Special carbon-based structure improver for saline-alkali soil as well as preparation method and application of special carbon-based structure improver

Abstract

The invention discloses a special carbon-based structure improver for saline-alkali soil as well as a preparation method and application thereof, and belongs to the technical field of soil improvement. The modifier is obtained by scientifically compounding the phosphoric acid or citric acid modified charcoal, the calcium-based conditioner, the organic acid complexing agent and the saline-alkaline tolerant functional microbial agent, and the modifier can significantly reduce the salt content and sodium adsorption ratio (SAR) of soil, effectively break soil hardening, greatly increase the capillary porosity and improve the soil quality. Therefore, the physical structure, the chemical environment and the microbial activity of the saline-alkali soil are rapidly improved. Besides, agricultural wastes are used as main raw materials, so that the method is environment-friendly and relatively low in cost, the yield of crops such as wheat and corn can be remarkably increased while rapid improvement of the saline-alkali soil is realized, and the method has remarkable ecological benefits and economic benefits and is suitable for large-area popularization and application.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, specifically to a carbon-based structural conditioner for saline-alkali land, its preparation method, and its application. Background Technology

[0002] Saline-alkali land is one of the major obstacle soil types restricting agricultural production and ecological security. Its main problems are excessively high salt concentration in the soil solution and a high proportion of harmful ions such as sodium ions, which leads to soil particle dispersion, structural deterioration, poor permeability, severe compaction, and causes physiological drought, ion toxicity, and nutrient imbalance in plants, seriously affecting crop emergence, growth, and yield.

[0003] Currently, the main technical measures for improving saline-alkali land include water conservancy engineering improvement (such as irrigation to leach salt), chemical improvement (such as the application of gypsum, phosphogypsum, desulfurized gypsum, etc.), and biological improvement (such as planting salt-tolerant plants). However, these methods have certain limitations: water conservancy engineering improvement consumes a large amount of water and is prone to causing groundwater level rise and secondary salinization risks; although traditional chemical amendments can replace sodium ions in the soil, they often have a short period of action and limited long-term improvement on soil physical structure, and may introduce new environmental problems; biological improvement, on the other hand, has a long cycle and slow results.

[0004] Biochar, as an emerging soil amendment material, possesses a porous structure, high specific surface area, abundant surface functional groups, and stable chemical properties, showing great potential in improving soil structure, enhancing water and fertilizer retention capacity, and regulating soil pH. However, the targeted improvement effect of biochar alone on saline-alkali land, especially on soils with high sodium ion ratio and high saturation level (ESP), remains unsatisfactory, particularly due to its limited ability to specifically adsorb and passivate high concentrations of sodium ions.

[0005] Therefore, there is an urgent need to develop a specialized soil conditioner that is efficient, durable, environmentally friendly, and can comprehensively improve the physical and chemical properties of saline-alkali land. Summary of the Invention

[0006] In view of the above-mentioned prior art, the purpose of this invention is to provide a carbon-based structural modifier for saline-alkali land, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a carbon-based structural modifier specifically for saline-alkali land, the modifier comprising the following components by weight: Modified biochar 60-80 parts; 15-25 parts calcium-based conditioning agent; 5-10 parts of organic acid complexing agent; 1-3 parts of functional microbial inoculant.

[0008] The modified biochar was prepared by the following method: (1) Agricultural waste is pyrolyzed and carbonized at 400-600℃ under oxygen-limited conditions to obtain primary biochar; (2) Impregnate the raw biochar with a 5% acid solution for 12-24 hours; (3) Dry at 80-105℃, then activate at 300-400℃ for 1-2 hours, cool and then crush and sieve to obtain modified biochar.

[0009] Preferably, the acid solution in step (2) is a phosphoric acid solution or a citric acid solution; the solid-liquid ratio of the virgin biochar to the acid solution is 1:(5-10).

[0010] Preferably, the calcium-based conditioning agent is selected from one or a mixture of two or more of gypsum, calcium silicate, calcium nitrate, and calcium citrate.

[0011] Preferably, the organic acid complexing agent is selected from one or a mixture of two or more of humic acid, fulvic acid, and polyaspartic acid.

[0012] Preferably, the functional microbial agent is a compound agent containing salt-tolerant phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and growth-promoting bacteria, wherein the effective viable count of the compound agent is ≥10 billion / gram.

[0013] Preferably, the application rate of the improver is 300-800 kg / mu, and the application method is to spread it evenly and then plow it into the soil to a depth of 20-30 cm.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned modifier, characterized by comprising the following steps: (1) Weigh each component according to the formula; (2) Mix the modified biochar, calcium-based conditioner and organic acid complexing agent evenly to obtain a mixed matrix; (3) The functional microbial agent is premixed with a small amount of mixed matrix, and then mixed with the remaining mixed matrix twice to prepare the modifier.

[0015] In a third aspect, the present invention provides the application of the above-mentioned amendment in the preparation of soil amendment products for improving saline-alkali land.

[0016] The saline-alkali land has a water-soluble total salt content ≥3.0 g / kg, pH ≥8.0, and sodium adsorption ratio ≥10.

[0017] The beneficial effects of this invention are: 1. This invention obtains a soil conditioner by scientifically compounding phosphoric acid or citric acid-modified biochar, calcium-based conditioner, organic acid complexing agent and salt-alkali tolerant functional microbial agent. This conditioner can significantly reduce soil salinity and sodium adsorption ratio (SAR), effectively break up soil compaction, and greatly increase capillary porosity, thereby rapidly improving the physical structure, chemical environment and microbial activity of saline-alkali soil.

[0018] 2. This invention uses agricultural waste as the main raw material, which is environmentally friendly and low-cost. While achieving rapid improvement of saline-alkali land, it can significantly increase the yield of crops such as wheat and corn, thus having significant ecological and economic benefits and is suitable for large-scale promotion and application. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] As mentioned earlier, existing saline-alkali land improvement technologies suffer from problems such as high water consumption, slow effectiveness, and easy rebound. The purpose of this invention is to provide a carbon-based structural improver specifically for saline-alkali land, using structural optimization to enhance the functionality of saline-alkali land. This improver uses biochar as a carrier and, through loading specific modifying substances, integrates physical structure adjustment, chemical ion replacement, and biostimulation functions. It can effectively reduce soil salinity and alkalinity, improve soil aggregate structure, and enhance soil permeability and water retention, thereby creating a favorable rhizosphere environment for crop growth.

[0021] Compared with the prior art, the present invention has the following outstanding effects: 1. Synergistic Effect, Targeted Salinity Reduction and Alkalinity Improvement, Significantly Improving Soil Structure: This invention organically combines four improvement mechanisms: physical adsorption (modified biochar), chemical replacement (calcium-based conditioner), ion complexation (organic acids), and biological activation (functional microbial agents). This multi-dimensional, rapid, and sustained improvement of the undesirable properties of saline-alkali land is achieved. Modified biochar and organic acids strongly adsorb and complex sodium ions, while the calcium-based conditioner provides ample calcium to replace sodium ions on soil colloids, effectively reducing the water-soluble salt content and sodium adsorption ratio (SAR) of the soil, mitigating the direct toxicity of salt and sodium ions. The porous carbonaceous material and organic matter in the conditioner promote the formation of soil aggregates, reduce soil bulk density, increase porosity, significantly improve soil permeability and water and fertilizer retention capacity, and break up soil compaction.

[0022] 2. Enhance soil fertility and biological activity: The soil conditioner itself contains certain nutrients, and the favorable environment it creates is conducive to the colonization and reproduction of functional microorganisms, which can continuously activate the inherent nutrients such as phosphorus and potassium in the soil and enhance soil fertility.

[0023] 3. Environmentally friendly and highly sustainable: The main raw materials are derived from agricultural waste, achieving resource utilization. The improvement process does not introduce harmful substances, and long-term application can gradually restore the soil's ecological function.

[0024] The specific embodiments of the present invention will be described in further detail below with reference to examples. The following detailed descriptions are illustrative and intended to provide further explanation of this application, rather than limiting the scope of the invention.

[0025] Example 1: Preparation of the Modifier 1. Preparation of modified biochar (1) Agricultural waste (rice husks with a moisture content of less than 15%) is pyrolyzed and carbonized at 500°C under oxygen-limited conditions (inert protective gas nitrogen is continuously introduced into the pyrolysis furnace to make the oxygen volume concentration in the furnace less than 5%) to obtain primary biochar. (2) Impregnate the raw biochar with a 5% phosphoric acid solution for 18 hours; (3) Dry at 90°C, then activate at 350°C for 1.5 hours, cool and then pulverize through a 60-mesh sieve to obtain modified biochar.

[0026] 2. Preparation of the modifier Weigh out 70g of modified biochar; 22g of calcium-based conditioning agent (gypsum and calcium nitrate mixed at a mass ratio of 2:1); 6g of organic acid complexing agent (humic acid); and 2g of functional microbial agent ("Aiwangda" compound microbial agent produced by Bangan Biotechnology (Qingdao) Co., Ltd., containing growth-promoting, phosphorus-solubilizing, and potassium-solubilizing bacteria, with an effective live bacteria count ≥10 billion / gram).

[0027] Modified biochar, calcium-based conditioner, and humic acid were added to a double-helix conical mixer and mixed for 30 minutes to obtain a mixed matrix. 2 g of functional microbial agent was first initially mixed with 10 g of the mixed matrix to obtain a premix. This premix was then mixed with the remaining mixed matrix for 20 minutes to obtain the modifier.

[0028] Comparative Example 1: Preparation of the Modifier Compared to Example 1, Comparative Example 1 modifier preparation only involved the addition of modified biochar and organic acid complexing agents. The specific preparation steps are as follows: 1. Preparation of modified biochar Same as Example 1.

[0029] 2. Preparation of the modifier Weigh out 70g of modified biochar and 6g of organic acid complexing agent (humic acid).

[0030] Modified biochar and humic acid were added to a double-helix conical mixer and mixed for 30 minutes to obtain the modifier.

[0031] Comparative Example 2: Preparation of the Modifier Compared to Example 1, Comparative Example 2 only added modified biochar, organic acid complexing agent, and calcium-based conditioner during the preparation of the improver. The specific preparation steps are as follows: 1. Preparation of modified biochar Same as Example 1.

[0032] 2. Preparation of the modifier Weigh out 70g of modified biochar; 22g of calcium-based conditioning agent (gypsum and calcium nitrate mixed at a mass ratio of 2:1); and 6g of organic acid complexing agent (humic acid).

[0033] Modified biochar, calcium-based conditioner, and humic acid were added to a double-helix conical mixer and mixed for 30 minutes to obtain the modifier.

[0034] Comparative Example 3: Preparation of Modifier Compared to Example 1, Comparative Example 3 only added modified biochar, organic acid complexing agent, and compound microbial agent during the preparation of the improver. The specific preparation steps are as follows: 1. Preparation of modified biochar Same as Example 1.

[0035] 2. Preparation of the modifier Weigh out 70g of modified biochar; 6g of organic acid complexing agent (humic acid); and 2g of functional microbial agent ("Aiwangda" compound microbial agent produced by Bangan Biotechnology (Qingdao) Co., Ltd., containing growth-promoting, phosphorus-solubilizing, and potassium-solubilizing bacteria, with an effective live bacteria count ≥10 billion / gram).

[0036] Modified biochar and humic acid were added to a double-helix conical mixer and mixed for 30 minutes to obtain a mixed matrix. 2 g of functional microbial agent was first initially mixed with 10 g of the mixed matrix to obtain a premix. This premix was then mixed with the remaining mixed matrix for 20 minutes to obtain the modifier.

[0037] Experimental example: Field application trial (1) Experimental site: moderately saline-alkali farmland in Guangrao County, Dongying City, Shandong Province.

[0038] (2) Trial period: October 2024 - October 2025.

[0039] (3) Soil background values: 0-20 cm soil layer, water-soluble total salt content 3.59 g / kg, pH 8.6, sodium adsorption ratio (SAR) 15, soil compaction is severe.

[0040] (4) Experimental design: The experiment consists of five treatment groups, with the following treatments for each group: Improved group: Apply 500 kg of the improver prepared in Example 1 of this invention per mu, spread it evenly before sowing wheat in autumn, and then plow it to a depth of 25 cm.

[0041] Blank control group: No this amendment was applied; conventional fertilization and management were performed.

[0042] Comparative Example 1: 500 kg of the improver prepared in Comparative Example 1 of this invention was applied per mu (unit of land area) and evenly spread before wheat sowing in autumn, followed by deep plowing to a depth of 25 cm.

[0043] Comparative Example 2: 500 kg of the improver prepared in Comparative Example 2 of this invention was applied per mu (unit of land area) and evenly spread before the autumn wheat sowing, followed by deep plowing to a depth of 25 cm.

[0044] Comparative Example 3: 500 kg of the improver prepared in Comparative Example 3 of this invention was applied per mu (unit of land area) and evenly spread before the autumn wheat sowing, followed by deep plowing to a depth of 25 cm.

[0045] Each treatment was replicated in triplicate using a randomized block design. A wheat-maize rotation pattern was adopted, with identical crop varieties, planting densities, irrigation, pest and disease control, and other field management practices.

[0046] (5) Measurement items and methods: Soil physicochemical properties: Soil samples from the 0-20cm topsoil layer were collected during the corn harvest (October) to determine the total salt content (mass method), pH value (potential method), sodium adsorption ratio (SAR), soil bulk density (ring cutter method), and capillary porosity (ring cutter method).

[0047] Crop yield: The yield is calculated based on the single harvest in each plot and converted to yield per mu.

[0048] (6) Experimental results: Table 1: Effects of different treatments on soil properties of saline-alkali land Table 2: Effects of different treatments on crop yields on saline-alkali land (7) Results Analysis: One year after applying the carbon-based structural conditioner for saline-alkali land of this invention, the soil improvement effect was significant. Compared with the blank control group, the total salt content of the soil in the improved group decreased by 46.3%, the pH value decreased by 0.4 units, and the sodium adsorption ratio (SAR), which is more harmful to crops, decreased by 51.3%, greatly alleviating saline-alkali stress. The bulk density of the soil in the improved group decreased by 15.5%, and the porosity increased by 19.7%, indicating that the soil became looser and more porous, and the water permeability, air permeability, and water retention capacity were enhanced. While the soil microenvironment was improved, the crop roots developed well and grew vigorously. Wheat and corn yields increased by 27.6% and 15.6% respectively compared with the control group, resulting in significant economic benefits.

[0049] This study designed both the improved group (Example 1) and the comparative groups (Comparative Examples 1-3) to treat saline-alkali soils with different formulations of soil conditioners, aiming to clarify the comprehensive advantages of the soil conditioner of Example 1 compared to other formulations. Comparison of soil properties and crop yield data showed that while Comparative Examples 1-3 had some improvement effects compared to the control group, they were inferior to the improved group in all indicators. This indicates that the combined use of modified biochar, calcium-based conditioner, organic acid complexing agent (humic acid), and functional microbial agents in the soil conditioner of Example 1 produced a synergistic effect in reducing saline-alkali stress, improving soil structure, and promoting crop yield, thereby achieving rapid, efficient, and sustainable comprehensive management of saline-alkali land.

[0050] In summary, the carbon-based structural improver for saline-alkali land provided by this invention can effectively and comprehensively manage saline-alkali land, achieving multiple goals of "reducing salinity, improving alkali, loosening soil, and increasing yield" in a short period of time, and has broad application prospects.

[0051] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A saline soil specific carbon-based structural amendment, characterized in that, The modifier is composed of the following weight parts of substances: Modified biochar 60-80 parts; Calcium-based conditioner 15-25 parts; Organic acid complexing agent 5-10 parts; Functional microbial agent 1-3 parts.

2. The improver according to claim 1, characterized in that, The modified biochar is prepared by the following method: (1) Pyrolysis and carbonization of agricultural waste under limited oxygen conditions at 400-600℃ to obtain primary biochar; (2) Immersion treatment of the primary biochar with a 5% acid solution for 12-24 hours; (3) Drying at 80-105℃, then activating at 300-400℃ for 1-2 hours, cooling and crushing and sieving to obtain modified biochar.

3. The improver according to claim 2, characterized in that, The acid solution in step (2) is a phosphoric acid solution or a citric acid solution; the solid-liquid ratio of the primary biochar to the acid solution is 1: (5-10).

4. The improver according to claim 1, characterized in that, The calcium-based conditioner is selected from one or a mixture of two or more of gypsum, calcium silicate, calcium nitrate, and calcium citrate.

5. The amendment of claim 1, characterized in that, The organic acid complexing agent is selected from one or a mixture of two or more of humic acid, fulvic acid, and polyaspartic acid.

6. The amendment of claim 1, wherein The functional microbial agent is a composite microbial agent containing salt-tolerant phosphorus-solubilizing bacteria, potassium-solubilizing bacteria, and growth-promoting bacteria, and the effective viable bacterial count of the composite microbial agent is ≥100 billion / g.

7. The amendment according to any one of claims 1 to 6, characterized in that The application amount of the modifier is 300-800 kg / mu, and the application method is uniform spreading and plowing into the soil with a plowing depth of 20-30 cm.

8. The method of producing the improver according to any one of claims 1 to 6, characterized by, The method comprises the following steps: (1) Weighing each component according to the formula; (2) Mixing the modified biochar, calcium-based conditioner, and organic acid complexing agent uniformly to obtain a mixed substrate; (3) Pre-mixing the functional microbial agent with a small amount of mixed substrate, then mixing it again with the remaining mixed substrate to obtain the modifier.

9. Use of the modifier of any one of claims 1-6 in the preparation of a soil improvement product for improving saline-alkali soil.

10. Use according to claim 7, characterized in that, The saline-alkali soil has a water-soluble total salt content ≥3.0 g / kg, a pH ≥8.0, and a sodium adsorption ratio ≥10.

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