Microbial agent for improving yield and quality of cotton and preparation method thereof

Abstract

The invention discloses a microbial agent for improving the yield and quality of cotton and a preparation method thereof, and belongs to the technical field of organic fertilizer and microbial fertilizer manufacturing. The microbial agent for improving the cotton yield and quality is prepared from the following raw materials in parts by weight: 50 to 60 parts of compound microbial liquid, 8 to 10 parts of alginate oligosaccharide, 6 to 8 parts of humic acid chelated boron zinc, 4 to 5 parts of polyglutamic acid, 12 to 15 parts of modified attapulgite and 2 to 3 parts of glycerol, the compound microorganism bacterial liquid is prepared from candida albicans, arthrobacter michaeli and cold-resistant pseudomonas. The three strains are colonized at the rhizosphere of the cotton together, have synergistic interaction, can promote the growth of the cotton in all directions, enable the cotton seeds to be full, improve the yield, effectively improve the quality of the ginned cotton, achieve the dual goals of increasing the yield and improving the quality, reduce the use of chemical fertilizers and pesticides, and reduce the production cost. The method is a promising technical scheme for promoting green, high-yield, high-quality and high-efficiency production of cotton.

Description

Technical Field

[0001] This invention belongs to the field of organic fertilizer and microbial fertilizer manufacturing technology, specifically relating to a microbial agent for improving cotton yield and quality and its preparation method. Background Technology

[0002] As a globally important economic crop, cotton's yield and quality directly affect the raw material supply for the textile industry and agricultural economic benefits. However, in traditional cotton cultivation, the long-term reliance on chemical fertilizers and pesticides has not only led to soil compaction, microbial community imbalance, and decreased nutrient utilization, but also caused environmental pollution and agricultural product safety risks. At the same time, cotton often faces problems such as micronutrient deficiencies, frequent soil-borne diseases, and abiotic stresses like drought and low temperatures during its growth process, severely impacting its yield and fiber quality.

[0003] In the past, excessive and irrational application of fertilizers in farmland has led to problems such as declining soil fertility and low fertilizer utilization. Microbial inoculants, as a green agricultural input, have attracted widespread attention due to their potential to promote crop growth, enhance stress resistance, and improve soil health. Furthermore, the activation effect of microbial inoculants on soil nutrients is significant for tapping into the soil's potential nutrients, reducing fertilizer application to some extent, and alleviating resource scarcity. However, existing microbial inoculants mostly focus on single strains or simple combinations. In practical applications, problems such as insufficient synergy between strains, poor environmental adaptability, or low survival rates often result in unstable effects and short-lasting effects. Simultaneously, soil structure deterioration and rhizosphere microecological degradation also limit the function of microorganisms, making it difficult to meet the comprehensive requirements of high-yield and high-quality cotton production.

[0004] Therefore, developing a compound microbial agent that can integrate multifunctional microorganisms for synergistic effect is of great significance for achieving green, high-yield and high-quality cotton cultivation. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a microbial agent specifically for cotton. Through the combination of specific functional strains, it effectively improves the growth performance of cotton and significantly increases cotton yield and quality.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A microbial agent for improving cotton yield and quality comprises the following raw materials in parts by weight: 50-60 parts of compound microbial inoculum, 8-10 parts of brown algae oligosaccharide, 6-8 parts of humic acid chelated boron zinc, 4-5 parts of polyglutamic acid, 12-15 parts of modified attapulgite, and 2-3 parts of glycerol. The compound microbial culture includes Candida valerate, Mysore bacillus, and psychrothermic pseudomonas.

[0007] Furthermore, the *Candida valerate* in the compound microbial culture was purchased from the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 2.5520 and original accession date of December 25, 2015; the *Arthrobacter mysore* was purchased from the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 1.15895 and original accession date of September 20, 2016; and the *Pseudomonas psychrophila* was purchased from the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 1.15631 and original accession date of February 25, 2015.

[0008] Furthermore, the preparation method of the composite microbial inoculum is as follows: (1) First, prepare a bacterial suspension from the freeze-dried powder of Candida valerate. Take 100 μL of the above bacterial suspension and add it to malt extract agar medium and culture for 48 h. Pick a single colony and inoculate it into malt extract liquid medium. Culture at 25 °C and 160 rpm until OD. 600 =0.6 to obtain seed culture, inoculate the seed culture into a small seed tank at an inoculum rate of 1%, and incubate at 25℃ and 160rpm until OD. 600 =3.0, yielding the Candida valerate fermentation broth; (2) First, prepare bacterial suspensions of Mysore's bacillus and cold-resistant Pseudomonas aeruginosa by freeze-drying powder. Take 100 μL of bacterial suspension and add it dropwise to nutrient gravy agar and incubate for 72 h. Then, pick single colonies and inoculate them into nutrient gravy liquid medium and incubate at 30 °C and 180 rpm until OD. 600 =0.6 to obtain seed culture, and then inoculate the seed culture into small seed tanks at an inoculum rate of 1% and incubate at 30℃ and 180rpm until OD. 600 =3.0, respectively, to obtain Mysore's Artemisia argyi fermentation broth and psychrogenic Pseudomonas fermentation broth; (3) Mix the fermentation broth of Candida valerian in step (1) with the fermentation broth of Mysore bacillus and the fermentation broth of Pseudomonas psychrophila in step (2) at a volume ratio of 1:1:2 to obtain a composite microbial culture.

[0009] Furthermore, the preparation method of the humic acid chelated boron zinc is as follows: (1) Add 70 kg of humic acid and 15 kg of deionized water to the reactor, stir slowly and add ammonia water dropwise to adjust the pH of the slurry to between 8.0 and 9.0 to obtain ammonium humate solution; (2) Dissolve 4.55 kg of zinc sulfate heptahydrate in 5 kg of hot water at 50°C to obtain a zinc sulfate solution. Under continuous stirring, slowly add the zinc sulfate solution to the ammonium humate solution, keep the reaction temperature at 50-60°C, and continue stirring for 30 min to obtain mixed slurry A. (3) Dissolve 9.52 kg of sodium tetraborate octaborate in 10 kg of hot water at 60°C. After complete dissolution, a sodium borate solution is obtained. Under vigorous stirring, the sodium borate solution is slowly added to the mixed slurry A. The temperature is maintained at 50-60°C. The mixture is stirred and reacted for 45 minutes to obtain mixed slurry B. (4) Transfer the mixed slurry B to a vacuum drying oven and dry it until the moisture content is less than 5%. Then crush the dried block with a pulverizer and pass it through an 80-mesh sieve to obtain uniform humic acid chelated boron zinc.

[0010] Furthermore, the method for preparing the modified attapulgite is as follows: (1) Mix 100kg of attapulgite clay with 300kg of deionized water in a reaction vessel and stir to form a uniform slurry. Slowly add 10% hydrochloric acid to adjust the pH of the slurry to 3.0-4.0. Stir and react at a constant temperature of 60-70℃ for 2 hours. After solid-liquid separation, wash with deionized water until the filtrate is neutral to obtain filter cake. (2) Add the filter cake to 300 kg of deionized water, stir to form a homogenate, add 5 kg of CTAB, heat to 75-80℃, and stir to react for 4 h; (3) The above reactants are repeatedly washed with deionized water until the filtrate does not contain Br⁻ when tested with silver nitrate solution. Solid-liquid separation is then performed, and the washed filter cake is sent to a drying room and dried by blowing at 105-110℃ until the moisture content is less than 8%. The cake is then passed through a 100-mesh sieve to obtain modified attapulgite.

[0011] A microbial agent for improving cotton yield and quality includes the following steps: First, the compound microbial inoculum is mixed with glycerol and then freeze-dried to make microbial powder. Then, the microbial powder, brown algae oligosaccharide, humic acid chelated boron zinc, polyglutamic acid and modified attapulgite are mixed in proportion, granulated, and screened into particles with a particle size of 1-2 mm to obtain the final product microbial inoculum.

[0012] All raw materials used in this invention are commercially available.

[0013] In this invention, humic acid chelated boron and zinc significantly improves the pollination success rate and boll retention rate of cotton by efficiently supplementing the key trace elements boron and zinc, and promotes vigorous plant growth. Attapulgite is a natural one-dimensional nano-sized silicate clay mineral. After acid washing and organic modification with hexadecyltrimethylammonium bromide, it prolongs its effectiveness by improving the physical and chemical properties of the soil, retaining water and fertilizer, and serving as a soil environment for microbial survival, thus creating a stable and superior rhizosphere growth environment for high-yield and high-quality cotton.

[0014] The composite microbial inoculum used in this invention includes *Candida valerate*, *Arthrobacter mysore*, and *Pseudomonas psychrophila*. *Candida valerate* secretes auxin IAA, which stimulates cotton root growth, promotes cell division and elongation, and allows for more efficient absorption of water and nutrients, improving drought resistance and overall plant physiological condition, laying the foundation for high yield. *Candida valerate* also performs potassium solubilization. *Arthrobacter mysore* converts insoluble phosphorus in the soil into soluble phosphate, significantly increasing soil phosphorus availability and promoting phosphorus absorption and utilization by cotton roots. It also decomposes silicate minerals to release potassium. *Pseudomonas psychrophila* possesses the ability to solubilize phosphorus and potassium, produce auxin IAA, and produce siderophores. Its potassium solubilization function releases fixed potassium in the soil, converting it into a soluble form for cotton absorption. The siderophores it produces efficiently chelate iron, forming siderophore-iron complexes that are utilized by the plant, helping to improve iron nutrition.

[0015] Beneficial effects The three strains of this invention co-colonize in the rhizosphere of cotton. Their metabolic activities can secrete organic acids, polysaccharides and other substances, improve soil aggregate structure, create a microenvironment more conducive to cotton root growth and nutrient absorption, and promote plant growth under adverse conditions such as drought. The three strains of this invention work synergistically to promote cotton growth in all aspects, resulting in fuller cotton grains, increased yield, and improved lint quality. This achieves the dual goals of increasing production and improving quality, while reducing the use of chemical fertilizers and pesticides. It is a very promising technical solution for promoting green, high-yield, high-quality and efficient cotton production. Attached Figure Description

[0016] Figure 1 This is a diagram of the co-culture experiment of the three strains used in this invention; Note: a is Candida valerate, b is Mysore bacterium, and c is psychrothermic Pseudomonas. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0018] Example 1 A microbial agent for improving cotton yield and quality comprises the following raw materials in parts by weight: 50 parts of compound microbial inoculum, 8 parts of brown algae oligosaccharide, 6 parts of humic acid chelated boron zinc, 4 parts of polyglutamic acid, 12 parts of modified attapulgite, and 2 parts of glycerol. The compound microbial culture includes Candida valerate, Mysore bacillus, and psychrothermic pseudomonas.

[0019] The *Candida valerate* in the composite microbial culture has the CGMCC No. 2.5520 preservation number; the *Arthrobacter mysore* has the CGMCC No. 1.15895 preservation number; and the *Pseudomonas psychrophila* has the CGMCC No. 1.15631 preservation number.

[0020] The preparation method of the aforementioned composite microbial inoculum is as follows: (1) First, prepare a bacterial suspension from the freeze-dried powder of Candida valerate. Take 100 μL of the above bacterial suspension and add it to malt extract agar medium and culture for 48 h. Pick a single colony and inoculate it into malt extract liquid medium. Culture at 25 °C and 160 rpm until OD. 600 =0.6 to obtain seed culture, inoculate the seed culture into a small seed tank at an inoculum rate of 1%, and incubate at 25℃ and 160rpm until OD. 600 =3.0, yielding the Candida valerate fermentation broth; (2) First, prepare bacterial suspensions of Mysore's bacillus and cold-resistant Pseudomonas aeruginosa by freeze-drying powder. Take 100 μL of bacterial suspension and add it dropwise to nutrient gravy agar and incubate for 72 h. Then, pick single colonies and inoculate them into nutrient gravy liquid medium and incubate at 30 °C and 180 rpm until OD. 600 =0.6 to obtain seed culture, and then inoculate the seed culture into small seed tanks at an inoculum rate of 1% and incubate at 30℃ and 180rpm until OD. 600 =3.0, respectively, to obtain Mysore's Artemisia argyi fermentation broth and psychrogenic Pseudomonas fermentation broth; (3) Mix the fermentation broth of Candida valerian in step (1) with the fermentation broth of Mysore bacillus and the fermentation broth of Pseudomonas psychrophila in step (2) at a volume ratio of 1:1:2 to obtain a composite microbial culture.

[0021] The method for preparing the humic acid chelated boron zinc is as follows: (1) Add 70 kg of humic acid and 15 kg of deionized water to the reactor, stir slowly and add ammonia water dropwise to adjust the pH of the slurry to 8.0 to obtain ammonium humate solution; (2) Dissolve 4.55 kg of zinc sulfate heptahydrate in 5 kg of hot water at 50°C to obtain a zinc sulfate solution. Under continuous stirring, slowly add the zinc sulfate solution to the ammonium humate solution, keep the reaction temperature at 50°C, and continue stirring for 30 min to obtain mixed slurry A. (3) Dissolve 9.52 kg of sodium tetraborate octaborate in 10 kg of hot water at 60°C. After complete dissolution, a sodium borate solution is obtained. Under vigorous stirring, the sodium borate solution is slowly added to the mixed slurry A. The temperature is maintained at 50°C, and the reaction is continued for 45 minutes to obtain mixed slurry B. (4) Transfer the mixed slurry B to a vacuum drying oven and dry it until the moisture content is less than 5%. Then crush the dried block with a pulverizer and pass it through an 80-mesh sieve to obtain uniform humic acid chelated boron zinc.

[0022] The method for preparing the modified attapulgite is as follows: (1) Mix 100kg of attapulgite clay with 300kg of deionized water in a reaction vessel and stir to form a uniform slurry. Slowly add 10% hydrochloric acid to adjust the pH of the slurry to 3.0. Stir and react at 60℃ for 2 hours. After solid-liquid separation, wash with deionized water until the filtrate is neutral to obtain filter cake. (2) Add the filter cake to 300 kg of deionized water, stir to form a homogenate, add 5 kg of CTAB, heat to 75°C, and stir to react for 4 h; (3) The above reactants are repeatedly washed with deionized water until the filtrate does not contain Br⁻ when tested with silver nitrate solution. Solid-liquid separation is then performed. The washed filter cake is sent to a drying room and dried at 105°C with forced air until the moisture content is less than 8%. It is then passed through a 100-mesh sieve to obtain modified attapulgite.

[0023] A microbial agent for improving cotton yield and quality includes the following steps: First, the compound microbial inoculum is mixed with glycerol and then freeze-dried to make microbial powder. Then, the microbial powder, brown algae oligosaccharide, humic acid chelated boron zinc, polyglutamic acid and modified attapulgite are mixed in proportion, granulated, and screened into particles with a particle size of 1-2 mm to obtain the final product microbial inoculum.

[0024] Example 2 A microbial agent for improving cotton yield and quality comprises the following raw materials in parts by weight: 55 parts of compound microbial inoculum, 9 parts of brown algae oligosaccharide, 7 parts of humic acid chelated boron zinc, 4 parts of polyglutamic acid, 13 parts of modified attapulgite, and 3 parts of glycerol. The compound microbial culture includes Candida valerate, Mysore bacillus, and psychrothermic pseudomonas.

[0025] The *Candida valerate* in the composite microbial culture has the CGMCC No. 2.5520 preservation number; the *Arthrobacter mysore* has the CGMCC No. 1.15895 preservation number; and the *Pseudomonas psychrophila* has the CGMCC No. 1.15631 preservation number.

[0026] The preparation method of the aforementioned composite microbial inoculum is as follows: (1) First, prepare a bacterial suspension from the freeze-dried powder of Candida valerate. Take 100 μL of the above bacterial suspension and add it to malt extract agar medium and culture for 48 h. Pick a single colony and inoculate it into malt extract liquid medium. Culture at 25 °C and 160 rpm until OD. 600=0.6 to obtain seed culture, inoculate the seed culture into a small seed tank at an inoculum rate of 1%, and incubate at 25℃ and 160rpm until OD. 600 =3.0, yielding the Candida valerate fermentation broth; (2) First, prepare bacterial suspensions of Mysore's bacillus and cold-resistant Pseudomonas aeruginosa by freeze-drying powder. Take 100 μL of bacterial suspension and add it dropwise to nutrient gravy agar and incubate for 72 h. Then, pick single colonies and inoculate them into nutrient gravy liquid medium and incubate at 30 °C and 180 rpm until OD. 600 =0.6 to obtain seed culture, and then inoculate the seed culture into small seed tanks at an inoculum rate of 1% and incubate at 30℃ and 180rpm until OD. 600 =3.0, respectively, to obtain Mysore's Artemisia argyi fermentation broth and psychrogenic Pseudomonas fermentation broth; (3) Mix the fermentation broth of Candida valerian in step (1) with the fermentation broth of Mysore bacillus and the fermentation broth of Pseudomonas psychrophila in step (2) at a volume ratio of 1:1:2 to obtain a composite microbial culture.

[0027] The method for preparing the humic acid chelated boron zinc is as follows: (1) Add 70 kg of humic acid and 15 kg of deionized water to the reactor, stir slowly and add ammonia water dropwise to adjust the pH of the slurry to 8.5, and obtain ammonium humate solution; (2) Dissolve 4.55 kg of zinc sulfate heptahydrate in 5 kg of hot water at 50°C to obtain a zinc sulfate solution. Under continuous stirring, slowly add the zinc sulfate solution to the ammonium humate solution, keep the reaction temperature at 55°C, and continue stirring for 30 min to obtain mixed slurry A. (3) Dissolve 9.52 kg of sodium tetraborate octaborate in 10 kg of hot water at 60°C. After complete dissolution, a sodium borate solution is obtained. Under vigorous stirring, the sodium borate solution is slowly added to the mixed slurry A. The temperature is maintained at 55°C, and the reaction is continued for 45 minutes to obtain mixed slurry B. (4) Transfer the mixed slurry B to a vacuum drying oven and dry it until the moisture content is less than 5%. Then crush the dried block with a pulverizer and pass it through an 80-mesh sieve to obtain uniform humic acid chelated boron zinc.

[0028] The method for preparing the modified attapulgite is as follows: (1) Mix 100kg of attapulgite clay with 300kg of deionized water in a reaction vessel and stir to form a uniform slurry. Slowly add 10% hydrochloric acid to adjust the pH of the slurry to 3.5. Stir and react at 65℃ for 2 hours. After solid-liquid separation, wash with deionized water until the filtrate is neutral to obtain filter cake. (2) Add the filter cake to 300 kg of deionized water, stir to form a homogenate, add 5 kg of CTAB, heat to 75°C, and stir to react for 4 h; (3) The above reactants are repeatedly washed with deionized water until the filtrate does not contain Br⁻ when tested with silver nitrate solution. Solid-liquid separation is then performed. The washed filter cake is sent to a drying room and dried at 105°C with forced air until the moisture content is less than 8%. It is then passed through a 100-mesh sieve to obtain modified attapulgite.

[0029] A microbial agent for improving cotton yield and quality includes the following steps: First, the compound microbial inoculum is mixed with glycerol and then freeze-dried to make microbial powder. Then, the microbial powder, brown algae oligosaccharide, humic acid chelated boron zinc, polyglutamic acid and modified attapulgite are mixed in proportion, granulated, and screened into particles with a particle size of 1-2 mm to obtain the final product microbial inoculum.

[0030] Example 3 A microbial agent for improving cotton yield and quality comprises the following raw materials in parts by weight: 60 parts of compound microbial inoculum, 10 parts of brown algae oligosaccharide, 8 parts of humic acid chelated boron zinc, 5 parts of polyglutamic acid, 15 parts of modified attapulgite, and 3 parts of glycerol. The compound microbial culture includes Candida valerate, Mysore bacillus, and psychrothermic pseudomonas.

[0031] The *Candida valerate* in the composite microbial culture has the CGMCC No. 2.5520 preservation number; the *Arthrobacter mysore* has the CGMCC No. 1.15895 preservation number; and the *Pseudomonas psychrophila* has the CGMCC No. 1.15631 preservation number.

[0032] The preparation method of the aforementioned composite microbial inoculum is as follows: (1) First, prepare a bacterial suspension from the freeze-dried powder of Candida valerate. Take 100 μL of the above bacterial suspension and add it to malt extract agar medium and culture for 48 h. Pick a single colony and inoculate it into malt extract liquid medium. Culture at 25 °C and 160 rpm until OD. 600 =0.6 to obtain seed culture, inoculate the seed culture into a small seed tank at an inoculum rate of 1%, and incubate at 25℃ and 160rpm until OD. 600 =3.0, yielding the Candida valerate fermentation broth; (2) First, prepare bacterial suspensions of Mysore's bacillus and cold-resistant Pseudomonas aeruginosa by freeze-drying powder. Take 100 μL of bacterial suspension and add it dropwise to nutrient gravy agar and incubate for 72 h. Then, pick single colonies and inoculate them into nutrient gravy liquid medium and incubate at 30 °C and 180 rpm until OD. 600 =0.6 to obtain seed culture, and then inoculate the seed culture into small seed tanks at an inoculum rate of 1% and incubate at 30℃ and 180rpm until OD. 600 =3.0, respectively, to obtain Mysore's Artemisia argyi fermentation broth and psychrogenic Pseudomonas fermentation broth; (3) Mix the fermentation broth of Candida valerian in step (1) with the fermentation broth of Mysore bacillus and the fermentation broth of Pseudomonas psychrophila in step (2) at a volume ratio of 1:1:2 to obtain a composite microbial culture.

[0033] The method for preparing the humic acid chelated boron zinc is as follows: (1) Add 70 kg of humic acid and 15 kg of deionized water to the reactor, stir slowly and add ammonia water dropwise to adjust the pH of the slurry to 9.0 to obtain ammonium humate solution; (2) Dissolve 4.55 kg of zinc sulfate heptahydrate in 5 kg of hot water at 50°C to obtain a zinc sulfate solution. Under continuous stirring, slowly add the zinc sulfate solution to the ammonium humate solution, keep the reaction temperature at 60°C, and continue stirring for 30 min to obtain mixed slurry A. (3) Dissolve 9.52 kg of sodium tetraborate octaborate in 10 kg of hot water at 60°C. After complete dissolution, a sodium borate solution is obtained. Under vigorous stirring, the sodium borate solution is slowly added to the mixed slurry A. The temperature is maintained at 60°C, and the reaction is continued for 45 minutes to obtain mixed slurry B. (4) Transfer the mixed slurry B to a vacuum drying oven and dry it until the moisture content is less than 5%. Then crush the dried block with a pulverizer and pass it through an 80-mesh sieve to obtain uniform humic acid chelated boron zinc.

[0034] The method for preparing the modified attapulgite is as follows: (1) Mix 100kg of attapulgite clay with 300kg of deionized water in a reaction vessel and stir to form a uniform slurry. Slowly add 10% hydrochloric acid to adjust the pH of the slurry to 4.0. Stir and react at 70℃ for 2 hours. After solid-liquid separation, wash with deionized water until the filtrate is neutral to obtain filter cake. (2) Add the filter cake to 300 kg of deionized water, stir to form a homogenate, add 5 kg of CTAB, heat to 80°C, and stir to react for 4 h; (3) The above reactants are repeatedly washed with deionized water until the filtrate does not contain Br⁻ when tested with silver nitrate solution. Solid-liquid separation is then performed, and the washed filter cake is sent to the drying room and dried at 110°C with forced air until the moisture content is less than 8%. The cake is then passed through a 100-mesh sieve to obtain modified attapulgite.

[0035] A microbial agent for improving cotton yield and quality includes the following steps: First, the compound microbial inoculum is mixed with glycerol and then freeze-dried to make microbial powder. Then, the microbial powder, brown algae oligosaccharide, humic acid chelated boron zinc, polyglutamic acid and modified attapulgite are mixed in proportion, granulated, and screened into particles with a particle size of 1-2 mm to obtain the final product microbial inoculum.

[0036] Comparative Example 1 Compared with Example 1, this comparative example is identical to Example 1 except that the volume ratio of Candida valerate fermentation broth, Arthrobacter mysore fermentation broth, and Pseudomonas psychrophila fermentation broth in the compound microbial culture is changed to 1:1:1.

[0037] Comparative Example 2 Compared with Example 1, this comparative example uses only Candida valerate fermentation broth and Mysore bacteria fermentation broth in the compound microbial culture solution, with a volume ratio of 1:1. All other raw materials and steps are the same as in Example 1.

[0038] Comparative Example 3 Compared with Example 1, this comparative example uses only Candida valerate fermentation broth and Pseudomonas psychrophila fermentation broth in the compound microbial culture, with a volume ratio of 1:1. All other raw materials and steps are the same as in Example 1.

[0039] Comparative Example 4 Compared with Example 1, this comparative example uses only Mysore's fermentation broth and psychrothermal Pseudomonas fermentation broth in the compound microbial culture, with a volume ratio of 1:1. All other raw materials and steps are the same as in Example 1.

[0040] Comparative Example 5 Compared with Example 1, this comparative example uses only Candida valerate fermentation broth in the compound microbial culture, while the other raw materials and steps are the same as in Example 1.

[0041] Comparative Example 6 Compared with Example 1, this comparative example uses only Mysore bacteria fermentation broth in the compound microbial culture, while the other raw materials and steps are the same as in Example 1.

[0042] Comparative Example 7 Compared with Example 1, this comparative example uses only the fermentation broth of cold-resistant Pseudomonas aeruginosa in the compound microbial culture, while the other raw materials and steps are the same as in Example 1.

[0043] Performance testing Strain antagonism test: After activating cryopreserved *Candida vulgaris*, *Mysole*, and *Pseudomonas psychrophila*, they were streaked in pairs onto LB agar plates. After incubation at 27°C for 2-3 days, the growth at the intersection of the streaks for each combination was observed. The results are as follows: Figure 1 The normal growth of each strain at the intersection shown (Note: a is Candida valerate, b is Mysore bacillus, c is psychrophilic Pseudomonas) indicates good compatibility among the strains, suggesting that there is no significant inhibition among the three strains, and they can be combined to form a compound microbial solution for use.

[0044] Growth-promoting ability test of strains: The phosphorus solubilization ability of the strain was determined by the molybdenum-antimony colorimetric method; the potassium solubilization ability was determined by the flame atomic emission spectrophotometry method; the indoleacetic acid secretion ability was determined by the Salkowski colorimetric method; and the siderophore synthesis ability was determined by the CAS detection method. Each group was tested in triplicate, and the mean value was taken.

[0045] Table 1. Identification of growth-promoting ability of each strain Note: "—" indicates that the function does not exist.

[0046] Planting Trial The test site is located in Awat County, Aksu Prefecture, Xinjiang Uygur Autonomous Region, on the northern edge of the Taklamakan Desert. It has a typical warm temperate extreme arid continental desert climate with abundant sunshine, large diurnal temperature range, low rainfall, and high evaporation.

[0047] The cotton variety used in the experiment was Tahe 2. The experiment employed a randomized block design with 11 treatment groups, including a blank control (CK0), and treatments using the microbial agents prepared in Examples 1-3 and Comparative Examples 1-7 of this invention. Each treatment group was replicated three times, and each plot was 200 m². 2 Cotton was planted on April 21, 2024, and harvested on October 12, 2024. The cotton was planted using a 2m wide film mulch, with 6 rows and 3 strips per mulch layer, a row spacing of 38cm, and a plant spacing of 10cm. When the cotton plants reached the three-leaf stage, the microbial inoculant for each treatment group was applied to the plant roots at a rate of 3kg / mu. A second application of the inoculant was made when the first young boll appeared (approximately 20 days after budding), at a rate of 1kg / mu. Other cultivation and management practices were the same as in conventional cotton fields in the local area.

[0048] Indicator Measurement Agronomic trait determination: Two weeks before harvest, 10 cotton plants with consistent growth were selected from the middle row of each plot to determine their plant height, number of fruiting branches per plant, stem diameter, and number of bolls per plant. Yield trait determination: From each plot, 100 bolls were continuously collected from cotton plants with uniform growth, starting from the bottom and moving upwards. The weight of each boll was measured, and the lint was extracted and measured to calculate the lint percentage. Actual yield was calculated for each plot to obtain cottonseed yield. Lint yield was then calculated based on seed cotton yield and lint percentage. Fiber quality determination: 20g of mixed cotton samples were selected from each plot and the quality was determined, including the average length of the upper half of the fiber, breaking strength, micronaire value, uniformity index and elongation. The above test data are shown in Tables 2, 3 and 4.

[0049] Table 2 Effects of different treatments on agronomic traits of cotton Table 3. Effects of different treatments on cotton yield As shown in Tables 2 and 3, compared with the blank control, the microbial inoculants of Examples 1-3 of this invention can effectively increase the number of bolls per plant and the weight of a single boll, thereby increasing yield. However, the cottonseed yield of Comparative Examples 1-7, which changed the composition of the microbial inoculants, decreased to varying degrees. This is because the three strains could not exert a synergistic effect, leading to varying degrees of decline in each phenotypic trait, and consequently, a decrease in yield.

[0050] Table 4 Effects of different treatments on cotton fiber quality As shown in Table 4, compared with the blank control, the quality of cotton treated with the microbial agent of the present invention has been improved to varying degrees in all aspects, especially the breaking strength and elongation. In particular, the breaking strength of Example 1 increased by 18.6% and the elongation increased by 12.4% compared with CK.

[0051] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A microbial inoculant for improving cotton yield and quality, characterized in that, The raw materials include the following parts by weight: 50-60 parts of compound microbial culture, 8-10 parts of brown algae oligosaccharide, 6-8 parts of humic acid chelated boron zinc, 4-5 parts of polyglutamic acid, 12-15 parts of modified attapulgite, and 2-3 parts of glycerol. The compound microbial culture includes Candida valerate, Mysore bacillus, and psychrothermic pseudomonas.

2. The microbial agent for improving cotton yield and quality according to claim 1, characterized in that, The preservation number of *Candida valerate* in the compound microbial culture is CGMCC No. 2.5520; the preservation number of *Arthrobacter mysore* is CGMCC No. 1.15895; and the preservation number of *Pseudomonas psychrophila* is CGMCC No. 1.15631.

3. The microbial agent for improving cotton yield and quality according to claim 1, characterized in that, The preparation method of the aforementioned composite microbial inoculum is as follows: (1) First, prepare a bacterial suspension from the freeze-dried powder of Candida valerate. Take 100 μL of the above bacterial suspension and add it to malt extract agar medium and culture for 48 h. Pick a single colony and inoculate it into malt extract liquid medium. Culture at 25 °C and 160 rpm until OD. 600 =0.6 to obtain seed culture, inoculate the seed culture into a small seed tank at an inoculum rate of 1%, and incubate at 25℃ and 160rpm until OD. 600 =3.0, yielding the Candida valerate fermentation broth; (2) First, prepare bacterial suspensions of Mysore's bacillus and cold-resistant Pseudomonas aeruginosa by freeze-drying powder. Take 100 μL of bacterial suspension and add it dropwise to nutrient gravy agar and incubate for 72 h. Then, pick single colonies and inoculate them into nutrient gravy liquid medium and incubate at 30 °C and 180 rpm until OD. 600 =0.6 to obtain seed culture, and then inoculate the seed culture into small seed tanks at an inoculum rate of 1% and incubate at 30℃ and 180rpm until OD. 600 =3.0, respectively, to obtain Mysore's Artemisia argyi fermentation broth and psychrogenic Pseudomonas fermentation broth; (3) Mix the fermentation broth of Candida valerian in step (1) with the fermentation broth of Mysore bacillus and the fermentation broth of Pseudomonas psychrophila in step (2) at a volume ratio of 1:1:2 to obtain a composite microbial culture.

4. The microbial agent for improving cotton yield and quality according to claim 1, characterized in that, The method for preparing the humic acid chelated boron zinc is as follows: (1) Add 70 kg of humic acid and 15 kg of deionized water to the reactor, stir slowly and add ammonia water dropwise to adjust the pH of the slurry to between 8.0 and 9.0 to obtain ammonium humate solution; (2) Dissolve 4.55 kg of zinc sulfate heptahydrate in 5 kg of hot water at 50°C to obtain a zinc sulfate solution. Under continuous stirring, slowly add the zinc sulfate solution to the ammonium humate solution, keep the reaction temperature at 50-60°C, and continue stirring for 30 min to obtain mixed slurry A. (3) Dissolve 9.52 kg of sodium tetraborate octaborate in 10 kg of hot water at 60°C. After complete dissolution, a sodium borate solution is obtained. Under vigorous stirring, the sodium borate solution is slowly added to the mixed slurry A. The temperature is maintained at 50-60°C. The mixture is stirred and reacted for 45 minutes to obtain mixed slurry B. (4) Transfer the mixed slurry B to a vacuum drying oven and dry it until the moisture content is less than 5%. Then crush the dried block with a pulverizer and pass it through an 80-mesh sieve to obtain uniform humic acid chelated boron zinc.

5. The microbial agent for improving cotton yield and quality according to claim 1, characterized in that, The method for preparing the modified attapulgite is as follows: (1) Mix 100kg of attapulgite clay with 300kg of deionized water in a reaction vessel and stir to form a uniform slurry. Slowly add 10% hydrochloric acid to adjust the pH of the slurry to 3.0-4.

0. Stir and react at a constant temperature of 60-70℃ for 2 hours. After solid-liquid separation, wash with deionized water until the filtrate is neutral to obtain filter cake. (2) Add the filter cake to 300 kg of deionized water, stir to form a homogenate, add 5 kg of CTAB, heat to 75-80℃, and stir to react for 4 h; (3) The above reactants are repeatedly washed with deionized water until the filtrate does not contain Br⁻ when tested with silver nitrate solution. Solid-liquid separation is then performed, and the washed filter cake is sent to a drying room and dried by blowing at 105-110℃ until the moisture content is less than 8%. The cake is then passed through a 100-mesh sieve to obtain modified attapulgite.

6. A microbial agent for improving cotton yield and quality according to any one of claims 1-5, characterized in that, Includes the following steps: First, the compound microbial inoculum is mixed with glycerol and then freeze-dried to make microbial powder. Then, the microbial powder, brown algae oligosaccharide, humic acid chelated boron zinc, polyglutamic acid and modified attapulgite are mixed in proportion, granulated, and screened into particles with a particle size of 1-2 mm to obtain the final product microbial inoculum.

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