A composite biological stimulant slow-release granule for promoting plant stress resistance and a preparation method and application thereof

Abstract

This invention provides a slow-release granule of a compound biostimulant for plant stress resistance and growth promotion, along with its preparation method and application. Specifically, a multi-level porous adsorption system composed of biochar and attapulgite is used as a carrier. After loading the compound biostimulant system, it is granulated using chitosan and humic acid to form a granular matrix. Then, sodium alginate is cross-linked and solidified with CaCl2 to form a calcium alginate gel film coating the surface of the granular matrix, thereby reducing the water penetration rate and delaying the diffusion and release of active ingredients in the compound biostimulant system. The slow-release granules prepared by this invention promote crop emergence and seedling vigor while maintaining the supply of rhizosphere active components under drought and salt stress conditions, exhibiting comprehensive advantages in stress resistance, fertilization, growth promotion, and increased local carbon input. The obtained slow-release granules can also be applied synergistically with compound fertilizers, organic fertilizers, or basal fertilizers to achieve simultaneous entry of growth-promoting components and nutrient supply into the rhizosphere soil, combining the convenience of fertilizer application with the feasibility of field operation.

Description

Technical Field

[0001] This invention belongs to the fields of agricultural biotechnology, new agricultural inputs and crop stress regulation technology, specifically relating to a compound biostimulant slow-release granule for plant stress resistance and growth promotion, its preparation method and application. Background Technology

[0002] Seed germination and early seedling growth are critical stages for crop seedling establishment. This stage is extremely sensitive to water, nutrients, osmotic regulation, and metabolic activation. When affected by adverse factors such as drought, salinity, low temperature, or poor substrate conditions, problems often arise, including slow water absorption, uneven germination, limited growth of the radicle and plumule, and insufficient seedling vigor. This is particularly pronounced in typical adverse farmland environments such as saline-alkali lands in Xinjiang, where difficulties in emergence after sowing, unstable seedling establishment, and the combined stresses of drought and salinity are especially prominent. High soil pH, high osmotic pressure, and ion toxicity further exacerbate the difficulties of seed germination and seedling establishment, becoming a significant bottleneck restricting local agricultural production.

[0003] Existing exogenous regulatory measures to promote seed germination and seedling growth mostly employ methods such as seed soaking, spraying, seed dressing, or root irrigation. The main targets include plant hormones, nutrient solutions, microbial preparations, or biostimulants. Although these methods can improve germination performance to some extent, they still have the following prominent problems: (1) Active ingredients are easily lost, especially water-soluble substances, which are difficult to effectively accumulate in the rhizosphere under irrigation or rainfall conditions; (2) The application uniformity is insufficient, and it is difficult to achieve precise quantitative application of liquid or powdered preparations in the field; (3) The field persistence is weak, and the effective time after a single application is limited, making it difficult to cover the complete cycle from seed germination to seedling establishment; (4) Repeated application is costly and labor-intensive, especially in adverse environments such as drought and salinity, where liquid preparations are often more difficult to maintain a continuous effect, and frequent application will exacerbate the accumulation of surface salts in the soil. In addition, existing biostimulant products are mostly single-function preparations, lacking composite products that systematically integrate growth promotion, stress resistance, rhizosphere microenvironment regulation, and synergistic application of fertilizers.

[0004] Therefore, it is necessary to provide a compound biostimulant slow-release granule with clearly defined components, a stable preparation process, and ease of field application, capable of addressing the stress requirements of crop germination, emergence, and early seedling stages. By applying these compound slow-release granules, a continuous and stable release of active components is provided during seed germination, promoting hydration and metabolic activation; during the seedling stage, root development is promoted, enhancing water and nutrient absorption capacity; and especially in arid and salt-stressed farmland environments such as saline-alkali lands in Xinjiang, it possesses the ability to be synergistically applied with basal fertilizers, improving the rhizosphere water and salt environment and enhancing the stability of the local carbon-based microenvironment, thereby alleviating the damage of salt-alkali stress to the root system. This achieves a multi-functional synergistic effect of stress resistance, fertilization, growth promotion, and rhizosphere carbon environment support, meeting the comprehensive needs of adverse farmland for seed treatment agents.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a sustained-release compound biostimulant granule for plant stress resistance and growth promotion, in order to solve the problems of insufficient duration of action, inconvenient application and low utilization efficiency of existing liquid compound biostimulants.

[0007] This invention provides a compound biostimulant sustained-release granule for plant stress resistance and growth promotion, specifically comprising: a compound biostimulant system, a porous carrier, a binder, and a coating layer;

[0008] The composite biostimulant system comprises a main ingredient and excipients, which are loaded as active ingredients on the surface and inside of a carrier; wherein, the main ingredient comprises polyglutamic acid fermentation broth and lactose peptide organic water-soluble fertilizer; the excipients are aqueous solutions containing inositol and tetrahydropyrimidine; based on the total mass of the composite biostimulant system, the mass fraction of the main ingredient is 94%-96%, and the mass fraction of the excipients is 4%-6%;

[0009] The porous carrier is biochar and attapulgite, which serve as the particle framework and sustained-release carrier.

[0010] The liquid-to-solid ratio of the composite biostimulant system and the porous carrier is (1-3) mL / g;

[0011] The binder is chitosan and humic acid, which are used to mix and granulate the composite biostimulant system and the carrier to form a particulate matrix.

[0012] The coating layer is a calcium alginate gel film formed on the surface of the particle matrix after sodium alginate solution is cross-linked and cured by CaCl2 solution. It is used to reduce the water penetration rate and delay the diffusion and release of active ingredients in the compound biostimulant system.

[0013] In a preferred embodiment, based on the total mass of the composite biostimulant system, the mass fraction of the main ingredient is 95%, and the mass fraction of the excipients is 5%.

[0014] In a preferred embodiment, the liquid-to-solid ratio of the composite biostimulant system to the porous carrier is 2 mL / g.

[0015] In a preferred embodiment, the mass ratio of polyglutamic acid fermentation broth to lactose peptide organic water-soluble fertilizer in the main ingredient is (1:9)-(3:7).

[0016] The polyglutamic acid fermentation broth is a fermentation broth of Bacillus and its metabolites.

[0017] The lactose peptide organic water-soluble fertilizer is a soluble peptide nutrient carrier in liquid state. Its effective component indicators include: the mass ratio of N, P2O5 and K2O is (18-22):(8-12):(45-55), the free amino acid content is 70-80 g / L, the organic matter content is 190-210 g / L, and the organic acid content is 230-250 g / L.

[0018] Preferably, in the main ingredient, the mass ratio of polyglutamic acid fermentation broth to lactose peptide organic water-soluble fertilizer is 1.5:8.5, 2:8, or 2.5:7.5.

[0019] In a preferred embodiment, the inositol content is 20-250 mg / kg and the tetrahydropyrimidine content is 10-110 mg / kg, based on the total mass of the excipients.

[0020] In a preferred embodiment, the porous carrier has a particle size of 80-160 mesh; and the mass ratio of biochar to attapulgite in the porous carrier is 1:(0.4-1.2).

[0021] Preferably, the biochar raw material includes at least one of cotton stalk biochar, wheat stalk biochar, or fruit shell biochar.

[0022] In a preferred embodiment, the mass of the binder is 2%-10% of the total mass of the porous carrier and the composite biostimulant system; preferably, the mass of the binder is 3%, 4%, 5%, 6%, 7%, 8%, or 9% of the total mass of the porous carrier and the composite biostimulant system.

[0023] In a preferred embodiment, the mass ratio of chitosan to humic acid in the adhesive is (2-4):1; preferably, both chitosan and humic acid are powdered solids.

[0024] In a preferred embodiment, the sodium alginate solution has a mass fraction of 1%-5%, the amount of sodium alginate solution used is 3%-10% of the mass of the granulated matrix, the CaCl2 solution has a mass fraction of 2%-3%, and the curing time is 30-40 min.

[0025] In a preferred embodiment, the particle size of the sustained-release particles is 1-3 mm.

[0026] Another object of the present invention is to provide a method for preparing any of the above-mentioned compound biostimulant sustained-release granules for plant stress resistance and growth promotion, specifically including the following steps:

[0027] (1) Crush and sieve biochar and attapulgite, mix them evenly, add deionized water to the resulting mixed powder to wet it, and obtain a pre-wetting carrier;

[0028] (2) Add the composite biostimulant system to the pre-wetted carrier obtained in step (1) and perform impregnation and adsorption under stirring conditions so that the composite biostimulant system is uniformly loaded on the surface and pores of the porous carrier to obtain a mixture.

[0029] (3) Add a binder to the mixture obtained in step (2), mix well, and then granulate using a disc granulator to obtain wet granules;

[0030] (4) The wet particles are coated with sodium alginate solution, and then the coated wet particles are immersed in CaCl2 solution for cross-linking and curing. After curing, they are dried and sieved to obtain the slow-release particles.

[0031] In a preferred embodiment, in step (1), the mass ratio of biochar to attapulgite is 1:(0.4-1.2), the solid-liquid ratio of the mixed powder to deionized water is (4-6) g:1 mL, and the wetting time is 10-20 min.

[0032] In a preferred embodiment, step (2) of the preparation method of the composite biostimulant system includes: mixing polyglutamic acid fermentation broth and lactose peptide organic water-soluble fertilizer at a mass ratio of (1:9)-(3:7) to obtain a first liquid; dispersing inositol and tetrahydropyrimidine in deionized water to obtain a second liquid; mixing the first liquid and the second liquid in proportion and stirring until uniform to obtain the composite biostimulant system; wherein, in the second liquid, the content of inositol is 20-250 mg / kg, the content of tetrahydropyrimidine is 10-110 mg / kg, and based on the total mass of the composite biostimulant system, the mass fraction of the first liquid is 94%-96%, and the mass fraction of the second liquid is 4%-6%.

[0033] In a preferred embodiment, in step (2), the liquid-to-solid ratio of the composite biostimulant system and the porous carrier is (1-3) mL / g.

[0034] In a preferred embodiment, in step (2), the stirring speed for the stirring impregnation adsorption is 100-300 rpm, and the adsorption time is 6-12 h.

[0035] In a preferred embodiment, in step (3), the mass of the binder is 2%-10% of the total mass of the porous carrier and the composite biostimulant system; the binder is obtained by mixing chitosan and humic acid in a mass ratio of (2-4):1.

[0036] In a preferred embodiment, in step (3), the wet particles obtained have a particle size of 1.5-3.5 mm.

[0037] In a preferred embodiment, in step (4), the mass fraction of the sodium alginate solution is 1%-5%, the amount of the sodium alginate solution is 3%-10% of the mass of the wet particles, and the surface coating can be carried out by conventional methods known to those skilled in the art, such as spraying or dripping in a disc granulator or in a rolling state, so that the sodium alginate solution is uniformly coated on the surface of the wet particles.

[0038] In a preferred embodiment, in step (4), the mass fraction of the CaCl2 solution is 2%-3%, and the curing time is 30-40 min.

[0039] In a preferred embodiment, in step (4), the drying can be carried out using conventional methods known to those skilled in the art, such as drying at 25-35°C to constant weight.

[0040] Another objective of this invention is to provide the application of any of the above-mentioned compound biostimulant slow-release granules for plant stress resistance and growth promotion in promoting crop growth under adverse conditions, specifically including: using the slow-release granules to promote crop emergence, rooting and seedling protection under drought, saline-alkali or drought-saline-alkali combined adverse conditions.

[0041] In a preferred embodiment, the crop is a solanaceous vegetable; preferably, the crop is tomato.

[0042] In a preferred embodiment, the slow-release granules are used to improve the germination rate of crop seeds under salt stress and / or improve the survival rate of seedlings under drought stress.

[0043] In a preferred embodiment, the slow-release granules are applied in the following ways: furrow application, hole application, root zone application, basal application mixed with base fertilizer, supplemental application in the root zone during the seedling stage, or pre-application before adverse conditions.

[0044] Preferably, the application method of the slow-release granules is selected according to the type of stress and the crop growth stage:

[0045] During the sowing period: apply the fertilizer by furrow or hole application at a rate of 70-90 kg / mu;

[0046] During the basal fertilizer period: Mix with basal fertilizer at a mass ratio of 1:(10-50) and apply to the soil at a rate of 50-60 kg / mu;

[0047] Before the seedling stage or before the onset of adverse conditions: apply the solution at the root zone or pre-application. The application rate during the seedling stage is 60-80 kg / mu. Before the onset of adverse conditions, that is, 7-14 days before the expected drought or salt stress, the application rate is 80-90 kg / mu.

[0048] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0049] 1. In this invention, an organic-inorganic composite carrier is constructed using biochar and attapulgite. Biochar provides the carbon-based interface and adsorption sites for active components, while attapulgite, with its rod-shaped porous structure, provides the interface for ion exchange and physical adsorption. The synergistic construction of a multi-level porous adsorption system using biochar and attapulgite not only improves the fixation and slow-release capacity of the composite biostimulant system but also helps improve rhizosphere water retention, buffer salinity, and provide a certain carbon source environment, thereby enhancing the crop's resistance to drought and salt stress.

[0050] 2. In this invention, a complex biostimulant system composed of polyglutamic acid fermentation broth, lactose peptide organic water-soluble fertilizer, inositol, and tetrahydropyrimidine serves as the core functional component. The polyglutamic acid fermentation broth contains Bacillus metabolites and polyglutamic acid-like active substances, which can improve rhizosphere water retention and nutrient complexation retention capacity, and can act as a regulatory factor for rhizosphere microbial activation and seedling root development. The lactose peptide organic water-soluble fertilizer contains soluble peptides, free amino acids, organic acids, and nitrogen, phosphorus, and potassium nutrients, providing easily absorbed nutrients for seed germination and early seedling growth. Small molecule organic nutrients and basic mineral nutrients promote seedling metabolism initiation, root elongation, and early biomass formation; inositol, as a small molecule involved in plant cell signal transduction and osmotic regulation, can participate in cell membrane stability, carbon metabolism regulation, and stress response processes, helping to alleviate the problems of water absorption obstruction and reduced metabolic activity in seedlings under drought and saline-alkali stress; tetrahydropyrimidine, as a compatible solute derived from salt-tolerant microorganisms, has osmotic protection and protein and cell membrane stabilization effects, which can reduce the damage to seedling cell structure and physiological activity caused by salt and drought stress.

[0051] In the above-mentioned compound formulation, polyglutamic acid fermentation broth focuses on rhizosphere water retention, nutrient maintenance, and microenvironment regulation; lactose peptide organic water-soluble fertilizer focuses on providing fast-acting organic nutrients and mineral nutrients; inositol focuses on regulating plant germination and early seedling stress resistance metabolism; and tetrahydropyrimidine focuses on enhancing osmotic protection under salt and drought stress. The synergistic effect of these four raw materials promotes water absorption and swelling and radicle breakthrough during seed germination, promotes root growth and nutrient absorption during seedling establishment, and maintains high cellular metabolic activity and seedling stability under saline-alkali soil, drought, or combined drought and saline-alkali stress. Furthermore, the compound biostimulant system is loaded onto a biochar-attapulgite porous carrier and bound by chitosan-humic acid and coated with a calcium alginate gel membrane. This prevents the rapid loss of water-soluble active components, allowing the above-mentioned growth-promoting and stress-resistance active ingredients to be continuously released in the rhizosphere, thereby achieving a synergistic effect of promoting germination, promoting root growth, stress resistance and seedling protection, and improving the rhizosphere microenvironment.

[0052] 3. In this invention, chitosan and humic acid are selected as binders. The purpose is to utilize the film-forming, adhesive, and adsorption-fixing properties of chitosan to improve the particle forming strength and water resistance, while utilizing the complexing, buffering, and rhizosphere growth-promoting effects of humic acid to enhance nutrient retention and the ability to regulate the microenvironment of saline-alkali soil. Thus, the binder has the functions of physical forming, fixation of active components, slow-release assistance, and stress resistance and growth promotion. In terms of dosage, this invention limits the mass ratio of chitosan to humic acid to (2-4):1. This is to ensure that chitosan fully exerts its particle bonding, film-forming, and structural stabilizing effects while avoiding excessive proportions that could hinder particle release. Appropriate amounts of humic acid are used to enhance the complexing and retention of active components, rhizosphere buffering, and the ability to regulate the growth of saline-alkali soil, thereby balancing particle mechanical strength, water resistance, slow-release performance, and rhizosphere biological activity. In addition, the present invention adopts a granular product form, which is convenient for storage and transportation, and is easy to apply in various field methods such as sowing furrow application, hole application, rhizosphere application, and basal application mixed with base fertilizer. It is suitable for promotion and use in adverse farmland such as saline-alkali land in Xinjiang.

[0053] 4. The present invention uses a gel membrane layer formed by cross-linking sodium alginate and CaCl2 as a coating layer, which helps to reduce the rapid penetration of external water into the particle interior and regulate the diffusion process of water-soluble active components, thereby improving the particle's persistence, water resistance stability and continuous rhizosphere supply capacity under saline-alkali soil and drought stress conditions.

[0054] 5. Through the above-described component design, the slow-release granules obtained by this invention not only promote crop emergence and seedling vigor but also maintain the supply of rhizosphere active components under drought and salt stress conditions, demonstrating comprehensive advantages in stress resistance, fertilization, growth promotion, and increased local carbon input. Furthermore, the slow-release granules obtained by this invention can be applied synergistically with compound fertilizers, organic fertilizers, or basal fertilizers, enabling the growth-promoting components and nutrient supply to enter the rhizosphere soil simultaneously, combining the convenience of fertilizer formulation with the feasibility of field operation. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0056] Figure 1 This is a physical image of the composite biostimulant sustained-release granules prepared according to the present invention. Detailed Implementation

[0057] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0058] Unless otherwise specified, the technical means used in this invention are conventional means well known to those skilled in the art. All raw materials, reagents, instruments, and equipment used in this invention can be purchased from the market or prepared using existing methods. Unless otherwise specified, all reagents used in this invention are of analytical grade. In the embodiments of this invention, the polyglutamic acid fermentation broth used was purchased from Shandong Freda Biotechnology Co., Ltd., and its product name is agricultural-grade polyglutamic acid fermentation, which is a fermentation broth of Bacillus and its metabolites; the lactopeptide organic water-soluble fertilizer used was purchased from Zhucheng Haochen Biotechnology Co., Ltd., and its product name is lactopeptide. Its nominal product indicators include: a relative ratio of N, P2O5, and K2O of 20:10:50, a free amino acid content of 75 g / L, an organic matter content of 200 g / L, and an organic acid content of 240 g / L.

[0059] In this invention, the weight parts can be weight units known in the art such as µg, mg, g, kg, or multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc.

[0060] Example 1

[0061] A method for preparing compound biostimulant sustained-release granules for plant stress resistance and growth promotion includes the following steps:

[0062] S1 Preparation of compound biostimulant system: Polyglutamic acid fermentation broth and liquid lactose peptide organic water-soluble fertilizer are mixed evenly at a mass ratio of 2:8 to obtain the first liquid;

[0063] Inositol and tetrahydropyrimidine were dispersed in deionized water to obtain a second liquid. The content of inositol in the second liquid was 20 mg / kg and the content of tetrahydropyrimidine was 10 mg / kg.

[0064] The first liquid and the second liquid are mixed in proportion and stirred until homogeneous to obtain a composite biostimulant system with the first liquid having a mass fraction of 95% and the second liquid having a mass fraction of 5%.

[0065] S2 Preparation of pre-wetting carrier: Weigh 45 g of cotton stalk biochar and 30 g of attapulgite as porous carriers, crush them separately and pass them through a 100-mesh sieve, mix the resulting powders evenly, add 15 mL of deionized water, and pre-wet for 20 min to obtain the pre-wetting carrier.

[0066] S3 Take 150 mL of the composite biostimulant system prepared in step S1 and mix it with the porous carrier (the solid phase in the pre-wetted carrier prepared in step S2) at a liquid-to-solid ratio of 2 mL / g. Stir and adsorb at 200 rpm for 6 h to ensure that the composite biostimulant system is uniformly loaded on the surface and pores of the composite carrier, thus obtaining a mixture.

[0067] S4. Chitosan powder and humic acid powder are mixed evenly at a mass ratio of 3:1 to obtain a powder binder. The prepared binder is added to the mixture obtained in step S3 at 5% of the total mass of the porous carrier and the composite biostimulant system. After thorough mixing, granulation is performed using a disc granulator to obtain wet particles, with the particle size controlled at 1.5-3.5 mm.

[0068] S5 Weigh out 5% of the mass of sodium alginate solution obtained in step S4 and spray it evenly onto the surface of the wet particles. After spraying, immerse the particles completely in CaCl2 solution for cross-linking and curing for 30 min. Remove the particles and remove the free liquid on the surface. Dry them at 30℃ to constant weight and sieve to obtain composite biostimulant sustained-release particles with a particle size of 1-3 mm. The mass fraction of sodium alginate solution is 2% and the mass fraction of CaCl2 solution is 3%.

[0069] Example 2

[0070] Compared with Example 1, the only difference is that in step S1, the content of inositol in the obtained second liquid is 50 mg / kg and the content of tetrahydropyrimidine is 30 mg / kg; other raw materials, dosages, steps and process conditions are exactly the same as in Example 1.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that in step S1, the content of inositol in the obtained second liquid is 100 mg / kg and the content of tetrahydropyrimidine is 50 mg / kg; other raw materials, dosages, steps and process conditions are exactly the same as in Example 1.

[0073] Example 4

[0074] Compared with Example 1, the only difference is that in step S1, the content of inositol in the obtained second liquid is 150 mg / kg and the content of tetrahydropyrimidine is 70 mg / kg; other raw materials, dosages, steps and process conditions are exactly the same as in Example 1.

[0075] Example 5

[0076] Compared with Example 1, the only difference is that in step S1, the content of inositol in the obtained second liquid is 200 mg / kg and the content of tetrahydropyrimidine is 90 mg / kg; other raw materials, dosages, steps and process conditions are exactly the same as in Example 1.

[0077] Example 6

[0078] Compared with Example 1, the only difference is that in step S1, the content of inositol in the obtained second liquid is 250 mg / kg and the content of tetrahydropyrimidine is 110 mg / kg; other raw materials, dosages, steps and process conditions are exactly the same as in Example 1.

[0079] Example 7

[0080] Compared with Example 3, the only difference is that in step S1, the polyglutamic acid fermentation broth and liquid lactopeptide organic water-soluble fertilizer are mixed evenly at a mass ratio of 1:9; other raw materials, dosages, steps and process conditions are exactly the same as in Example 3.

[0081] Example 8

[0082] Compared with Example 3, the only difference is that in step S1, the polyglutamic acid fermentation broth and liquid lactose peptide organic water-soluble fertilizer are mixed evenly at a mass ratio of 3:7; other raw materials, dosages, steps and process conditions are exactly the same as in Example 3.

[0083] Example 9

[0084] Compared with Example 3, the only difference is that in step S2, 53.57 g of cotton stalk biochar and 21.43 g of attapulgite were weighed, crushed and passed through a 100-mesh sieve, the resulting powders were mixed evenly, 15 mL of deionized water was added, and the mixture was pre-wetted for 20 min to obtain a pre-wetted carrier; wherein, the mass ratio of cotton stalk biochar to attapulgite was 1:0.4. Other raw materials, dosages, steps, and process conditions were exactly the same as in Example 3.

[0085] Example 10

[0086] Compared with Example 3, the only difference is that in step S2, 34.09 g of cotton stalk biochar and 40.91 g of attapulgite are weighed, crushed and passed through a 100-mesh sieve, the resulting powders are mixed evenly, 15 mL of deionized water is added, and the mixture is pre-wetted for 20 min to obtain a pre-wetted carrier; wherein, the mass ratio of cotton stalk biochar to attapulgite is 1:1.2. Other raw materials, dosages, steps, and process conditions are exactly the same as in Example 3.

[0087] Example 11

[0088] Compared with Example 3, the only difference is that in step S5, the amount of sodium alginate solution used is 10% of the mass of the wet particles, and the mass fraction of the sodium alginate solution is 5%; the mass fraction of the CaCl2 solution used is 2%. Other raw materials, amounts, steps, and process conditions are exactly the same as in Example 3.

[0089] Comparative Example 1

[0090] Compared with Example 3, the only difference is that in step S1, the second liquid is deionized water of equal mass that does not contain inositol and tetrahydropyrimidine. The mass fractions of the first liquid and the second liquid remain 95% and 5% respectively, so as to keep the total mass, liquid-solid ratio and water content of the compound biostimulant system unchanged. Other raw materials, dosages, steps and process conditions are also exactly the same as in Example 3.

[0091] Comparative Example 2

[0092] Compared with Example 3, the only difference is that in step S1, the first liquid is only liquid lactose peptide organic water-soluble fertilizer. The composition of the second liquid, the concentration of inositol and tetrahydropyrimidine and their mass fraction in the compound biostimulant system are the same as in Example 3, and other raw materials, dosages, steps and process conditions are also exactly the same as in Example 3.

[0093] Comparative Example 3

[0094] Compared with Example 3, the only difference is that in step S1, the first liquid is only polyglutamic acid fermentation broth. The composition of the second liquid, the concentrations of inositol and tetrahydropyrimidine, and their mass fractions in the complex biostimulant system are the same as in Example 3. Other raw materials, amounts, steps, and process conditions are also exactly the same as in Example 3.

[0095] Comparative Example 4

[0096] Compared with Example 3, the only difference is that in step S2, only 75 g of cotton stalk biochar is weighed, crushed and passed through a 100-mesh sieve, 15 mL of deionized water is added, and it is pre-wetted for 20 min to obtain a porous carrier; other raw materials, dosages, steps and process conditions are exactly the same as in Example 3.

[0097] Comparative Example 5

[0098] Compared with Example 3, the only difference is that in step S2, only 75 g of attapulgite is weighed, crushed and passed through a 100-mesh sieve, 15 mL of deionized water is added, and it is pre-wetted for 20 min to obtain a porous carrier; other raw materials, dosages, steps and process conditions are exactly the same as in Example 3.

[0099] Comparative Example 6

[0100] Compared with Example 3, the only difference is that in step S3, the liquid-to-solid ratio of the composite biostimulant system and the porous carrier is 5 mL / g. All other raw materials, amounts, steps, and process conditions are exactly the same as in Example 3.

[0101] Comparative Example 7

[0102] Compared with Example 3, the only difference is that in step S3, the stirring and adsorption time is 3 hours. All other raw materials, amounts, steps, and process conditions are exactly the same as in Example 3.

[0103] Comparative Example 8

[0104] Compared with Example 3, the only difference is that in step S4, the binder is only chitosan powder. The amount of binder added is still 5% of the total mass of the porous carrier and the composite biostimulant system, and the other raw materials, amounts, steps and process conditions are exactly the same as in Example 3.

[0105] Comparative Example 9

[0106] Compared with Example 3, the only difference is that in step S4, the binder is only humic acid powder. The amount of binder added is still 5% of the total mass of the porous carrier and the composite biostimulant system, and the other raw materials, amounts, steps and process conditions are exactly the same as in Example 3.

[0107] Comparative Example 10

[0108] Compared with Example 3, the only difference is that in step S4, the amount of binder added is 1% of the total mass of the porous carrier and the composite biostimulant system. The binder is still obtained by mixing chitosan powder and humic acid powder in a mass ratio of 3:1, and the other raw materials, amounts, steps and process conditions are exactly the same as in Example 3.

[0109] Comparative Example 11

[0110] Compared with Example 3, the only difference is that in step S4, the amount of binder added is 12% of the total mass of the porous carrier and the composite biostimulant system. The binder is still obtained by mixing chitosan powder and humic acid powder in a mass ratio of 3:1, and the other raw materials, amounts, steps and process conditions are exactly the same as in Example 3.

[0111] Comparative Example 12

[0112] Compared with Example 3, the only difference is that in step S5, the amount of sodium alginate solution used is 1% of the mass of the wet particles, and the mass fraction of the sodium alginate solution is 2%. Other raw materials, amounts, steps, and process conditions are exactly the same as in Example 3.

[0113] Comparative Example 13

[0114] Compared with Example 3, steps S1-S3 are exactly the same as in Example 3, steps S4 and S5 are omitted, and the mixture obtained in step S3 is dried at a low temperature of 30°C to constant weight.

[0115] Comparative Example 14

[0116] Compared with Example 3, steps S1-S4 are exactly the same as in Example 3, step S5 is omitted, and the wet particles obtained in step S4 are dried at a low temperature of 30°C to constant weight.

[0117] Application Example 1: Investigating the germination-promoting effect of slow-release granules under salt stress conditions.

[0118] 1. Experimental materials:

[0119] Experimental crop: Tomato, variety Jingfan 309, selected seeds that are plump, uniform in size, and free from pests and diseases.

[0120] Experimental Soil and Containers: Saline-alkali soil from the top 0-20cm layer of farmland in Baicheng County, Aksu Prefecture, Xinjiang (40.8789°N, 80.5269°E) was collected. Its physicochemical properties are shown in Table 1, and its aggregate composition and organic carbon content are shown in Table 2. After air-drying, the soil was sieved through a 2mm sieve. The sieved material was then sterilized by high-pressure steam and poured into black plastic seedling trays. The trays had a mouth diameter of 90mm, a bottom diameter of 60mm, and a height of 100mm. Each tray contained 400g of air-dried, sieved soil.

[0121] Table 1 Basic physicochemical properties of saline-alkali soils in Xinjiang

[0122]

[0123] Table 2. Aggregate composition and organic carbon content of saline-alkali soils in Xinjiang

[0124]

[0125] 2. Experimental steps:

[0126] (1) At a ratio of 100 mg of fertilizer per 1 kg of dry soil, the fertilizer granules prepared in the examples and comparative examples were mixed with 400 g of air-dried soil, placed in seedling pots, and distilled water was added at a field water holding capacity of 60%, and sealed for 24 h; another 400 g of air-dried soil without any fertilizer was used as a control group.

[0127] (2) Disinfect the surface of tomato seeds with 1% sodium hypochlorite solution for 10 minutes, rinse with sterile water 5 times, dry the surface moisture with sterile filter paper, and then sow them into seedling trays. Sow 5 seeds evenly in each tray at a depth of 1.5 cm. Plant 4 trays for one treatment, for a total of 20 seeds.

[0128] (3) The seedling pots were placed in an artificial climate culture room. The culture conditions were: daytime temperature 25℃, nighttime temperature 18℃, light duration 12h / d, light intensity 3000lx, and relative humidity 65%. Distilled water was added daily at 18:00 by weighing to maintain the soil moisture content of each treatment within the target range. No additional fertilizer was applied during the experiment.

[0129] 3. Measurement Indicators and Calculation Methods:

[0130] The criteria for normal germination were determined by the radicle breaking through the seed coat and the radicle length being greater than or equal to the seed length itself. The surface soil of each pot was carefully removed at fixed time points for observation and statistical analysis. After the observation, the soil was backfilled in the same condition.

[0131] Germination rate = (Number of seeds that germinate normally on the same day / Total number of seeds sown) * 100%;

[0132] Germination potential = (Total number of seeds that germinated normally in the first three days / Total number of seeds sown) * 100%.

[0133] 4. Results and Discussion:

[0134] The germination-promoting effects of the fertilizer granules prepared in the examples and comparative examples are shown in Table 3.

[0135] Table 3 Germination rate and germination potential of different treatments

[0136]

[0137] As shown in Table 3, under saline-alkali stress conditions, the compound biostimulant slow-release granules prepared in Examples 1-11 all exhibited a promoting effect on tomato seed germination. The total number of germinating seeds in each example over three days was 16-19, with a germination potential of 80%-95%, significantly higher than the 45% in the blank control. This indicates that the slow-release granules described in this invention can effectively alleviate the adverse effects of saline-alkali stress on seed germination, promote faster initiation of the tomato seed germination process, and improve germination uniformity.

[0138] Comparing the different embodiments, Example 3 showed 8 germinated seeds on the first day, a germination rate of 40%, and a total of 19 germinated seeds over three days, with a germination potential of 95%. This was the optimal treatment among the embodiments, indicating that the combination of inositol and tetrahydropyrimidine concentrations and the proportion of the compound biostimulant components were suitable, effectively promoting rapid seed germination under salt-alkali stress. The germination potentials of Examples 1, 5, 6, 7, and 11 were 85%, 85%, 80%, 85%, and 85%, respectively, while the germination potentials of Examples 2, 4, 8, 9, and 10 all reached 90%. This demonstrates that even with adjustments to the concentration of functional components, carrier ratio, loading conditions, or coating conditions, the system of the present invention can still maintain a high germination-promoting effect. Although many seeds continued to germinate on the third day in Examples 7 and 8, and the early germination rate was lower than that in Example 3, the total number of germinated seeds in three days still reached 17 and 18 respectively, with germination potential of 85% and 90% respectively. This indicates that the germination-promoting effect remained stable after the relevant parameters were adjusted, but the rapid germination ability was slightly lower than that of the preferred formula.

[0139] In contrast, comparative examples 1-14 and the blank control showed varying degrees of germination lag or decreased germination levels. The total number of germinated seeds in each comparative example over three days was 8-12, with a germination potential of 40%-60%, all lower than in examples 1-11. The blank control had only 9 germinated seeds over three days, with a germination potential of 45%, indicating that salt-alkali stress significantly inhibited the germination process of tomato seeds without the application of the slow-release granules of this invention.

[0140] Specifically, Comparative Example 1, lacking inositol and tetrahydropyrimidine, lacked key osmotic regulators and stress buffering components, resulting in only 10 seeds germinating over three days, with a germination potential of 50%, significantly lower than the examples. This indicates that inositol and tetrahydropyrimidine play important roles in maintaining seed cell osmotic balance and promoting early metabolic recovery under saline-alkali stress. Comparative Examples 2 and 3, lacking lactopeptide organic water-soluble fertilizer or polyglutamic acid fermentation broth respectively, had 11 and 9 seeds germinating over three days, with germination potentials of 55% and 45%, respectively. This suggests that the lack of corresponding organic nutrients and microbial active substances weakens the exogenous nutrient support and metabolic regulation required for seed germination, leading to a decrease in germination levels.

[0141] Comparative Examples 4 and 5, whose carrier systems consisted of only biochar or attapulgite, had a total germination rate of 11 and 10 seeds respectively over three days, with germination potentials of 55% and 50%. This indicates that a single carrier cannot simultaneously exert pore adsorption, mineral interface regulation, and slow-release effects, and cannot effectively maintain the stability of the microenvironment around the seeds under salt-alkali stress. Comparative Examples 6 and 7, due to an increased liquid-to-solid ratio or a shortened adsorption time, had a total germination rate of 11 and 10 seeds respectively over three days, with germination potentials of 55% and 50%. This indicates that when the loading conditions deviate from the suitable range, the adsorption sufficiency and uniform distribution of the active components in the carrier decrease, thereby weakening the subsequent slow-release supply effect.

[0142] In Comparative Examples 8-11, the binder composition or dosage deviated from the preferred range, resulting in a total of 8-12 germinations over three days, with a germination potential of 40%-60%. Comparative Example 8, with a germination potential of only 40%, was the lowest among the treatments, indicating that an unreasonable binder system affects particle shape, pore structure, and water diffusion, thus impacting the release of active substances and the synchronization of seed germination. Comparative Example 12, due to insufficient sodium alginate coating, had a total of 11 germinations over three days, with a germination potential of 55%. This indicates that when the coating layer is incomplete, the surface barrier structure formed by CaCl2 cross-linking and solidification is insufficient, reducing the slow-release control capacity and easily leading to unstable early release and insufficient later supply. Comparative Examples 13 and 14, lacking key granulation or coating steps, had a total of 8 and 10 germinations over three days, with germination potentials of 40% and 50%, respectively. This indicates that without a complete particle structure or a stable slow-release system, effective active ingredients are easily lost rapidly, shortening the rhizosphere regulation time window and ultimately resulting in a significantly lower germination effect than the examples.

[0143] Overall, Examples 1-11 all maintained tomato seed germination potential above 80% under salt-alkali stress, with the preferred Example 3 reaching 95%; while the comparative examples and blank control only achieved 40%-60% and 45%, respectively. These results indicate that the present invention does not rely on a single growth-promoting component, but rather achieves its effect through the synergistic interaction of inositol, tetrahydropyrimidine, polyglutamic acid fermentation broth, lactopeptide organic water-soluble fertilizer, and biochar-attapulgite composite carrier and encapsulated slow-release structure. This synergistic effect improves the osmotic regulation, nutrient supply, and continuous release of active substances in seeds under salt-alkali stress, thereby significantly increasing the germination speed, uniformity, and cumulative germination level of tomato seeds.

[0144] Application Example 2: Investigating the seedling protection effect of slow-release granules under saline-alkali-drought stress conditions.

[0145] To further evaluate the effects of the compound biostimulant sustained-release granules prepared in this invention on the establishment and survival of tomato seedlings under continuous stress conditions, a salt-alkali-drought combined stress seedling survival experiment was conducted, building upon the salt-alkali stress germination experiment in Example 1. This experiment used tomato seedlings that had germinated under salt-alkali stress as the research subject, examining the survival of seedlings under subsequent drought stress conditions under different treatments, thereby evaluating the sustained promoting effect of the sustained-release granules of this invention on the early stress resistance of tomato seedlings after seed germination.

[0146] 1. Experimental Design:

[0147] Normal seedlings that germinated under saline-alkali stress conditions in each treatment of Application Example 1 were selected as the subjects of drought treatment. The criteria for determining normal seedlings were: the radicle broke through the seed coat and was not less than 2 mm in length; the cotyledons were unfolded or showed a normal unfolding trend; and the seedlings had no obvious rot, deformity, or mechanical damage. The number of normal seedlings before entering the drought experiment for each treatment was the "number of seedlings before drought treatment," excluding ungerminated seeds and deformed seedlings.

[0148] The experimental treatments were consistent with Application Example 1, including the treatment with the compound biostimulant sustained-release granules prepared in Examples 1-11, the treatments in Comparative Examples 1-14, and the blank control treatment. The blank control did not contain any sustained-release granules or exogenous stress-regulating materials and was cultured only under the same saline-alkali and drought stress conditions. The number of tomato seeds used, the initial saline-alkali stress conditions, the culture medium, environmental parameters (temperature, light, air humidity), and the germination stage culture time were all consistent with Application Example 1 to ensure the comparability of results between different treatments.

[0149] After the salt-alkali stress germination experiment in Application Example 1 was completed, the germinating and morphologically normal seedlings from each treatment, along with their culture medium, were transferred to the subsequent drought stress treatment. Before the drought treatment, the substrate moisture content of each treatment was uniformly adjusted to 60% of the field capacity to avoid affecting subsequent survival results due to initial moisture differences. Subsequently, watering was stopped, and the substrate moisture content was reduced to 20%-30% of the field capacity through self-heating evaporation, maintained for 14 days, thus keeping the seedlings under continuous water restriction. During the drought treatment, each treatment was cultured under the same environmental conditions, maintaining consistent temperature, light, air humidity, and culture time, and no other differentiating factors were introduced except for water stress.

[0150] During the drought stress treatment, the seedling growth status was observed daily, and wilting, lodging, drying, and death were recorded. After the drought treatment ended, the number of surviving seedlings in each treatment was counted. The criteria for seedling survival were: the base of the seedling stem was not completely dried out, the cotyledons or true leaves still retained some green color, and after a single watering with 5 mL of distilled water and continued cultivation for 24 hours, the seedling could recover its upright posture or maintain its ability to continue growing; if the seedling was completely dried out, the base of the stem was necrotic, the roots were browned and rotten, or it could not recover growth after watering, it was considered dead.

[0151] Seedling survival rate is calculated using the following formula: Seedling survival rate (%) = Number of seedlings surviving after drought treatment / Number of seedlings before drought treatment × 100%.

[0152] The number of seedlings before drought treatment refers to the number of normal seedlings formed after germination under saline-alkali stress in each treatment, and the number of surviving seedlings after drought treatment refers to the number of seedlings that still meet the survival criteria after drought stress treatment. By comparing the seedling survival rates of the examples, comparative examples, and blank controls, the seedling preservation effect of the compound biostimulant sustained-release granules of the present invention under drought stress conditions after germination under saline-alkali stress was evaluated.

[0153] To reduce random errors, all treatments used the same initial seeds, culture containers, saline-alkali stress conditions, and drought treatment duration as in Application Example 1. For statistical analysis, only plants that had successfully germinated and entered the seedling stage under saline-alkali stress were used as the baseline before drought treatment; ungerminated seeds were not included in the drought survival rate calculation. This design can distinguish between the "germination promotion effect" and the "post-drought seedling survival effect": Application Example 1 reflects the promoting effect of slow-release granules on seed germination under saline-alkali stress, while Application Example 2 further reflects its effect on maintaining the survival of germinating seedlings under drought stress.

[0154] 2. Results and Discussion:

[0155] The seedling survival effects of the fertilizer granules prepared in the examples and comparative examples are shown in Table 4.

[0156] Table 4

[0157]

[0158] The experimental results in Table 4 show that, under drought stress, the compound biostimulant slow-release granules prepared in each example all exhibited certain stress resistance and growth-promoting effects on tomato seedlings, significantly improving seedling survival rates after drought treatment. The seedling survival rates after drought in Examples 1-11 ranged from 70.6% to 94.7%, significantly higher than the 33.3% of the blank control and the 25.0%-60.0% of the comparative examples. Examples 3 and 9 showed the best performance, with seedling survival rates reaching 94.7% and 94.4%, respectively. The seedling survival rates in Examples 1, 4, 5, 10, and 11 were all above 88%, indicating that under suitable conditions of compound biostimulant component ratio, osmotic regulator concentration, and biochar-attapulgite composite carrier structure, the slow-release granules of this invention can effectively maintain the survival ability of tomato seedlings under drought stress.

[0159] Comparing the different embodiments, the seedling survival rates of Examples 2, 6, 7, and 8 were 77.8%, 81.3%, 70.6%, and 77.8%, respectively, which were lower than those of Examples 3 and 9. This indicates that when the concentration of functional components, carrier structural parameters, or coating conditions deviate from the preferred range, the buffering effect of the slow-release particles on drought stress will decrease. However, even so, Example 7, as the treatment with the lowest survival rate among the embodiments, still achieved a seedling survival rate of 70.6%, which was still significantly higher than all comparative examples and the blank control. This shows that the complete composite system of the present invention can still maintain a good drought resistance and growth promotion effect within a certain parameter perturbation range.

[0160] In contrast, the seedling survival rates of Comparative Examples 1-14 and the blank control were significantly lower. The survival rates of drought-exposed seedlings in Comparative Examples 1-14 ranged from 25.0% to 60.0%, all lower than those in the examples. Specifically, the seedling survival rate of Comparative Example 10 was only 25.0%, lower than the 33.3% of the blank control; the seedling survival rate of Comparative Example 12 was 36.4%, close to the blank control, indicating that when key structural units or preparation conditions deviate significantly from the suitable range, the resulting particles not only fail to provide stable drought protection but may even affect seedling establishment due to uneven release, structural instability, or insufficient local environmental regulation. The seedling survival rates of Comparative Examples 5 and 11 were 40.0% and 45.5%, respectively; the seedling survival rates of Comparative Examples 1, 4, 7, 8, 13, and 14 were 45.5%-50.0%; and the seedling survival rates of Comparative Examples 2, 3, 6, and 9 were 54.5%-60.0%. Although these were partially improved compared to the blank control, they were still significantly lower than those treated in the examples.

[0161] Specifically, Comparative Example 1, lacking inositol and tetrahydropyrimidine, lacked key osmotic regulators and stress buffering components, resulting in a seedling survival rate of only 50.0%. This indicates that these osmotic regulators play a crucial role in maintaining seedling cell water status and early physiological recovery under drought stress. Comparative Examples 2 and 3, lacking lactopeptide organic water-soluble fertilizer or polyglutamic acid fermentation broth, respectively, had seedling survival rates of 54.5% and 55.6%, indicating that the lack of corresponding organic active substances and microbial metabolites weakened the system's support for early seedling nutrient supply, rhizosphere regulation, and stress recovery. Comparative Examples 4 and 5, with carrier systems composed only of biochar or attapulgite, had seedling survival rates of 45.5% and 40.0%, respectively. This suggests that a single carrier cannot simultaneously achieve adsorption and water retention, pore regulation, and slow release of active components, leading to insufficient stability of the microenvironment surrounding seedlings under drought conditions.

[0162] Comparative Examples 6 and 7 showed seedling survival rates of 54.5% and 50.0% respectively due to increased liquid-to-solid ratio or shortened adsorption time. This indicates that unsuitable loading conditions affect the sufficiency and uniformity of adsorption and distribution of active components in the carrier, thereby weakening the sustained supply capacity of the slow-release particles under drought stress. In Comparative Examples 8-11, the composition or amount of binder deviated from the preferred range, resulting in seedling survival rates of 25.0%-50.0%, with Comparative Example 10 showing a survival rate of only 25.0%. This indicates that an unreasonable binder system affects particle strength, pore structure, and water diffusion processes, thus reducing the buffering effect of the particles on seedling drought stress. Comparative Example 12 showed a seedling survival rate of only 36.4% due to insufficient sodium alginate coating, indicating that an incomplete coating layer leads to a decrease in slow-release control capacity, making it difficult to maintain the continuous and stable release of active substances under drought stress. Comparative Examples 13 and 14 had a seedling survival rate of 50.0% due to the absence of key granulation or coating steps. This indicates that when a complete particle structure or stable slow-release system is not formed, the active ingredients are easily lost quickly, the rhizosphere regulation time is shortened, and the seedling survival level is significantly lower than that of the Examples.

[0163] The experimental results of Application Examples 1 and 2 show that the composite biostimulant slow-release granules provided by this invention can not only promote tomato seed germination under saline-alkali stress, but also improve seedling survival rate under subsequent drought stress. Moreover, the above effects are not produced by a single component, but by the combined action of inositol, tetrahydropyrimidine, polyglutamic acid fermentation broth, lactopeptide organic water-soluble fertilizer, biochar-attapulgite composite carrier, and the encapsulated slow-release structure. These components and structural units synergistically improve osmotic regulation, nutrient supply, water retention, and continuous release of active substances during seed germination and early seedling growth, resulting in the treatments in the examples exhibiting superior germination-promoting and stress-resistance-promoting effects compared to the comparative and blank controls under both saline-alkali and drought stress.

[0164] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed. Clearly, based on the foregoing teachings, those skilled in the art can make various changes and modifications to the invention. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize different exemplary embodiments of the invention, as well as corresponding selections and modifications. The scope of protection of the present invention should be determined by the claims and their equivalents.

Claims

1. A compound biostimulant sustained-release granule for plant stress resistance and growth promotion, characterized in that, The sustained-release particles comprise: a composite biostimulant system, a porous carrier, a binder, and a coating layer; The composite biostimulant system comprises a main ingredient and excipients, which are loaded as active ingredients on the surface and inside of a carrier; wherein, the main ingredient comprises polyglutamic acid fermentation broth and lactose peptide organic water-soluble fertilizer; the excipients are aqueous solutions containing inositol and tetrahydropyrimidine; based on the total mass of the composite biostimulant system, the mass fraction of the main ingredient is 94%-96%, and the mass fraction of the excipients is 4%-6%; The porous carrier is biochar and attapulgite, which serve as the particle framework and sustained-release carrier. The liquid-to-solid ratio of the composite biostimulant system and the porous carrier is (1-3) mL / g; The binder is chitosan and humic acid, which are used to mix and granulate the composite biostimulant system and the carrier to form a particulate matrix. The coating layer is a calcium alginate gel film formed on the surface of the particle matrix after sodium alginate solution is cross-linked and cured by CaCl2 solution. It is used to reduce the water penetration rate and delay the diffusion and release of active ingredients in the compound biostimulant system.

2. The compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in claim 1, characterized in that, In the main ingredients, the mass ratio of polyglutamic acid fermentation broth to lactose peptide organic water-soluble fertilizer is (1:9)-(3:7). The polyglutamic acid fermentation broth is a fermentation broth of Bacillus and its metabolites; The lactose peptide organic water-soluble fertilizer is a soluble peptide nutrient carrier. Its effective component indicators include: the mass ratio of N, P2O5 and K2O is (18-22):(8-12):(45-55), the free amino acid content is 70-80 g / L, the organic matter content is 190-210 g / L, and the organic acid content is 230-250 g / L.

3. The compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in claim 1, characterized in that, Based on the total mass of the excipients, the content of inositol is 20-250 mg / kg, the content of tetrahydropyrimidine is 10-110 mg / kg, and the mass ratio of inositol to tetrahydropyrimidine is 1:(0.4-0.6).

4. The compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in claim 1, characterized in that, The porous carrier has a particle size of 80-160 mesh; In the porous carrier, the mass ratio of biochar to attapulgite is 1:(0.4-1.2).

5. The compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in claim 1, characterized in that, The mass of the binder is 2%-10% of the total mass of the porous carrier and the composite biostimulant system; In the adhesive, the mass ratio of chitosan to humic acid is (2-4):

1.

6. The method for preparing the compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Crush and sieve biochar and attapulgite, mix them evenly, add deionized water to the resulting mixed powder to wet it, and obtain a pre-wetting carrier; (2) Add the composite biostimulant system to the pre-wetted carrier obtained in step (1) and perform impregnation and adsorption under stirring conditions so that the composite biostimulant system is uniformly loaded on the surface and pores of the porous carrier to obtain a mixture. (3) Add a binder to the mixture obtained in step (2), mix well, and then granulate using a disc granulator to obtain wet granules; (4) The wet particles are coated with sodium alginate solution, and then the coated wet particles are immersed in CaCl2 solution for cross-linking and curing. After curing, they are dried and sieved to obtain the slow-release particles.

7. The method for preparing the compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in claim 6, characterized in that, In step (1), the mass ratio of biochar to attapulgite is 1:(0.4-1.2), the solid-liquid ratio of the mixed powder to deionized water is (4-6) g:1 mL, and the wetting time is 10-20 min; In step (2), the liquid-to-solid ratio of the solid phase component in the composite biostimulant system and the pre-wetted carrier is (1-3) mL / g; the stirring speed for the stirring impregnation adsorption is 100-300 rpm, and the adsorption time is 6-12 h. In step (3), the mass of the binder is 2%-10% of the total mass of the porous carrier and the composite biostimulant system; the particle size of the obtained wet particles is 1.5-3.5 mm. In step (4), the sodium alginate solution has a mass fraction of 1%-5%, the amount of sodium alginate solution used is 3%-10% of the mass of wet particles, the CaCl2 solution has a mass fraction of 2%-3%, and the curing time is 30-40 min.

8. The application of the compound biostimulant sustained-release granules for plant stress resistance and growth promotion as described in any one of claims 1-5 in promoting crop growth under adverse conditions, characterized in that, The slow-release granules are used to promote crop germination, emergence, rooting, and seedling protection under drought, saline-alkali, or combined drought-saline-alkali adverse conditions.

9. The application as described in claim 8, characterized in that, The slow-release granules are used to improve the germination rate of crop seeds under salt stress and / or improve the survival rate of seedlings under drought stress.

10. The application as described in claim 8, characterized in that, The slow-release granules can be applied in the following ways: furrow application during sowing, hole application, fixed-point application at the root zone, basal application mixed with base fertilizer, supplemental application in the root zone during the seedling stage, or pre-application before adverse conditions.

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