Special polyglutamic acid composite improved fertilizer for saline-alkali soil

Abstract

The invention discloses a special polyglutamic acid compound improved fertilizer for saline-alkali soil. The special polyglutamic acid compound improved fertilizer comprises the following components in parts by mass: 5-15 parts of polyglutamic acid; 10 to 25 parts of citric acid-humic acid composite modified biomass charcoal; 3 to 8 parts of a bacillus mucilaginosus-attapulgite composite bacterial agent; 2 to 6 parts of an acrylamide-acrylic acid-2-methacryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer; 8 to 15 parts of urea; 5 to 12 parts of monopotassium phosphate; 3-8 parts of potassium sulfate; 5 to 15 parts of desulfurized gypsum; 3 to 10 parts of humic acid; the synergistic salt-reducing effect is remarkable, Na and Cl in soil are synergistically adsorbed through the porous structure of the composite modified biomass charcoal and acidic groups of citric acid and humic acid, and the ion exchange effect of the desulfurized gypsum is matched, so that the salt content of the soil after application is reduced, and the pH value is reduced; the water and fertilizer retention capacity is high, a three-dimensional water retention network is formed by the zwitterionic polymer and polyglutamic acid, and the water retention rate of soil is greatly increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural fertilizers, and specifically relates to a polyglutamic acid composite improved fertilizer special for saline-alkali soil. BACKGROUND

[0002] The saline-alkali soil has problems such as high soil salt content (EC value > 4 mS / cm), pH value > 8.5, poor water and fertilizer retention capacity, low microbial activity, and the like, which causes the crop root system to be hindered in development and the nutrient absorption efficiency to be low, and seriously restricts agricultural production. The existing saline-alkali soil improved fertilizers have the following deficiencies: 1. Single improvement function: only relying on physical salt reduction components such as gypsum and desulfurized gypsum, the soil water retention and microbial activation problems cannot be solved simultaneously; 2. Low nutrient utilization rate: ordinary chemical fertilizers are easily lost with saline-alkali soil leaching water, and lack of absorption promoting components, and the crop absorption rate is less than 30%; 3. Poor microbial stability: the added microbial agents are easily inhibited by high salt environment, and have a short survival period (usually < 15 days), and cannot continuously play a role; 4. Weak improvement durability: easy to rebound after short-term salt reduction, and unable to form a long-term improvement mechanism of soil granular structure.

[0003] Although polyglutamic acid (γ-PGA) has the functions of water retention, nutrient chelation and root promotion, its salt reduction capacity is limited when used alone, and it is easily degraded in a high saline-alkali environment. Therefore, developing a composite improved fertilizer that combines polyglutamic acid and multi-effect innovative components and can realize the functions of “salt reduction-water retention-fertilizer efficiency-microbial activation” simultaneously has become the key to solving the saline-alkali soil planting problem.

[0004] Based on this, a polyglutamic acid composite improved fertilizer special for saline-alkali soil is designed. SUMMARY

[0005] In view of the above situation, in order to overcome the defects of the prior art, the application provides a polyglutamic acid composite improved fertilizer special for saline-alkali soil and a preparation method thereof, which effectively solves the problems raised in the background.

[0006] To achieve the above purpose, the application provides the following technical scheme: a polyglutamic acid composite improved fertilizer special for saline-alkali soil, which comprises the following components in mass fraction: Polyglutamic acid: 5-15 parts; Citric acid-humic acid composite modified biomass charcoal: 10-25 parts; Bacillus mucilaginosus-attapulgite composite microbial agent: 3-8 parts; Acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethylammonium chloride zwitterionic polymer: 2-6 parts; Urea: 8-15 parts; Potassium dihydrogen phosphate: 5-12 parts; Potassium sulfate: 3-8 parts; Desulfurized gypsum: 5-15 parts; Humic acid: 3-10 parts.

[0007] Preferably, the preparation method of the citric acid-humic acid composite modified biomass charcoal is as follows: S1, biomass charcoal pretreatment: corn cob is selected as raw material, crushed to 2-5 mm particles, placed in a muffle furnace, heated to 400-500°C at a heating rate of 5-8°C / min under nitrogen atmosphere, and kept for 2-3 hours for carbonization; after carbonization, cool to room temperature, crush and pass through an 80-100 mesh sieve to obtain the original biomass charcoal; S2, composite modification treatment: prepare a 5-10wt% citric acid solution and a 3-5wt% humic acid solution, mix them in a volume ratio of 1:1 to obtain a modification liquid; add the original biomass charcoal and the modification liquid to a reaction kettle at a liquid-solid ratio of 3-5mL:1g, stir at 60-75°C at a speed of 180-220rpm for 2-3 hours; after stirring, place the mixture in an oven and dry at 60-80°C until the water content is ≤5%, then crush and pass through an 80-100 mesh sieve to obtain the composite modified biomass charcoal.

[0008] Preferably, the preparation method of the Bacillus mucilaginosus-attapulgite composite microbial agent is as follows: S1, strain activation: select Bacillus mucilaginosus, inoculate in LB medium, cultivate in a 30-35°C, 180-220rpm shaker for 18-24 hours to obtain a seed liquid with a viable cell count ≥10 8 CFU / mL; S2, fermentation culture: prepare a fermentation medium: 20-30g / L sucrose, 5-10g / L yeast extract, 1-2g / L potassium dihydrogen phosphate, 0.5-1g / L magnesium sulfate, pH 7.0-7.5; inoculate the seed liquid into a fermenter at a 5-8% inoculation amount, ferment at 30-35°C, 200-250rpm stirring speed, 1:0.8-1.2v / v / min aeration rate for 24-30 hours, until the viable cell count of the fermentation broth is ≥10 9 CFU / mL; S3, carrier loading and drying: crush the attapulgite to 100-120 mesh sieve, mix with sodium alginate at a mass ratio of 8-10:1, add distilled water to form a paste, solid content 30-40%, sterilize at 115-121℃ for 20-30 minutes; cool to 25-30℃, then add fermentation broth at a ratio of 2-3 mL:1 g, stir at 150-180 rpm for 1-2 hours; then place in a vacuum drying oven, dry at 40-50℃, 0.06-0.08 MPa vacuum degree to a water content of ≤8%, crush to 60-80 mesh sieve to obtain the compound microbial inoculant.

[0009] Preferably, the preparation method of the acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer is as follows: S1, monomer pretreatment: weigh acrylamide, acrylic acid, and 2-methyl acryloyloxyethyl trimethyl ammonium chloride at a mass ratio of 5-7:2-3:1-2; neutralize the acrylic acid to pH 6.0-7.0 with 10-15 wt% sodium hydroxide solution to obtain a neutralized acrylic acid solution; S2, aqueous solution polymerization: add acrylamide, neutralized acrylic acid solution, and 2-methyl acryloyloxyethyl trimethyl ammonium chloride to a reaction bottle, add distilled water to make the total monomer concentration 20-30 wt%; after deoxygenation by nitrogen for 30 minutes, add initiator, and react at 40-55℃ for 3-5 hours to obtain a gel-like polymer; S3, post-treatment: crush the gel-like polymer to 5-10 mm particles, dry in a 60-75℃ oven to a water content of ≤5%, then crush to 80-100 mesh sieve to obtain the zwitterionic polymer.

[0010] Preferably, in S2, aqueous solution polymerization, the initiator is a mixture of ammonium persulfate and sodium bisulfite at a mass ratio of 1:1, and the amount used is 0.1-0.3% of the total monomer mass.

[0011] Preferably, the preparation method of the polyglutamic acid compound improved fertilizer is as follows: S1, raw material pretreatment: crush urea, potassium dihydrogen phosphate, potassium sulfate, and desulfurized gypsum to 80-100 mesh sieve, and crush humic acid to 60-80 mesh sieve to ensure uniform particle size of the raw materials; S2, mixing of base materials: add the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, and humic acid to a double screw mixer at the prescribed ratio, mix at a speed of 150-200 rpm for 15-20 minutes to obtain a base mixture; S3, functional component mixing: add polyglutamic acid, citric acid-humic acid composite modified biomass charcoal, bacillus mucilaginosus-attapulgite composite microbial agent, acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethylammonium chloride zwitterionic polymer into the base mixture, continue mixing at a speed of 180-220 rpm for 20-30 minutes until the uniformity of the material is ≥95%, and a total mixture is obtained; S4, extrusion granulation: the total mixture is sent into a double screw extrusion granulator, the granulation temperature is set to 50-65 DEG C, the extrusion speed is set to 80-120 rpm, and the die hole diameter is set to 2-4 mm, and wet granules are obtained by extrusion, with a water content of 15-20%.

[0012] S5, drying and cooling: the wet granules are sent into a fluidized bed dryer, the drying temperature is set to 60-75 DEG C, the air speed is set to 1.5-2.0 m / s, and the granules are dried for 20-30 minutes until the water content is ≤5%; then the granules are sent into a cooler and cooled to room temperature, and the cooling time is 15-20 minutes.

[0013] S6, screening and packaging: the cooled granules are screened by a vibrating screen with a mesh size of 1.5-4.5 mm, and the fine powder with a size of <1.5 mm and the large pieces with a size of >4.5 mm are removed to obtain qualified granules; after detecting the nutrient content and the number of live bacteria of the granules, the product is obtained by vacuum packaging.

[0014] Compared with the prior art, the beneficial effects of the present application are: 1. The synergistic salt reduction effect of the present application is significant, the porous structure of the composite modified biomass charcoal and the acidic groups of citric acid and humic acid synergistically adsorb Na⁺ and Cl⁻ in the soil, and the ion exchange of desulfurization gypsum is combined, so that the salt content of the soil is reduced after application, and the pH value is decreased; 2. The water and fertilizer retention capacity of the present application is strong, the zwitterionic polymer and polyglutamic acid form a three-dimensional water retention network, the soil water retention rate is greatly improved; at the same time, nitrogen, phosphorus, potassium and trace elements are chelated, and the nutrient loss rate is reduced; 3. The microbial activity of the present application is durable, the attapulgite-sodium alginate carrier provides protection for bacillus mucilaginosus, the survival period of the microbial agent in saline-alkali soil is greatly prolonged, and the activities of soil urease and phosphatase are greatly improved; 4. It has the effect of improving and fertilizing simultaneously, and once application can realize the triple effect of soil structure improvement, salt reduction and nutrient supply, so as to improve the emergence rate of crops and increase the yield. DETAILED DESCRIPTION

[0015] The technical solutions of the present application will be clearly and completely described below in combination with specific embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application; based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0016] The present application provides a polyglutamic acid composite improved fertilizer special for saline-alkali soil, which comprises the following components in mass fraction: Polyglutamic acid: 5-15 parts; Citric acid-humic acid composite modified biomass charcoal: 10-25 parts; Bacillus mucilaginosus-attapulgite composite microbial agent: 3-8 parts; Acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride amphoteric ion polymer: 2-6 parts; Urea: 8-15 parts; Monopotassium phosphate: 5-12 parts; Potassium sulfate: 3-8 parts; Desulfurized gypsum: 5-15 parts; Humic acid: 3-10 parts.

[0017] The preparation method of the citric acid-humic acid composite modified biomass charcoal in the present embodiment is as follows: S1, biomass charcoal pretreatment: corn cob is selected as raw material, which is crushed to 2-5 mm particles, and is heated to 400-500℃ at a heating rate of 5-8℃ / min under nitrogen atmosphere in a muffle furnace, and is carbonized for 2-3 hours; after carbonization, it is cooled to room temperature, crushed and passed through an 80-100 mesh sieve to obtain original biomass charcoal; S2, composite modification treatment: 5-10wt% citric acid solution and 3-5wt% humic acid solution are prepared, and a modified liquid is obtained by mixing them at a volume ratio of 1:1; the original biomass charcoal and the modified liquid are added to a reaction kettle at a liquid-solid ratio of 3-5mL:1g, and are stirred at 60-75℃ and a stirring speed of 180-220rpm for 2-3 hours; after stirring, the mixture is placed in an oven and dried at 60-80℃ until the water content is ≤5%, and then crushed and passed through an 80-100 mesh sieve to obtain the composite modified biomass charcoal.

[0018] The preparation method of the bacillus mucilaginosus-attapulgite composite microbial agent in the present embodiment is as follows: S1, strain activation: bacillus mucilaginosus is selected, inoculated into LB culture medium, and cultured in a 30-35℃, 180-220rpm shaking bed for 18-24 hours to obtain seed liquid with a viable bacterial count of ≥10 8 CFU / mL; S2, fermentation culture: prepare fermentation medium: 20-30 g / L sucrose, 5-10 g / L yeast extract, 1-2 g / L potassium dihydrogen phosphate, 0.5-1 g / L magnesium sulfate, pH 7.0-7.5; the seed liquid is inoculated into the fermenter at an inoculation amount of 5-8%, and is fermented at 30-35℃, 200-250 rpm stirring speed, 1:0.8-1.2 v / v / min aeration rate for 24-30 hours, until the viable cell count of the fermentation broth is ≥10 9 CFU / mL; S3, carrier loading and drying: the attapulgite is crushed to pass through a 100-120 mesh sieve, mixed with sodium alginate at a mass ratio of 8-10:1, added with distilled water to form a paste, the solid content is 30-40%, sterilized at 115-121℃ for 20-30 minutes; after cooling to 25-30℃, the fermentation broth is added at 2-3 mL:1 g, stirred at 150-180 rpm for 1-2 hours; then placed in a vacuum drying oven, dried at 40-50℃, 0.06-0.08 MPa vacuum degree until the water content is ≤8%, crushed to pass through a 60-80 mesh sieve, to obtain the compound microbial inoculant.

[0019] The preparation method of the acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer of the embodiment is as follows: S1, monomer pretreatment: weigh acrylamide, acrylic acid and 2-methyl acryloyloxyethyl trimethyl ammonium chloride according to a mass ratio of 5-7:2-3:1-2; neutralize the acrylic acid to pH 6.0-7.0 with 10-15 wt% sodium hydroxide solution to obtain neutralized acrylic acid solution; S2, aqueous solution polymerization: add acrylamide, neutralized acrylic acid solution and 2-methyl acryloyloxyethyl trimethyl ammonium chloride into a reaction bottle, add distilled water to make the total monomer concentration 20-30 wt%; after oxygen removal by nitrogen for 30 minutes, add initiator, and react at 40-55℃ for 3-5 hours to obtain a gel-like polymer; S3, post-treatment: crush the gel-like polymer into 5-10 mm particles, dry in a 60-75℃ oven until the water content is ≤5%, and then crush to pass through an 80-100 mesh sieve to obtain the zwitterionic polymer.

[0020] In S2, aqueous solution polymerization of the embodiment, the initiator is a mixture of ammonium persulfate and sodium bisulfite at a mass ratio of 1:1, and the amount is 0.1-0.3% of the total mass of monomers.

[0021] The preparation method of the polyglutamic acid compound modified fertilizer of the embodiment is as follows: S1, raw material pretreatment: crush urea, potassium dihydrogen phosphate, potassium sulfate and desulfurized gypsum to pass through an 80-100 mesh sieve, and crush humic acid to pass through a 60-80 mesh sieve to ensure uniform particle size of the raw materials; S2, base material mixing: the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, humic acid were added into the double screw mixer according to the formula ratio, and mixed at a speed of 150-200 rpm for 15-20 minutes to obtain a base mixture; S3, functional component mixing: the polyglutamic acid, citric acid-humic acid composite modified biomass charcoal, bacillus mucilaginosus-attapulgite composite microbial agent, acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride amphoteric ion polymer were added into the base mixture, and the mixture was continuously mixed at a speed of 180-220 rpm for 20-30 minutes until the uniformity of the material was greater than or equal to 95%, to obtain a total mixture; S4, extrusion granulation: the total mixture was sent into a double screw extrusion granulator, and the granulation temperature was set to 50-65°C, the extrusion speed was set to 80-120 rpm, and the die hole diameter was set to 2-4 mm, so that wet granules were obtained, and the water content was 15-20%.

[0022] S5, drying and cooling: the wet granules were sent into a fluidized bed dryer, the drying temperature was set to 60-75°C, the air speed was set to 1.5-2.0 m / s, and the granules were dried for 20-30 minutes until the water content was less than or equal to 5%; then the granules were sent into a cooling machine and cooled to room temperature, and the cooling time was 15-20 minutes.

[0023] S6, screening and packaging: the cooled granules were screened by a vibrating screen with a mesh size of 1.5-4.5 mm, and the fine powder less than 1.5 mm and the large pieces greater than 4.5 mm were removed to obtain qualified granules; after detecting the nutrient content and viable bacterial count of the granules, the product was obtained by vacuum packaging.

[0024] Example 1: A polyglutamic acid composite improved fertilizer special for saline-alkali soil, which comprises the following components in mass fraction: Polyglutamic acid: 5 parts; Citric acid-humic acid composite modified biomass charcoal: 10 parts; Bacillus mucilaginosus-attapulgite composite microbial agent: 3 parts; Acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride amphoteric ion polymer: 2 parts; Urea: 8 parts; Potassium dihydrogen phosphate: 5 parts; Potassium sulfate: 3 parts; Desulfurized gypsum: 5 parts; Humic acid: 3 parts.

[0025] The preparation method of the citric acid-humic acid composite modified biomass charcoal in this example is as follows: S1, biomass charcoal pretreatment: select corn cob as raw material, crush to 2mm particles, place in muffle furnace, heat to 400℃ under nitrogen atmosphere, with a heating rate of 5℃ / min, keep for 2 hours for carbonization; after carbonization, cool to room temperature, crush and pass through an 80 mesh sieve to obtain the original biomass charcoal; S2, composite modification treatment: prepare a 5wt% citric acid solution and a 3wt% humic acid solution, mix them in a volume ratio of 1:1 to obtain a modification liquid; add the original biomass charcoal and the modification liquid to a reaction kettle in a liquid-solid ratio of 3mL:1g, stir at 60℃ with a stirring speed of 180rpm for 2 hours; after stirring, place the mixture in an oven and dry at 60℃ until the water content is ≤5%, then crush and pass through an 80 mesh sieve to obtain the composite modified biomass charcoal.

[0026] The preparation method of the bacillus mucilaginosus-attapulgite composite microbial agent of the present example is as follows: S1, strain activation: select bacillus mucilaginosus, inoculate in LB medium, cultivate in a 30℃, 180rpm shaking bed for 18 hours to obtain a seed liquid with a viable cell count ≥10 8 CFU / mL; S2, fermentation culture: prepare a fermentation medium: 20g / L sucrose, 5g / L yeast extract, 1g / L potassium dihydrogen phosphate, 0.5g / L magnesium sulfate, pH 7.0; inoculate the seed liquid into a fermenter at a 5% inoculation amount, ferment at 30℃, 200rpm stirring speed, 1:0.8v / v / min aeration rate for 24 hours, until the viable cell count of the fermentation broth is ≥10 9 CFU / mL; S3, carrier loading and drying: crush the attapulgite to pass through a 100 mesh sieve, mix with sodium alginate at a mass ratio of 8:1, add distilled water to form a paste with a solid content of 30%, sterilize at 115℃ for 20 minutes; after cooling to 25℃, add the fermentation broth to the fermentation broth in a ratio of 2mL:1g, stir at 150rpm for 1 hour; then place it in a vacuum drying oven, dry at 40℃, 0.06MPa vacuum degree until the water content is ≤8%, crush to pass through a 60 mesh sieve to obtain the composite microbial agent.

[0027] The preparation method of the acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer of the present example is as follows: S1, monomer pretreatment: weigh acrylamide, acrylic acid and 2-methyl acryloyloxyethyl trimethyl ammonium chloride in a mass ratio of 5:2:1; neutralize the acrylic acid to pH 6.0 with a 10wt% sodium hydroxide solution to obtain a neutralized acrylic acid solution; S2, aqueous solution polymerization: acrylamide, neutralized acrylic acid solution, 2-methyl acryloyloxyethyl trimethyl ammonium chloride were added into a reaction bottle, and distilled water was added to make the total monomer concentration 20wt%; after oxygen removal by nitrogen for 30 minutes, initiator was added, and the reaction was carried out at 40℃ for 3 hours to obtain a gel-like polymer; S3, post-treatment: the gel-like polymer was crushed to 5mm particles, dried in an oven at 60℃ to a water content of ≤5%, then crushed through an 80 mesh sieve to obtain a zwitterionic polymer.

[0028] In S2, aqueous solution polymerization of this example, the initiator was a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the amount was 0.1% of the total mass of monomers.

[0029] The preparation method of the polyglutamic acid composite improved fertilizer of this example is as follows: S1, raw material pretreatment: urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum were crushed through an 80-100 mesh sieve, and humic acid was crushed through a 60 mesh sieve to ensure uniform particle size of the raw materials; S2, mixing of base materials: the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, and humic acid were added into a double screw mixer according to the formula ratio, mixed at a speed of 150rpm for 15 minutes to obtain a base mixture; S3, mixing of functional components: polyglutamic acid, citric acid-humic acid composite modified biochar, bacillus mucilaginosus-anatase composite microbial agent, and acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer were added into the base mixture, and the mixture was continuously mixed at a speed of 180rpm for 20 minutes until the uniformity of the materials was ≥95% to obtain a total mixture; S4, extrusion granulation: the total mixture was sent into a double screw extrusion granulator, and the granulation temperature was set to 50℃, the extrusion speed was set to 80rpm, and the die diameter was set to 2mm, and wet granules were obtained by extrusion with a water content of 15%.

[0030] S5, drying and cooling: the wet granules were sent into a fluidized bed dryer, and the drying temperature was set to 60℃ and the air speed was set to 1.5m / s, and the granules were dried for 20 minutes until the water content was ≤5%; then the granules were sent into a cooling machine and cooled to room temperature for 15 minutes.

[0031] S6, screening and packaging: the cooled granules were screened by a vibrating screen with a mesh size of 1.5mm to remove fine powder <1.5mm and large pieces >4.5mm to obtain qualified granules; after detecting the nutrient content and viable bacterial count of the granules, the product was obtained by vacuum packaging.

[0032] Example 2: A polyglutamic acid composite improved fertilizer for saline-alkali soil, comprising the following components in mass fraction: Polyglutamic acid: 15 parts; Citric acid-humic acid complex modified biomass charcoal: 25 parts; Bacillus mucilaginosus-attapulgite composite microbial agent: 8 parts; Acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride amphoteric ion polymer: 6 parts; Urea: 15 parts; Monopotassium phosphate: 12 parts; Potassium sulfate: 8 parts; Desulfurized gypsum: 15 parts; Humic acid: 10 parts.

[0033] The preparation method of the citric acid-humic acid complex modified biomass charcoal of the present embodiment is as follows: S1, biomass charcoal pretreatment: corn cob is selected as raw material, crushed to 5mm particles, placed in a muffle furnace, heated to 500℃ at a heating rate of 8℃ / min under nitrogen atmosphere, and carbonized for 3 hours; after carbonization, cooled to room temperature, crushed and passed through a 100 mesh sieve to obtain the original biomass charcoal; S2, complex modification treatment: prepare a 10wt% citric acid solution and a 5wt% humic acid solution, mix them in a volume ratio of 1:1 to obtain a modification liquid; add the original biomass charcoal and the modification liquid to the reaction kettle at a liquid-solid ratio of 5mL:1g, stir at 75℃ and a stirring speed of 220rpm for 3 hours; after stirring, place the mixture in an oven and dry at 80℃ until the water content is ≤5%, then crush and pass through a 100 mesh sieve to obtain the complex modified biomass charcoal.

[0034] The preparation method of the bacillus mucilaginosus-attapulgite composite microbial agent of the present embodiment is as follows: S1, strain activation: select bacillus mucilaginosus, inoculate in LB medium, cultivate in a 35℃, 220rpm shaking bed for 24 hours to obtain a seed liquid with a viable cell count ≥10 8 CFU / mL; S2, fermentation culture: prepare a fermentation medium: 30g / L sucrose, 10g / L yeast extract, 2g / L monopotassium phosphate, 1g / L magnesium sulfate, pH 7.5; inoculate the seed liquid into the fermenter at an inoculation amount of 8%, ferment at 35℃, 250rpm stirring speed, 1:1.2v / v / min aeration rate for 30 hours, until the viable cell count of the fermentation broth is ≥10 9 CFU / mL; S3, carrier loading and drying: attapulgite was crushed through a 120 mesh screen, mixed with sodium alginate at a mass ratio of 10:1, distilled water was added to form a paste with a solid content of 40%, sterilized at 121℃ for 30 minutes; after cooling to 30℃, the fermentation broth was added at a ratio of 3mL:1g, stirred at 180rpm for 2 hours; then placed in a vacuum drying oven, dried at 50℃, 0.08MPa vacuum degree to a water content of ≤8%, crushed through an 80 mesh screen to obtain the complex microbial inoculant.

[0035] The preparation method of the acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer of the present embodiment is as follows: S1, monomer pretreatment: acrylamide, acrylic acid, and 2-methyl acryloyloxyethyl trimethyl ammonium chloride were weighed at a mass ratio of 7:3:2; 15wt% sodium hydroxide solution was used to neutralize the acrylic acid to pH 7.0 to obtain a neutralized acrylic acid solution; S2, aqueous solution polymerization: acrylamide, the neutralized acrylic acid solution, and 2-methyl acryloyloxyethyl trimethyl ammonium chloride were added to a reaction bottle, and distilled water was added to make the total monomer concentration 30wt%; after oxygen removal by nitrogen for 30 minutes, the initiator was added, and the reaction was carried out at 55℃ for 5 hours to obtain a gel-like polymer; S3, post-treatment: the gel-like polymer was crushed to 10mm particles, dried in a 75℃ oven to a water content of ≤5%, and then crushed through a 100 mesh screen to obtain the zwitterionic polymer.

[0036] In S2, aqueous solution polymerization of the present embodiment, the initiator was a mixture of ammonium persulfate and sodium bisulfite at a mass ratio of 1:1, and the amount used was 0.3% of the total monomer mass.

[0037] The preparation method of the polyglutamic acid complex modified fertilizer of the present embodiment is as follows: S1, raw material pretreatment: urea, potassium dihydrogen phosphate, potassium sulfate, and desulfurized gypsum were crushed through a 100 mesh screen, and humic acid was crushed through an 80 mesh screen to ensure uniform particle size of the raw materials; S2, mixing of base materials: the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, and humic acid were added to a double screw mixer in the proportions specified in the formula, and mixed at a speed of 200rpm for 20 minutes to obtain a base mixture; S3, mixing of functional components: polyglutamic acid, citric acid-humic acid complex modified biochar, Bacillus mucilaginosus-attapulgite complex microbial inoculant, and acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer were added to the base mixture, and the mixture was continuously mixed at a speed of 220rpm for 30 minutes until the uniformity of the material was ≥95% to obtain a total mixture; S4, extrusion granulation: the total mixture is sent into a double screw extrusion granulator, the granulation temperature is set to 65℃, the extrusion speed is 120 rpm, the die hole diameter is 4 mm, and wet granules are obtained by extrusion, with a water content of 20%.

[0038] S5, drying and cooling: the wet granules are sent into a fluidized bed dryer, the drying temperature is set to 75℃, the air speed is 2.0 m / s, and the granules are dried for 30 minutes until the water content is ≤5%; then they are sent into a cooler and cooled to room temperature, with a cooling time of 20 minutes.

[0039] S6, screening and packaging: the cooled granules are screened by a vibrating screen with a mesh size of 4.5 mm, and the fine powder (<1.5 mm) and large pieces (>4.5 mm) are removed to obtain qualified granules; after detecting the nutrient content and viable bacterial count of the granules, the product is obtained by vacuum packaging.

[0040] Example 3: A polyglutamic acid compound improved fertilizer special for saline-alkali soil, comprising the following components in mass fraction: Polyglutamic acid: 10 parts; Citric acid-humic acid compound modified biomass charcoal: 17.5 parts; Bacillus mucilaginosus-attapulgite compound microbial agent: 5.5 parts; Acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer: 4 parts; Urea: 11.5 parts; Monopotassium phosphate: 8.5 parts; Potassium sulfate: 5.5 parts; Desulfurized gypsum: 10 parts; Humic acid: 6.5 parts.

[0041] The preparation method of the citric acid-humic acid compound modified biomass charcoal of the present example is as follows: S1, biomass charcoal pretreatment: corn cob is selected as raw material, crushed to 3 mm particles, placed in a muffle furnace, heated to 450℃ at a heating rate of 6℃ / min under nitrogen atmosphere, and carbonized for 2.5 hours; after carbonization, cooled to room temperature, crushed and passed through a 90 mesh sieve to obtain raw biomass charcoal; S2, compound modification treatment: prepare 8wt% citric acid solution and 4wt% humic acid solution, mix them in a volume ratio of 1:1 to obtain a modification liquid; add the raw biomass charcoal and the modification liquid into a reaction kettle in a liquid-solid ratio of 4mL:1g, stir at 200 rpm at 67℃ for 2.5 hours; after stirring, place the mixture in an oven and dry at 70℃ until the water content is ≤5%, then crush and pass through a 90 mesh sieve to obtain the compound modified biomass charcoal.

[0042] The preparation method of the bacillus mucilaginosus-attapulgite compound microbial agent of the present example is as follows: S1, strain activation: select bacillus mucilaginosus, inoculate in LB medium, cultivate in 33℃, 200rpm shaker for 21 hours, get seed liquid with viable count ≥10 8 CFU / mL; S2, fermentation culture: prepare fermentation medium: 25g / L sucrose, 8g / L yeast extract, 2g / L potassium dihydrogen phosphate, 0.7g / L magnesium sulfate, pH7.3; seed liquid is inoculated into fermenter at 6.5% inoculation amount, ferment at 32℃, 225rpm stirring speed, 1:1v / v / min aeration amount for 27 hours, until the viable count of fermentation broth is ≥10 9 CFU / mL; S3, carrier loading and drying: crush the attapulgite through a 110 mesh screen, mix with sodium alginate at a mass ratio of 9:1, add distilled water to form a paste with a solid content of 35%, sterilize at 118℃ for 25 minutes; after cooling to 28℃, add fermentation broth at a ratio of 3mL:1g, stir at 165rpm for 1.5 hours; then place in a vacuum drying oven, dry at 45℃, 0.07MPa vacuum degree until the water content is ≤8%, crush through a 70 mesh screen to obtain the compound microbial agent.

[0043] The preparation method of the acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride zwitterionic polymer of this embodiment is as follows: S1, monomer pretreatment: weigh acrylamide, acrylic acid and 2-methyl acryloyloxyethyl trimethyl ammonium chloride at a mass ratio of 6:2:1; neutralize the acrylic acid to pH6.5 with 12.5wt% sodium hydroxide solution to obtain the neutralized acrylic acid solution; S2, aqueous solution polymerization: add acrylamide, neutralized acrylic acid solution and 2-methyl acryloyloxyethyl trimethyl ammonium chloride into a reaction bottle, add distilled water to make the total monomer concentration 25wt%; after oxygen removal by nitrogen for 30 minutes, add initiator, react at 48℃ for 4 hours to obtain a gel-like polymer; S3, post-treatment: crush the gel-like polymer into 8mm particles, dry in a 67℃ oven until the water content is ≤5%, then crush through a 90 mesh screen to obtain the zwitterionic polymer.

[0044] In S2, aqueous solution polymerization of this embodiment, the initiator is a mixture of ammonium persulfate and sodium bisulfite at a mass ratio of 1:1, and the amount is 0.2% of the total monomer mass.

[0045] The preparation method of the polyglutamic acid compound modified fertilizer of this embodiment is as follows: S1, raw material pretreatment: crush urea, potassium dihydrogen phosphate, potassium sulfate and desulfurized gypsum through a 90 mesh screen, and crush humic acid through a 70 mesh screen to ensure uniform particle size of the raw materials; S2, base material mixing: the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, humic acid were added into the double screw mixer according to the formula proportion, mixed at 175 rpm for 18 minutes, and the base mixture was obtained; S3, functional component mixing: the polyglutamic acid, citric acid-humic acid composite modified biomass charcoal, bacillus mucilaginosus-attapulgite composite microbial agent, acrylamide-acrylic acid-2-methyl acryloyloxyethyl trimethyl ammonium chloride amphoteric ion polymer were added into the base mixture, and the mixture was continuously mixed at 200 rpm for 25 minutes until the uniformity of the material was greater than or equal to 95%, and the total mixture was obtained; S4, extrusion granulation: the total mixture was sent into the double screw extrusion granulator, and the granulation temperature was set to 58 DEG C, the extrusion speed was set to 100 rpm, and the die hole diameter was set to 3 mm, and the wet granules were obtained by extrusion, and the water content was 17.5%.

[0046] S5, drying and cooling: the wet granules were sent into the fluidized bed dryer, the drying temperature was set to 68 DEG C, the air speed was set to 1.8 m / s, and the granules were dried for 25 minutes until the water content was less than or equal to 5%; then the granules were sent into the cooling machine and cooled to room temperature, and the cooling time was 18 minutes.

[0047] S6, screening and packaging: the cooled granules were screened by the vibrating screen with a mesh size of 3 mm, and the fine powder less than 1.5 mm and the large pieces greater than 4.5 mm were removed to obtain qualified granules; after detecting the nutrient content and the number of live bacteria and other indicators, the product was obtained by vacuum packaging.

[0048] It should be noted that the relational terms herein such as first and second and the like are used only to differentiate one entity or operation from another, and do not necessarily require or imply that any such actual relationship or order exists between or among the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or equipment.

[0049] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A polyglutamic acid compound fertilizer specifically for saline-alkali land, characterized in that, The composition includes the following parts by weight: Polyglutamic acid: 5-15 parts; Citric acid-humic acid composite modified biochar: 10-25 parts; Bacillus mucilaginosus-attapulgite soil compound inoculant: 3-8 parts; Acrylamide-acrylate-2-methacryloyloxyethyltrimethylammonium chloride zwitterionic polymer: 2-6 parts; Urea: 8-15 parts; Potassium dihydrogen phosphate: 5-12 parts; Potassium sulfate: 3-8 parts; Desulfurized gypsum: 5-15 parts; Humic acid: 3-10 parts.

2. The polyglutamic acid compound fertilizer for saline-alkali land according to claim 1, characterized in that, The preparation method of the citric acid-humic acid composite modified biochar is as follows: S1. Biochar pretreatment: Select corn cobs as raw material, crush them into 2-5mm particles, place them in a muffle furnace, heat them to 400-500℃ at a heating rate of 5-8℃ / min under a nitrogen atmosphere, and hold them at that temperature for 2-3 hours for carbonization; after carbonization, cool them to room temperature, crush them and pass them through an 80-100 mesh sieve to obtain primary biochar. S2. Composite modification treatment: Prepare a 5-10 wt% citric acid solution and a 3-5 wt% humic acid solution, and mix them in a volume ratio of 1:1 to obtain a modification solution. Add the raw biochar and the modified liquid to the reactor at a liquid-solid ratio of 3-5 mL: 1 g, and stir at 180-220 rpm for 2-3 hours at 60-75℃. After stirring, place the mixture in an oven and dry it at 60-80℃ until the moisture content is ≤5%. Then pulverize it through an 80-100 mesh sieve to obtain the composite modified biochar.

3. The polyglutamic acid compound fertilizer for saline-alkali land according to claim 1, characterized in that, The preparation method of the Bacillus mucilaginosus-attapulgite composite inoculant is as follows: S1. Strain activation: Select Bacillus mucilaginosus, inoculate it into LB medium, and culture it in a shaker at 30-35℃ and 180-220rpm for 18-24 hours to obtain a viable count ≥10. 8 CFU / mL seed culture; S2. Fermentation Culture: Prepare the fermentation medium: 20-30 g / L sucrose, 5-10 g / L yeast extract, 1-2 g / L potassium dihydrogen phosphate, 0.5-1 g / L magnesium sulfate, pH 7.0-7.5; inoculate the seed culture into the fermenter at a rate of 5-8%, and ferment for 24-30 hours at 30-35℃, 200-250 rpm stirring speed, and an aeration rate of 1:0.8-1.2 v / v / min, until the viable cell count in the fermentation broth is ≥10. 9 CFU / mL; S3. Carrier loading and drying: Pulverize attapulgite soil through a 100-120 mesh sieve, mix it with sodium alginate at a mass ratio of 8-10:1, add distilled water until a paste is formed with a solid content of 30-40%, sterilize at 115-121℃ for 20-30 minutes; after cooling to 25-30℃, add fermentation broth at a ratio of 2-3 mL:1 g to carrier, stir at 150-180 rpm for 1-2 hours; then place it in a vacuum drying oven and dry it at 40-50℃ and 0.06-0.08 MPa vacuum until the moisture content is ≤8%, pulverize it through a 60-80 mesh sieve to obtain the compound microbial agent.

4. The polyglutamic acid compound fertilizer for saline-alkali land as described in claim 1, characterized in that, The preparation method of the acrylamide-acrylic acid-2-methacryloyloxyethyltrimethylammonium chloride zwitterionic polymer is as follows: S1. Monomer pretreatment: Weigh acrylamide, acrylic acid, and 2-methacryloyloxyethyltrimethylammonium chloride in a mass ratio of 5-7:2-3:1-2; neutralize the acrylic acid to pH 6.0-7.0 with 10-15wt% sodium hydroxide solution to obtain a neutralized acrylic acid solution; S2, Aqueous Solution Polymerization: Acrylamide, neutralized acrylic acid solution, and 2-methacryloyloxyethyltrimethylammonium chloride are added to a reaction flask, and distilled water is added to make the total monomer concentration 20-30wt%; after purging with nitrogen for 30 minutes to remove oxygen, an initiator is added, and the reaction is carried out at 40-55℃ for 3-5 hours to obtain a gel polymer. S3. Post-processing: The gel polymer is crushed into 5-10mm particles, dried in an oven at 60-75℃ until the moisture content is ≤5%, and then crushed through an 80-100 mesh sieve to obtain the zwitterionic polymer.

5. A polyglutamic acid compound fertilizer for saline-alkali land as described in claim 4, characterized in that, The S2 aqueous solution polymerization uses an initiator that is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the amount used is 0.1-0.3% of the total mass of the monomers.

6. A polyglutamic acid compound fertilizer for saline-alkali land as described in any one of claims 1-5, characterized in that, The preparation method of the polyglutamic acid compound modified fertilizer is as follows: S1. Raw material pretreatment: Urea, potassium dihydrogen phosphate, potassium sulfate, and desulfurized gypsum are crushed and passed through an 80-100 mesh sieve, and humic acid is crushed and passed through a 60-80 mesh sieve to ensure uniform particle size of raw materials. S2. Basic material mixing: Add the pretreated urea, potassium dihydrogen phosphate, potassium sulfate, desulfurized gypsum, and humic acid to a twin-screw mixer according to the formula ratio, and mix at 150-200 rpm for 15-20 minutes to obtain the basic mixture. S3. Functional component mixing: Add polyglutamic acid, citric acid-humic acid composite modified biochar, Bacillus mucilaginosus-attapulgite composite bacterial agent, and acrylamide-acrylic acid-2-methacryloyloxyethyltrimethylammonium chloride zwitterionic polymer to the basic mixture. Continue mixing at 180-220 rpm for 20-30 minutes until the material uniformity is ≥95% to obtain the total mixture. S4. Extrusion granulation: The total mixture is fed into a twin-screw extruder, and the granulation temperature is set to 50-65℃, the extrusion speed to 80-120rpm, and the die diameter to 2-4mm. Wet granules are obtained by extrusion with a moisture content of 15-20%. S5. Drying and Cooling: The wet granules are fed into a fluidized bed dryer, and the drying temperature is set to 60-75℃ and the air velocity is 1.5-2.0m / s. The dryer is dried for 20-30 minutes until the moisture content of the granules is ≤5%. Then the granules are sent to a cooler and cooled to room temperature for 15-20 minutes. S6. Screening and Packaging: The cooled granules are screened using a vibrating screen with a mesh size of 1.5-4.5mm to remove fine powder <1.5mm and large pieces >4.5mm to obtain qualified granules; after testing the nutrient content, viable bacteria count and other indicators of the granules, they are vacuum packaged to obtain the finished product.