Saline-alkali soil improver and application thereof in improvement of saline-alkali soil

Abstract

The invention relates to the technical field of soil improvement, and discloses a saline-alkali soil improver and application thereof in saline-alkali soil improvement. The saline-alkali soil improver comprises biochar and humic acid in a content ratio of 4: (1.5-3), the average particle size of the biochar is less than or equal to 2mm; the average particle size of the humic acid is less than or equal to 2mm. Salt in soil is adsorbed through a porous structure of the biochar, mobility of the salt in the soil is reduced, meanwhile, a large number of calcium ions and magnesium ions are released by the biochar in the soil, sodium ions on soil colloid can be replaced by the calcium ions and the magnesium ions, and therefore the salt content in the saline-alkali soil is reduced; humic acid can reduce the pH value of soil, contains rich functional groups, can release hydrogen ions in the soil, has strong complexing ability, can complex calcium and magnesium ions, improves the availability of minerals containing the calcium and magnesium ions in the soil, enhances the replacement of sodium ions in soil colloid, and improves the soil quality. The effect of promoting the reduction of soil salinity is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of soil improvement, and in particular to a saline-alkali soil improver and application thereof in improving saline-alkali soil. Background Art

[0002] Saline-alkali soil refers to a type of soil that contains high concentrations of soluble salts and alkaline substances, and is widely distributed in many regions around the world. The presence of saline-alkali soil leads to the destruction of soil structure, reduced fertility, and limited effective supply of water and nutrients, which in turn poses significant challenges to agricultural production. Research on new saline-alkali soil conditioners is of great significance for expanding arable land resources and protecting food supply.

[0003] Agricultural and forestry waste (such as crop residues, straw, wood waste, etc.) is a common by-product of agricultural and forestry production. If it is directly piled up or burned without treatment, it is easy to cause environmental pollution and affect air quality, soil fertility and water health. By converting these wastes into biochar, it can effectively reduce the accumulation and burning of waste, reduce the emission of harmful gases, and alleviate environmental pollution.

[0004] CN118048157A discloses a method for improving saline-alkali soil by compounding sulfur with biochar-based materials, comprising the following steps: (1) pyrolyzing wheat straw in an anaerobic state to generate biochar, and then mixing the biochar with titanium gypsum; (2) pouring the mixture of biochar and titanium gypsum into a ball mill for modification; (3) compounding the modified biochar with 0.5% sulfur. This technical solution reduces the pH and alkalinity of saline-alkali soil, while regulating the soil bulk density, increasing the soil nutrient content, and improving the ecological environment of saline-alkali land. However, in the above technical solution, the process is complicated, the material cost is high, and the agricultural cost is increased. For this reason, the present invention provides a saline-alkali soil improver with biochar and humic acid to solve the above-mentioned problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problems in the prior art of complex preparation process of modified biochar, high raw material cost, poor environmental friendliness and small practical application range.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a saline-alkali soil improver, which includes biochar and humic acid in a content ratio of 4:1.5-3;

[0007] The average particle size of the biochar is ≤2 mm; the average particle size of the humic acid is ≤2 mm.

[0008] Preferably, the saline-alkali soil conditioner comprises biochar and humic acid in a content ratio of 4:3.

[0009] Further preferably, the biochar has a pH value <9.5, an ash content <35 wt%, and an average particle size ≤2 mm.

[0010] Preferably, the biochar is corn straw biochar.

[0011] According to a preferred specific embodiment, the corn straw biochar is obtained by pyrolyzing corn straw in the absence of oxygen at 500°C for 2 hours; the pH of the obtained corn straw biochar is 9.15, the ash content is 32.35wt%, the organic carbon content is 17.4%, the N content is 1.39%, the C content is 53.62%, the H content is 2.06%, and the O content is 10.58%.

[0012] Preferably, the average particle size of the humic acid is ≤2 mm, and the C content, H content, and O content of the humic acid are 36.9%, 2.99%, and 29.26%.

[0013] Preferably, the preparation method of the saline-alkali soil conditioner comprises: weighing biochar and humic acid according to a weight ratio and mixing them; the mixing conditions meet the following conditions: the speed of the stirring equipment is 300 to 500 rpm, and the time is 3 to 6 minutes.

[0014] The second aspect of the present invention provides the use of the saline-alkali soil conditioner as described in the first aspect of the present invention in improving saline-alkali soil, wherein the saline-alkali soil conditioner is applied to saline-alkali soil for soil improvement treatment, 70% of the maximum field water holding capacity of the soil is maintained during the treatment, crops are planted after half a month, fertilization treatment during the planting process is the same as that in the field, and the planting time is 45 days.

[0015] Preferably, based on the total mass of soil for growing crops, the amount of the saline-alkali soil conditioner is 5.5wt% to 7wt%.

[0016] The method provided by the present invention has at least the following effects:

[0017] (1) In the saline-alkali soil conditioner provided by the present invention, the biochar has a lower pH and ash content than other biochars obtained by pyrolysis of agricultural and forestry wastes, and has less negative impact on soil salinity and pH after being applied to saline-alkali soil.

[0018] (2) The porous structure of biochar can absorb salt in the soil, reducing the mobility of salt in the soil. At the same time, biochar releases a large amount of calcium ions and magnesium ions in the soil. Calcium ions and magnesium ions will replace sodium ions on soil colloids, thereby reducing the salt content in saline-alkali soil. Humic acid can lower the pH of the soil. It contains rich functional groups and can release hydrogen ions in the soil. At the same time, humic acid has a strong chelating ability and can chelate calcium and magnesium ions, increasing the availability of minerals containing calcium and magnesium ions in the soil, strengthening the replacement of sodium ions in soil colloids, and promoting the reduction of soil salinity.

[0019] (3) Applying the mixed amendment of biochar and humic acid to saline-alkali soil can improve the soil structure of saline-alkali soil and increase the air permeability and water permeability of the soil. This helps to reduce the accumulation of salt in the soil, promote the respiration of plant roots and the flow of water, and avoid soil compaction and poor drainage. Both biochar and humic acid have a certain water retention effect. The combined application of the two can further improve the durability of soil moisture. Humic acid is a natural substance rich in organic matter that can effectively improve the cation exchange capacity of the soil and increase the soil's nutrient retention capacity, thereby enhancing the soil's adsorption and supply capacity for nutrients such as nitrogen, phosphorus, and potassium, and reducing nutrient loss. The addition of biochar can further increase the soil's nutrient exchange capacity and nutrient supply capacity, and improve the nutrient deficiency in saline-alkali soil. The improved saline-alkali soil environment can promote the healthy growth of plant roots and improve the stress resistance of crops, especially the growth performance of salt-alkali tolerant plants will be significantly improved. By reducing the salt concentration in the soil and improving soil fertility and water retention capacity, crops can better absorb nutrients and water, thereby improving crop growth rate, yield and quality.

[0020] (4) The technical solution of the present invention uses agricultural waste and commercially available humic acid as raw materials. Compared with the expensive or difficult-to-obtain materials used in the prior art, biochar raw materials are easy to obtain and low in cost, which is more in line with the current concept of sustainable development and green agriculture; the preparation process of this technology only requires raw material mixing and screening, and does not involve complex chemical treatment or expensive equipment (such as ball mills, chemical modification steps, etc.). Compared with some technical solutions that require multi-step reactions and high temperature and high pressure treatment, it is easier to promote and apply on a large scale.

[0021] (5) The conversion and utilization of agricultural and forestry waste not only improves the soil, but also avoids the pollution caused by waste accumulation and incineration (such as CO2 and PM2.5 emissions). Compared with other non-resourced saline-alkali soil conditioners, this is more in line with the national agricultural green development policy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a comparison diagram of the electrical conductivity of the soil after treatment in Application Example 1, Application Example 2, Comparative Application Example 3, and Comparative Application Example 4;

[0023] Figure 2 It is a comparison diagram of soil pH after treatment in Application Example 1, Application Example 2, Comparative Application Example 3, and Comparative Application Example 4;

[0024] Figure 3 It is a comparison chart of soil organic matter content after treatment in Application Example 1, Application Example 2, Comparative Application Example 3, and Comparative Application Example 4;

[0025] Figure 4 It is a comparison diagram of fresh Chinese cabbage seeds after being treated in Application Example 1, Application Example 2, Comparative Application Example 3, and Comparative Application Example 4;

[0026] Figure 5 is a scanning electron microscope image of corn stalks in an embodiment of the present invention;

[0027] Figure 6 1 is a scanning electron microscope image of humic acid in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0029] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0030] In the following examples, the saline-alkali soil used was collected from Chongming District, Shanghai. The basic physical and chemical properties are: pH 8.56, electrical conductivity 2.02ms / cm, soil sodium adsorption ratio 9.91, soil organic matter content 11.03g / kg; the soil salt content is relatively high and is not suitable for general crop growth.

[0031] In the following example, corn straw biochar is obtained by pyrolyzing corn straw in the absence of oxygen at 500°C for 2 hours; the pH of the obtained corn straw biochar is 9.15, the ash content is 32.35wt%, the organic carbon content is 17.4%, the N content is 1.39%, the C content is 53.62%, the H content is 2.06%, and the O content is 10.58%.

[0032] Humic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd. The humic acid was solid, and its average particle size was ≤2 mm. The C content of the humic acid was 36.9%, the H content was 2.99%, and the O content was 29.26%.

[0033] Example 1

[0034] This example is used to provide a method for preparing a saline-alkali soil conditioner, the method comprising:

[0035] Biochar and humic acid in a weight ratio of 4:3 are mixed to obtain a saline-alkali soil conditioner; wherein the weight of the humic acid is 15g; wherein the biochar is corn straw biochar, weighs 20g, and its average particle size is ≤2mm, and the average particle size of the humic acid is ≤2mm.

[0036] The mixing process is carried out under the following conditions: the stirring speed is 500 rpm and the mixing time is 3 min.

[0037] Example 2

[0038] This example is used to provide a method for preparing a saline-alkali soil conditioner, the method comprising:

[0039] Biochar and humic acid in a weight ratio of 4:1.5 are mixed to obtain a saline-alkali soil conditioner; wherein the weight of the humic acid is 7.5g; wherein the biochar is corn straw biochar, weighs 20g, and its average particle size is ≤2mm, and the average particle size of the humic acid is ≤2mm.

[0040] The mixing process is carried out under the following conditions: the stirring speed is 300 rpm and the mixing time is 6 min.

[0041] Comparative Example 1

[0042] The method of Example 1 was followed, except that no biochar was added, and the remaining steps and parameters were the same as in Example 1.

[0043] Comparative Example 2

[0044] The method of Example 1 was followed, except that humic acid was not added, the weight of the biochar was 20 g, and the remaining steps and parameters were the same as in Example 1.

[0045] Application Example 1

[0046] The saline-alkali soil conditioner obtained in Example 1 was applied to saline-alkali soil for soil improvement treatment (wherein, the amount of the saline-alkali soil conditioner was 35 g), and 70% of the maximum field water holding capacity of the soil was maintained during the treatment. Half a month later, Chinese cabbage was planted, and the fertilization treatment during the planting process was the same as that in the field, and the planting time was 45 days.

[0047] Application Example 2

[0048] The saline-alkali soil conditioner obtained in Example 2 was applied to saline-alkali soil for soil improvement treatment (wherein, the amount of the saline-alkali soil conditioner was 27.5 g), and 70% of the maximum field water holding capacity of the soil was maintained during the treatment. Half a month later, Chinese cabbage was planted, and the fertilization treatment during the planting process was the same as that in the field, and the planting time was 45 days.

[0049] Comparative application example 1

[0050] The method of Application Example 1 is followed, except that the saline-alkali soil conditioner is not applied, and the remaining steps and parameters are the same as those of Application Example 1.

[0051] Comparative Application Example 2

[0052] The method of Application Example 1 was followed, except that the product obtained in Comparative Example 2 was used to replace the saline-alkali soil conditioner, and the remaining steps and parameters were the same as those of Application Example 1.

[0053] Summarizing the above results of saline-alkali soil improvement, Figures 1 to 4 shown.

[0054] in, Figure 1 The following is a comparison chart of the electrical conductivity of the soil after treatment in Application Example 1, Application Example 2, Comparative Application Example 1, and Comparative Application Example 2. Figure 1 It can be seen that the improver obtained in the embodiment of the present invention can effectively reduce the conductivity of saline-alkali soil after treatment; among them, after using the improver obtained in Example 1 of the present invention, the conductivity of the saline-alkali soil is 1.059ms / cm, and after using the improver obtained in Example 2 of the present invention, the conductivity of the saline-alkali soil is 1.083ms / cm.

[0055] in, Figure 2 The following is a comparison chart of soil pH after treatment in Application Example 1, Application Example 2, Comparative Application Example 1, and Comparative Application Example 2. Figure 2 It can be seen that the improver obtained in the embodiment of the present invention can effectively reduce the pH of saline-alkali soil after treatment; wherein, after using the improver obtained in Example 1 of the present invention, the pH of the saline-alkali soil is 7.77, and after using the improver obtained in Example 2 of the present invention, the pH of the saline-alkali soil is 7.85.

[0056] in, Figure 3 The following is a comparison chart of the organic matter content of the soil after treatment in Application Example 1, Application Example 2, Comparative Application Example 1, and Comparative Application Example 2. Figure 3It can be seen that the improver obtained in the embodiment of the present invention can effectively increase the organic matter content of saline-alkali soil after treatment; among them, after using the improver obtained in Example 1 of the present invention, the organic matter content of saline-alkali soil is 68.36 g / kg, and after using the improver obtained in Example 2 of the present invention, the organic matter content of saline-alkali soil increases by 56.8 g / kg.

[0057] in, Figure 4 The following is a comparison chart of the fresh weight of Chinese cabbage after being treated in Application Example 1, Application Example 2, Comparative Application Example 1, and Comparative Application Example 2. Figure 4 It can be seen that the improver obtained in the embodiment of the present invention can effectively increase the fresh weight of Chinese cabbage after treatment; among them, after using the improver obtained in Example 1 of the present invention, the fresh weight of Chinese cabbage is 2313 mg, and after using the improver obtained in Example 2 of the present invention, the fresh weight of Chinese cabbage is 1861 mg.

[0058] In order to more clearly express the technical solution of the present invention, Figure 5 The scanning electron microscope image of corn straw biochar in an embodiment of the present invention is shown. Figure 6 A scanning electron microscope image of humic acid in an example of the present invention is shown.

[0059] Depend on Figure 5 It can be seen that corn straw biochar has rich pore structure and irregular surface, which helps to adsorb salt in the soil.

[0060] Depend on Figure 6 It can be seen that humic acid is mainly in the form of irregular flakes and block particles, with many gaps between the particles, which is conducive to the penetration and adsorption of water and base ions.

[0061] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A saline-alkali soil conditioner, characterized in that: The saline-alkali soil improver includes biochar and humic acid in a content ratio of 4:1.5-3; The average particle size of the biochar is ≤2 mm; the average particle size of the humic acid is ≤2 mm.

2. The saline-alkali soil conditioner according to claim 1, wherein The saline-alkali soil improver comprises biochar and humic acid in a content ratio of 4:

3.

3. The saline-alkali soil conditioner according to claim 1 or 2, wherein The biochar has a pH value of less than 9.5, an ash content of less than 35 wt%, and an average particle size of less than 2 mm.

4. The saline-alkali soil conditioner according to claim 1 or 2, wherein The biochar is corn straw biochar; And / or, the corn straw biochar is obtained by pyrolyzing corn straw in the absence of oxygen at 500°C for 2 hours; the obtained corn straw biochar has a pH of 9.15, an ash content of 32.35wt%, an organic carbon content of 17.4%, a N content of 1.39%, a C content of 53.62%, a H content of 2.06%, and an O content of 10.58%.

5. The saline-alkali soil conditioner according to claim 1 or 2, wherein The average particle size of the humic acid is ≤2 mm, and the C content, H content and O content of the humic acid are 36.9%, 2.99% and 29.26%.

6. The saline-alkali soil conditioner according to claim 1 or 2, wherein: The preparation method of the saline-alkali soil conditioner comprises: weighing biochar and humic acid according to a weight ratio and mixing them; the mixing conditions meet the following conditions: the speed of the stirring equipment is 300 to 500 rpm and the time is 3 to 6 minutes.

7. Use of the saline-alkali soil conditioner according to any one of claims 1 to 6 in improving saline-alkali soil, characterized in that: The saline-alkali soil conditioner was applied to the saline-alkali soil for soil improvement treatment. During the treatment, 70% of the maximum field water holding capacity of the soil was maintained. Crops were planted half a month later. The fertilization treatment during the planting process was the same as that in the field. The planting time was 45 days.

8. The use according to claim 7, wherein: Based on the total mass of soil for planting crops, the dosage of the saline-alkali soil conditioner is 5.5wt% to 7wt%.

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