB liquid medium at an inoculation rate of 1% (v / v) and cultured at 28°C and 180 rpm for 24 hours until the late logarithmic growth phase. The bacterial suspension was centrifuged at 10,000 rpm for 10 minutes, and the bacterial cells were collected. The cells were resuspended in sterile physiological saline and washed three times to remove residual culture medium. Finally, the bacterial cells were resuspended in sterile physiological saline, and the OD was measured. 600 The concentration of the bacterial suspension was adjusted to an absorbance of 1.0 (approximately 10). 8 -10 9(CFU / mL) yields a high-concentration compound microbial agent suspension, which is used for subsequent inoculation and testing.

[0112] Eighth Example: Preparation of Attapulgite / Microbial Slow-Release Fertilizer.

[0113] (1) Material pretreatment: Crush and grind the attapulgite ore and pass it through a 200-mesh sieve. Grind the soybean meal powder to a similar particle size.

[0114] (2) Microbial-mineral coupling: Take 30 parts by weight of attapulgite powder after sieving and mix it thoroughly with 5 parts by weight of the high-concentration composite microbial agent prepared in the seventh embodiment, so that the bacteria are fully loaded on the porous structure and surface of attapulgite to form a "microbial-mineral" complex. Let it stand at room temperature for 2 hours to adsorb.

[0115] (3) Mixing and granulation: Mix the “microbial-mineral” complex obtained in step (2) with 65 parts by weight of soybean meal powder evenly. During the mixing process, spray an appropriate amount of diluted molasses water to adjust the total moisture content to 20%-25%. Feed the moist mixture into a granulator for granulation.

[0116] (4) Low temperature drying: The granular material is dried in a ventilated environment at 45-50℃ until the moisture content drops to below 15%, which yields the finished product of attapulgite / microbial slow-release fertilizer.

[0117] Ninth Example: Verification of the ability of slow-release fertilizer to enhance the cold stress resistance of tobacco.

[0118] Experimental Design: Tobacco seedlings were planted in sterilized seedling substrate. When the seedlings had 5-6 true leaves, plants with uniform growth were selected for the following treatments, with each treatment having 3 replicates: CK group (blank control): watered with clean water.

[0119] Group BF (the present invention group): Attapulgite / microbial slow-release fertilizer prepared in the eighth embodiment was applied.

[0120] All treatments were carried out under normal management in the greenhouse. When the tobacco plants reached the six-leaf stage, the control (CK) and BF groups were subjected to 4°C low-temperature stress for 48 hours. After the stress was completed, samples were taken to measure various physiological indicators.

[0121] Experimental results: Phenotypic traits: After low temperature stress, the tobacco plants in the BF group (in this invention) showed less wilting of leaves, stronger new leaf germination ability, and dark green leaf color, which were significantly better than the control group.

[0122] Physiological indicators: Compared with the CK group after stress, tobacco leaves in the BF group: Total chlorophyll content increased significantly; Proline content increased by 78.2%; The activities of peroxidase (POD) and superoxide dismutase (SOD) increased by 29% and 63.7%, respectively. The malondialdehyde (MDA) content and relative conductivity decreased by 24.8% and 67.4%, respectively.

[0123] Conclusion: The slow-release fertilizer prepared in this invention can significantly activate the physiological response of tobacco to cold stress, effectively reduce cell membrane damage, maintain photosynthetic capacity, and thus significantly enhance the plant's cold resistance.

[0124] The attapulgite bio-organic silicon fertilizer of this invention is manufactured in accordance with the People's Republic of China agricultural industry standard "Bio-organic Fertilizer" NY884-2012, and its main technical indicators are higher than the standard. Among them, the effective live bacteria count (CFU) is 0.2 billion / g, the organic matter content is 47%, the moisture content is 25%, the pH is 5.8, the fecal coliform count is 88 / g, the ascarid egg mortality rate is 96.5%, and the shelf life is 6 months.

[0125] This application discloses the application of the above-mentioned slow-release organic fertilizer in enhancing plant resistance to low-temperature stress and promoting plant growth under low-temperature stress.

[0126] Furthermore, the plants are tobacco, solanaceous crops, or silicon-tolerant cruciferous crops; low-temperature stress is low-temperature environmental stress of 4°C or below.

[0127] This embodiment verifies the cold resistance and growth-promoting effects of the slow-release organic fertilizer of the present invention on different crops.

[0128] 1. Experimental materials and methods.

[0129] The test fertilizer was the slow-release organic fertilizer prepared in the fifth embodiment (30 parts attapulgite powder, 60 parts soybean meal powder, 10 parts compound microbial agent, strain ratio 1:1, viable count ≥10). 8 CFU / g).

[0130] The test crop was tobacco (Nicotiana abacum).

[0131] Processing settings: CK group: blank control, no fertilizer applied; Group BF: Apply 5g of slow-release organic fertilizer to each pot (15cm in diameter) and mix it with the seedling substrate.

[0132] After the plants were cultivated in a greenhouse to the appropriate leaf age, they were placed in a 4℃ artificial climate chamber for stress treatment for 48 hours, and samples were taken to measure physiological indicators.

[0133] 2. Results.

[0134] 2.1 Tobacco.

[0135] Compared with the CK group, the BF group showed a 78.2% increase in proline content, a significant increase in total chlorophyll, a 24.8% decrease in malondialdehyde (MDA) content, a 63.7% increase in superoxide dismutase (SOD) activity, and a 67.4% decrease in relative conductivity.

[0136] 2.2 Tomatoes.

[0137] Compared with the CK group, the BF group showed a 65.3% increase in proline content, a 42.1% increase in chlorophyll content, a 28.5% decrease in MDA content, and a 55.2% increase in SOD activity in tomato leaves.

[0138] 2.3 Rapeseed.

[0139] Compared with the CK group, the BF group showed a 71.6% increase in proline content, a 38.7% increase in chlorophyll content, a 26.9% decrease in MDA content, and a 48.5% increase in SOD activity in rapeseed leaves.

[0140] 3. Conclusion.

[0141] This embodiment demonstrates that the slow-release organic fertilizer of the present invention, when applied to tobacco, tomato (Solanaceae), and rapeseed (Brassicaceae), can enhance the plant's resistance to 4°C low-temperature stress, manifested by increased proline accumulation, reduced membrane lipid peroxidation, increased antioxidant enzyme activity, and maintained photosynthetic capacity. Therefore, the slow-release organic fertilizer of the present invention is suitable for cold-resistant and growth-promoting cultivation of tobacco, Solanaceae crops, and silicon-tolerant Brassicaceae crops under low-temperature stress of 4°C and below.

[0142] In summary, the plant growth-promoting and cold-resistant microbial slow-release organic fertilizer, its preparation method, and its application, as described in this application, utilize the unique structure of attapulgite to fix and protect functional microorganisms. It achieves synergistic effects of "cold resistance" and "growth promotion" by leaching effective silicon from the mineral through Bacillus subtilis and simultaneously utilizing Enterobacteriaceae to secrete auxins and activate nutrients. Experiments show that this product can significantly increase the proline and chlorophyll content of plants under stress, reduce MDA content, and promote plant growth, with effects significantly superior to single microbial agents. This provides a highly efficient and environmentally friendly new solution to address the problem of low-temperature stress in plants.

[0143] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0144] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0145] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A plant cold-resistant and growth-promoting slow-release organic fertilizer made by microorganisms, characterized in that, It includes the following components in parts by weight: attapulgite powder 20-40 parts by weight, organic fertilizer carrier 40-60 parts by weight, and compound microbial agent 5-10 parts by weight. The compound microbial agent includes Bacillus mucilaginosus and Enterobacter.

2. The slow-release organic fertilizer according to claim 1, characterized in that, The ratio of Bacillus mucilaginosus to Enterobacter is 1:1 to 1:

2.

3. The slow-release organic fertilizer according to claim 1, characterized in that, The viable count of the compound microbial agent is not less than 10×10^8 CFU / g.

4. The slow-release organic fertilizer according to claim 1, characterized in that, The attapulgite powder is a hydrous magnesium aluminosilicate clay mineral powder that has been pre-treated by crushing and passed through a 100-200 mesh sieve. The organic fertilizer carrier is a decomposed plant-derived organic material with a particle size that matches the attapulgite powder.

5. The slow-release organic fertilizer according to claim 1, characterized in that, The organic fertilizer carrier is soybean meal powder, and the organic matter content of the soybean meal powder is ≥40%.

6. A method for preparing the slow-release organic fertilizer according to any one of claims 1-5, characterized in that, Includes the following steps: S1 prepares high-concentration bacterial suspensions of Bacillus mucilaginosus and Enterobacter spp., respectively; S2 involves crushing and pre-treating the attapulgite powder; S3 After mixing the two bacterial suspensions from step S1, it is thoroughly stirred and mixed with the attapulgite powder from step S2, and allowed to stand for adsorption to obtain a mineral-carrying bacterial premix. S4. The mineral-carrying bacterial premix is ​​mixed with the organic fertilizer carrier, granulated, and dried in a ventilated manner to obtain the finished product.

7. The preparation method according to claim 6, characterized in that, The high-concentration bacterial suspension in step S1 has a viable count of not less than 10×10^8 CFU / mL. The bacterial suspension is obtained by inoculating the corresponding strain into LB medium and culturing it at 30°C and 220 rpm for 30 hours.

8. The preparation method according to claim 6, characterized in that, In step S3, the two bacterial suspensions are mixed at a live bacteria ratio of 1:1 to 1:2, and then mixed with attapulgite powder and allowed to stand at room temperature for 2 hours for adsorption. In step S4, diluted molasses water is sprayed in during mixing to adjust the total moisture content to 20%–25% before granulation. The mixture is then dried in a ventilated environment at a temperature not exceeding 50°C until the moisture content of the material is ≤15%.

9. The application of the slow-release organic fertilizer according to any one of claims 1-5 in enhancing plant resistance to low-temperature stress and promoting plant growth under low-temperature stress.

10. The application according to claim 9, characterized in that, The plants mentioned are tobacco, solanaceous crops, or silicon-tolerant cruciferous crops; The low-temperature stress refers to low-temperature environmental stress of 4°C and below.

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