Weeding granules based on astragalus sinicus and preparation method thereof

Abstract

The invention discloses weeding granules based on astragalus sinicus and a preparation method of the weeding granules. The preparation method comprises the following steps: (1) preparing astragalus sinicus leach liquor; (2) preparing an astragalus sinicus decomposition liquid; (3) preparing hydrogel; (4) preparing starch-based latex; and (5) preparing the weeding granules. Allelochemicals in the astragalus sinicus extract liquid and decomposition liquid are used for inhibiting germination and growth of weeds, the weeding granules have an obvious inhibiting effect on growth of the weeds, and the weeding granules do not contain chemical herbicide components, do not cause excessive burden to soil and are more natural and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the field of herbicides, and in particular to a herbicide granule based on astragalus membranaceus and a preparation method thereof. Background Art

[0002] Weeds are one of the important yield-limiting factors in agricultural production. Due to their biodiversity, weed problems have long occupied an important position in agricultural production. Weeds adapt to and occupy the remaining ecological niches in agricultural ecosystems, snatch physical living space, and compete with crops for growth. In order to solve the weed problem, a large amount of chemical herbicides are usually applied to inhibit the growth of weeds. Due to the evolutionary process of species, weeds have developed resistance to chemical herbicides, and herbicide resistance has become a new agricultural production problem. At the same time, excessive application of chemical herbicides pollutes the soil ecological environment and water resources, affects crop yield and quality, and has an adverse effect on human health. The demand for safe food production and the eco-friendly trend in weed management have forced scholars to create new solutions. People are increasingly in need of new herbicides with safer toxicological and environmental properties.

[0003] Natural compounds provide a wide range of new environmentally safe herbicides, the so-called "bioherbicides". Bioherbicides generally refer to products from organisms or their secondary metabolism that can suppress target weed populations without harming the environment. Among them, research on allelopathic effects is becoming more and more common in weed management in agricultural ecosystems. Allelopathic effects are a process in which a component or organism affects another component or organism by producing allelopathic substances. It is an environmentally friendly strategy to control weed germination and growth, improve crop productivity and reduce the use of chemical herbicides. Astragalus sinensis is one of the most important green fertilizers for increasing crop yields and preventing soil degradation. In addition, studies have shown that it is feasible to use astragalus sinensis to control the growth of weeds in the field. The allelopathic substances it contains have an inhibitory effect on weeds, and the inhibitory effect is related to the concentration of the substance. It is difficult to control the concentration of allelopathic substances by direct tillage, and the inhibitory effect is not good. At the same time, some allelopathic substances are easily soluble in water. When applied directly to the soil, they will be affected by external factors, resulting in the loss of active ingredients or decomposition failure, which limits their use in weed control. Therefore, measures need to be taken to fully utilize the active ingredients in astragalus sinensis.

[0004] Encapsulating allelopathic substances in nanocarriers can protect them from external factors, thereby improving the stability, lifespan and availability of allelopathic substances in soil. Among them, hydrogel is a material with water retention and sustained release capabilities, which is often used in soil improvement. Natural polymers have the advantages of degradability, non-toxicity and low cost, making them suitable candidate materials for natural-based polymer hydrogels. In particular, starch, as one of the most effective and cheap polysaccharides, has been widely used in the preparation of polymers such as hydrogels. Usually, starch mostly requires a certain amount of surfactants during use, but chemically synthesized surfactants pose potential hazards to the environment. Studies have shown that components with surfactant replacement effects can be extracted from natural plants. Summary of the invention

[0005] In view of the above problems in the prior art, the present invention provides a herbicide granule based on astragalus and a preparation method thereof, with the aim of developing a green and natural herbicide, the herbicide ingredients of which are green and environmentally friendly, do not contain chemical ingredients that may pollute the soil, and have a significant inhibitory effect on the germination and growth of weeds.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A herbicide granule based on astragalus and a preparation method thereof, wherein the preparation of the herbicide granule comprises the following steps: (1) Preparation of astragalus extract: Astragalus plants (without roots) were freeze-dried at −40-60°C and 90-110 Pa for 42-54 h, then crushed and sieved with a 200-mesh sieve. The sieved astragalus powder was soaked in deionized water and placed in a constant temperature shaker at 25-31°C and 150-250 rpm for 42-54 h. The mixed solution was initially filtered with filter paper and centrifuged at 10,000-14,000 rpm for 8-12 min. The supernatant was filtered with a 0.20-0.25 µm microporous membrane to obtain the astragalus extract. (2) Preparation of astragalus decomposition liquid: Mix the astragalus powder, fresh paddy soil and deionized water in step (1), put into a plastic bottle with an inner cover, place in a constant temperature shaker at 25-31° C. and 150-250 rpm for 7-20 days, filter the mixture with filter paper, centrifuge at 10000-14000 rpm for 8-12 min, and filter the supernatant with a 0.20-0.25 µm microporous membrane to obtain the astragalus decomposition liquid; (3) Preparation of hydrogel: suspend the attapulgite powder in deionized water, perform ultrasonic treatment for 10 to 20 minutes, pour it into a reaction bottle containing sodium alginate solution and stir it for 25 to 35 minutes, add methyl methacrylate (MMA), acrylic acid (AA, neutralized with 60% KOH), N,N-methylenebisacrylamide (MBA) and ammonium persulfate (APS) to the mixture in the reaction bottle in sequence, and stir vigorously at 70 to 90°C until a viscous gel is prepared, then the viscous gel is solidified in excess methanol and washed 3 to 5 times, and then dried in an oven at 55 to 65°C to constant weight; mix the astragalus extract of step (1) and the astragalus decomposition solution of step (2) in a certain proportion, and immerse the hydrogel in the mixed solution to swell it to form a uniform gel, dry the gel in an oven at 35 to 45°C overnight, grind it into powder, and sieve it with a 30 to 70 mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: adding the astragalus powder obtained in step (1) to deionized water, shaking at a speed of 150-250 rpm for 2-5 min in a shaking table at 25-31° C., and then ultrasonically treating at 28-32° C. for 1-3 h to obtain an astragalus dispersion, dispersing starch in deionized water, adding the astragalus dispersion, stirring for 8-12 min, and sequentially adding methyl methacrylate (MMA), butyl acrylate (BA), and ammonium persulfate (APS) solution to the mixture, stirring for 15-25 min, raising the reaction temperature to 80-90° C. and stirring at this temperature for 2-4 h, and finally cooling to 22-28° C. to obtain starch-based latex; (5) Preparation of herbicidal granules: The hydrogel prepared in step (3) is poured into a granulator, which is rotated at a speed of 50 to 70 rpm, and the contents of the drum are heated at 80 to 90° C. for about 15 to 25 min. While heating, the starch-based latex prepared in step (4) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0007] Preferably, in the preparation of the extract in step (1), the ratio of the mass (g) of the astragalus powder to the volume (ml) of deionized water is 1:(20-30).

[0008] Preferably, in the preparation of the decomposition solution in step (2), the mass ratio of fresh paddy soil, astragalus powder and deionized water is 1:(1-2):(25-35).

[0009] Preferably, in the hydrogel preparation process, the ratio of sodium alginate mass (g) to deionized water volume (ml) is (3~7):100; the mass ratio of deionized water to attapulgite powder is 40:(1~2); the ratio of N,N-methylenebisacrylamide mass (g), sodium alginate mass (g), attapulgite powder mass (mg), methyl methacrylate mass (g), ammonium persulfate mass (g) and acrylic acid volume (ml) is 1:(8~19):(133~267):(13~15):(1~3):(66~103); the ratio of the volume (ml) of the astragalus extract in step (1), the volume (ml) of the astragalus decomposition solution in step (2) and the mass (g) of the hydrogel material is 1:(1~3):(0.04~0.16).

[0010] Preferably, in the preparation process of starch-based latex, the ratio of starch mass (g) to deionized water volume (ml) is (3~8):100, the ratio of astragalus powder mass (g) to deionized water volume (ml) is (1~3):2; the ratio of methyl methacrylate volume (ml), astragalus powder mass (g), starch mass (g), ammonium persulfate mass (g) and butyl acrylate volume (ml) is 1:(0.3~1):(0.2~0.6):(0.006~0.02):(0.5~1.5), and the ratio of ammonium persulfate mass (g) to deionized water volume (ml) in the ammonium persulfate solution is (1~3):200.

[0011] Preferably, when preparing the herbicidal granules, the mass ratio of the hydrogel to the starch-based latex is 3:(2-4).

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The herbicidal granules prepared by the present invention contain allelopathic substances in the added astragalus extract and decomposition liquid, which affect the activity of weed plants and reduce weed photosynthesis. The allelopathic effect of the extract and the decomposition liquid can reduce the weed germination rate, inhibit weed growth, and effectively solve the problem of weeds in farmland. The herbicidal granules prepared by the present invention have high weed control efficiency, are safe and environmentally friendly, and will not pollute the soil ecological environment and water resources.

[0013] 2. The present invention extracts the allelopathic substances in Astragalus membranaceus and adsorbs them into hydrogel, which can protect them from external factors, make them not easily degraded by soil microorganisms, slow down the dissolution rate of allelopathic substances, improve the stability and effectiveness of allelopathic substances in the soil, and prolong their action time. Compared with chemically synthesized polymers, the polysaccharide hydrogel is degradable and will not burden the soil.

[0014] 3. In the process of preparing starch-based latex of the present invention, the astragalus dispersion is used as a surfactant to increase the dispersibility of starch in deionized water. The source of the material is green and environmentally friendly and will not cause pollution to the soil and groundwater. At the same time, the hydrogel is modified with attapulgite powder to improve the water absorption of the hydrogel, so that more astragalus extract and decomposition liquid can be absorbed.

[0015] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] none DETAILED DESCRIPTION The present invention is specifically described below by way of examples, which are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. It should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0017] Example 1 The preparation steps of the herbicidal granules based on Astragalus membranaceus: (1) Preparation of astragalus extract: Astragalus plants (without roots) were freeze-dried at −50°C and 100 Pa for 48 h, then crushed and sieved with a 200-mesh sieve. 20 g of the sieved astragalus powder was weighed and soaked in 500 ml of deionized water. The mixture was placed in a constant temperature shaker at 28°C and 200 rpm for 48 h. The mixed solution was initially filtered with filter paper and centrifuged at 12,000 rpm for 10 min. The supernatant was filtered with a 0.22 µm microporous membrane to obtain the astragalus extract. (2) Preparation of astragalus decomposition liquid: 10 g of astragalus powder prepared in step (1), 10 g of fresh paddy soil and 300 g of deionized water were mixed and placed in a plastic bottle with an inner cover, and placed in a constant temperature shaker at 28° C. and 200 rpm for 15 days. The mixture was filtered with filter paper and centrifuged at 12,000 rpm for 10 min. The supernatant was filtered with a 0.22 µm microporous membrane to obtain astragalus decomposition liquid. (3) Preparation of hydrogel: 5 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution. 75 mg of attapulgite powder was suspended in 2 g of deionized water, subjected to ultrasonic treatment for 15 min, poured into a reaction bottle containing the sodium alginate solution and stirred for 30 min. 5.3 g of methyl methacrylate (MMA), 31 ml of acrylic acid (AA, neutralized with 60% KOH), 0.375 g of N,N-methylenebisacrylamide (MBA) and 0. 75g of ammonium persulfate (APS) was added, and the mixture was stirred vigorously at 80°C until a viscous gel was prepared. The viscous gel was then solidified in an excess of methanol and washed 4 times, and then dried in a 60°C oven to constant weight; 100ml of the astragalus extract of step (1) and 200ml of the astragalus decomposition solution of step (2) were mixed, and 9g of the hydrogel was immersed in 300ml of the mixed solution to swell it to form a uniform gel. The gel was dried in an oven at 40°C overnight, ground into powder, and sieved with a 50-mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: 10 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 200 rpm for 3 min in a shaking table at 28° C., and then ultrasonically treated at 30° C. for 2 h to obtain an astragalus dispersion. 5 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 10 min. 0.2 g of ammonium persulfate (APS) was dissolved in 20 ml of deionized water to obtain an ammonium persulfate (APS) solution. 15 ml of methyl methacrylate (MMA), 15 ml of butyl acrylate (BA), and the ammonium persulfate (APS) solution were sequentially added to the mixture, and stirred for 20 min. The reaction temperature was then increased to 85° C. and stirred at this temperature for 3 h. Finally, the mixture was cooled to 25° C. to obtain a starch-based latex. (5) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (3) is poured into a granulator, which is rotated at 60 rpm. The contents of the drum are heated at 85° C. for about 20 min. While heating, 10 g of the starch-based latex prepared in step (4) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0018] Example 2 The preparation steps of the herbicidal granules based on Astragalus membranaceus: (1) Preparation of astragalus extract: Astragalus plants (without roots) were freeze-dried at −40°C and 90 Pa for 42 h, then crushed and sieved with a 200-mesh sieve. 20 g of the sieved astragalus powder was soaked in 600 ml of deionized water and placed in a constant temperature shaker at 25°C and 150 rpm for 42 h. The mixed solution was initially filtered with filter paper and centrifuged at 10,000 rpm for 8 min. The supernatant was filtered with a 0.20 µm microporous membrane to obtain the astragalus extract. (2) Preparation of astragalus decomposition liquid: 10 g of astragalus powder prepared in step (1), 10 g of fresh paddy soil and 350 g of deionized water were mixed, placed in a plastic bottle with an inner cover, and placed in a constant temperature shaker at 25° C. and 150 rpm for 7 days. The mixture was filtered with filter paper, centrifuged at 10,000 rpm for 8 min, and the supernatant was filtered with a 0.20 µm microporous membrane to obtain astragalus decomposition liquid; (3) Preparation of hydrogel: 3 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution. 50 mg of attapulgite powder was suspended in 2 g of deionized water and subjected to ultrasonic treatment for 10 min. The suspension was poured into a reaction bottle containing the sodium alginate solution and stirred for 25 min. 5 g of MMA, 25 ml of AA (neutralized with 60% KOH), 0.375 g of MBA and 0.375 g of APS were added to the mixture in the reaction bottle in sequence and stirred at 70 °C. ℃, stirring vigorously until a viscous gel is prepared, then the viscous gel is solidified in excess methanol and washed 3 times, and then dried in a 55℃ oven to constant weight; 100ml of the astragalus extract of step (1) and 100ml of the astragalus decomposition solution of step (2) are mixed, and 4g of the hydrogel is immersed in 200ml of the mixed solution to swell it to form a uniform gel, the gel is dried in an oven at 35℃ overnight, ground into powder, and sieved with a 30-mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: 5 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 150 rpm for 2 min in a shaking table at 25° C., and then ultrasonically treated at 28° C. for 1 h to obtain an astragalus dispersion. 3 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 8 min. 0.1 g of APS was dissolved in 20 ml of deionized water to obtain an APS solution. 15 ml of MMA, 7.5 ml of BA, and the APS solution were sequentially added to the mixture, and stirred for 15 min. The reaction temperature was then increased to 80° C. and stirred at this temperature for 2 h. Finally, the mixture was cooled to 22° C. to obtain a starch-based latex. (5) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (3) was poured into a granulator, which was rotated at 50 rpm. The contents of the drum were heated at 80° C. for about 15 min. While heating, 6.67 g of the starch-based latex prepared in step (4) was sprayed on the surface of the hydrogel until a uniform coating was formed on the hydrogel and the water was completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0019] Example 3 The preparation steps of the herbicidal granules based on Astragalus membranaceus: (1) Preparation of astragalus extract: Astragalus plants (without roots) were freeze-dried at −60°C and 110 Pa for 54 h, then crushed and sieved with a 200-mesh sieve. 20 g of the sieved astragalus powder was soaked in 400 ml of deionized water and placed in a constant temperature shaker at 31°C and 250 rpm for 54 h. The mixed solution was initially filtered with filter paper and centrifuged at 14,000 rpm for 12 min. The supernatant was filtered with a 0.25 µm microporous membrane to obtain the astragalus extract. (2) Preparation of astragalus decomposition liquid: 20 g of astragalus powder prepared in step (1), 10 g of fresh paddy soil and 250 g of deionized water were mixed, placed in a plastic bottle with an inner cover, and placed in a constant temperature shaker at 31° C. and 250 rpm for 20 days. The mixture was filtered with filter paper, centrifuged at 14,000 rpm for 12 min, and the supernatant was filtered with a 0.25 µm microporous membrane to obtain astragalus decomposition liquid; (3) Preparation of hydrogel: 7 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution. 100 mg of attapulgite powder was suspended in 2 g of deionized water and subjected to ultrasonic treatment for 20 min. The suspension was poured into a reaction bottle containing the sodium alginate solution and stirred for 35 min. 5.5 g of MMA, 38.5 ml of AA (neutralized with 60% KOH), 0.375 g of MBA and 1.125 g of APS were added to the mixture in the reaction bottle in sequence. Stir vigorously at 90° C. until a viscous gel is prepared, then the viscous gel is solidified in excess methanol and washed 5 times, and then dried in a 65° C. oven to constant weight; 100 ml of the astragalus extract of step (1) and 300 ml of the astragalus decomposition solution of step (2) are mixed, and 16 g of the hydrogel is immersed in 400 ml of the mixed solution to swell it to form a uniform gel, the gel is dried in an oven at 45° C. overnight, ground into powder, and sieved with a 70-mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: 15 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 250 rpm for 5 min in a shaking table at 31° C., and then ultrasonically treated at 32° C. for 3 h to obtain an astragalus dispersion. 8 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 12 min. 0.3 g of APS was dissolved in 20 ml of deionized water to obtain an APS solution. 15 ml of MMA, 22.5 ml of BA, and the APS solution were sequentially added to the mixture, and stirred for 25 min. The reaction temperature was then increased to 90° C. and stirred at this temperature for 4 h. Finally, the mixture was cooled to 28° C. to obtain a starch-based latex. (5) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (3) was poured into a granulator, which was rotated at 70 rpm. The contents of the drum were heated at 90° C. for about 25 min. While heating, 13.34 g of the starch-based latex prepared in step (4) was sprayed on the surface of the hydrogel until a uniform coating was formed on the hydrogel and the water was completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0020] Comparative Example 1 A preparation step of a hydrogel without astragalus: (1) Preparation of Astragalus sinensis powder: Astragalus sinensis plants (without roots) were freeze-dried at −50°C and 100 Pa for 48 h in vacuum, then crushed and sieved with a 200-mesh sieve.

[0021] (2) Preparation of hydrogel: 5 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution. 75 mg of attapulgite powder was suspended in 2 g of deionized water, subjected to ultrasonic treatment for 15 min, poured into a reaction bottle containing the sodium alginate solution and stirred for 30 min. 5.3 g of MMA, 31 ml of AA (neutralized with 60% KOH), 0.375 g of MBA and 0.75 g of APS were added to the mixture in the reaction bottle in sequence, and then vigorously stirred at 80 °C until a viscous gel was prepared. The viscous gel was then solidified in excess methanol and washed 4 times, and then dried in an oven at 60 °C to constant weight. (3) Preparation of starch-based latex: 10 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 200 rpm for 3 min in a shaking table at 28° C., and then ultrasonically treated at 30° C. for 2 h to obtain an astragalus dispersion. 5 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 10 min. 0.2 g of ammonium persulfate (APS) was dissolved in 20 ml of deionized water to obtain an ammonium persulfate (APS) solution. 15 ml of methyl methacrylate (MMA), 15 ml of butyl acrylate (BA), and the ammonium persulfate (APS) solution were added to the mixture in sequence. After stirring for 20 min, the reaction temperature was increased to 85° C. and stirred at this temperature for 3 h. Finally, the mixture was cooled to 25° C. to obtain a starch-based latex. (4) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (2) is poured into a granulator, which is rotated at 60 rpm. The contents of the drum are heated at 85° C. for about 20 min. While heating, 10 g of the starch-based latex prepared in step (3) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0022] Comparative Example 2 A preparation process of herbicidal granules without astragalus extract: (1) Preparation of Astragalus sinensis powder: Astragalus sinensis plants (without roots) were freeze-dried at −50°C and 100 Pa for 48 h in vacuum, then crushed and sieved with a 200-mesh sieve.

[0023] (2) Preparation of Astragalus membranaceus decomposition liquid: Same as Example (1).

[0024] (3) Preparation of hydrogel: 5 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution; 75 mg of attapulgite powder was suspended in 2 g of deionized water, subjected to ultrasonic treatment for 15 min, poured into a reaction bottle containing the sodium alginate solution and stirred for 30 min, 5.3 g of MMA, 31 ml of AA (neutralized with 60% KOH), 0.375 g of MBA and 0.75 g of APS were added to the mixture in the reaction bottle in sequence, and then stirred vigorously at 80° C. until a viscous gel was prepared. The viscous gel was then solidified in excess methanol and washed 4 times, and then dried in an oven at 60° C. to constant weight; 9 g of the hydrogel was immersed in 300 ml of the astragalus decomposition solution of step (2) to swell it and form a uniform gel. The gel was dried in an oven at 40° C. overnight, ground into powder, and sieved with a 50-mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: 10 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 200 rpm for 3 min in a shaking table at 28° C., and then ultrasonically treated at 30° C. for 2 h to obtain an astragalus dispersion. 5 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 10 min. 0.2 g of ammonium persulfate (APS) was dissolved in 20 ml of deionized water to obtain an ammonium persulfate (APS) solution. 15 ml of methyl methacrylate (MMA), 15 ml of butyl acrylate (BA), and the ammonium persulfate (APS) solution were sequentially added to the mixture, and stirred for 20 min. The reaction temperature was then increased to 85° C. and stirred at this temperature for 3 h. Finally, the mixture was cooled to 25° C. to obtain a starch-based latex. (5) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (3) is poured into a granulator, which is rotated at 60 rpm. The contents of the drum are heated at 85° C. for about 20 min. While heating, 10 g of the starch-based latex prepared in step (4) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0025] Comparative Example 3 The preparation steps of a herbicide granule without astragalus decomposition liquid: (1) Preparation of Chinese astragalus extract: Same as Example (1).

[0026] (2) Preparation of hydrogel: 5 g of sodium alginate was dissolved in 100 ml of deionized water using a mechanical stirrer to obtain a sodium alginate solution; 75 mg of attapulgite powder was suspended in 2 g of deionized water, subjected to ultrasonic treatment for 15 min, poured into a reaction bottle containing the sodium alginate solution and stirred for 30 min, 5.3 g of MMA, 31 ml of AA (neutralized with 60% KOH), 0.375 g of MBA and 0.75 g of APS were added to the mixture in the reaction bottle in sequence, and then stirred vigorously at 80° C. until a viscous gel was prepared. The viscous gel was then solidified in excess methanol and washed 4 times, and then dried in an oven at 60° C. to constant weight; 9 g of the hydrogel was immersed in 300 ml of the astragalus extract of step (1) to swell it and form a uniform gel. The gel was dried in an oven at 40° C. overnight, ground into powder, and sieved with a 50-mesh sieve to obtain a hydrogel; (3) Preparation of starch-based latex: 10 g of the astragalus powder obtained in step (1) was added to 10 ml of deionized water, and the mixture was shaken at 200 rpm for 3 min in a shaking table at 28° C., and then ultrasonically treated at 30° C. for 2 h to obtain an astragalus dispersion. 5 g of starch was dispersed in 100 ml of deionized water, and the astragalus dispersion was added thereto, and stirred for 10 min. 0.2 g of ammonium persulfate (APS) was dissolved in 20 ml of deionized water to obtain an ammonium persulfate (APS) solution. 15 ml of methyl methacrylate (MMA), 15 ml of butyl acrylate (BA), and the ammonium persulfate (APS) solution were added to the mixture in sequence. After stirring for 20 min, the reaction temperature was increased to 85° C. and stirred at this temperature for 3 h. Finally, the mixture was cooled to 25° C. to obtain a starch-based latex. (4) Preparation of herbicidal granules: 10 g of the hydrogel prepared in step (2) is poured into a granulator, which is rotated at 60 rpm. The contents of the drum are heated at 85° C. for about 20 min. While heating, 10 g of the starch-based latex prepared in step (3) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

[0027] Comparative Example 4 A herbicide granule based on astragalus, wherein no attapulgite powder is added during the preparation of the hydrogel, and the remaining steps are the same as those in Example (1).

[0028] Comparative Example 5 The preparation steps of a herbicide based on anhydrous gel and starch-based coating of astragalus: (1) Preparation of Chinese astragalus extract: Same as Example (1).

[0029] (2) Preparation of Astragalus membranaceus decomposition liquid: Same as Example (1).

[0030] (3) Mix the astragalus extract and decomposition solution in a ratio of 1:2.

[0031] Comparative Example 6 A herbicide, the herbicide is 10% glyphosate aqueous solution.

[0032] Experimental methods The embodiments and comparative examples were tested, wherein the testing methods for the germination rate of weeds and corn, plant height and fresh weight determination, soil aggregates, etc. are as follows: Germination rate of weeds and corn: Selected goosegrass, barnyard grass, purslane, goosegrass as test weeds, respectively, put 20g of the herbicides prepared in Examples 1-3 and Comparative Examples 1-6 into 500ml of deionized water, let stand for 30min, stir evenly and take 100ml for standby, soak each weed seed for 24h, set up a blank control group, treat the seeds with deionized water, then take 50 seeds each and inoculate them into a culture dish, set up 5 repeated experiments for each treatment, and place the inoculated culture dish in an artificial climate incubator at a temperature of 26°C, a relative humidity of 75%, and a light-dark cycle of 12h / 12h. Supplement water appropriately, record the number of germinations every day, take the appearance of radicle as the index of germination, stop recording when the germination rate remains unchanged for 3 days, calculate the germination rate, germination rate (%) = (number of germinated seeds / number of test seeds) × 100. The test method of corn germination rate is the same as above.

[0033] Plant height and fresh weight determination of weeds and corn: Each weed seed was soaked in clean water and inoculated into a culture dish. The culture conditions were the same as above. After germination, 50 seeds of each weed seed were transplanted into 2 kg of dry nutrient soil for planting. 20 g of herbicides prepared in Examples 1-3 and Comparative Examples 1-6 were respectively put into 300 ml of deionized water and poured on the surface of the nutrient soil. A blank control group was also set up and poured with 300 ml of deionized water. Five repeated experiments were set up for each treatment. The average temperature during the test was 24°C and the relative humidity was 85%. After 12 days of cultivation, 10 uniformly grown seedlings were selected from each group to determine the plant height and fresh weight. In addition, one more experimental group of Example 1 and Comparative Example 5 was set up to extract representative weeds on the 1st, 3rd, 6th, 9th and 12th days of cultivation to determine the plant height and fresh weight. The test method for corn is the same as above.

[0034] Wet screening of soil aggregates: Take out a portion (500.0 g) of the nutrient soil from which corn was planted by quartering, sieve out the corn roots in the soil, and pass it through a dry sieve set (5 mm, 2 mm, 1 mm, 0.5 mm and 0.25 mm). The sieving time is 15 min, weigh 100 g of aggregates of each dry sieve particle size, and place them on the top layer of the wet sieve set (5 mm, 2 mm, 1 mm, 0.5 mm and 0.25 mm), adjust the height of the water level in the barrel so that when the set of sieves moves to the highest position, the aggregates in the top layer of the sieve are just submerged below the water surface, soak for 5 min, oscillate at a frequency of 330 times / min for 20 min, collect the water-stable aggregates on each layer of the sieve after the screening is completed, dry at 65°C to constant weight, and weigh them.

[0035] Equilibrium water absorption rate: Weigh 5 g of the hydrogel sample synthesized in step (3) of Examples 1 to 3 and Comparative Example 4 without soaking in the astragalus extract and decomposition solution, and soak it in 3000 ml of deionized water at 25°C until equilibrium swelling occurs. Filter the swollen sample to remove excess deionized water, and then weigh it to obtain the equilibrium water absorption rate (Q eq ,gg -1 ) From the equation Q eq =(w 2 -w 1 ) / w 1 calculate.

[0036] The test results are as follows: Table 1, Table 2, and Table 3 are the test results of weed germination rate, plant height, and fresh weight of Examples 1 to 3 and Comparative Examples 1 to 6, respectively. The results show that the weed germination rate, plant height, and fresh weight of Examples 1 to 3 are significantly lower than those of Comparative Examples 1 to 4 and the blank control group, and slightly higher than Comparative Example 6, indicating that the herbicidal granules prepared by the present invention have an obvious effect of inhibiting the germination and subsequent growth of weed seeds. The germination rate, plant height, and fresh weight of weeds in Comparative Example 1 are not much different from those in the blank control group, and are significantly higher than those in other experimental groups, indicating that the hydrogel and starch-based latex without astragalus have no effect on weed germination, and the effective ingredients in the herbicidal granules of the present invention are mainly astragalus extract and decomposition liquid. Compared with Comparative Examples 2 to 3, the germination rate of weed seeds in Examples 1 to 3 is lower, and the plant height and fresh weight of weeds are smaller, which may be because there is a certain synergistic effect between the astragalus decomposition liquid and the extract, which improves the inhibitory effect of the herbicidal granules of the embodiments on weed germination and growth. The weed seed germination rate, plant height and fresh weight of the comparative example 4 are higher than those of the examples 1 to 3, indicating that the addition of the porous material in the preparation of the hydrogels of the examples 1 to 3 improves the water absorption performance of the hydrogels, increases the content of the astragalus extract and the decomposition liquid in the herbicidal granules, increases the content of the active ingredient in the herbicidal granules, and enhances the inhibitory effect of the herbicidal granules on weeds. The weed germination rate of the comparative example 5 is significantly lower than that of the other groups except the comparative example 6, indicating that the astragalus extract and the decomposition liquid have a significant inhibitory effect on the germination of weeds. The plant height and fresh weight of the comparative example 5 are higher than those of the examples 1 to 3, which may be because the active ingredients in the herbicide of the comparative example 5 are not protected by the hydrogel and the starch-based latex, and are decomposed by microorganisms in the soil in the later stage, and the inhibitory effect on the growth of weeds is reduced. Therefore, the astragalus-based herbicidal granules prepared by the present invention have a significant inhibitory effect on the germination and growth of weeds.

[0037] Table 1: Weed germination rates of Examples 1 to 3 and Comparative Examples 1 to 6 Table 2: Weed heights of Examples 1 to 3 and Comparative Examples 1 to 6 Table 3: Fresh weight of weeds in Examples 1 to 3 and Comparative Examples 1 to 6 Table 4 shows the germination rate, plant height and fresh weight of corn in Examples 1 to 3 and Comparative Examples 1 to 6. The results show that the addition of the herbicide in Comparative Example 6 has a significant adverse effect on the growth of corn, while the germination rate, plant height and fresh weight of the corn in Examples 1 to 3 are not much different from those in the blank control group, indicating that the herbicidal granules prepared by the present invention have no toxic effect on corn and do not affect the germination and growth of corn seeds. In addition, the germination rate of corn seeds in Comparative Example 5 is significantly lower than that of other groups except Comparative Example 6, which may be due to the direct application of the astragalus extract and decomposition liquid, the sustained release effect of the absence of hydrogel and starch coating, and the high concentration of astragalus inhibits the germination and subsequent growth of corn seeds to a certain extent. By observing the data of Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the growth of corn in Comparative Example 1 is slightly poor, and the low concentration of astragalus extract and decomposition liquid may have a certain promoting effect on the growth and development of corn seeds. Therefore, compared with the lethal herbicides such as glyphosate, the herbicidal granules based on Astragalus prepared by the present invention are safer and more environmentally friendly and will not affect the growth and development of crops such as corn.

[0038] Table 4: Germination rate, plant height and fresh weight of corn in Examples 1 to 3 and Comparative Examples 1 to 6 Table 5 shows the changes in plant height and fresh weight of weeds after the herbicides prepared in Example 1 and Comparative Example 5 were applied. By comparing the data in Table 5, it can be seen that on the first day, the growth conditions of Example 1 and Comparative Example 5 were not much different. The input concentration of Comparative Example 5 was high, and the inhibition effect was generally slightly better than that of Example 1. After the sixth day, the plant height and fresh weight of the weeds in Example 1 began to be lower than those in Comparative Example 5. On the twelfth day, there was a significant difference in the growth of the two groups of weeds. The growth condition of the weeds in Comparative Example 5 was better than that in Example 1, indicating that after the astragalus extract and the decomposition liquid were encapsulated in the hydrogel, the long-term plant height and fresh weight of the weeds were more obvious, and the growth of the weeds was significantly inhibited. This is because the hydrogel protects the allelopathic substances from being decomposed by microorganisms in the soil, prolonging the action time of the allelopathic substances. Comparative Example 5 directly applied the astragalus extract and the decomposition liquid, and the action time was short. After the allelopathic substances were decomposed in the early stage, the weeds lost inhibition and resumed normal growth.

[0039] Table 5: Changes in plant height and fresh weight of weeds in Example 1 and Comparative Example 5 over time Table 6 shows the average weight diameter of soil after application of Examples 1 to 3 and Comparative Examples 1 to 6. The average weight diameter (MWD) of soil is an important parameter for measuring the stability of soil aggregates. It reflects the size and distribution of aggregates in the soil. Soil with good aggregation has appropriate water permeability, effective water content, air permeability, easy tillage and erosion resistance, which is more conducive to the growth of crops. From the data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 6, it can be seen that the MWD of Examples 1 to 3 is significantly higher than that of other test groups, indicating that the herbicidal granules prepared by the present invention increase the stability of soil aggregates to a certain extent. This may be due to the role played by the organic acids in the astragalus extract and decomposition liquid and the starch in the starch-based latex. The phenolic acid in the organic acid promotes the reproduction of fungi in the soil and can also prevent the dispersion of soil particles in the soil environment with low fungal activity; the starch-based latex contains carbohydrates, which are fermented and decomposed into humus in the soil. As the internal particles of the aggregates, they work together with the phenolic acid to increase the cohesion of the soil aggregates. The average weight diameter of the soil in Comparative Example 2 is significantly greater than that in Comparative Example 3, indicating that the soil aggregate stability in Comparative Example 2 is better, which may be due to the fact that the organic acid content in the decomposition solution of Astragalus sinensis is higher than that in the extract. Therefore, the astragalus sinensis-based herbicidal granules prepared in the present invention are beneficial to improving the stability of soil aggregates.

[0040] Table 6: Average weight diameter of soil after application of Examples 1 to 3 and Comparative Examples 1 to 6 Table 7 shows the equilibrium water absorption rate of the hydrogels of Examples 1 to 3 and Comparative Example 4. By comparing the data of Examples 1 to 3 and Comparative Example 4, it can be seen that after adding the porous material attapulgite powder, the water absorption performance of the hydrogel is significantly increased, and the equilibrium water absorption rate is significantly higher than the equilibrium water absorption rate of Comparative Example 4.

[0041] Table 7: Equilibrium water absorption of hydrogels in Examples 1 to 3 and Comparative Example 4 The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A herbicide granule based on astragalus and a preparation method thereof, characterized in that: The following steps are involved: (1) Preparation of astragalus extract: Astragalus plants (without roots) were freeze-dried at −40-60°C and 90-110 Pa for 42-54 h, then crushed and sieved with a 200-mesh sieve. The sieved astragalus powder was soaked in deionized water and placed in a constant temperature shaker at 25-31°C and 150-250 rpm for 42-54 h. The mixed solution was initially filtered with filter paper and centrifuged at 10,000-14,000 rpm for 8-12 min. The supernatant was filtered with a 0.20-0.25 µm microporous membrane to obtain the astragalus extract. (2) Preparation of astragalus decomposition liquid: Mix the astragalus powder, fresh paddy soil and deionized water in step (1), put into a plastic bottle with an inner cover, place in a constant temperature shaker at 25-31° C. and 150-250 rpm for 7-20 days, filter the mixture with filter paper, centrifuge at 10000-14000 rpm for 8-12 min, and filter the supernatant with a 0.20-0.25 µm microporous membrane to obtain the astragalus decomposition liquid; (3) Preparation of hydrogel: suspend the attapulgite powder in deionized water, perform ultrasonic treatment for 10 to 20 minutes, pour it into a reaction bottle containing sodium alginate solution and stir it for 25 to 35 minutes, add methyl methacrylate (MMA), acrylic acid (AA, neutralized with 60% KOH), N,N-methylenebisacrylamide (MBA) and ammonium persulfate (APS) to the mixture in the reaction bottle in sequence, and stir vigorously at 70 to 90°C until a viscous gel is prepared, then the viscous gel is solidified in excess methanol and washed 3 to 5 times, and then dried in an oven at 55 to 65°C to constant weight; mix the astragalus extract of step (1) and the astragalus decomposition solution of step (2) in a certain proportion, and immerse the hydrogel in the mixed solution to swell it to form a uniform gel, dry the gel in an oven at 35 to 45°C overnight, grind it into powder, and sieve it with a 30 to 70 mesh sieve to obtain a hydrogel; (4) Preparation of starch-based latex: adding the astragalus powder obtained in step (1) to deionized water, shaking at a speed of 150-250 rpm for 2-5 min in a shaking table at 25-31° C., then ultrasonically treating at 28-32° C. for 1-3 h to obtain an astragalus dispersion, dispersing starch in deionized water, adding the astragalus dispersion, stirring for 8-12 min, adding methyl methacrylate (MMA), butyl acrylate (BA), and ammonium persulfate (APS) solution to the mixture in sequence, stirring for 15-25 min, raising the reaction temperature to 80-90° C. and stirring at this temperature for 2-4 h, and finally cooling to 22-28° C. to obtain starch-based latex; (5) Preparation of herbicidal granules: The hydrogel prepared in step (3) is poured into a granulator, which is rotated at a speed of 50 to 70 rpm, and the contents of the drum are heated at 80 to 90° C. for about 15 to 25 min. While heating, the starch-based latex prepared in step (4) is sprayed on the surface of the hydrogel until a uniform coating is formed on the hydrogel and the water is completely evaporated, thereby obtaining herbicidal granules with a diameter of 2 to 4 mm.

2. The herbicidal granules based on astragalus and the preparation method thereof according to claim 1, characterized in that: In the preparation of the extract in step (1), the mass ratio of astragalus powder to deionized water is 1:(20-30).

3. The herbicidal granules based on astragalus and the preparation method thereof according to claim 1, characterized in that: In the preparation of the decomposition solution in step (2), the mass ratio of fresh paddy soil, astragalus powder and deionized water is 1:(1-2):(25-35).

4. The herbicidal granules based on astragalus and the preparation method thereof according to claim 1, characterized in that: During the preparation of the hydrogel, the ratio of the mass (g) of sodium alginate to the volume (ml) of deionized water is (3-7):100; the mass ratio of deionized water to attapulgite powder is 40:(1-2); the ratio of the mass (g) of N,N-methylenebisacrylamide, the mass (g) of sodium alginate, the mass (mg) of attapulgite powder, the mass (g) of methyl methacrylate, the mass (g) of ammonium persulfate and the volume (ml) of acrylic acid is 1:(8-19):(133-267):(13-15):(1-3):(66-103); the ratio of the volume (ml) of the extract in step (1), the volume (ml) of the decomposition solution in step (2) and the mass (g) of the hydrogel material is 1:(1-3):(0.04-0.16).

5. The herbicidal granules based on astragalus and the preparation method thereof according to claim 1, characterized in that: In the preparation process of starch-based latex, the ratio of starch mass (g) to deionized water volume (ml) is (3~8):100, the ratio of astragalus powder mass (g) to deionized water volume (ml) is (1~3):2; the ratio of methyl methacrylate volume (ml), astragalus powder mass (g), starch mass (g), ammonium persulfate mass (g) and butyl acrylate volume (ml) is 1:(0.3~1):(0.2~0.6):(0.006~0.02):(0.5~1.5), and the ratio of ammonium persulfate mass (g) to deionized water volume (ml) in the ammonium persulfate solution is (1~3):

200.

6. The herbicidal granules based on Astragalus sinensis and the preparation method thereof according to claim 1, characterized in that: When preparing the herbicide granules, the mass ratio of the hydrogel to the starch-based latex is 3:(2-4).

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