Alginic acid type multifunctional long-acting soil conditioner as well as preparation method and application thereof

Abstract

The invention relates to the technical field of land improvement, in particular to an alginic acid type multifunctional long-acting soil conditioner and a preparation method and application of the alginic acid type multifunctional long-acting soil conditioner. The core particle layer comprises an organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and an adhesive, and the slow release layer comprises clay minerals and alginate; the mass ratio of the clay mineral to the alginate to the organic material to the calcium magnesium polyphosphate to the nano silicon to the magnesium hydride to the ammonium borate to the rhamnose to the binder is controlled within a certain range. The soil conditioner provided by the invention is good in slow release performance, can release effective components durably and slowly, and has multiple effects of improving soil quality, providing nutrition, promoting crop growth, improving resistance and the like; the problems of soil acidification, heavy metal pollution, micro-plastic pollution, pesticide pollution, antibiotic pollution and the like in agricultural production can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of land improvement, and in particular to an alginate-based multifunctional long-acting soil conditioner and a preparation method and application thereof. Background Art

[0002] The quality of cultivated land is related to national food security and the people's livelihood. In recent years, with the acceleration of industrialization, the intensification of agricultural production and the advancement of urbanization, a large number of agricultural chemical inputs have been used, and a variety of harmful substances have been continuously input, which has caused a series of problems such as soil quality degradation and ecosystem dysfunction, seriously restricting the comprehensive production capacity of cultivated land, and thus affecting food safety and human health. Soil degradation and pollution have become important global environmental issues. Soil ecological restoration and sustainable utilization are of great significance to the realization of green and sustainable development of my country's agriculture. Soil conditioners can effectively improve the physical and chemical properties of soil, supplement organic matter and mineral nutrients, and enhance soil biological functions. However, soil barrier factors are relatively complex, interrelated and mutually influential. The soil conditioners on the market currently have problems such as relatively single functions, short duration, and poor ecological restoration effects. Therefore, it is urgent to develop a new multifunctional and long-lasting soil conditioner, which is of great significance for repairing degraded and polluted soil, improving the quality of cultivated land, and maintaining food security and sustainable agricultural development. Summary of the invention

[0003] One of the purposes of the present invention is to provide an alginate-based multifunctional long-acting soil conditioner in view of the deficiencies in the prior art. The soil conditioner has good sustained-release performance and can release effective ingredients slowly and persistently, and has multiple functions such as improving soil quality, providing nutrition, promoting crop growth, and improving resistance.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A multifunctional long-acting alginate soil conditioner comprises a core particle layer and a slow-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the slow-release layer comprises clay minerals and alginate; wherein the mass ratio of the clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and the binder is (50.0-50.9): (1.0-1.9): (100.0-100.9): (20.0-29.9): (2.0-2.9): (3.0-3.9): (2.0-2.9): (1.0-1.9): (6.0-6.9).

[0006] Preferably, the particle size of the soil conditioner is 4 to 5 mm, wherein the core particle size of the core particle layer is 1 to 2 mm.

[0007] Preferably, the clay mineral includes at least one of kaolinite, montmorillonite, attapulgite, sepiolite, rectorite, diatomaceous earth, illite, quartz, sericite, dickite, bentonite, chlorite and zeolite; and the alginate includes at least one of sodium alginate, potassium alginate and calcium alginate.

[0008] Preferably, the pH value of the clay mineral is 7.0-8.5, the main clay mineral in the clay mineral is ≥70wt%, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, Cr≤50mg / kg; and the uronic acid content in the alginate is ≥85%.

[0009] Preferably, the pH value of the clay mineral is 8.2-8.5, the main clay mineral in the clay mineral is ≥72wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤0.15mg / kg, As ≤10mg / kg, Pb ≤25mg / kg, Cd ≤0.1mg / kg, Cr ≤20mg / kg; the uronic acid content in the alginate is ≥90%, and the uronic acid includes а-L-mannuronic acid and bD-guluronic acid in a mass ratio of (6-8):(2-4).

[0010] Preferably, the organic material includes at least one of organic fertilizer, manure, compost, fermented manure, green manure, wine lees, vinegar lees, cassava residue, oil residue, sugar residue, furfural residue, mushroom residue, kelp residue, protein mud, amino acid, humic acid, plant straw, plant ash, cake fertilizer, soybean meal, cotton meal, peanut shell powder, biogas fertilizer, kitchen waste, and urban sludge; the binder includes lignin sulfonate, lignin phenolic resin, carboxyethyl cellulose, carboxymethyl cellulose, biomass tar, carboxymethyl shell At least one of polysaccharide salts, polyglutamic acid salts, humates, acrylamide, starch, dextrin, polyvinyl alcohol, locust bean gum, guaiac gum, xanthan gum, gum arabic, guar gum, broad bean gum, citrus aurantium, coca gum, carrageenan, agar, egg white protein, tyrosine, fish paste, bacterial protein, wheat germ protein, gluten, gelatin, polyvinyl alcohol, sodium polyacrylate, propylene glycol, carboxymethyl starch, phosphate cross-linked starch, urea-formaldehyde condensate, vegetable oil, and mineral oil.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned alginic acid-based multifunctional long-acting soil conditioner, comprising the following steps:

[0012] S1. Dry-mix the organic material, nano silicon, magnesium calcium polyphosphate, magnesium hydride, ammonium borate and rhamnose in a mass ratio of , then add a binder and mix, and then perform the first granulation to obtain core particles;

[0013] S2. Mixing the clay mineral and alginate with the core particles obtained in step S1 according to a mass ratio, and then performing a second granulation to obtain a soil conditioner comprising a core particle layer and a slow-release layer.

[0014] Preferably, the first granulation is steam granulation, the granulation time is 3 to 10 minutes, and the obtained particles have a particle size of 1 to 2 mm; the second granulation is steam granulation, the granulation time is 4 to 12 minutes, and the obtained particles have a particle size of 4 to 5 mm.

[0015] Preferably, in step S2, the clay mineral is pretreated before being mixed with alginate and core particles; the pretreatment step is: firstly sorting by autoclave-steaming hydrothermal reaction method, and then removing harmful elements therein, so that the main material of the clay mineral in the clay mineral is ≥70wt%, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, and Cr≤50mg / kg.

[0016] The third object of the present invention is to provide the above-mentioned alginic acid-based multifunctional long-acting soil conditioner and the use of the soil conditioner prepared by the above-mentioned preparation method in soil improvement.

[0017] The beneficial effects of the present invention are as follows: the soil conditioner provided by the present invention uses a mixture of clay minerals and alginate as a coating material, which, on the one hand, isolates various substances such as organic materials and calcium magnesium polyphosphate in the core particle layer, has good sustained-release performance, and can release the effective ingredients in the core particle layer slowly and persistently, so as to improve soil quality in a long-term manner, provide organic matter and mineral nutrition, enhance crop resistance, etc.; on the other hand, clay minerals also have the advantages of regulating the pH value, physical structure, nutrient status of the soil and accelerating the degradation of organic pollutants, while alginate also has various functions such as promoting growth, resisting stress, and accelerating the decomposition of organic pollutants. Both of them are also involved in soil improvement, and through the synergistic effect of various components, they can effectively solve the problems of soil acidification, heavy metal pollution, microplastic pollution, pesticide pollution and antibiotic pollution in agricultural production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the electrospray ionization mass spectrum of sodium alginate in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] Soil conditioners are widely used in soil ecological restoration such as soil acidification, heavy metal pollution, microplastic pollution, pesticide pollution and antibiotic pollution. However, due to the current limitations of soil conditioners, such as relatively single functions, short duration and poor ecological restoration effects, the quality of the improved soil is often poor. When the soil is subsequently used to grow various crops, it does not significantly increase the crop fruit rate.

[0020] The alginate-based multifunctional long-acting soil conditioner provided by the present invention can improve the soil so that the soil can be suitable for economic crops, food crops, vegetables, fruit trees, economic trees, flowers, Chinese medicinal materials or lawns; among them, the flower and fruit retention rate of flowering and fruiting plants can reach 50% to 99%, and the synthesis of various enzymes and secondary metabolites related to crop resistance is also increased by 10 to 90%.

[0021] Among them, applicable cash crops include tobacco, cotton, oil tea, rapeseed, sugar beet, sugar cane, soybean, tea tree, peanut, etc. Applicable food crops include wheat, rice, corn, sorghum, etc. Applicable vegetables include cabbage, bitter gourd, loofah, celery, eggplant, tomato, wax gourd, spinach, garlic, onion, pepper, cucumber, spinach, kohlrabi, potato, sweet potato, radish, carrot, pea, kidney bean, green bean, edamame, etc. Applicable fruits include mango, watermelon, apple, pear, banana, papaya, citrus, orange, grape, cherry, lychee, peach, plum, apricot, strawberry, pineapple, blueberry, kiwi, jujube, persimmon, Hami melon, etc. Applicable economic trees include rubber, coconut, walnut, chestnut, hazelnut, etc.; applicable flowers include dianthus, marigold, calendula, impatiens, mirabilis, poppy, californica, salvia, violet, morning glory, mimosa, cockscomb, etc. one- and two-year herbaceous flowers; asparagus fern, impatiens, spider plant, Clivia, vanilla, violet, strelitzia, crinum, amaryllis, etc. perennial herbaceous flowers; lily, daylily, peony, chrysanthemum, etc. deciduous perennial and bulbous grass flowers; Aquatic flowers such as lotus and water lily; ferns such as kidney fern and maidenhair fern; orchids such as spring orchid, cymbidium orchid and calanthe; evergreen shrubs such as Milan, gardenia and Michelia; deciduous shrubs such as rose, rose and rose; evergreen trees such as cycad, mountain palm, fan palm and banyan; deciduous trees such as peach, plum, cherry and magnolia; evergreen vines such as Clerodendrum thomsoniae, Monstera and bougainvillea; deciduous vines such as trumpet creeper, vine and costusroot; cacti and succulents such as Epiphyllum, aloe and Sedum. Applicable Chinese medicinal materials include ginseng, Panax notoginseng, rhubarb, Chuanxiong, Gastrodia elata, Auricularia auricula, costus root, Ophiopogon japonicus, Bupleurum chinense, Codonopsis pilosula, Astragalus membranaceus, Coptis chinensis, Areca nut, mint, Strychnos nux vomica, Schisandra chinensis, Gallnut, Burdock fruit, Cordyceps sinensis, nutmeg, benzoin, Corydalis yanhusuo, Zanthoxylum bungeanum, Polygonum multiflorum, Isatis root, Acanthopanax senticosus, Momordica grosvenori, etc. Applicable lawns include weak bentgrass, velvety bentgrass, creeping bentgrass, small bran grass, tough-leaved red fescue, creeping red fescue, fescue, fine-leaved fescue and tall fescue, etc.; meadow bluegrass, common bluegrass, woodland bluegrass and bluegrass, perennial ryegrass, foxtail grass, timothy grass, zoysia, large-spiked zoysia, Chinese zoysia, Manila zoysia, fine-leaved zoysia, white-graeded carex, fine-leaved carex, heterostachys and egg-spiked carex, etc.; white clover, red clover, variable crown flower, creeping horsetail, sedge, thyme, creeping Potentilla, etc.

[0022] The alginate-based multifunctional long-acting soil conditioner comprises a core particle layer and a slow-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the slow-release layer comprises clay minerals and alginate; wherein the mass ratio of the clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and the binder is (50.0-50.9): (1.0-1.9): (100.0-100.9): (20.0-29.9): (2.0-2.9): (3.0-3.9): (2.0-2.9): (1.0-1.9): (6.0-6.9).

[0023] The clay minerals used in the sustained-release layer include at least one of kaolinite, montmorillonite, attapulgite, sepiolite, rectorite, diatomite, illite, quartz, sericite, dickite, bentonite, chlorite and zeolite; the pH value of the clay minerals is 7.0-8.5, the content of the main material of the clay minerals is ≥70wt%, and other beneficial nutrient elements are contained, while the content of harmful elements is very low after removal, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, Cr≤50mg / kg, so the clay minerals used in the present invention are not only a cheap coating material, but also can better adjust the pH, physical structure and nutrient status of the barrier soil, and can accelerate the degradation of organic pollutants. The pH value of the clay mineral after activation and magnetic separation is 8.2-8.5, and the clay mineral main material in the clay mineral is ≥72wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤0.15mg / kg, As ≤10mg / kg, Pb ≤25mg / kg, Cd ≤0.1mg / kg, and Cr ≤20mg / kg.

[0024] The slow-release layer also contains alginate, a green, safe and environmentally friendly coating material. It is a natural polysaccharide carbohydrate extracted from kelp. The selected uronic acid content is ≥85%. It is a copolymer composed of а-L-mannuronic acid (mannuronic acid, M) and bD-guluronic acid (guluronic acid, G) connected by 1,4-glycosidic bonds and composed of different GGGMMM fragments. Alginate also has the functions of regulating plant growth, inducing plant stress resistance, accelerating the decomposition of organic pollutants and directly acting on plant pathogens. Together with clay minerals as a slow-release layer, it can give priority to conditioning the soil, improve the soil environment, and make the effective ingredients in the subsequent core particle layer more effective; at the same time, the two as coating materials can well isolate organic materials, calcium magnesium polyphosphate and other substances in the core particle layer, ensuring that the effective ingredients in the core particle layer are released slowly and persistently, playing a role in long-term improvement of soil quality, providing organic matter and mineral nutrition, and enhancing crop resistance. Preferably, the uronic acid content of the selected alginate is ≥90%, and the uronic acid includes а-L-mannuronic acid (M) and bD-guluronic acid (G) in a mass ratio of (6-8):(2-4). The alginate can be at least one of sodium alginate, potassium alginate, and calcium alginate, preferably sodium alginate, with a molecular formula of (C6H7O6Na)n, a degree of polymerization of 2-20, a uronic acid composition of M / G=7:3, and a uronic acid content of>90%.

[0025] Compared with using only alginate or clay mineral as the sustained-release layer, the above two substances selected by the present invention are used together as the sustained-release layer, which has a good synergistic effect and a better and more excellent effect in long-term effect.

[0026] The organic material in the core particle layer can be at least one of organic fertilizer, manure, compost, fermented manure, green manure, wine lees, vinegar lees, cassava residue, oil residue, sugar residue, furfural residue, mushroom residue, kelp residue, protein mud, amino acid, humic acid, plant straw, plant ash, cake fertilizer, soybean meal, cottonseed meal, peanut shell powder, biogas fertilizer, kitchen waste, and urban sludge. This organic material can not only improve the physical structure of the soil, increase soil organic matter, and promote the reproduction of soil microorganisms, but also regulate the soil pH, reduce the activity of heavy metals, and promote crop growth. The preferred organic material in the present invention is seaweed organic fertilizer, which is made of natural seaweed as raw material, extracted and developed by physical and biochemical processes, so that the organic matter content is ≥40%, contains a variety of active substances such as alginic acid, minerals, amino acids, polysaccharides, betaine, plant growth hormones, and has the characteristics of promoting growth, increasing production, resisting adversity, improving soil, and accelerating the decomposition of organic pollutants.

[0027] The selected nano silicon has the characteristics of large surface area, good biocompatibility, high stability and good adsorption performance. As a slow-release fertilizer, it can not only provide nutritional support for crop growth, but also enhance the various resistance of crops, block the absorption of heavy metals by crops, thereby improving the quality of agricultural products and helping the safe production of crops in obstructive soils.

[0028] The selected calcium magnesium polyphosphate is a new type of slow-release fertilizer. When calcium magnesium polyphosphate is applied to the soil, the release rate of phosphorus, calcium and magnesium can be regulated, and it is wrapped in a slow-release layer, thereby slowly releasing orthophosphate, calcium ions and magnesium ions for a long time, thereby slowing down the fixation of phosphorus and the loss of calcium and magnesium ions, better meeting the needs of crop growth, and then improving nutrient utilization efficiency and promoting crop yield increase. The preferred calcium magnesium polyphosphate of the present invention is a porous amorphous structure, in which the effective phosphorus, calcium and magnesium nutrient content exceeds 85%.

[0029] The selected magnesium hydride has the characteristics of high hydrogen storage capacity, low cost and easy use. It is hydrolyzed at room temperature to generate hydrogen and magnesium hydroxide, of which hydrogen can promote the development of plant roots, improve tolerance to abiotic stresses such as acidification and heavy metals, and accelerate the decomposition of organic pollutants. The produced magnesium hydroxide can not only provide magnesium nutrition, but also regulate soil acidity and alkalinity and passivate soil heavy metals.

[0030] The selected ammonium borate can not only provide boron nutrition and quick-acting nitrogen for crop growth, but also regulate soil pH, reduce the activity of heavy metals, sterilize and disinfect, and enhance the crop's resistance to various stresses.

[0031] The selected rhamnose can not only enhance the immunity of crops by activating the inherent immune response mechanism of crops, making them more resistant and adaptable to adverse environments; it can also improve the soil environment, increase the soil organic matter content, promote the reproduction of soil microorganisms, and improve soil fertility, thereby promoting crop nutrient absorption and storage.

[0032] By using the above substances together as the effective ingredients of the core particles, each component can not only play its own role independently to increase the content of nutrients needed in the soil, but also work synergistically to improve the soil environment. For example, nano-silicon can block the absorption of heavy metals by crops, while organic materials, magnesium hydroxide and ammonium borate can also inhibit the activity of heavy metals. Together, they can effectively control the impact of heavy metals in the soil on crops.

[0033] The binder selected includes at least one of lignin sulfonate, lignin phenolic resin, carboxyethyl cellulose, carboxymethyl cellulose, biomass tar, carboxymethyl chitosan salt, polyglutamate, humate, acrylamide, starch, dextrin, polyvinyl alcohol, locust bean gum, guaiac gum, xanthan gum, gum arabic, guar gum, broad bean gum, citrus aurantium, coca gum, carrageenan, agar, egg white protein, tyrosine, fish paste, bacterial protein, wheat germ protein, gluten, gelatin, polyvinyl alcohol, sodium polyacrylate, propylene glycol, carboxymethyl starch, phosphate cross-linked starch, urea-formaldehyde condensate, vegetable oil, and mineral oil.

[0034] After many experiments and verifications, the inventors have controlled the contents of clay minerals, alginate, organic materials, calcium magnesium polyphosphate, nano-silicon, magnesium hydride, ammonium borate, and rhamnose within the above ranges, with a high degree of matching, which not only ensures that the thickness of the sustained-release layer composed of clay minerals and alginate is appropriate, but also ensures a sufficient amount of effective ingredients in the core particle layer. Specifically, the mass ratios of clay minerals, alginate, organic materials, calcium magnesium polyphosphate, nano-silicon, magnesium hydride, ammonium borate, rhamnose, and binder include but are not limited to 50:1:100:20:2:3:2:1:6, 50.3:1.3:100.3:20.3:2.3:3.3:2.3:1.3:6.3, 50.5:1.5:100.4:20.6:2.5:3.5:2.5:1.5:6.5 or 50.9:1.9:100.9:20.9:2.9:3.9:2.9:1.9:6.9.

[0035] In some embodiments, the particle size of the soil conditioner is 4 to 5 mm, wherein the core particle size of the core particle layer is 1 to 2 mm.

[0036] The present invention also provides a method for preparing the soil conditioner, comprising the following steps:

[0037] S1. Dry-mix the organic material, nano silicon, magnesium calcium polyphosphate, magnesium hydride, ammonium borate and rhamnose in a mass ratio, add a binder and mix, and then perform the first granulation to obtain core particles;

[0038] S2. Mixing the clay mineral and alginate with the core particles obtained in step S1 according to a mass ratio, and then performing a second granulation to obtain a soil conditioner comprising a core particle layer and a slow-release layer.

[0039] The preparation method provided by the present invention adopts double-layer granulation technology for preparation, wherein the core particles are first prepared and then mixed with clay minerals and alginate, and the sustained-release layer formed by the clay minerals and alginate can well wrap the core particles therein, thereby forming a double-layer structure of the core particle layer and the sustained-release layer, thereby ensuring the long-term release of the active ingredients. In addition, the preparation method also has the advantages of low energy consumption, low cost, and environmental protection.

[0040] Compared with the method of directly mixing all the components, the method of the present invention prepares the soil conditioner comprising a double-layer structure with small and uniform particles, and also mixes clay minerals and alginate as the outer slow-release layer, thereby ensuring the long-term effect of soil improvement.

[0041] In some embodiments, the first granulation is steam granulation, the granulation time is 3 to 10 minutes, and the obtained granules have a particle size of 1 to 2 mm; the second granulation is steam granulation, the granulation time is 4 to 12 minutes, and the obtained granules have a particle size of 4 to 5 mm. The particles of the steam granulation of the present invention have a small and uniform particle size, and the coating thickness of the sustained-release layer is appropriate, which avoids the problem that the sustained-release layer is too thick and affects the release of the active ingredients of the inner core particles, and also avoids the problem that the thickness is too small and leads to poor long-term effect.

[0042] In some embodiments, in step S2, the clay mineral is pretreated before being mixed with alginate and core particles; the pretreatment step is: firstly sorting by autoclaving-steaming hydrothermal reaction method, and then removing harmful elements therein, so that the clay mineral main material in the clay mineral is ≥70wt%, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, Cr≤50mg / kg. The present invention also innovatively uses autoclaving-steaming hydrothermal reaction activation technology to treat clay minerals, and after activation treatment, many harmful elements therein are removed, and the content of effective calcium, magnesium, silicon and other clay minerals is increased by more than 30% compared with the traditional process, and then it is mixed with alginate as a slow-release layer to further ensure the long-term effect of soil improvement.

[0043] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be described in further detail below in conjunction with specific implementation methods and accompanying drawings, but the implementation methods of the present invention are not limited thereto.

[0044] Example 1

[0045] A multifunctional long-acting alginate soil conditioner comprises a core particle layer and a slow-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the slow-release layer comprises clay minerals and alginate; wherein the mass ratio of the clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and the binder is 50:1:100:20:2:3:2:1:6.

[0046] The preparation method of the alginic acid-based multifunctional long-acting soil conditioner is as follows:

[0047] 1) Drying, crushing and sieving the organic material kelp residue, grinding and homogenizing calcium magnesium polyphosphate (total phosphorus 50%, polymerized phosphorus ≥ 40%, polymerization rate ≥ 80%) in a ball mill to make the particle size less than 30 μm; weighing the organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate and rhamnose according to 100:2:20:3:2:1, and dry mixing; then mixing with a binder carboxymethyl chitosan salt, adding to a drum granulator, steam granulating, the granulation time is 5 minutes, and preparing core particles with an average particle size of 1 to 2 mm;

[0048] 2) Grind the clay minerals (kaolinite and chlorite) in a ball mill, separate the effective calcium, magnesium, silicon and other clay minerals by autoclave-steam hydrothermal reaction process, remove harmful elements by magnetic separation and other methods, so that the main material content of the clay mineral is ≥80wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤5mg / kg, As ≤10mg / kg, Pb ≤15mg / kg , Cd≤8mg / kg, Cr≤25mg / kg; then weigh the activated and magnetically separated kaolinite, chlorite and sodium alginate in a ratio of 25:25:1, mix them with the core particles prepared above and add them into the drum granulator again for steam granulation. The granulation time is 8min. After the particle size is 4-5mm, hot air is blown into the dryer to dry the particles, sieve and cool to obtain a soil conditioner comprising a core particle layer and a slow-release layer, with a pH value of 8.5.

[0049] The test methods after the soil conditioner test include: (1) pH value is measured by potentiometric method in accordance with HJ962-2018; (2) organic matter is measured in accordance with GB9834-88; (3) phosphorus is measured in accordance with national standard GB20412-2006; (4) calcium, magnesium and silicon content are measured in accordance with NY / T2272-2012; (5) the degree of polymerization of sodium alginate is determined by the formula The determination was performed using an electrospray ionization (ESI) liquid chromatography-mass spectrometry instrument; (6) the chromatographic determination conditions were: the mass spectrometry mode was a positive ion mode, the electrospray ionization (ESI) source was a spray voltage of 4.5 kV, the transmission capillary temperature was 350°C, the sheath gas (N2) pressure was 30 au (1 au is approximately 1 psi), the auxiliary gas (N2) pressure was 5 au, the ion sweep gas (N2) pressure was 0 au, the scanning range was 150 to 2000, and the electrospray ionization mass spectrum was as follows: Figure 1 ; (7) The content of each component was determined by colorimetry.

[0050] The soil conditioner obtained above was tested experimentally.

[0051] Experiment 1: Experiment on reducing acid and increasing production by applying the alginic acid-based multifunctional long-acting soil conditioner of the present invention

[0052] The experiment was completed in Wuyang from October 2020 to October 2022. The test plots are flat, neat, uniform in fertility, with a pH value of 4.53, and obvious acidification. The experimental wheat varieties are Zhengmai 7698, and the corn varieties are Zhengdan 1002. The experiment set up three treatments, namely Treatment 1: Control, no soil conditioner treatment; Treatment 2, 100kg / mu of quicklime; Treatment 3, 100kg / mu of alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention. Quicklime and the alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention were both spread before planting the first season of wheat, and sown 15 days after rotary tillage. The soil acidification index and crop yield were measured after each crop was harvested. The specific results are shown in Tables 1 and 2.

[0053] Table 1 Effect of soil conditioner of the present invention on soil acidification index

[0054]

[0055] It can be seen from Table 1 above that in 2020-2021, the soil pH of the wheat harvest season in which the alginate-based multifunctional long-acting soil conditioner of the present invention was applied increased by 0.48 compared with the control, but was lower than the lime treatment by 0.16; in the corn harvest season, it increased significantly by 0.44 and 0.21 compared with the control and lime treatment, respectively. In 2021-2022, the soil pH of the wheat harvest season in which the alginate-based multifunctional long-acting soil conditioner of the present invention was applied increased by 0.46 and 0.27 compared with the control and lime treatment, respectively; in the corn season, it increased by 0.48 and 0.31, respectively. Table 1 also shows that in 2020-2021, the soil exchangeable total acid content in the wheat harvest season in which the alginate-based multifunctional long-acting soil conditioner of the present invention was applied was significantly reduced by 34.4% compared with the control, but was significantly higher than the lime treatment by 37.4%; in the corn harvest season, it increased significantly by 66.2% and 3.7% compared with the control and lime treatment, respectively. In 2021-2022, the total exchangeable acid content of the soil in the wheat season and corn season after the application of the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly reduced by 34.5% and 33.9% respectively compared with the control, but there was no significant difference with the lime treatment. This result shows that compared with lime, the acid reduction effect of the alginate-based multifunctional long-acting soil conditioner of the present invention on acidified soil is more lasting.

[0056] Table 2 Effect of soil conditioner of the present invention on crop yield and cadmium content in grain

[0057]

[0058] As can be seen from Table 2 above, in 2020-2021, the wheat and corn yields of the application of the alginate-based multifunctional long-acting soil conditioner of the present invention were significantly higher than the control by 14.2% and 8.8%, respectively, but there was no significant difference with the lime treatment. In 2021-2022, the wheat yield of the application of the alginate-based multifunctional long-acting soil conditioner of the present invention increased by 14.0% and 3.0% compared with the control and lime treatment, respectively, and the corn yield was significantly higher than the control by 11.3%, but there was no significant difference with the lime treatment. Table 2 also shows that in 2020-2021, the cadmium content of wheat grains applied with the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly reduced by 39.6% compared with the control, but significantly higher than the lime treatment by 11.5%; the cadmium content of corn grains was significantly reduced by 31.7% and 10.4% compared with the control and lime treatment, respectively. In 2021-2022, the cadmium content of wheat grains treated with the alginate multifunctional long-acting soil conditioner of the present invention was significantly reduced by 45.5% and 13.3% compared with the control and lime treatment, respectively; the cadmium content of corn grains was significantly reduced by 34.8% and 22.8% compared with the control and lime treatment, respectively. The results show that the application of the alginate multifunctional long-acting soil conditioner of the present invention on acidified soil can increase crop yields, reduce the cadmium content in grains, and has better persistence than lime.

[0059] Test 2: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for acidified soil improvement test

[0060] The experiment was completed in Zhengyang from October 2020 to June 2021. The pH of the test plot was 3.83, with obvious acidification, and the crop planted was Zhengmai 139. The experiment set up three treatments, namely treatment 1, control; treatment 2, 150 kg / mu of biochar; treatment 3, 150 kg / mu of alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention. After wheat was harvested, the molybdenum antimony colorimetric method was used to determine the effective phosphorus content in the soil; the flame photometry was used to determine the available potassium content in the soil. The oil bath heating-potassium dichromate method was used to determine the soil organic matter content. The ammonium acetate exchange atomic absorption spectrophotometry was used to determine the exchangeable calcium and magnesium content in the soil. The PHSJ-3FX pH was used to determine the soil pH; the DTPA extraction-atomic absorption spectrometry flame method and the graphite furnace method were used to determine the effective copper and cadmium contents in the soil. The specific results are shown in Table 3.

[0061] Table 3 Effects of soil conditioner of the present invention on wheat yield and soil physical and chemical properties

[0062]

[0063] As shown in Table 3, the wheat yield of the alginate multifunctional long-acting soil conditioner of the present invention was significantly higher than that of the control and biochar treatment, with an increase of 25.0% and 8.1%, respectively; the soil pH value increased by 0.73 and 0.50 compared with the control and biochar treatment, respectively; the soil organic matter content increased by 42.8% and 12.8% compared with the control and biochar treatment, respectively; the soil exchangeable magnesium content increased by 60.0% and 54.3% compared with the control and biochar treatment, respectively; the soil exchangeable calcium content increased by 177.8% and 174.7% compared with the control and biochar treatment, respectively. The soil available potassium content increased by 59.0% and 31.3% compared with the control and biochar treatment, respectively; the soil available phosphorus content increased by 78.2% and 67.0% compared with the control and biochar treatment, respectively; the soil available copper content decreased by 30.9% and 20.0% compared with the control and biochar content, respectively; the soil available cadmium content decreased by 32.3% and 17.9% compared with the control and biochar content, respectively. The results show that the application of the alginate-based multifunctional long-acting soil conditioner of the present invention can increase soil pH and the content of available nutrients, reduce the activity of heavy metals, and thus promote wheat yield.

[0064] Experiment 3: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for heavy metal contaminated soil improvement experiment

[0065] The experiment was completed in Dakuai Town, Fengquan District, Xinxiang City from October 2020 to June 2021. The soil cadmium content was 28.35 mg / kg. Xinmai 26 was used as the material. Four treatments were set up in the experiment, namely treatment 1, control; treatment 2, biochar 140 kg / mu; treatment 3, calcium magnesium phosphate fertilizer 40 kg / mu; treatment 4: 140 kg / mu of alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention. Wheat yield, cadmium absorption, soil pH at maturity, and soil heavy metal cadmium forms were determined, including exchangeable state (EXC-Cd), carbonate-bound state (CAR-Cd), iron-manganese oxide-bound state (OX-Cd), organic-bound state (OM-Cd) and residual state (RES-Cd). The results are shown in Tables 4 and 5.

[0066] Table 4 Effect of soil conditioner of the present invention on soil pH and cadmium form

[0067]

[0068] As can be seen from Table 4 above, after wheat harvest, the soil pH of the alginate-based multifunctional long-acting soil conditioner of the present invention increased by 0.35, 0.09 and 0.07 respectively compared with the control, biochar and calcium magnesium phosphate fertilizer treatments. The proportion of soil EXC-Cd in the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly lower than that of the control, biochar and calcium magnesium phosphate fertilizer treatments, but the proportion of CAR-Cd, OX-Cd and OM-Cd was significantly increased, and the proportion of RES-Cd was also significantly higher than that of the control. This result shows that the application of the alginate-based multifunctional long-acting soil conditioner of the present invention increases soil pH and promotes the conversion of exchangeable Cd to residual Cd.

[0069] Table 5 Effect of soil conditioner of the present invention on wheat yield and cadmium absorption

[0070]

[0071] As can be seen from Table 5, the wheat yield of the alginate-based multifunctional long-acting soil conditioner of the present invention increased by 23.5%, 2.5%, and 4.2% compared with the control, biochar, and calcium magnesium phosphate fertilizer treatments, respectively. The cadmium content of the root system was reduced by 48.8%, 42.9%, and 17.0% compared with the control, biochar, and calcium magnesium phosphate fertilizer treatments, respectively; the cadmium content of the straw was significantly reduced by 36.5%, 29.0%, and 12.9% compared with the control, biochar, and calcium magnesium phosphate fertilizer treatments, respectively; the cadmium content of the grain was significantly reduced by 57.1%, 33.3%, and 20.0% compared with the control, biochar, and calcium magnesium phosphate fertilizer treatments, respectively. The results show that the application of the alginate-based multifunctional long-acting soil conditioner of the present invention can reduce the absorption of heavy metal Cd by wheat and increase wheat yield.

[0072] Experiment 4: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for the improvement of soil contaminated by heavy metals

[0073] The experiment was completed from October 2022 to June 2023 in a sewage-irrigated farmland near a battery factory in Xinxiang County, Henan Province. The crop planted was radish and the soil type was tidal soil. Due to long-term sewage irrigation, heavy metals accumulated in the soil, with a cadmium content of 31.53 mg / kg, an arsenic content of 18.56 mg / kg, and a lead content of 25.48 mg / kg, which was a compositely contaminated soil of cadmium, arsenic and lead. The experiment set up four treatments, namely treatment 1, control; treatment 2, 150 kg / mu of biochar; treatment 3, application of 150 kg / mu of alginate-type multifunctional long-acting soil conditioner prepared in Example 1 of the present invention. The determination of radish yield and its heavy metal content is shown in Table 6.

[0074] Table 6 Effect of soil conditioner of the present invention on radish yield and heavy metal content

[0075] deal with <![CDATA[Yield (t / hm 2 )]]> Cadmium content (mg / kg) Arsenic content (mg / kg) Lead content (mg / kg) Comparison 18.57 15.65 0.55 3.18 Biochar 23.45 13.23 0.48 2.84 Soil Conditioner 25.59 9.45 0.32 2.56

[0076] As can be seen from Table 6 above, the yield of radish planted in the bauxite-type acidic nutrient soil of the present invention is significantly higher than that of the control and biochar, with increases of 37.8% and 9.1%, respectively. The cadmium content in radish is significantly reduced by 39.6% and 28.6% compared with the control and biochar, respectively. The arsenic content in radish is significantly reduced by 41.8% and 33.3% compared with the control and biochar, respectively; the lead content in radish is significantly reduced by 19.5% and 9.9% compared with the control and biochar treatment, respectively. The results show that the application of the alginate-type multifunctional long-acting soil conditioner of the present invention can increase radish yield and reduce heavy metal content.

[0077] Experiment 5: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for the improvement of soil contaminated by cadmium, microplastics and single and combined pollution

[0078] The experiment was completed in the light culture room of Henan Academy of Agricultural Sciences from October 2020 to June 2021. The experiment adopted an indoor potted experiment, using Zhengmai 139 as the material to study the improvement effects of single and combined pollution of soil heavy metal cadmium (4 mg / kg) and polyethylene microplastics (PP-MPs, 5%). The experiment set up two treatments, namely the control and the application of the alginate-type multifunctional long-acting soil conditioner prepared in Example 1 of the present invention, with an addition amount of 10 g / kg. The photosynthetic characteristics of wheat functional leaves were determined at the jointing stage, and some samples were harvested to determine the activity of leaf antioxidant enzymes. After wheat was harvested, the effective cadmium content in the soil and the microplastic occurrence characteristics were determined. The results are shown in Tables 7 and 8.

[0079] Table 7 Effects of the soil conditioner of the present invention on photosynthetic characteristics and antioxidant enzyme activities of wheat

[0080]

[0081] As can be seen from Table 7, under the condition of single cadmium pollution, the SPAD value, net photosynthetic rate, SOD, POD and CAT activity of wheat functional leaves applied with the multifunctional long-acting soil conditioner of alginic acid of the present invention increased by 26.5%, 29.3%, 9.5%, 78.3% and 42.1% respectively compared with the control. Under the condition of single microplastic pollution, the SPAD value, net photosynthetic rate, SOD, POD and CAT activity of wheat functional leaves applied with the multifunctional long-acting soil conditioner of alginic acid of the present invention increased by 11.7%, 9.0%, 5.1%, 93.3% and 40.7% respectively compared with the control. Under the condition of combined pollution of cadmium and microplastics, the SPAD value, net photosynthetic rate, SOD, POD and CAT activity of wheat functional leaves applied with the multifunctional long-acting soil conditioner of alginic acid of the present invention increased by 28.1%, 26.5%, 7.0%, 76.5% and 32.1% respectively compared with the control. The results show that the application of the alginate-based multifunctional long-acting soil conditioner of the present invention can increase the content of wheat photosynthetic pigments, promote photosynthesis, and alleviate the damage of single and combined pollution of soil cadmium and microplastics to the growth of wheat seedlings by increasing the activity of antioxidant enzymes.

[0082] Table 8 Effects of the soil conditioner of the present invention on soil cadmium content and microplastics occurrence characteristics

[0083]

[0084]

[0085] As can be seen from Table 8 above, in soils contaminated with cadmium alone, the effective cadmium content of the soil after the application of the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly reduced by 34.2%; under the conditions of cadmium and microplastics combined pollution, the effective cadmium content of the soil after the application of the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly reduced by 37.8%. Under the conditions of single microplastic pollution, the abundance of soil microplastics was significantly reduced by 18.4%, and under the conditions of cadmium and microplastics combined pollution, the abundance of soil microplastics after the application of the alginate-based multifunctional long-acting soil conditioner of the present invention was significantly reduced by 19.4%. Under the conditions of single microplastic pollution or combined pollution with cadmium, the application of the alginate-based multifunctional long-acting soil conditioner of the present invention can increase the proportion of microplastics with particle sizes of <0.5mm and 0.5-1mm, and reduce the proportion of microplastics with particle sizes of 1-2mm and 2-5mm. This result shows that the application of this alginate-based multifunctional long-acting soil conditioner can reduce the effective cadmium content in the soil, accelerate the degradation of microplastics, and thus reduce the abundance of microplastics.

[0086] Experiment 6: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for improving pesticide-contaminated soil

[0087] The experiment was completed in Lankao vegetable greenhouse from 2022 to 2024. The experiment set up two treatments, control and application of 100 kg / mu of alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention, once a year. After 2 years, the topsoil was collected, and the residues of thiamethoxam, carbendazim, avermectin and carbofuran were determined by ultra-high performance liquid chromatography tandem mass spectrometry. The specific results are shown in Table 9.

[0088] Table 9 Effect of the alginic acid-based multifunctional long-acting soil conditioner of the present invention on the pesticide content in the soil

[0089] deal with Thiamethoxam (mg / kg) Imidacloprid(mg / kg) Avermectin (mg / kg) Carbofuran (mg / kg) Comparison 0.885 0.265 0.225 0.065 Soil Conditioner 0.645 0.132 0.137 0.037

[0090] As shown in Table 9, compared with the control, the contents of thiamethoxam, imidacloprid, avermectin and carbofuran in the soil treated with the alginic acid multifunctional long-acting soil conditioner of the present invention were significantly reduced by 27.1%, 50.2%, 39.1% and 43.1%, respectively. This result shows that the application of the alginic acid multifunctional long-acting soil conditioner of the present invention can accelerate the degradation of pesticides in the soil, reduce pesticide pollution, and thus be beneficial to the safe production of vegetables.

[0091] Experiment 7: Application of the alginic acid-based multifunctional long-acting soil conditioner of the present invention for improving antibiotic-contaminated soil

[0092] The experiment was completed in Lankao vegetable greenhouse from 2021 to 2022. The greenhouse has been applying livestock and poultry manure as organic fertilizer (about 250kg / mu) for a long time, and a certain amount of fertilizer is applied at the same time. The experiment set up two treatments, control and application of 100kg / mu of alginate-based multifunctional long-acting soil conditioner prepared in Example 1 of the present invention, which was applied once a year. After 2 years, the topsoil was collected, and the contents of 4 tetracycline compounds (tetracycline, oxytetracycline, chlortetracycline and doxycycline) were determined by LC-MS. See Table 10 for details.

[0093] Table 10 Effect of soil conditioner of the present invention on the content of tetracyclic compounds in soil

[0094] deal with Oxytetracycline (μg / kg) Tetracycline (μg / kg) Chlortetracycline (μg / kg) Doxycycline (μg / kg) Comparison 11.12 4.65 4.25 6.58 Soil Conditioner 6.45 3.23 2.37 3.74

[0095] As shown in Table 10, compared with the control, the content of oxytetracycline, tetracycline, chlortetracycline and doxycycline in the soil treated with the alginic acid multifunctional long-acting soil conditioner of the present invention was significantly reduced, with a reduction of 42.0%, 30.5%, 44.2% and 43.2% respectively. This result shows that the application of the alginic acid multifunctional long-acting soil conditioner of the present invention can reduce the content of tetracyclic compounds in the soil and reduce antibiotic pollution.

[0096] Example 2

[0097] A multifunctional long-acting alginate soil conditioner comprises a core particle layer and a slow-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the slow-release layer comprises clay minerals and alginate; wherein the mass ratio of the clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and the binder is 50.5:1.5:100.4:20.6:2.5:3.5:2.5:1.5:6.3.

[0098] The preparation method of the alginic acid-based multifunctional long-acting soil conditioner is as follows:

[0099] 1) Drying, crushing and sieving the organic material mushroom, grinding and homogenizing calcium magnesium polyphosphate (total phosphorus 55%, polymerized phosphorus ≥ 42%, polymerization rate ≥ 81%) in a ball mill to make the particle size less than 25 μm; weighing the organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate and rhamnose according to 100.4:20.6:2.5:3.5:2.5:1.5, and dry mixing; then mixing with adhesive carboxymethyl starch, adding into a drum granulator, steam granulating, granulating time is 3 minutes, and preparing core particles with an average particle size of 1 to 2 mm;

[0100] 2) grinding the clay mineral (sepiolite) in a ball mill, separating effective calcium, magnesium, silicon and other clay minerals by autoclaving-steaming hydrothermal reaction process, removing harmful elements by magnetic separation and other methods, so that the main material content of the clay mineral is ≥75wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤4mg / kg, As ≤35mg / kg, Pb ≤45mg / kg, Cd ≤9mg / kg, Cr ≤40mg / kg; then weighing the activated and magnetically separated sepiolite and potassium alginate in a ratio of 50.5:1.5, mixing them with the core particles prepared above, and adding them into a drum granulator again for steam granulation, the granulation time is 5min, and the particles are blown into a dryer with hot air after the particle size is 4-5mm to dry the particles, sieve and cool to obtain a soil conditioner comprising a core particle layer and a slow-release layer, with a pH value of 8.8.

[0101] Example 3

[0102] A multifunctional long-acting alginate soil conditioner comprises a core particle layer and a slow-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the slow-release layer comprises clay minerals and alginate; wherein the mass ratio of clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and the binder is 50.9:1.9:100.9:20.9:2.9:3.9:2.9:1.9:6.9.

[0103] The preparation method of the alginic acid-based multifunctional long-acting soil conditioner is as follows:

[0104] 1) Drying, crushing and sieving organic material kitchen waste, grinding and homogenizing calcium magnesium polyphosphate (total phosphorus 45%, polymerized phosphorus ≥38%, polymerization rate ≥75%) in a ball mill to make the particle size less than 28 μm; weighing organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate and rhamnose in the ratio of 100.9:20.9:2.9:3.9:2.9:1.9, and dry mixing; then mixing with a binder locust bean gum, adding into a drum granulator, steam granulating, the granulating time is 9 minutes, and preparing core particles with an average particle size of 1 to 2 mm;

[0105] 2) Grinding the clay mineral (diatomite) in a ball mill, separating effective calcium, magnesium, silicon and other clay minerals by autoclaving-steaming hydrothermal reaction process, removing harmful elements by magnetic separation and other methods, so that the main material content of the clay mineral is ≥73wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤0.15mg / kg, As ≤10mg / kg, Pb ≤25mg / kg, Cd≤0.1mg / kg, Cr≤20mg / kg; then, the activated and magnetically separated diatomaceous earth and calcium alginate are weighed in a ratio of 50.9:1.9, mixed with the core particles prepared above, and added into the drum granulator again for steam granulation. The granulation time is 12 minutes. After the particle size is 4-5mm, hot air is blown into a dryer to dry the particles, sieved and cooled to obtain a soil conditioner comprising a core particle layer and a slow-release layer, with a pH value of 8.6.

[0106] In summary, it can be seen that the soil conditioner provided by the present invention has been verified by multiple experiments and can be used in soil ecological restoration such as soil acidification, heavy metal pollution, microplastic pollution, pesticide pollution and antibiotic pollution. It can not only provide nutrition, regulate soil acidity and alkalinity, enhance resistance, accelerate the decomposition of organic pollutants and other multiple functions, but also has good sustained release properties and can improve soil quality in the long term. It effectively solves the problems of soil acidification, heavy metal pollution, microplastic pollution, pesticide pollution and antibiotic pollution in agricultural production, and also has the advantages of being green, environmentally friendly, pollution-free and pollution-free.

[0107] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A multifunctional long-acting soil conditioner of alginic acid type, characterized in that: The invention comprises a core particle layer and a sustained-release layer coated on the surface of the core particle layer, wherein the core particle layer comprises organic material, nano silicon, calcium magnesium polyphosphate, magnesium hydride, ammonium borate, rhamnose and a binder, and the sustained-release layer comprises clay minerals and alginate; wherein the mass ratio of clay minerals, alginate, organic material, calcium magnesium polyphosphate, nano silicon, magnesium hydride, ammonium borate, rhamnose and binder is (50.0-50.9): (1.0-1.9): (100.0-100.9): (20.0-29.9): (2.0-2.9): (3.0-3.9): (2.0-2.9): (1.0-1.9): (6.0-6.9).

2. The alginic acid-based multifunctional long-acting soil conditioner according to claim 1, characterized in that: The particle size of the soil conditioner is 4-5 mm, wherein the core particle size of the core particle layer is 1-2 mm.

3. The alginic acid-based multifunctional long-acting soil conditioner according to claim 1, characterized in that: The clay mineral includes at least one of kaolinite, montmorillonite, attapulgite, sepiolite, rectorite, diatomaceous earth, illite, quartz, sericite, dickite, bentonite, chlorite and zeolite; the alginate includes at least one of sodium alginate, potassium alginate and calcium alginate.

4. The alginic acid-based multifunctional long-acting soil conditioner according to claim 3, characterized in that: The pH value of the clay mineral is 7.0-8.5, the main clay mineral in the clay mineral is ≥70wt%, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, Cr≤50mg / kg; the uronic acid content in the alginate is ≥85%.

5. The alginic acid-based multifunctional long-acting soil conditioner according to claim 4, characterized in that: The pH value of the clay mineral is 8.2-8.5, the main clay mineral in the clay mineral is ≥72wt%, Ca ≥0.2wt%, Mg ≥0.05mg / kg, N ≥0.1wt%, P2O5 ≥0.15wt%, Hg ≤0.15mg / kg, As ≤10mg / kg, Pb ≤25mg / kg, Cd ≤0.1mg / kg, Cr ≤20mg / kg; the uronic acid content in the alginate is ≥90%, and the uronic acid includes а-L-mannuronic acid and bD-guluronic acid in a mass ratio of (6-8):(2-4).

6. The alginic acid-based multifunctional long-acting soil conditioner according to claim 1, characterized in that: The organic material includes at least one of organic fertilizer, manure, compost, fermented manure, green manure, wine lees, vinegar lees, cassava residue, oil residue, sugar residue, furfural residue, mushroom residue, kelp residue, protein mud, amino acid, humic acid, plant straw, wood ash, cake fertilizer, soybean meal, cotton meal, peanut shell powder, biogas fertilizer, kitchen waste, and urban sludge; the binder includes lignin sulfonate, lignin phenolic resin, carboxyethyl cellulose, carboxymethyl cellulose, biomass tar, carboxymethyl chitosan At least one of salt, polyglutamate, humate, acrylamide, starch, dextrin, polyethylene alcohol, locust bean gum, guaiac gum, xanthan gum, gum arabic, guar gum, broad bean gum, citric acid, coca gum, carrageenan, agar, egg white protein, tyrosine, fish paste, bacterial protein, wheat germ protein, gluten, gelatin, polyvinyl alcohol, sodium polyacrylate, propylene glycol, carboxymethyl starch, phosphate cross-linked starch, urea-formaldehyde condensate, vegetable oil, and mineral oil.

7. A method for preparing the alginic acid-based multifunctional long-acting soil conditioner according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Dry-mix the organic material, nano silicon, magnesium calcium polyphosphate, magnesium hydride, ammonium borate and rhamnose in a mass ratio, add a binder and mix, and then perform the first granulation to obtain core particles; S2. Mixing the clay mineral and alginate with the core particles obtained in step S1 according to a mass ratio, and then performing a second granulation to obtain a soil conditioner comprising a core particle layer and a slow-release layer.

8. The method for preparing the alginic acid-based multifunctional long-acting soil conditioner according to claim 7, characterized in that: The first granulation is steam granulation, the granulation time is 3 to 10 minutes, and the obtained granules have a particle size of 1 to 2 mm; the second granulation is steam granulation, the granulation time is 4 to 12 minutes, and the obtained granules have a particle size of 4 to 5 mm.

9. The method for preparing the alginic acid-based multifunctional long-acting soil conditioner according to claim 7, characterized in that: In step S2, the clay mineral is pretreated before mixing it with alginate and core particles; the pretreatment step is: firstly sorting it by autoclave-steam hydrothermal reaction method, and then removing harmful elements therein, so that the main material of the clay mineral in the clay mineral is ≥70wt%, Hg≤5mg / kg, As≤50mg / kg, Pb≤50mg / kg, Cd≤10mg / kg, and Cr≤50mg / kg.

10. Use of the alginic acid-based multifunctional long-acting soil conditioner according to any one of claims 1 to 6 and the soil conditioner prepared by the preparation method according to any one of claims 7 to 9 in soil improvement.

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