A preparation method and application of soil conditioner

Abstract

The invention discloses a method for preparing a soil conditioner and its application, and belongs to the technical field of soil conditioners. The method for preparing a soil conditioner provided by the invention comprises the following steps: extraction of humic acid and fulvic acid from humus; preparation of fulvic acid cross-linked chitosan; fulvic acid cross-linked chitosan, bentonite, fly ash, earthworm feces, biomass ash and humic acid are uniformly mixed in proportion to prepare the soil conditioner. Among them, fulvic acid cross-linked chitosan can improve the water absorption performance of chitosan, reduce the acidity and leaching solubility of fulvic acid, and fulvic acid can be gradually released along with the slow degradation of chitosan, which can achieve the effect of long-term improvement of soil performance.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioners, and in particular to a preparation method of a soil conditioner and application thereof. Background Art

[0002] Soil conditioners refer to non-fertilizer substances that are applied to make soil conditions more suitable for crop growth after plants or crops are affected by various natural or human factors, such as soil degradation such as sandification, compaction, salinization, and pollution by heavy metal ions and chemical substances. Suitable soil conditioners can improve soil physical properties, increase soil porosity, and improve soil water and fertilizer retention. They can also improve soil structural stability, promote the formation of a stable aggregate structure, and make the soil structure more stable and less likely to be washed away by rain or irrigation water. For acidic and saline-alkali lands, soil conditioners can also adjust soil pH, absorb heavy metal ions in the soil, keep soil pH within a range suitable for plant growth, and reduce the toxic effects of heavy metal ions on plants. There are many kinds of raw materials for soil conditioners, including natural conditioners such as inorganic natural minerals such as limestone, bentonite, gypsum, vermiculite, perlite, etc.; inorganic solid wastes such as fly ash, etc.; organic solid wastes such as papermaking sludge, urban sewage sludge, bean green manure, earthworm feces, etc.; naturally extracted high molecular compounds such as polysaccharides, cellulose, lignin, humic acid, etc.; also including artificial synthetic conditioners such as polyacrylates, polyvinyl alcohol and polyethylene glycol, etc.; however, artificial synthetic conditioners have the problems of high cost and difficult degradation.

[0003] Red soil is a zonal soil distributed in the subtropical areas of southern my country. It has the distinct characteristics of "acidic, sticky, thin, and hard", that is, the soil is acidic, with a high clay content, severe hardening, and low content of nutrients (such as nitrogen, phosphorus, potassium, effective calcium, magnesium, boron, molybdenum, etc.). Humus is a natural high-molecular organic compound and an important component of soil organic matter. According to the difference in solubility under different pH conditions, humus is divided into three categories: humic acid, fulvic acid, and humin. Among them, humic acid and fulvic acid are very different. Humic acid has a higher degree of condensation, a larger molecular weight, less carboxyl groups, is weakly acidic, has a strong ability to adsorb and replace cations, and has a good effect on the formation of soil aggregates, but it accounts for a small proportion in southern red soil. The degree of condensation of fulvic acid is relatively low, the molecular weight is small, and the carboxyl group content is about 2.5 times that of humic acid. It is strongly acidic, has weak cation exchange capacity, is soluble in water, and has a high proportion in southern red soil. It is highly dispersible and mobile (leaching), which is not conducive to the formation of aggregate structure and the improvement of soil comprehensive fertility. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a soil conditioner and a preparation method thereof, and to provide a soil conditioner that can effectively utilize humic acid and fulvic acid in humus while achieving degradability and regulating soil water retention capacity and physical properties, so that it can fully play the function of improving soil.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a soil conditioner comprises the following steps:

[0007] S1. Composting agricultural waste, garden waste, and earthworm feces at a weight ratio of (10-25):(5-15):1 to obtain humus, and extracting humic acid and fulvic acid from the humus;

[0008] S2. dissolving fulvic acid in chloroform, adding thionyl chloride, stirring at 60-80°C for 1-2h, then evaporating to remove thionyl chloride to obtain fulvic acid chloride, and re-dissolving the fulvic acid chloride in a mixed solution of methanol and water; then dissolving chitosan in a 2wt% acetic acid solution, adding fulvic acid chloride solution and triethylamine, heating and refluxing at 60-80°C for 2-6h under nitrogen protection to generate a gel-like substance, and then drying and crushing to obtain powdered fulvic acid cross-linked chitosan;

[0009] S3. The fulvic acid cross-linked chitosan, bentonite, fly ash, earthworm castings, biomass ash and humic acid are mixed evenly in proportion to prepare a soil conditioner.

[0010] Chitosan is derived from chitin, which is a biomass resource second only to cellulose in nature. Chitosan is the only alkaline polysaccharide in nature and is particularly suitable for use in acidic soil improvement applications. However, the amino groups on the chitosan molecular chain have poor hydrophilicity, and the water absorption capacity of the gel material prepared from it is significantly lower than that of cellulose, starch and its derivatives. Fulvic acid contains a large number of cyclic structures, including benzene rings, condensed rings and various heterocyclic rings. A large number of active groups such as carboxyl, phenolic hydroxyl, hydroxyl, carbonyl, methoxy, amino, quinone, etc. are connected to the rings and side chains. The present application forms fulvic acid-crosslinked chitosan by adding acyl chloride to acylate the carboxyl groups on fulvic acid and then cross-linking them with the amino groups on chitosan. On the one hand, the water absorption performance of chitosan is improved, and the toxic effects of conventional cross-linking agents such as glutaraldehyde and epichlorohydrin on the soil are avoided. On the other hand, the acidity of fulvic acid is reduced. The obtained fulvic acid-cross-linked chitosan macromolecules effectively reduce the leaching solubility of fulvic acid. After the application of the soil conditioner, fulvic acid can be gradually released along with the slow degradation of chitosan, which can achieve the effect of long-term improvement of soil performance.

[0011] The biomass ash is the remaining material after burning agricultural waste and garden waste, preferably straw biomass ash and rice husk biomass ash.

[0012] The agricultural waste is selected from at least one of wheat straw, rice straw, corn straw, vegetable leaves, fruit tree branches, and rice husks; the garden waste is selected from at least one of dead branches and leaves and lawn clippings.

[0013] The deacetylation degree of the chitosan is greater than 90%, and the viscosity is 50-200 mPa·S.

[0014] The steps for extracting humic acid and fulvic acid from humus include:

[0015] S1. remove impurities from the humus, dry and pass through a 400-600 mesh sieve, mix the humus and a 0.1-1 mol / L hydrochloric acid solution, control the pH value to be in the range of 1-2, and the solid-liquid ratio of the humus to the hydrochloric acid is (0.1-1 g) / 10 ml, heat and shake for 1-2 hours, separate the sediment 1 from the supernatant 1, and retain the supernatant 1 for extracting fulvic acid;

[0016] S2. Sediment 1 was neutralized with 0.1-1 mol / L sodium hydroxide solution to a pH of 7, 0.1-1 mol / L sodium hydroxide solution was added, the solid-liquid ratio was 1:10, and the mixture was stirred under ultrasonic conditions for 4-6 hours, and centrifuged to obtain supernatant 2;

[0017] S3. Add 5-6 mol / L hydrochloric acid solution to the supernatant 2 to adjust the pH value to 1, heat and shake for 1-2 hours, separate the supernatant 3 and the precipitate 3, and retain the supernatant 3 for extracting fulvic acid;

[0018] S4. Add 0.1-1 mol / L sodium hydroxide solution to the precipitate 3, and add solid potassium chloride to make the potassium ion concentration in the solution 0.3 mol / L, and centrifuge to obtain a supernatant 4;

[0019] S5. Add 5-6 mol / L hydrochloric acid solution to the supernatant 4 to adjust the pH to 1, precipitate humic acid, centrifuge to obtain precipitate 4, mix precipitate 4 with 0.1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid in a plastic container to obtain a turbid solution, shake and centrifuge to remove the precipitate, repeat the operation of washing the precipitate with 0.1-1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid until the solid residue content is less than 1%, make the residue into a slurry with water, transfer it to a Visking dialysis tube, dialyze it in distilled water until no chloride ions are detected in the water, and freeze-dry it to obtain humic acid;

[0020] S6. The supernatant 1 and the supernatant 3 are mixed, and then extracted with XRD-8 macroporous adsorption resin and freeze-dried.

[0021] The molar ratio of fulvic acid to thionyl chloride in step S2 is 1:(5-10).

[0022] The mass ratio of the fulvic acid chloride to chitosan is (2-5):1.

[0023] Another object of the present invention is to protect the soil conditioner, which comprises the following components by weight: 20 to 50 parts of fulvic acid cross-linked chitosan, 5 to 20 parts of bentonite, 5 to 10 parts of fly ash, 1 to 5 parts of earthworm castings, 10 to 30 parts of biomass ash, and 10 to 25 parts of humic acid.

[0024] The mass ratio of the bentonite to the humic acid is 1:(1-3).

[0025] Another object of the present invention is to protect the application of the soil conditioner in acidic soil landscaping and acidic soil crop planting.

[0026] Beneficial Effects

[0027] The present invention prepares a soil conditioner, including fulvic acid cross-linked chitosan, bentonite, fly ash, earthworm feces, biomass ash, and humic acid components. Wherein fulvic acid cross-linked chitosan can improve the water absorption performance of chitosan, reduce the acidity and leaching solubility of fulvic acid, and fulvic acid can be gradually released with the slow degradation of chitosan, and the effect of long-term improvement of soil performance can be achieved. Humic acid can promote the formation of soil aggregates, and this aggregate structure is conducive to the improvement of soil air permeability and water permeability, so that air and moisture can circulate better in the soil, and the effect of using it alone is better. The present invention effectively improves the soil improvement effect by the targeted use of humic acid and fulvic acid in humus. Bentonite has strong water absorption, swelling, adsorption, and adhesion, and can be applied to sandy soil to increase the number of aggregates in the soil and reduce the soil bulk density. When bentonite and humic acid are compounded in a certain mass ratio, an organic-inorganic complex can be formed. After being applied to the soil, it can reduce the decomposition rate of organic materials, increase the humification coefficient, and increase the accumulation of soil organic matter. The physical and chemical properties of fly ash itself are the material basis for improving sandy soil. Its water holding capacity can reach 45% to 60%, which is significantly higher than sandy soil. Compared with conventional organic fertilizers such as chicken manure and cow dung, earthworm manure has basically no odor, no harm from pathogens (such as Escherichia coli, Salmonella, etc.) and parasite eggs, and the nutrients it contains are relatively stable and easy to be absorbed by plants. It will not cause root burns and other fertilizer damage to plants due to excessive nutrient concentration. In addition, earthworm manure has unique agglomeration properties and can effectively improve soil structure. It can bond soil particles into stable aggregates, increase soil porosity, and improve soil permeability and water retention.

[0028] The soil conditioner provided by the present invention has high porosity, makes the soil have excellent air permeability and porosity, improves soil structure, has the functions of retaining water and fertilizer, loosening and ventilation, and its nutrients are beneficial to plant rooting and rooting. At the same time, it can provide nutrition for seeds, improve survival rate, promote seed germination and plant growth, and is beneficial to the development of plant root systems. It is convenient to tighten the soil and prevent soil loss, and can effectively improve the soil granular structure, which is beneficial to the plant's absorption of water and nutrients. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Infrared spectra of chitosan, fulvic acid, and fulvic acid cross-linked chitosan. DETAILED DESCRIPTION

[0030] The technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0031] The raw materials used in the embodiments and comparative examples are described as follows:

[0032] Chitosan 1: viscosity 100-200 mPa·s, deacetylation ≥ 95%, product number M81003, Shanghai Myril Biochemical Technology Co., Ltd.;

[0033] Chitosan 2: viscosity 50-100 mPa·s, deacetylation ≥ 95%, product number R013967, Shanghai Yien Chemical Technology Co., Ltd.;

[0034] Chitosan 3: viscosity 200-400 mPa·s, deacetylation ≥ 95%, product number R013969, Shanghai Yien Chemical Technology Co., Ltd.;

[0035] Chitosan 4: viscosity 50-200 mPa·s, deacetylation 80-90%, product number R049136, Shanghai Yien Chemical Technology Co., Ltd.;

[0036] Fly ash: purity: 50-99.9%, Wuhan Jiyesheng Chemical Co., Ltd.;

[0037] Bentonite: PA092118, Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0038] Biomass charcoal: The ash is the remaining material after burning rice husk and rice straw;

[0039] Agricultural waste, garden waste, and earthworm manure are recycled waste from farmland, landscaping, and earthworm farms, removing gravel, glass, and plastic waste;

[0040] Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0041] Example 1 Preparation method of a soil conditioner

[0042] S1. Composting agricultural waste, garden waste and earthworm feces at a weight ratio of 25:5:1 to obtain humus, and extracting humic acid and fulvic acid from the humus;

[0043] The composting is carried out in a composting pool. First, a layer of hay or dead branches 10-15 cm thick is spread on the bottom of the composting pool, and agricultural waste, garden waste, and earthworm feces are evenly spread layer by layer in the composting pool according to the weight ratio, with a thickness of 1-1.5 meters. In the early stage, it can be turned over every 3-7 days. In order to speed up the progress of composting, special microbial agents can be added to the compost raw materials to keep the water content of the compost at about 50%-60%. When the air is dry, water is sprayed appropriately; when the humidity is too high, some dry raw materials are added for adjustment, and the pH value of the compost is measured regularly. When the pH value tends to be stable, the composting is finished, the humus is taken out, and the impurities that cannot be decomposed are removed, and the next step of extraction is carried out.

[0044] The extraction step of humic acid and fulvic acid comprises:

[0045] Remove impurities from the humus, dry and pass through a 400-mesh sieve, mix the humus and 1 mol / L hydrochloric acid solution in a nitrogen atmosphere, control the pH value to be in the range of 1 to 2, and the solid-liquid ratio of the humus to the hydrochloric acid to be 1 g / 10 ml, heat to boil and shake for 2 hours, centrifuge and filter the sediment 1 and the supernatant 1, and retain the supernatant 1 for extracting fulvic acid;

[0046] Sediment 1 was neutralized with 1 mol / L sodium hydroxide solution to pH 7, 1 mol / L sodium hydroxide solution was added, the solid-liquid ratio was 1:10, and the mixture was stirred for 6 hours under ultrasonic conditions, and then centrifuged to obtain supernatant 2;

[0047] Add 6 mol / L hydrochloric acid solution to the supernatant 2 to adjust the pH value to 1, heat to boil and shake for 2 hours, separate the supernatant 3 and the precipitate 3, and retain the supernatant 3 for extracting fulvic acid.

[0048] Add 1 mol / L sodium hydroxide solution to the precipitate 3, and add solid potassium chloride to make the potassium ion concentration in the solution 0.3 mol / L, and centrifuge to obtain a supernatant 4;

[0049] Add 6 mol / L hydrochloric acid solution to the supernatant 4 to adjust the pH to 1, precipitate humic acid, and centrifuge to obtain precipitate 4; mix the precipitate 4 with 0.1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid in a plastic container to obtain a turbid solution, shake and centrifuge to remove the precipitate, repeat the operation of washing the precipitate with a mixture of 0.1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid until the solid residue content is less than 1%, make the residue into a slurry with water, transfer it to a Visking dialysis tube, and dialyze it in distilled water until no chloride ions are detected in the water, and freeze-dry to obtain humic acid;

[0050] Mix supernatant 1 and supernatant 3, and pass through XRD-8 macroporous adsorption resin. XAD-8 resin needs to be soaked in 75% ethanol for 1-2 hours before use. Take a certain amount of XAD-8 resin, slowly flush it into the resin column with distilled water, and then rinse the resin repeatedly with distilled water until there is no residual ethanol in the effluent. After the resin column is balanced for 1 hour, use a peristaltic pump to pass the fulvic acid solution through the XAD-8 resin at a certain flow rate. When the amount of fulvic acid adsorbed by the resin reaches two-thirds of the saturated adsorption amount, the loading is completed. Then rinse the resin column repeatedly with distilled water until no chloride ions are detected in the effluent. Finally, elute the resin with a formic acid-ethanol solution with a volume ratio of 1:1, collect the eluate, concentrate and freeze-dry, and obtain fulvic acid solid.

[0051] S2. In a nitrogen atmosphere, 1 eq of fulvic acid was dissolved in chloroform, 10 eq of dichlorothionyl was added, and the mixture was stirred at 80°C for 2 h, and then the excess dichlorothionyl and chloroform solvents were evaporated to obtain fulvic acid chloride. Without further purification, the fulvic acid chloride was redissolved in a mixed solution of methanol and water; then 1 eq of chitosan 1 was dissolved in a 2 wt% acetic acid solution, 3 eq of fulvic acid chloride solution and 0.01 eq of triethylamine were added, and the mixture was heated to reflux at 80°C for 6 hours under nitrogen protection to generate a gel-like substance, which was then dried and crushed to obtain a powdery fulvic acid-cross-linked chitosan 1. The infrared spectra of the fulvic acid, chitosan 1 and fulvic acid-cross-linked chitosan 1 are as follows: Figure 1 As shown, the fulvic acid cross-linked chitosan 1 after reaction is at 3300-3500 cm -1 The stretching vibration of -OH was obviously shown at the position, indicating that fulvic acid was successfully cross-linked with chitosan 1.

[0052] S3. 30 parts by weight of fulvic acid-crosslinked chitosan, 15 parts by weight of bentonite, 8 parts by weight of fly ash, 3 parts by weight of earthworm castings, 20 parts by weight of biomass ash, and 15 parts by weight of humic acid were mixed uniformly to obtain a soil conditioner.

[0053] Example 2

[0054] The preparation method is the same as that of Example 1, except that: chitosan 1 is replaced by chitosan 2;

[0055] Example 3

[0056] The preparation method is the same as that of Example 1, except that: chitosan 1 is replaced by chitosan 3;

[0057] Example 4

[0058] The preparation method is the same as that of Example 1, except that: chitosan 1 is replaced by chitosan 4;

[0059] Example 5

[0060] The preparation method is the same as that of Example 1, except that: bentonite is 7.5 parts by weight, humic acid is 22.5 parts by weight;

[0061] Example 6

[0062] The preparation method is the same as that of Example 1, except that: bentonite is 5 parts by weight, humic acid is 25 parts by weight;

[0063] Example 7

[0064] The preparation method is the same as that of Example 1, except that: bentonite is 20 parts by weight, humic acid is 10 parts by weight;

[0065] Example 8

[0066] The preparation method is the same as that of Example 1, except that: fulvic acid cross-linked chitosan is 20 parts by weight, bentonite is 5 parts by weight, fly ash is 5 parts by weight, earthworm castings is 5 parts by weight, biomass ash is 10 parts by weight, and humic acid is 10 parts by weight.

[0067] Example 9

[0068] The preparation method is the same as that of Example 1, except that: fulvic acid cross-linked chitosan is 50 parts by weight, bentonite is 20 parts by weight, fly ash is 10 parts by weight, earthworm castings is 1 part by weight, biomass ash is 30 parts by weight, and humic acid is 25 parts by weight.

[0069] Example 10

[0070] The preparation method is the same as that of Example 1, except that: 1 eq of chitosan 1 is dissolved in a 2 wt % acetic acid solution, and 5 eq of fulvic acid chloride solution and 0.01 eq of triethylamine are added;

[0071] Embodiment 11

[0072] The preparation method is the same as that of Example 1, except that: 1 eq of chitosan 1 is dissolved in a 2 wt % acetic acid solution, and 1 eq of fulvic acid chloride solution and 0.01 eq of triethylamine are added;

[0073] Example 12

[0074] The preparation method is the same as that of Example 1, except that: 1 eq of chitosan 1 is dissolved in a 2 wt% acetic acid solution, and 6 eq of fulvic acid chloride solution and 0.01 eq of triethylamine are added;

[0075] Comparative Example 1

[0076] No soil conditioners were applied.

[0077] Comparative Example 2:

[0078] Compared with Example 1, the difference is that fulvic acid cross-linked chitosan is not added.

[0079] Comparative Example 3

[0080] Compared with Example 1, the difference is that humic acid is not added.

[0081] Comparative Example 4

[0082] Compared with Example 1, the difference is that 3 parts by weight of earthworm castings are not added.

[0083] Comparative Example 5

[0084] Compared with Example 1, the difference is that fulvic acid and chitosan 1 are added separately, 22.5 parts by weight of fulvic acid and 7.5 parts by weight of chitosan respectively.

[0085] Comparative Example 6

[0086] Compared with Example 1, the difference is that step S2 is: in a nitrogen atmosphere, fulvic acid is dissolved in a mixed solution of methanol and water; then 1eq chitosan 1 is dissolved in a 2wt% acetic acid solution, 3eq fulvic acid solution and 0.01eq glutaraldehyde are added, and heated to reflux at 40°C for 6 hours under nitrogen protection to generate a gel-like substance, which is then dried and crushed to obtain powdered fulvic acid chitosan.

[0087] Performance Testing

[0088] A green plot beside a main driveway in Guangzhou and a planting plot in a vegetable planting base in Huizhou were selected as research objects. The soil physical and chemical properties are shown in Table 1. The green plot and the planting plot were divided into 1m×1m test plots, and the soil conditioners of the embodiment and the comparative example were applied respectively.

[0089] Table 1 Physicochemical properties of the study plots

[0090]

[0091] Among them, the glass electrode method (soil: water is 1:2.5) is used to determine the pH; the potassium dichromate volumetric method is used to determine the organic matter content; the alkaline hydrolysis diffusion method is used to determine the alkaline nitrogen content; the molybdenum antimony colorimetric method is used to determine the effective phosphorus content; the ammonium acetate extraction method is used to determine the available potassium content; the hydrometer method is used to determine the soil texture, and the American texture standard is used for classification.

[0092] The soil conditioners of the embodiments and comparative examples were evenly spread on the surface of the corresponding plots, and sufficient water was sprayed. Salvia affine plants were selected and transplanted to the greening plots, and lettuce seeds were selected and planted in the planting plots. The soil conditioners were watered once every 1 to 2 days, and the following properties were tested:

[0093] (1) Water retention rate: Take a certain mass m0 of the soil of the embodiment and the comparative example, place it at 25°C and 50% RH, and remeasure the weight m1 after 96 hours to calculate the water retention rate: water retention rate = (m0 / m1) × 100%.

[0094] (2) Measurement of soil physical and chemical properties: 30 days after transplantation or planting, the organic matter, alkaline nitrogen, available phosphorus, and available potassium of the soil of the embodiment and the comparative example were measured; wherein the alkaline nitrogen content was determined by the alkaline diffusion method; the available phosphorus content was determined by the molybdenum antimony colorimetric method; and the available potassium content was determined by the ammonium acetate extraction method;

[0095] (3) Greening transplant survival rate: 14 days after transplantation, the survival rate of transplanted green plants was calculated;

[0096] (4) Root length of greening transplantation: 30 days after transplantation, randomly select 1m 2 The length of the main root of the transplanted green plants was measured in the sample plot;

[0097] (5) Planting germination rate: observe and record the number of seed germinations every day. After the seed germination becomes constant, count the total number of germinations and calculate the germination rate.

[0098] (6) Planting root length: 30 days after transplantation, randomly select 1m 2 The main root length of vegetables was measured in the sample plots;

[0099] (7) Green vegetation coverage rate: After one year, record the vegetation coverage rate of the green area.

[0100] Table 2 Soil physical and chemical property improvement results of the comparative examples of the embodiments

[0101]

[0102]

[0103] Table 3 Plant growth results of the comparative examples of the embodiments

[0104]

[0105]

[0106] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a soil conditioner, characterized in that: The following steps are involved: S1. Composting agricultural waste, garden waste, and earthworm feces at a weight ratio of (10-25):(5-15):1 to obtain humus, and extracting humic acid and fulvic acid from the humus; S2. dissolving fulvic acid in chloroform, adding thionyl chloride, stirring at 60-80°C for 1-2h, then evaporating to remove thionyl chloride to obtain fulvic acid chloride, and re-dissolving the fulvic acid chloride in a mixed solution of methanol and water; then dissolving chitosan in a 2wt% acetic acid solution, adding fulvic acid chloride solution and triethylamine, heating and refluxing at 60-80°C for 2-6h under nitrogen protection to generate a gel-like substance, and then drying and crushing to obtain powdered fulvic acid cross-linked chitosan; S3. Mix 20-50 parts of fulvic acid cross-linked chitosan, 5-20 parts of bentonite, 5-10 parts of fly ash, 1-5 parts of earthworm castings, 10-30 parts of biomass ash, and 10-25 parts of humic acid to obtain a soil conditioner.

2. The method for preparing the soil conditioner according to claim 1, characterized in that: The biomass ash is the remaining material after burning agricultural waste and garden waste.

3. The method for preparing the soil conditioner according to claim 1, characterized in that: The agricultural waste is selected from at least one of wheat straw, rice straw, corn straw, vegetable leaves, fruit tree branches, and rice husks; the garden waste is selected from at least one of dead branches and leaves and lawn clippings.

4. The method for preparing the soil conditioner according to claim 1, characterized in that: The deacetylation degree of the chitosan is greater than 90%, and the viscosity is 50-200 mPa·S.

5. The method for preparing the soil conditioner according to claim 1, characterized in that: The steps for extracting humic acid and fulvic acid from humus include: S1. remove impurities from the humus, dry and pass through a 400-600 mesh sieve, mix the humus and a 0.1-1 mol / L hydrochloric acid solution, control the pH value to be in the range of 1-2, and the solid-liquid ratio of the humus to the hydrochloric acid is (0.1-1 g) / 10 ml, heat and shake for 1-2 hours, separate the sediment 1 from the supernatant 1, and retain the supernatant 1 for extracting fulvic acid; S2. Sediment 1 was neutralized with 0.1-1 mol / L sodium hydroxide solution to a pH of 7, 0.1-1 mol / L sodium hydroxide solution was added, the solid-liquid ratio was 1:10, stirred under ultrasonic conditions for 4-6 hours, and centrifuged to obtain supernatant 2; S3. Add 5-6 mol / L hydrochloric acid solution to the supernatant 2 to adjust the pH value to 1, heat and shake for 1-2 hours, separate the supernatant 3 and the precipitate 3, and retain the supernatant 3 for extracting fulvic acid; S4. Add 0.1-1 mol / L sodium hydroxide solution to the precipitate 3, and add solid potassium chloride to make the potassium ion concentration in the solution 0.3 mol / L, and centrifuge to obtain a supernatant 4; S5. Add 5-6 mol / L hydrochloric acid solution to the supernatant 4 to adjust the pH to 1, precipitate humic acid, centrifuge to obtain precipitate 4, mix precipitate 4 with 0.1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid in a plastic container to obtain a turbid solution, shake and centrifuge to remove the precipitate, repeat the operation of washing the precipitate with 0.1-1 mol / L hydrochloric acid and 0.3 mol / L hydrofluoric acid until the solid residue content is less than 1%, make the residue into a slurry with water, transfer it to a Visking dialysis tube, dialyze it in distilled water until no chloride ions are detected in the water, and freeze-dry it to obtain humic acid; S6. The supernatant 1 and the supernatant 3 are mixed, and then extracted by XRD-8 macroporous adsorption resin and freeze-dried to obtain fulvic acid.

6. The method for preparing the soil conditioner according to claim 1, characterized in that: The mass ratio of fulvic acid to thionyl chloride in step S2 is 1:(5-10).

7. The method for preparing the soil conditioner according to claim 1, characterized in that: The mass ratio of the fulvic acid chloride to chitosan is (2-5):

1.

8. The method for preparing the soil conditioner according to claim 1, characterized in that: The mass ratio of the bentonite to the humic acid is 1:(1-3).

9. Use of the soil conditioner prepared by the method for preparing the soil conditioner according to any one of claims 1 to 8 in acidic soil landscaping and acidic soil crop planting.

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