A saline-alkali soil conditioner for improving soil fertility and structure of coastal saline-alkali farmland, and its preparation method and application

Abstract

The present invention relates to the technical field of saline-alkali land improvement, and specifically to a saline-alkali soil conditioner for improving the fertility of coastal saline-alkali farmland soil and improving its structure, as well as its preparation method and application. The present invention adopts calcium aluminum potassium silicon-based bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar and activated lignite mixed as mineral-based organic improvers, silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate mixed as aggregate binders, urea formaldehyde and ammonium sulfate mixed as nitrogen-increasing agents to prepare saline-alkali soil conditioners. The saline-alkali soil conditioner of the present invention can increase the content of organic carbon, nutrients and biomass in the soil, promote the bonding of dispersed soil particles, thereby accelerating the formation of aggregates and maintaining stability. The saline-alkali soil conditioner and improvement method of the present invention are economical, environmentally friendly, and easy to apply. They can effectively and long-term improve the physical and chemical properties of coastal saline-alkali farmland soil, increase crop yields, and are conducive to improving carbon sinks in coastal saline-alkali areas.

Description

Technical Field

[0001] The invention relates to the technical field of saline-alkali land improvement, and in particular to a saline-alkali soil conditioner that improves the soil fertility and structure of coastal saline-alkali farmland, and a preparation method and application thereof. Background Art

[0002] Soil salinization is one of the biggest obstacles to land resource utilization and agricultural production in the world. Excessive soil salinity and pH can limit plant growth and the activity of enzymes and microorganisms, thereby reducing agricultural productivity. The area of ​​coastal saline-alkali soil in my country is as high as 1.0×10 6 Hectares, the main reasons for soil salinization are shallow groundwater, high evaporation-precipitation ratio, and continuous seawater intrusion. Soil salinization causes problems such as low fertility, low microbial activity and poor soil structure, which seriously affect grain production and agricultural development. Therefore, the development of scientific, reasonable and technically efficient saline-alkali soil remediation technology is crucial to the development of coastal saline-alkali land resources and the increase of grain production.

[0003] Soil organic matter is the largest active carbon cycle reservoir on land, storing more carbon than the atmosphere and vegetation combined. Its maintenance is crucial for soil quality, sustainable crop production and climate change mitigation. Limited vegetation cover and microbial activity in saline-alkali areas restrict organic matter input, soil nutrient cycling and carbon storage. In poorly structured sodic soils, highly dispersed clay particles may lead to rapid disintegration of stable aggregates. Improving the soil structure of saline-alkali land (such as aggregate stability and pore space) can increase soil water conductivity, reduce the capillary action of salt, and create a favorable soil growth environment for crop growth. Increasing soil organic matter can reduce soil bulk density and is an important soil component for improving the physical properties of coastal saline soils. In addition, the high microbial activity near the organic matter source contributes to the production of microbial biomass and residues, which play a dominant role in the persistence of organic carbon in microaggregates. Therefore, improving coastal saline-alkali soils to improve soil organic carbon accumulation, soil fertility and crop yield is conducive to improving its soil carbon sequestration capacity.

[0004] In the prior art, the properties of saline-alkali soil can be improved by adding exogenous organic amendments, expanding the capacity of the activated carbon pool, and maintaining the balance between supply and demand of the organic carbon pool. Among them, CN116606657A discloses a new composite conditioner and comprehensive improvement technology for soda saline-alkali soil. Specifically, organic materials (such as lignite humic acid activation powder), composite calcium sources and trace elements are mixed to form a new composite conditioner, and combined with agronomic technology, it can increase soil organic matter and significantly increase crop yields. However, the lignite humic acid activation powder used is sodium humate, which will increase the Na in saline-alkali soil. +content, and a large amount of powdered organic materials and composite calcium sources are used, which will generate a large amount of dust during transportation and use, which is polluting and unsafe. CN115625194A discloses a method for improving carbonate soil by using waste building materials and waste biomass materials. Specifically, waste, furfural residue, calcium-based bentonite, biochar and fulvic acid are mixed to prepare a saline-alkali soil improver. Although the improver can improve the physical properties of saline-alkali soil and reduce salt, the odor of furfural residue during production and subsequent transportation of conditioners is difficult to solve, and the tillage depth also limits the rapid increase of carbon pools in the sub-arable layer of saline-alkali areas.

[0005] It can be seen that the saline-alkali soil conditioners in the prior art have problems such as difficult storage of raw materials, high humidity, strong odor, easy degradation, need for annual application, powdery and dusty, uneven particle size and easy uneven application, etc.

[0006] Therefore, preparing a saline-alkali soil conditioner that improves the fertility of coastal saline-alkali soil and improves its structure is of great significance for improving the quality of cultivated soil and crop yield in coastal saline-alkali areas. Summary of the invention

[0007] In view of the above-mentioned prior art, the purpose of the present invention is to provide a saline-alkali soil conditioner and its preparation method and application that can improve the soil fertility and structure of coastal saline-alkali farmland. The present invention uses a mixture of calcium aluminum potassium silicon-based bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar and activated lignite as a mineral-based organic improver, a mixture of silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate as an aggregate binder, and a mixture of urea formaldehyde and ammonium sulfate as a nitrogen-increasing agent. The saline-alkali soil conditioner and improvement method provided by the present invention are economical, environmentally friendly, and easy to apply. They can effectively and long-term improve the physical and chemical properties of coastal saline-alkali farmland soil, increase crop yields, and are conducive to improving carbon sinks in coastal saline-alkali areas.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] In a first aspect of the present invention, a saline-alkali soil conditioner is provided, wherein the saline-alkali soil conditioner comprises the following raw materials in parts by weight:

[0010] 82-90 parts of mineral-based organic improver, 5-12 parts of aggregate binder and 5-6 parts of nitrogen enhancer;

[0011] The mineral-based organic improver is prepared by mixing calcium-aluminum-potassium-silicon-based bagasse hydrothermal carbon, calcium-bentonite furfural residue biochar and activated lignite in a mass ratio of (40-55): (20-30): (25-30); the aggregate binder is prepared by mixing silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate in a mass ratio of (35-50): (30-45): (20-30).

[0012] Preferably, the nitrogen-increasing agent is a mixture of urea-formaldehyde and ammonium sulfate in a mass ratio of (1-1.2): (0.7-1.5).

[0013] Preferably, calcium aluminum potassium silicon-based bagasse hydrothermal charcoal is prepared by the following method:

[0014] The bagasse, potassium feldspar, desulfurized gypsum and shells are mixed to obtain a mixture; the mixture is mixed with a sulfuric acid solution and subjected to a hydrothermal reaction. After the reaction is completed, the reaction product is dried and crushed to obtain calcium aluminum potassium silicon-based bagasse hydrothermal charcoal.

[0015] Further preferably, the bagasse is the residual waste after sugarcane juice is squeezed, and the shells include scallop shells, oyster shells, and clam shells.

[0016] Further preferably, the mass ratio of bagasse, potassium feldspar, desulfurized gypsum and shell is (52-60):(15-24):(12-16):(8-15).

[0017] Further preferably, the mass ratio of the mixture to the sulfuric acid solution is 3:7.

[0018] Further preferably, the concentration of the sulfuric acid solution is 1 mol / L.

[0019] Further preferably, during the hydrothermal reaction, the reaction temperature is 180-220° C. and the reaction time is 4-6 h.

[0020] More preferably, the powder is crushed to 60 mesh.

[0021] Preferably, the calcium-based bentonite furfural residue biochar is prepared by the following method:

[0022] The furfural residue and the calcium-based expanded soil powder are mixed to obtain a mixed material; the mixed material is pyrolyzed, and after the pyrolysis is completed, the pyrolysis product is ground to obtain the calcium-based bentonite furfural residue biochar.

[0023] More preferably, the mass ratio of furfural residue to calcium-based expanded soil powder is (5-9):(1-2).

[0024] Further preferably, the specific operation of pyrolysis is: placing the mixed material under nitrogen protection, heating it to 400-600° C. at a heating rate of 5° C. / min, and pyrolyzing it for 2-3.5 hours.

[0025] More preferably, the pyrolysis product is ground to a particle size of 60 mesh.

[0026] Preferably, activated lignite is prepared by the following method:

[0027] The activated lignite is obtained by mixing lignite, ammonium sulfite, ammonium sulfate and ferric chloride, ball milling and drying.

[0028] More preferably, the mass ratio of lignite, ammonium sulfite, ammonium sulfate and ferric chloride is (52-58):(32-36):(8-9):(1-3).

[0029] More preferably, the ball milling speed is 250-450 r / min, and the ball milling time is 20 min.

[0030] The second aspect of the present invention provides a method for preparing a saline-alkali soil conditioner, comprising the following steps:

[0031] (1) Calcium aluminum potassium silicon-based bagasse hydrothermal carbon, calcium bentonite furfural residue biochar, and activated lignite are mixed to obtain a mineral-based organic improver; silicate cement, cationic hydroxyethyl cellulose, and calcium lignin sulfonate are mixed to obtain an aggregate binder; urea formaldehyde and ammonium sulfate are mixed to obtain a nitrogen-increasing agent;

[0032] (2) A mineral-based organic improver, an aggregate binder and a nitrogen-increasing agent are mixed to obtain a mixture, water is added to the mixture, and the mixture is granulated, dried and crushed to obtain a saline-alkali soil conditioner.

[0033] Preferably, the mass of water is 3-5% of the mass of the mixture.

[0034] Preferably, the particle size of the saline-alkali soil conditioner is 3-5 mm.

[0035] The third aspect of the present invention provides a use of a saline-alkali soil conditioner in improving coastal saline-alkali soil.

[0036] Preferably, improving the coastal saline-alkali soil includes increasing the fertility of the coastal saline-alkali soil and / or improving the structure of the coastal saline-alkali soil.

[0037] A fourth aspect of the present invention provides a method for improving coastal saline-alkali soil, comprising the following steps:

[0038] First, crush the straw and spread it evenly on the soil, then evenly apply the saline-alkali soil conditioner to the soil, and then perform rotary tillage, plowing, rotary tillage again, and compaction.

[0039] Preferably, the application amount of the saline-alkali soil conditioner is 25-35 tons / hectare, the application frequency is once every three years, and the application time is autumn or spring.

[0040] Preferably, the rotary tillage depth is 15-20 cm, the plowing depth is 30-35 cm, and the re-rotary tillage depth is 15-20 cm.

[0041] Preferably, the straw is crushed and evenly spread on the soil every season, and rotary tilled to a depth of 15-20 cm.

[0042] Beneficial effects of the present invention:

[0043] The present invention uses mineral-based organic improvers, aggregate binders and nitrogen-increasing agents as raw materials to prepare saline-alkali soil conditioners, wherein the mineral-based organic improvers can increase the organic carbon content, nutrient content and growth-promoting substances in the soil, thereby improving microbial activity, promoting crop growth and indirectly improving soil structure, and the mineral components can provide metal ions to replace the exchangeable sodium in the soil, and can also combine with organic matter to form an organic-inorganic complex that can be more stably retained in the cultivated land. The debris of the organic improver and the secretions produced by stimulating microbial growth can be used as biological adhesives for aggregate formation, and the porous structure can also adsorb more soil particles, thereby promoting aggregate formation. The cations and high molecular polymers in the aggregate binder can promote the bonding of dispersed soil particles and increase the bonding between soil particles, thereby accelerating the formation of aggregates and maintaining stability; and are also conducive to the bonding of the conditioner raw materials into granules during the extrusion granulation process. The nitrogen-increasing agent in the present invention mainly supplements the nitrogen absorbed by the organic improver and the straw return to the field during the degradation process, and the urea-formaldehyde is more stable than the common nitrogen fertilizer after extrusion granulation, which can reduce the nitrogen loss in the field.

[0044] The present invention applies the saline-alkali soil conditioner to a tillage layer depth of 30-35 cm, thereby increasing the thickness of the fertile tillage layer, thereby reducing the amount of salt accumulation in the root zone, and increasing the soil carbon storage capacity and carbon pool. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0046] As mentioned in the background technology, the soil organic matter content in coastal saline-alkali land is low, and the organic matter content in the soil is crucial to soil quality, crop production, etc., and the highly dispersed clay particles in poorly structured sodium soil may lead to the rapid disintegration of stable aggregates. Therefore, soil conditioners are often added to increase the organic matter content in coastal saline-alkali soil, thereby improving soil structure and composition and increasing crop yields. Among them, organic amendments can provide rich organic matter, improve soil structure, and stimulate microbial activity; inorganic amendments can provide Ca 2+ / Mg 2+ / Al 3+ Replace exchangeable Na +, and promote the formation of calcium-OM-mineral complexes. By adding exogenous organic amendments, the properties of saline-alkali soils can be improved, the capacity of the active carbon pool can be expanded, and the balance of supply and demand of the organic carbon pool can be maintained. Studies have shown that the adsorption interaction between mineral particles and organic matter is the main factor in the long-term storage potential of organic carbon in the soil. Even though irrigation and salt washing is an efficient measure to reduce salt in saline-alkali areas, some coastal saline-alkali areas have limited water resources and can only rely on natural precipitation.

[0047] Based on this, the purpose of the present invention is to provide a saline-alkali soil conditioner and its preparation method and application for improving the fertility of coastal saline-alkali cultivated land soil and improving its structure. Specifically, the present invention uses mineral-based organic improvers, aggregate binders and nitrogen-increasing agents as raw materials to prepare saline-alkali soil conditioners, and uses them for coastal saline-alkali soil improvement. Among them, the organic matter in the mineral-based organic improver can increase the organic carbon content, nutrient content and growth-promoting substances in the soil, thereby improving microbial activity, promoting crop growth and indirectly improving soil structure; mineral components can provide metal ions to replace exchangeable sodium in the soil, and combine with organic matter to form an organic-inorganic complex to slow down the degradation process of organic materials, thereby reducing soil warming, carbon loss and nitrogen competition, and more stably retaining them in cultivated land. The metal cations and high molecular polymers in the aggregate binder can promote the bonding of dispersed soil particles and increase the bonding between soil particles, thereby accelerating the formation of aggregates and maintaining stability. The nitrogen-increasing agent mainly supplements the nitrogen absorbed by organic improvers and straw return to the field during the degradation process.

[0048] The bagasse in calcium aluminum potassium silicon-based bagasse hydrothermal charcoal is a byproduct of food processing and has a wide range of sources. It contains a large amount of polysaccharides, such as lignin, cellulose and hemicellulose. It can be efficiently converted into stable, porous, functional group-rich carbon-containing compounds through environmentally friendly hydrothermal carbonization technology, which can stably increase the organic matter content of saline-alkali farmland. Potassium feldspar, desulfurized gypsum and shellfish shells are combined with bagasse hydrothermal charcoal as metal minerals after hydrothermal reaction, and play an improving role as a mineral improver. Among them, potassium feldspar is a potassium aluminum silicate mineral with a framework crystal structure composed of silicon oxygen tetrahedrons, with a chemical formula of K2O·Al2O3·6SiO2, and its main components are SiO2, Al2O3, K2O, CaO, etc. The main components of desulfurized gypsum are calcium sulfate dihydrate (CaSO4·2H2O), silicon dioxide, calcium carbonate, calcium sulfite, calcium chloride, and magnesium chloride, and the content of calcium sulfate dihydrate is ≥93%.

[0049] The furfural residue in the calcium-bentonite furfural residue biochar is an industrial waste with a pungent odor, high water content, and is not easy to store. Similar to bagasse, furfural residue also contains a large amount of lignin, cellulose, and hemicellulose. These polysaccharides are converted into stable, porous aromatic carbon compounds after pyrolysis, and the odor is greatly reduced. Compared with the common practice of directly adding furfural residue to saline-alkali land, furfural residue biochar can solve the problems of large volume, high humidity, and strong odor during transportation, as well as reduce the problems of soil warming, carbon loss, and nitrogen competition caused by soil application. The porosity of furfural residue biochar can be further increased by modification with calcium-bentonite, and calcium-bentonite can be used as an adsorption binding site for input carbon decomposition products and microbial source carbon to be more stably stored in saline-alkali soil.

[0050] The activated lignite is catalyzed by ball milling with ammonium sulfite and ammonium sulfate. Firstly, it avoids the conventional alkaline catalysis and selects a neutral or acidic catalyst for better application in saline-alkali soil. Secondly, the ammonium ions contained in the catalyst can provide nutrients for the growth of microorganisms and plants as nitrogen. Moreover, the ball milling method is more labor-saving and time-saving than the liquid catalysis method, and it eliminates the steps of preparing solution, shaking, filtering, drying, screening, etc. The raw lignite powder contains humic acid, which can be used as an exogenous stable organic carbon to store long-term organic carbon in the soil, thus realizing the long-term storage of organic matter. The activated lignite can quickly dissolve in water, providing available carbon and nitrogen for the growth and reproduction of microorganisms, and providing nutrients such as amino acids and secondary hormones for plants to promote crop growth, and improve their stress resistance (resistance to salt damage) and nutrient absorption and utilization.

[0051] The present invention adopts calcium aluminum potassium silicon-based bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar and activated lignite combination as mineral-based organic improvers. After applying them to saline-alkali farmland, the organic improvers can increase the organic carbon content, nutrient content and growth-promoting substances in the soil, thereby improving microbial activity, promoting crop growth and indirectly improving soil structure.

[0052] At the same time, the present invention adopts a combination of silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate as an aggregate binder, and its good physical properties can improve the air permeability and water permeability of the soil, accelerate the leaching of salt in saline-alkali farmland to create a good soil habitat. A good soil environment can promote crop growth, root elongation and the secretion of root secretions, thereby further promoting the improvement of the physical properties of saline-alkali soil, and ultimately the crops grow vigorously and the yield is greatly increased. Moreover, calcium lignin sulfonate, as a lignin sulfonate, can play a certain growth-promoting role on plants. In addition, the present invention squeezes the conditioning agent components together through extrusion granulation technology, which solves the field application problems of the current common powdery conditioning agents, such as easy dusting, uneven particle size and easy uneven application.

[0053] The present invention also utilizes the saline-alkali soil conditioner to improve coastal saline-alkali soil. During the improvement process, the saline-alkali soil conditioner is applied to saline-alkali farmland together with returning straw to the field. The easily degradable carbon contained in the straw will be rapidly degraded after being applied to the soil. During the straw degradation process, the rapid growth and reproduction of microorganisms will cause various problems such as soil warming, carbon loss, and nitrogen competition. The mineral components in the present invention will slow down the straw degradation process by combining straw-source carbon and inhibiting microbial activity, thereby reducing soil warming, carbon loss, and nitrogen competition. More and longer-term residues of straw in saline-alkali farmland are also conducive to increasing the air permeability in the soil. Innovations in raw materials, processing methods, and application methods can effectively and long-term improve the physical and chemical properties of saline-alkali soils and increase crop yields.

[0054] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0055] The experimental materials used in the examples of the present invention are all conventional experimental materials in the field and can be purchased through commercial channels. Among them, the coastal saline-alkali soil was taken from Kenli District, Dongying City, Shandong Province (118°36′5″E, 37°35′37″N), with a texture of sandy loam, containing 37.0% sand, 59.4% silt, and 3.6% clay. The soil bulk density is 1.54 g·cm -3 , the organic carbon content is 3.03 g·kg -1 , the salt content is 21.58g·kg -1 , which is a heavily saline soil.

[0056] Embodiment 1:

[0057] 1. Raw material composition (by mass):

[0058] 86 parts of mineral-based organic improver, 10 parts of aggregate binder and 5.5 parts of nitrogen enhancer;

[0059] Among them, the mineral-based organic modifier is a mixture of calcium-aluminum-potassium-silicon-based sugarcane bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar and activated lignite in a mass ratio of 48:25:28; the aggregate binder is a mixture of silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate in a mass ratio of 35:45:20; the nitrogen-enhancing agent is a mixture of urea-formaldehyde and ammonium sulfate in a mass ratio of 1.1:1.1.

[0060] 2. Preparation method:

[0061] (1) After crushing bagasse, potassium feldspar, desulfurized gypsum and shells to 60 meshes respectively, the mixture is mixed in a mass ratio of 52:24:16:8 to obtain a mixture; the mixture is mixed with a 1 mol / L sulfuric acid solution in a mass ratio of 3:7, placed in a hydrothermal reactor, and subjected to a hydrothermal reaction at 200° C. for 5 hours. After the reaction is completed, the reaction product is dried and crushed through a 60-mesh sieve to obtain calcium aluminum potassium silicon-based bagasse hydrothermal carbon powder;

[0062] The specific surface area and elemental analysis of calcium aluminum potassium silicon-based bagasse hydrothermal carbon powder showed that the specific surface area was 6.24 m 2 ·g -1 , the calcium content is 8.37% and the organic carbon content is 32.25%.

[0063] (2) Furfural slag and calcium-based expanded soil powder were mixed in a mass ratio of 5:1 (furfural slag was calculated by dry weight) to obtain a mixed material; the mixed material was placed under nitrogen protection, heated to 400°C at a heating rate of 5°C / min, and pyrolyzed at this temperature for 3.5 hours. After the pyrolysis was completed, it was naturally cooled to room temperature, and the pyrolysis product was ground to a particle size of 60 meshes to obtain calcium-based bentonite furfural slag biochar powder;

[0064] The specific surface area of ​​calcium-based bentonite furfural residue biochar powder was measured and elemental analysis was performed. The specific surface area was 6.97 m 2 ·g -1 , the organic carbon content is 61.25%.

[0065] (3) mixing lignite, ammonium sulfite, ammonium sulfate and ferric chloride in a mass ratio of 58:32:9:1, placing the mixture in a ball mill, milling the mixture at 300 r / min for 20 min, and drying the mixture to obtain activated lignite powder;

[0066] The water-soluble humic acid content in activated lignite and ordinary lignite (the content of lignite is the same) was determined by hot water extraction-K2Cr2O7 volumetric method. The water-soluble humic acid content in activated lignite was 32.74%, which was 30.24% higher than that in ordinary lignite.

[0067] (4) Calcium aluminum potassium silicon-based sugarcane bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar, and activated lignite are mixed to obtain a mineral-based organic improver; Calcium aluminum potassium silicon-based sugarcane bagasse hydrothermal charcoal, calcium-based bentonite furfural residue biochar, and activated lignite are mixed to obtain a mineral-based organic improver.

[0068] (5) A mineral-based organic improver, an aggregate binder and a nitrogen-increasing agent are mixed to obtain a mixture, water is added to the mixture, wherein the mass of the water is 4% of the mass of the mixture, and the mixture is granulated, dried and crushed to obtain a saline-alkali soil conditioner with a particle size of 4 mm.

[0069] Comparative Example 1:

[0070] The difference between this comparative example and Example 1 is that only mineral-based organic improver is used as saline-alkali soil conditioner, wherein the preparation method of the mineral-based organic improver is the same as that of Example 1.

[0071] Comparative Example 2:

[0072] The difference between this comparative example and Example 1 is that only the aggregate binder is used as the saline-alkali soil conditioner, wherein the preparation method of the aggregate binder is the same as that of Example 1.

[0073] Comparative Example 3:

[0074] The difference between this comparative example and Example 1 is that only a nitrogen-enhancing agent is used as a saline-alkali soil conditioner, wherein the preparation method of the nitrogen-enhancing agent is the same as that of Example 1.

[0075] Comparative Example 4:

[0076] The difference between this comparative example and Example 1 is that the mineral-based organic modifier is only calcium-aluminum-potassium-silicon-based sugarcane bagasse hydrothermal charcoal. The preparation method of calcium-aluminum-potassium-silicon-based sugarcane bagasse hydrothermal charcoal is the same as that of Example 1.

[0077] Comparative Example 5:

[0078] The difference between this comparative example and Example 1 is that the mineral-based organic modifier is only calcium-based bentonite furfural residue biochar. The preparation method of calcium-based bentonite furfural residue biochar is the same as that of Example 1.

[0079] Comparative Example 6:

[0080] The difference between this comparative example and Example 1 is that the mineral-based organic modifier is only activated lignite. The preparation method of activated lignite is the same as that of Example 1.

[0081] Test Example 1:

[0082] The calcium-based bentonite furfural residue biochar powder prepared in Example 1 was used as the test group (BFC) and the mixture was heated to 40 g kg -1 The amount of soil added was added to 100g of coastal saline-alkali soil passed through a 2mm sieve, stored in a 180mL plastic cup, and stirred thoroughly. In addition, two control groups were set up, namely a blank control group (CK) and a furfural residue control group (FR). The amount of furfural residue added was the same as the amount of calcium bentonite furfural residue biochar powder added, and each treatment was repeated 3 times.

[0083] Deionized water was added to the soil every week to fill 60% of the pore volume, and a layer of aluminum foil (with 6 holes of 0.5 cm in diameter) was wrapped on each plastic cup. Soil sampling was carried out on the 400th day of incubation to measure the soil organic carbon content, particulate organic carbon (POC) and mineral-bound organic carbon (MAOC) content. The results are shown in Table 1.

[0084] Among them, soil organic carbon content was determined by potassium dichromate oxidation-external heating method;

[0085] The content determination method of particulate organic carbon (POC) and mineral-bound organic carbon (MAOC) is as follows: sodium hexametaphosphate (dispersant) solution oscillation separation-potassium dichromate external heating method (Yao Zhongkai, 2023). Weigh 4g of soil that has passed a 60-mesh sieve, add 40mL of sodium hexametaphosphate, and oscillate for 18 hours. Pass the soil suspension through a 0.053mm sieve, collect the remaining soil samples on and under the sieve into an aluminum box of known weight, dry the aluminum box and soil sample at 60°C, and weigh them. The mineral-bound organic matter in the dried sample under the sieve is used to measure the organic carbon content using the method for determining soil organic carbon.

[0086] Particulate organic carbon content = total organic carbon content - mineral-bound organic carbon content.

[0087] Table 1

[0088]

[0089]

[0090] As can be seen from Table 1, compared with the blank control group, although the direct addition of furfural residue can increase the content of soil organic carbon, POC and MAOC, the furfural residue is processed into biochar in the present application, and its effect of increasing organic matter in the soil is much higher than that of the FR group compared with the blank control group.

[0091] Test Example 2:

[0092] The agglomerate binder powder prepared in Example 1 was heated to 5 g·kg -1 The amount of soil added was added to 100 g of coastal saline soil through a 2 mm sieve and stored in a 180 mL plastic cup and stirred thoroughly, and a blank control was made, and each treatment was repeated four times. Deionized water was added to the soil to fill 60% of the pore volume, and a layer of aluminum foil (with 6 holes of 0.5 cm diameter) was wrapped on each plastic cup, and the soil was sampled after 7 days of constant temperature incubation at 25 °C.

[0093] The water-stable aggregate components and their contents of the two treated soils were determined by wet sieving method: the soil was spread on a 0.25 mm sieve surface and soaked in water for 5 min. – 1 The vibration frequency was vibrated in water with an amplitude of 3 cm and passed through 0.25 mm and 0.053 mm mesh sieves in turn.

[0094] The content of macroaggregates (>0.25mm) in the blank treatment was 3.12%, the content of microaggregates (0.053-0.25mm) was 33.48%, and the content of clay (<0.053mm) was 63.4%; the content of macroaggregates in the soil treated with aggregate binder was 21.87%, the content of microaggregates was 41.53%, and the content of clay was 36.6%.

[0095] Test Example 3:

[0096] 1. The saline-alkali soil conditioner prepared in Example 1 was added at 40 g kg -1 The amount of soil added was added to 100 g of coastal saline-alkali soil passed through a 2 mm sieve and stored in a 180 mL plastic cup and stirred thoroughly; deionized water was added to the soil every week to fill 60% of the pore volume, and a layer of aluminum foil (with 6 holes of 0.5 cm diameter) was wrapped on each plastic cup. Soil sampling was carried out on the 400th day of cultivation to detect the content of organic carbon, particulate organic carbon and mineral-related organic carbon in the soil. The detection method was the same as in Experimental Example 1. The results are shown in Table 2.

[0097] Table 2

[0098]

[0099] 2. The saline-alkali soil conditioners prepared in Example 1 and Comparative Examples 1-6 were respectively added at 5 g·kg -1 The amount of soil added was added to 100 g of coastal saline-alkali soil that passed through a 2 mm sieve, stored in a 180 mL plastic cup and fully stirred, and a blank control was made. Each treatment was repeated four times. Deionized water was added to the soil to fill 60% of the pore volume, and a layer of aluminum foil (with 6 holes of 0.5 cm diameter) was wrapped on each plastic cup. The soil was sampled after 7 days of constant temperature incubation at 25 ° C. The water-stable aggregate components of the two treated soils were determined by wet sieving: the soil was spread on a 0.25 mm sieve surface, soaked in water for 5 min, and then sieved at 25 times / min. – 1 The vibration frequency was vibrated in water with an amplitude of 3 cm and passed through 0.25 mm and 0.053 mm mesh sieves in turn. The content of macroaggregates, microaggregates and clay content in the soil were detected, and the results are shown in Table 3.

[0100] Table 3

[0101]

[0102] It can be seen from Table 2 and Table 3 that the use of the saline-alkali soil conditioner prepared by the present invention in coastal saline-alkali soil can significantly increase the organic carbon content in the soil to 17.78 g·kg -1 , the particle organic carbon content reaches 12.37g·kg-1 , mineral-related organic carbon content to 7.41 g kg -1 It can be seen that the saline-alkali soil conditioner of the present invention can significantly improve the fertility of coastal saline-alkali soil. At the same time, the saline-alkali soil conditioner prepared by the present invention is used in coastal saline-alkali soil, which can also significantly improve the structure of coastal saline-alkali soil, increase the content of macroaggregates and microaggregates in the soil, and reduce the content of clay particles in the soil.

[0103] Test example 4: Potted plant experiment

[0104] There are 8 treatment groups in the experiment, as follows:

[0105] Treatment group 1: coastal saline soil with a 5 mm sieve, compound fertilizer (application rate: 4 g per pot -1 ), the saline-alkali soil conditioner prepared in Example 1 (application amount is 73g per pot -1 );

[0106] Treatment group 2: The saline-alkali soil conditioner prepared in comparative example 1 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0107] Treatment group 3: The saline-alkali soil conditioner prepared in comparative example 2 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0108] Treatment group 4: The saline-alkali soil conditioner prepared in comparative example 3 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0109] Treatment group 5: The saline-alkali soil conditioner prepared in comparative example 4 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0110] Treatment group 6: The saline-alkali soil conditioner prepared in comparative example 5 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0111] Treatment group 7: The saline-alkali soil conditioner prepared in comparative example 6 was used to replace the saline-alkali soil conditioner in treatment group 1, and the other components and application amounts were the same as those in treatment group 1;

[0112] Treatment group 8: blank control group, including only coastal saline-alkali soil and compound fertilizer, and the application amount was the same as that of treatment group 1.

[0113] Among them, the compound fertilizer is humic acid compound fertilizer, purchased from Shandong Agricultural University Fertilizer Technology Co., Ltd., and the product model is 18-10-12 humic acid compound fertilizer.

[0114] After mixing the materials of each treatment group, they were placed in plastic pots (22.5 cm high, 22 cm in diameter, 18 cm in bottom diameter) with a soil height of about 20 cm. First, about 17 cm of soil was added and watered to make the soil completely moist to ensure that the soil environment for wheat growth was moist. After one day, 30 wheat seeds were sown in each pot, covering the remaining 3 cm of soil. The irrigation water was tap water. During the wheat growth process, small granular urea (application amount 1 g per pot) was applied at the jointing stage. -1 ), wheat yield was measured during wheat harvest (wheat was dried and weighed after threshing) and soil was sampled, the water stability of soil aggregates was determined by wet sieving method, and the mean mass diameter (MWD) of aggregates was calculated based on the aggregate composition data. The results are shown in Table 4.

[0115] The calculation formula of the average mass diameter of the aggregates is:

[0116]

[0117] Where W i is the percentage of mass of aggregates in the ith particle size (%); is the average diameter of aggregates of a certain level (mm).

[0118] Table 4

[0119]

[0120]

[0121] As can be seen from Table 4, the saline-alkali soil conditioner prepared by the present invention (treatment group 1) can increase the wheat yield to 34.41 g / cm2. -1 Compared with treatment group 8 (control group), the yield increased by 13.29g per pot -1 The average mass diameter of the aggregates was 0.1974 mm. The wheat yield was 23.35-27.12 g / pot using the saline-alkali soil conditioner prepared in Comparative Examples 1-6 (treatment groups 2-7). -1 Compared with treatment group 8 (control group), only 2.23-6.0g of basin weight was increased -1 It can be seen that the combination of the mineral-based organic improver, the aggregate binder and the nitrogen enhancer used in the present invention has a synergistic effect in increasing wheat yield and the average mass diameter of aggregates.

[0122] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A saline-alkali soil conditioner, characterized in that: The saline-alkali soil conditioner comprises the following raw materials in parts by weight: 82-90 parts of a mineral-based organic improver, 5-12 parts of an aggregate binder, and 5-6 parts of a nitrogen enhancer; The mineral-based organic improver is prepared by mixing calcium-aluminum-potassium-silicon-based bagasse hydrothermal carbon, calcium-bentonite furfural residue biochar and activated lignite in a mass ratio of (40-55): (20-30): (25-30); the aggregate binder is prepared by mixing silicate cement, cationic hydroxyethyl cellulose and calcium lignin sulfonate in a mass ratio of (35-50): (30-45): (20-30); Among them, calcium aluminum potassium silicon-based bagasse hydrothermal carbon is prepared by the following method: The sugarcane bagasse, potassium feldspar, desulfurized gypsum and shells are mixed in a mass ratio of (52-60): (15-24): (12-16): (8-15) to obtain a mixture; the mixture is mixed with a sulfuric acid solution in a mass ratio of 3:7, and a hydrothermal reaction is carried out at 180-220° C. for 4-6 hours. After the reaction is completed, the reaction product is dried and crushed to obtain calcium aluminum potassium silicon-based sugarcane bagasse hydrothermal charcoal; Calcium-based bentonite furfural residue biochar is prepared by the following method: The furfural residue and calcium-based bentonite powder are mixed in a mass ratio of (5-9): (1-2) to obtain a mixed material; the mixed material is pyrolyzed, and after the pyrolysis is completed, the pyrolysis product is ground to obtain calcium-based bentonite furfural residue biochar; the specific pyrolysis operation is: the mixed material is placed under nitrogen protection, the temperature is increased to 400-600°C at a heating rate of 5°C / min, and the pyrolysis is performed for 2-3.5h; Activated lignite is prepared by the following method: Lignite, ammonium sulfite, ammonium sulfate and ferric chloride are mixed in a mass ratio of (52-58):(32-36):(8-9):(1-3), ball-milled and dried to obtain activated lignite.

2. The saline-alkali soil conditioner according to claim 1, characterized in that The nitrogen-enhancing agent is prepared by mixing urea-formaldehyde and ammonium sulfate in a mass ratio of (1-1.2): (0.7-1.5).

3. The method for preparing the saline-alkali soil conditioner according to claim 1 or 2, characterized in that: The following steps are involved: (1) Calcium aluminum potassium silicon-based bagasse hydrothermal carbon, calcium bentonite furfural residue biochar, and activated lignite are mixed to obtain a mineral-based organic improver; silicate cement, cationic hydroxyethyl cellulose, and calcium lignin sulfonate are mixed to obtain an aggregate binder; urea formaldehyde and ammonium sulfate are mixed to obtain a nitrogen enhancer; (2) A mineral-based organic improver, an aggregate binder and a nitrogen-increasing agent are mixed to obtain a mixture, water is added to the mixture, and the mixture is granulated, dried and crushed to obtain a saline-alkali soil conditioner.

4. Use of the saline-alkali soil conditioner according to claim 1 or 2 in improving coastal saline-alkali soil.

5. The use according to claim 4, characterized in that Improving coastal saline-alkali soil includes improving the fertility of coastal saline-alkali soil and / or improving the structure of coastal saline-alkali soil.

6. A method for improving coastal saline-alkali soil, characterized in that: The following steps are involved: First, the straw is crushed and evenly spread on the soil, then the saline-alkali soil conditioner according to claim 1 or 2 is evenly applied to the soil, and rotary tillage, plowing, rotary tillage again, and compaction are performed; The application rate of saline-alkali soil conditioner is 25-35 tons / hectare, the application frequency is 3 years / time, the application time is autumn or spring, the rotary tillage depth is 15-20cm, the plowing depth is 30-35cm, and the re-rotary tillage depth is 15-20cm.

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