Barrier material for improving high saline alkali soil, preparation method and improvement method

Abstract

The invention provides a barrier material for improving high saline alkali soil, a preparation method and an improvement method. The method comprises the following steps: S1, preparing a carbon-based silicon fertilizer composed of blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar; s2, after the carbon-based silicon fertilizer is subjected to solid-liquid separation, the blended biochar and the nutrient solution are put into the reaction kettle again to obtain a solid-liquid mixture, the carbon-silicon ratio in the solid-liquid mixture is kept to be (5-6): 1, constant-temperature stirring is conducted till silica gel-shaped flocculation substances appear, then gel is obtained through constant-temperature evaporation, and the carbon-based silicon fertilizer is obtained. Washing with water and filtering to obtain the barrier material composed of the blended biochar and the polysilicic acid gel. According to the method, the barrier material composed of the blended biochar and the polysilicic acid gel is used as a barrier layer to block or slow down upward movement of salt caused by hydrological movement, the zoysia japonica is used as a biological improvement medium, the method is simple and efficient, the improvement cost is low, effective components in soil can be increased and reserved, and the method is suitable for large-area popularization.

Description

Technical Field

[0001] The invention relates to the technical field of soil improvement, and in particular to a barrier material for improving highly saline-alkali soil, a preparation method and an improvement method. Background Art

[0002] Soil salinization is one of the major challenges facing global agricultural production, especially in arid and semi-arid regions. It not only affects the growth and yield of crops, but also has a profound impact on agricultural ecosystems. The salt in the soil mainly comes from natural processes such as geological causes, marine fog deposition, and groundwater evaporation and concentration, as well as secondary salinization caused by human activities such as unreasonable irrigation, fertilization and drainage systems. When the concentration of soluble salts in the soil exceeds the range that plants can withstand, it will cause plant growth to be stunted or even die.

[0003] Conventional salt-tolerant plants refer to those plant species that can adapt to saline-alkali environments within a certain range, and they can usually withstand soil salinity of 1-5‰. However, for soils with higher salinity (over 10‰), the adaptability of these plants is obviously insufficient, and it is difficult to effectively improve soil conditions through biological improvement. This is because high salinity interferes with plant water absorption and nutrient utilization, causing osmotic pressure imbalance, thereby limiting the development and overall health of plant roots. In addition, high-salinity soils can inhibit microbial activity, affect soil structure, reduce its fertility, and are not conducive to the sustainable development of agricultural production.

[0004] In order to deal with highly saline-alkali soils, the traditional method is usually to dig canals around fields and combine salt washing and leaching. This method aims to reduce soil salinity by introducing fresh water to wash the salt in the soil and discharge it into external water bodies. Although this method can reduce the salt on the soil surface in the short term, it has many problems. First, the project is large in scale, costly and time-consuming, requiring a large amount of water resources and infrastructure construction. Secondly, since soil salinity easily rises again with changes in groundwater levels, there is a serious phenomenon of salt return, resulting in unstable treatment effects. Finally, during the salt washing and leaching process, the beneficial components in the soil will also be taken away, so that the soil fertility not only does not improve, but may decline, further exacerbating the risk of land degradation. Summary of the invention

[0005] In view of the technical problems of high cost, serious salt return and easy land degradation in the current treatment methods for highly saline-alkali soil, the present invention provides a barrier material, preparation method and improvement method for improving highly saline-alkali soil. The barrier material composed of blended biochar and polysilicate gel is used as a barrier layer to block or slow down the upward migration of salt caused by hydrological movement, and Zoysia knotweed is used as a biological improvement medium. The method is simple and efficient, with low improvement cost, and can increase and retain the effective ingredients in the soil, and is suitable for large-scale promotion.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A method for preparing a barrier material for improving highly saline-alkali soil comprises the following steps:

[0008] S1: Preparation of carbon-based silicon fertilizer:

[0009] S1.1: Pulverized straw and / or rice husk is put into a reactor, water and potassium hydroxide are added, and a pyrolysis reaction is carried out in an oxygen-free environment at 200-250°C and 0.1-0.5MPa. After the reaction is completed, the mixture is cooled to room temperature to obtain a blended biochar and an organic solution containing potassium silicate and bio-vinegar;

[0010] S1.2: Sulfuric acid is added to the reactor, and then, under a constant temperature environment of 30-50°C, potassium silicate in the organic solution is contacted with sulfuric acid to undergo a double decomposition reaction to generate water-soluble metasilicic acid and potassium sulfate; after the double decomposition reaction is completed, the mixture is cooled to room temperature to obtain a carbon-based silicon fertilizer consisting of a blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar;

[0011] S2: Preparation of barrier material:

[0012] S2.1: performing solid-liquid separation on the carbon-based silicon fertilizer in step S1.2 to obtain blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar, and measuring the carbon content in the blended biochar and the silicon content in the nutrient solution;

[0013] S2.2: Add the blended biochar and nutrient solution into the reactor again to obtain a solid-liquid mixture, and keep the carbon-silicon ratio in the solid-liquid mixture at 5-6:1; then add ethanol, continue stirring at 70-75°C until silica gel-like flocculent material appears on the inner wall of the reactor, then stop stirring, raise the temperature to 80-85°C, and obtain a gel by constant temperature evaporation;

[0014] S2.3: The gel in step S2.2 is washed and filtered to obtain a barrier material composed of blended biochar and polysilicate gel.

[0015] Furthermore, in step S2.1, the carbon content in the blended biochar and the silicon content in the nutrient solution are detected by X-ray fluorescence spectroscopy.

[0016] Furthermore, in step S2.2, the amount of ethanol added is 15-20% of the total mass of the solid-liquid mixture.

[0017] The barrier material prepared by any of the above preparation methods.

[0018] The method for improving highly saline-alkali soil using the above barrier material comprises the following steps:

[0019] K1: Plough the highly saline-alkali soil and lay a layer of barrier material on the plowed bottom layer. The plowing depth and the thickness of the barrier material should be controlled at 10cm / 3-5mm;

[0020] K2: Add blended biochar to the plowed highly saline-alkali soil, plow it evenly and then level it again, wherein the amount of blended biochar added accounts for 2.5wt.% of the total mass of the plowed highly saline-alkali soil;

[0021] K3: Plowing a plurality of planting grooves on the paved highly saline-alkali soil, first laying a layer of alkaline biochar at the bottom of the planting grooves, then moving Zoysia japonica into the planting grooves, and then covering the original soil when the grooves were opened; the depth of the planting grooves and the thickness of the alkaline biochar are controlled at 10 cm / 3 to 5 mm, and the depth of the planting grooves is less than the plowing depth in step K1;

[0022] K4: Use nutrient solution for fertilization, control the amount of fertilizer per square meter of soil to 1-3L, and apply fertilizer once every 3-10 days.

[0023] Furthermore, in step K1, the tillage depth is controlled at 20 to 40 cm.

[0024] Furthermore, in step K3, the preparation method of the alkaline biochar is as follows: the crushed straw and / or rice husk is put into a reactor, and after adding water, a pyrolysis reaction is carried out in an anaerobic environment of 200-250° C. and 0.1-0.5 MPa. After the reaction is completed, it is cooled to room temperature to obtain alkaline biochar and an organic solution containing biological vinegar, which is then filtered, washed, and dried to obtain alkaline biochar.

[0025] Furthermore, in step K3, 5 to 6 equally spaced planting grooves are plowed out on each square meter of highly saline-alkali soil, the depth of the planting grooves is controlled at 6 to 10 cm, and the Zoysia japonica planted in the planting grooves is Zoysia japonica macrostachia.

[0026] Furthermore, the nutrient solution used in step K4 needs to be diluted according to the sodium ion concentration in the highly saline-alkali soil to ensure that when the sodium ion concentration in the highly saline-alkali soil is 15-20 g / kg, the silicon ion concentration in the nutrient solution is controlled at 0.05-0.2 g / kg.

[0027] Furthermore, in step K4, fertilizer is applied every 3 to 5 days in summer and every 7 to 10 days in spring and autumn.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. The present invention can significantly slow down or prevent the upward movement of salt caused by hydrological movement by laying a barrier material composed of blended biochar and polysilicic acid gel at the bottom of the soil as a salt return barrier layer. This measure not only helps to maintain the improved low-salinity environment, but also prevents the occurrence of soil salt return problems, ensuring long-term and stable improvement effects. In addition, the barrier layer can also retain the effective ingredients in the soil and reduce nutrient loss.

[0030] 2. The present invention uses blended biochar mixed with highly saline-alkali soil to regulate the basic properties of the soil, such as pH value, bulk density, etc., without the need for prior salt reduction treatment, creating suitable growth conditions for salt-tolerant Zoysia japonica and significantly improving its survival rate in high-salinity soil. At the same time, the application of silicon potassium nutrient solution promotes the rapid growth of plants, enhances their salt precipitation ability, and further reduces soil salinity.

[0031] 3. The present invention uses salt-tolerant Zoysia japonica as a biological improvement medium. This is a perennial lawn grass with strong salt tolerance. This grass species can not only survive in a high-salinity environment, but also effectively reduce soil salinity and improve soil structure and quality during its growth. Through its powerful root system, Zoysia japonica can fix the soil and prevent erosion.

[0032] 4. The present invention uses alkaline biochar as a soil high-salt buffer layer, which not only avoids the problem that the root system of Zoysia japonica is difficult to take root due to direct contact with high-salt soil, but also plays the role of alkaline biochar in promoting rooting. In addition, alkaline biochar can also neutralize the buffer layer, prevent the pH in the soil from being too low due to the acidic blended biochar and the nutrient solution used in the later fertilization, and maintain a suitable acid-base balance in the soil.

[0033] 5. The present invention controls the carbon-silicon ratio in the solid-liquid mixture to 5-6:1. Within this specific ratio range, the blended biochar and water-soluble metasilicic acid can exist in a concentration that is conducive to the formation of a siloxane network, and this network structure is the key to forming a stable gel.

[0034] 6. The soil improvement process of the present invention is efficient and low-cost, and the construction is simple and easy to promote. After improvement, the improvement of soil quality not only brings about an increase in crop yields, but also reduces dependence on water resources and chemical agents. The overall economic benefits are significantly better than traditional methods. This not only helps to improve agricultural production efficiency, but also complies with the principle of sustainable development, and is of great significance for promoting agricultural modernization and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a comparison chart of the leaf length, root length and upright stem height of Zoysia macrostachya A and Zoysia macrostachya B in the examples.

[0036] Figure 2 It is a comparison chart of POD, SOD and CAT activities of Zoysia macrostachia A and Zoysia macrostachia B in the examples.

[0037] Figure 3 This is a comparison chart of the cumulative amounts of MDA and H2O2 in Zoysia macrostachia A and Zoysia macrostachia B in the examples.

[0038] Figure 4 It is a comparison chart of chlorophyll a, chlorophyll b and the total amount of chlorophyll in Zoysia macrostachya A and Zoysia macrostachya B in the examples.

[0039] Figure 5 It is a comparison chart of the Na, K and Si contents in Zoysia macrostachia A and Zoysia macrostachia B in the examples. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0041] The method for preparing the barrier material for improving highly saline-alkali soil described in this embodiment comprises the following steps:

[0042] S1: Preparation of carbon-based silicon fertilizer:

[0043] S1.1: Put the crushed straw and / or rice husk into a reactor, add water and potassium hydroxide, and carry out pyrolysis reaction in an oxygen-free environment at 220°C and 0.5MPa for 3 hours. After the reaction is completed, cool to room temperature to obtain a blended biochar and an organic solution containing potassium silicate and biological vinegar.

[0044] The pyrolysis reaction is:

[0045] SiO2+2KOH→K2SiO3+H2O

[0046] Here, assuming that the theoretical amount of potassium hydroxide required to completely decompose SiO2 in straw and rice husk is M1, the actual amount of potassium hydroxide added is M≤M1.

[0047] S1.2: Sulfuric acid is added into the reactor, and then under a constant temperature environment of 50°C, potassium silicate in the organic solution comes into contact with sulfuric acid to undergo a double decomposition reaction to generate water-soluble metasilicic acid and potassium sulfate; after the double decomposition reaction is completed, the mixture is cooled to room temperature to obtain a carbon-based silicon fertilizer consisting of blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar.

[0048] The metathesis reaction is:

[0049] K2SiO3+H2SO4→K2SO4+H2SiO3

[0050] Here, assuming that the theoretical amount of sulfuric acid required to completely decompose potassium silicate is m1, the actual amount of sulfuric acid added is m≤m1.

[0051] S2: Preparation of barrier material:

[0052] S2.1: The carbon-based silicon fertilizer in step S1.2 is subjected to solid-liquid separation to obtain a blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar. The carbon content in the blended biochar and the silicon content in the nutrient solution are measured by X-ray fluorescence spectroscopy.

[0053] S2.2: The blended biochar and nutrient solution are put into the reactor again to obtain a solid-liquid mixture, and the carbon-silicon ratio in the solid-liquid mixture is maintained at 5 to 6:1. Too high a silicon content is prone to rapid condensation or forming an uneven gel structure, and too low a silicon content will not form enough silicon-oxygen bonds to build a stable three-dimensional network. In this embodiment, the carbon-silicon ratio is 6:1. Then, 20% of the total mass of the solid-liquid mixture is added to promote gel formation, and stirring is continued at 75°C at a speed of 150 to 200 r / min until silica gel-like flocculent material appears on the inner wall of the reactor, and stirring is stopped. The temperature is raised to 80°C, and a gel is obtained by constant temperature evaporation. The evaporation temperature should not be too high, otherwise a gel cannot be obtained, but a powder is obtained.

[0054] S2.3: The gel in step S2.2 is washed and filtered to obtain a mixed solution containing potassium sulfate and a barrier material composed of blended biochar and polysilicate gel, and the obtained mixed solution containing potassium sulfate is added back into the nutrient solution.

[0055] This embodiment uses the Yangkou Port reclamation land in Nantong, Jiangsu as the improvement object. The salinity of the highly saline-alkali soil in the area is quickly measured by spectrumEC 110 to be 11-15‰. The method of using the above barrier material to improve the highly saline-alkali soil includes the following steps:

[0056] K1: Plough the highly saline-alkali soil to a depth of 20 cm, and lay a 7 mm thick barrier material on the bottom of the plow. Considering the cost and the problem that too thick barrier material will inhibit plant growth, the thickness of the barrier material needs to be controlled. It should not be too thick, but it should not be too thin, otherwise the isolation effect will be poor.

[0057] K2: Add blended biochar to the plowed highly saline-alkali soil, plow it evenly and then level it again, wherein the amount of blended biochar added accounts for 2.5wt.% of the total mass of the plowed highly saline-alkali soil.

[0058] K3: After paving, 5 equally spaced planting grooves are plowed out on each square meter of highly saline-alkali soil. The depth of the planting grooves is 10 cm. First, a layer of alkaline biochar with a thickness of 3 mm is laid on the bottom of the planting grooves, and then Zoysia japonica is moved into the planting grooves, and then the soil from the original grooves is covered.

[0059] The preparation method of the alkaline biochar is as follows: crushed straw and / or rice husk is put into a reactor, and after adding water, a pyrolysis reaction occurs in an anaerobic environment at 200-250° C. and 0.1-0.5 MPa. After the reaction is completed, the mixture is cooled to room temperature to obtain a blended biochar and an organic solution containing biological vinegar, which is then filtered, washed, and dried to obtain the alkaline biochar.

[0060] K4: Detect the silicon ion concentration in the nutrient solution and the sodium ion concentration in the highly saline-alkali soil respectively, dilute the nutrient solution according to the sodium ion concentration in the highly saline-alkali soil, ensure that the silicon ion concentration in the nutrient solution is controlled at 0.1g / kg when the sodium ion concentration is 15-20g / kg, and avoid problems such as soil compaction due to excessive potassium ion content after fertilization. Use the diluted nutrient solution for fertilization, control the fertilizer amount per square meter of soil to 1-3L, fertilize once every 3-5 days in summer, and once every 7-10 days in spring and autumn. This experiment is in summer, so fertilize twice a week.

[0061] The improvement cycle was 30 days. After 30 days of improvement, soil at a depth of 15CM was tested. Table 1 shows the pH value, bulk density and element changes of the original soil, the soil at the initial stage of improvement, and the soil 30 days after improvement. Among them, a, b, c, and d are significantly different, and the differences are statistically significant at the P<0.05 and P<0.01 levels.

[0062] Table 1 Changes in pH value, bulk density and elements of original soil, soil at the initial stage of improvement, and soil after 30 days of improvement

[0063] original soil Early stage of improvement After 30 days of improvement pH 8.63±0.12a 7.84±0.19b 8.06±0.11a <![CDATA[Unit weight g / cm 3 > 1.27±0.14a 0.65±0.09b 0.55±0.23b <![CDATA[K + g / kg]]> 0.41±0.1b 0.71±0.11b 1.66±0.13a <![CDATA[Na + g / kg]]> 15.54±1.1a 13.77±0.89b 2.87±0.65c <![CDATA[Ca 2+ g / kg]]> 0.19±0.08b 0.14±0.07b 0.29±0.06a <![CDATA[Mg 2+ g / kg]]> 2.06±0.26a 1.56±0.18b 0.38±0.11c <![CDATA[Cl - g / kg]]> 28.64±2.3a 25.5±1.81b 4.56±1.1c <![CDATA[HCO3 - g / kg]]> 0.25±0.08b 0.24±0.07b 0.75±0.11a <![CDATA[SO4 2- g / kg]]> 5.17±0.49a 3.72±0.38b 5.26±0.41a Organic matter content g / kg 4.87±5.6b 30.61±6.6a 65.44±4.8a Available phosphorus content mg / kg 12.74±2.2c 18.71±3.4a 33.67±3.8a Effective nitrogen content mg / kg 21.77±1.8b 22.25±1.9b 25.45±2.1a

[0064] As can be seen from Table 1, 30 days after planting, the sodium ion concentration in the highly saline-alkali soil was greatly reduced, the soil salinity was reduced, and there was no salt return phenomenon. The soil bulk density was further reduced, which enhanced the soil's aeration and water retention, and promoted root expansion and nutrient absorption. With the growth of plants and the increase of root secretions, the soil microbial community has undergone positive changes, further increasing the content of organic matter and effective nitrogen, phosphorus, and potassium, improving soil fertility and soil quality.

[0065] Furthermore, this embodiment also evaluates the effect of the above-mentioned improved method on the growth effect of Zoysia japonica, and conducts comparative experiments to determine whether its growth performance is significantly different from that planted in conventional nutrient soil. Taking 30 days as the planting cycle, after 30 days, the coverage rate of Zoysia japonica planted using the above-mentioned improved method, hereinafter referred to as Zoysia japonica A, exceeded 80%, and the plant as a whole showed a good growth state. The following is a comparison with the performance of the same variety of Zoysia japonica planted using traditional nutrient matrix soil, hereinafter referred to as Zoysia japonica B:

[0066] Comparison of leaf length, root length and upright stem height: Figure 1 This is a comparison chart of the leaf length, root length and upright stem height of Zoysia macrostachia A and Zoysia macrostachia B. It can be seen that the leaf length of Zoysia macrostachia A is almost the same as that of Zoysia macrostachia B, indicating that the growth rate and length of the leaves are equivalent under the two planting conditions. It has a slight disadvantage in root length and upright stem height compared to Zoysia macrostachia B, but the overall deviation does not exceed 2 cm, indicating that the plant can still maintain a good growth trend in highly saline-alkali soil.

[0067] Comparison of POD, SOD and CAT activities: Figure 2 This is a comparison of the POD, SOD and CAT activities of Zoysia grandis A and Zoysia grandis B. It can be seen that the POD and CAT activities of Zoysia grandis A are almost the same as those of Zoysia grandis B, but the SOD activity is significantly higher than that of Zoysia grandis B, with a difference of nearly 600U / g. SOD is one of the important antioxidant enzymes in plants, responsible for scavenging superoxide free radicals and protecting cells from oxidative damage. Higher SOD activity means that Zoysia grandis A has stronger antioxidant capacity and can better cope with environmental stress, such as high salinity and drought.

[0068] Comparison of oxidative stress indicators: Figure 3This is a comparison of the MDA and H2O2 accumulation in Zoysia grandis A and Zoysia grandis B. It can be seen that the MDA accumulation in Zoysia grandis A is almost the same as that in Zoysia grandis B, but the H2O2 accumulation in Zoysia grandis A is nearly 10 μmol / g lower than that in Zoysia grandis B. H2O2 is a reactive oxygen species, and excessive accumulation can cause oxidative damage to plant cells. The lower H2O2 accumulation indicates that Zoysia grandis A can more effectively remove reactive oxygen species, reduce oxidative stress reactions, and maintain the stability of the intracellular environment.

[0069] Comparison of photosynthesis related parameters: Figure 4 This is a comparison chart of chlorophyll a, chlorophyll b and the total amount of chlorophyll in Zoysia macrostachya A and Zoysia macrostachya B. It can be seen that whether it is chlorophyll a, chlorophyll b or the total amount of chlorophyll, Zoysia macrostachya A is significantly higher than Zoysia macrostachya B, which not only improves the efficiency of photosynthesis, but also enhances the autotrophic ability of Zoysia macrostachya A, and promotes the synthesis and accumulation of organic matter in Zoysia macrostachya A.

[0070] Comparison of mineral element content: Figure 5 This is a comparison chart of the Na, K, and Si contents in Zoysia A and Zoysia B. It can be seen that the Na, K, and Si contents in Zoysia A are higher than those in Zoysia B, especially the Si content is nearly 7000 mg / Kg higher. Silicon is an important trace element for plants, which can enhance the mechanical strength of plants, improve root development, and increase stress resistance. The higher silicon content not only enhances the disease and pest resistance of Zoysia A, but also promotes its adaptability and growth in high-salt environments.

[0071] In summary, the improved method planted Zoysia japonica A performed well in many growth indicators, especially in antioxidant capacity and photosynthesis, which was superior to the same variety of Zoysia japonica B planted in traditional nutrient matrix soil. In addition, the improved method significantly increased the content of mineral elements, especially silicon, in the plant, further enhancing the stress resistance and adaptability of Zoysia japonica A. These results prove the effectiveness of the improved method in improving the growth performance and survival ability of Zoysia japonica in highly saline-alkali soil.

[0072] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A method for preparing a barrier material for improving highly saline-alkali soil, characterized in that: The following steps are involved: S1: Preparation of carbon-based silicon fertilizer: S1.1: Pulverized straw and / or rice husk is put into a reactor, water and potassium hydroxide are added, and a pyrolysis reaction is carried out in an oxygen-free environment at 200-250°C and 0.1-0.5MPa. After the reaction is completed, the mixture is cooled to room temperature to obtain a blended biochar and an organic solution containing potassium silicate and bio-vinegar; S1.2: Sulfuric acid is added to the reactor, and then, under a constant temperature environment of 30-50°C, potassium silicate in the organic solution is contacted with sulfuric acid to undergo a double decomposition reaction to generate water-soluble metasilicic acid and potassium sulfate; after the double decomposition reaction is completed, the mixture is cooled to room temperature to obtain a carbon-based silicon fertilizer consisting of a blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar; S2: Preparation of barrier material: S2.1: performing solid-liquid separation on the carbon-based silicon fertilizer in step S1.2 to obtain blended biochar and a nutrient solution containing water-soluble metasilicic acid, potassium sulfate and biological vinegar, and measuring the carbon content in the blended biochar and the silicon content in the nutrient solution; S2.2: Add the blended biochar and nutrient solution into the reactor again to obtain a solid-liquid mixture, and keep the carbon-silicon ratio in the solid-liquid mixture at 5-6:1; then add ethanol, continue stirring at 70-75°C until silica gel-like flocculent material appears on the inner wall of the reactor, then stop stirring, raise the temperature to 80-85°C, and obtain a gel by constant temperature evaporation; S2.3: The gel in step S2.2 is washed and filtered to obtain a barrier material composed of blended biochar and polysilicate gel.

2. The method for preparing a barrier material for improving highly saline-alkali soil according to claim 1, characterized in that: In step S2.1, the carbon content in the blended biochar and the silicon content in the nutrient solution are detected by X-ray fluorescence spectroscopy.

3. The method for preparing a barrier material for improving highly saline-alkali soil according to claim 1, characterized in that: In step S2.2, the amount of ethanol added is 15-20% of the total mass of the solid-liquid mixture.

4. The barrier material prepared by the preparation method according to any one of claims 1 to 3.

5. A method for improving highly saline-alkali soil using the barrier material according to claim 4, characterized in that: The following steps are involved: K1: Plough the highly saline-alkali soil and lay a layer of barrier material on the plowed bottom layer. The plowing depth and the thickness of the barrier material should be controlled at 10cm / 3-5mm; K2: Add blended biochar to the plowed highly saline-alkali soil, plow it evenly and then level it again, wherein the amount of blended biochar added accounts for 2.5wt.% of the total mass of the plowed highly saline-alkali soil; K3: Plowing a plurality of planting grooves on the paved highly saline-alkali soil, first laying a layer of alkaline biochar at the bottom of the planting grooves, then moving Zoysia japonica into the planting grooves, and then covering the original soil when the grooves were opened; the depth of the planting grooves and the thickness of the alkaline biochar are controlled at 10 cm / 3 to 5 mm, and the depth of the planting grooves is less than the plowing depth in step K1; K4: Use nutrient solution for fertilization, control the amount of fertilizer per square meter of soil to 1-3L, and apply fertilizer once every 3-10 days.

6. The method for improving highly saline-alkali soil according to claim 5, characterized in that: In step K1, the tillage depth is controlled at 20 to 40 cm.

7. The method for improving highly saline-alkali soil according to claim 5, characterized in that: In step K3, the preparation method of the alkaline biochar is as follows: the crushed straw and / or rice husk is put into a reactor, and after adding water, a pyrolysis reaction occurs in an anaerobic environment at 200-250°C and 0.1-0.5MPa. After the reaction is completed, it is cooled to room temperature to obtain alkaline biochar and an organic solution containing biological vinegar, which is then filtered, washed, and dried to obtain alkaline biochar.

8. The method for improving highly saline-alkali soil according to claim 5, characterized in that: In step K3, 5 to 6 equally spaced planting grooves are ploughed out on each square meter of highly saline-alkali soil, the depth of the planting grooves is controlled at 6 to 10 cm, and the Zoysia japonica planted in the planting grooves is Zoysia japonica macrostachia.

9. The method for improving highly saline-alkali soil according to claim 5, characterized in that: The nutrient solution used in step K4 needs to be diluted according to the sodium ion concentration in the highly saline-alkali soil to ensure that when the sodium ion concentration in the highly saline-alkali soil is 15-20 g / kg, the silicon ion concentration in the nutrient solution is controlled at 0.05-0.2 g / kg.

10. The method for improving highly saline-alkali soil according to claim 5, characterized in that: In step K4, fertilizer is applied every 3 to 5 days in summer and every 7 to 10 days in spring and autumn.

Images