Decomposted fertilizer for saline-alkali soil remediation as well as preparation method and application of decomposed fertilizer

Abstract

The invention belongs to the technical field of soil remediation, and particularly relates to a decomposed fertilizer for saline-alkali soil remediation and a preparation method and application thereof. The livestock and poultry manure and the saline-alkali soil are used as raw materials, the decomposed fertilizer with low pH and conductivity and high nutritional ingredients can be obtained by controlling the properties of the raw materials, and when the decomposed fertilizer is applied to the saline-alkali soil, the salinization degree of the saline-alkali soil can be obviously improved, the humic acid content in the saline-alkali soil can be increased, and the nutritional structure of the saline-alkali soil can be improved; the soil ecological system of the saline-alkali area is restored. And the preparation method of the decomposed fertilizer is simple, the fermentation period is short, secondary pollution is avoided, and the saline-alkali soil can be repaired at low cost. The preparation method of the decomposed fertilizer is also a preliminary restoration method of saline-alkali soil, the saline-alkali soil and livestock manure are used as raw materials for aerobic composting, the saline-alkali soil is subjected to innocent treatment and then is applied to the saline-alkali soil for in-situ restoration, the two modes cooperate with each other and act together, and the restoration efficiency of the saline-alkali soil can be greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and particularly relates to a matured fertilizer for saline-alkali soil remediation, a preparation method thereof, and an application thereof. Background Art

[0002] Soil salinization is one of the soil degradation problems commonly faced in the world. Due to long-term drought of the soil and excessive floods or insufficient drainage caused by the aggregated rainfall patterns, the salts in the deep layer of the soil continuously accumulate on the soil surface layer, resulting in soil salinization. Soil salinization will not only cause drastic changes in the soil structure and microenvironment, but also make it difficult for plants to grow due to ion imbalance in cells, thus seriously affecting agricultural production and the soil ecosystem.

[0003] In the prior art, the formula of the saline-alkali land improvement fertilizer is basically prepared by mixing humic acid, organic matter, microbial improvement bacteria, saline-alkali land improvement chemical reagents, and chemical fertilizers. The core technologies mainly include four points: one is to use chemical reagents to displace soil salt ions; the second is to use organic acids to neutralize soil alkalinity; the third is to increase organic matter to improve the soil aggregate structure; the fourth is to add microbial agents to improve the soil microenvironment through microbial activities. The existing saline-alkali land improvement fertilizers have complex production processes, unstable product quality, cumbersome use processes, uneven improvement effects, and the repair effect needs to be further improved.

[0004] At the present stage, the focus of saline-alkali soil remediation is mainly to reduce the salt input through precision irrigation. However, due to various conditions in some areas, it is difficult to achieve the above method. Therefore, in order to better improve the remediation efficiency of saline-alkali land, it is usually chosen to apply saline-alkali land improvement fertilizer. However, in the prior art, the formula of the saline-alkali land improvement fertilizer is basically prepared by mixing humic acid, organic matter, microbial improvement bacteria, saline-alkali land improvement chemical reagents, and chemical fertilizers. The production process is complex, the product quality is unstable, the use process is cumbersome, the improvement effect is uneven, and the repair effect on saline-alkali soil needs to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a matured fertilizer for saline-alkali soil remediation, a preparation method thereof, and an application thereof, to prepare a matured fertilizer with low pH and conductivity and high nutrient content, repair saline-alkali soil at low cost, reduce secondary pollution, and improve the remediation efficiency of saline-alkali soil.

[0006] To achieve the above purpose, the present invention provides a matured fertilizer, and the raw materials of the matured fertilizer include livestock and poultry manure and saline-alkali soil;

[0007] The C / N of the raw materials is (20-40):1, the water content is 40-70%, and the pH is 6-9;

[0008] The pH of the saline-alkali soil is 9.9 - 10.5, the electrical conductivity is 1.1 - 1.5 ds / m, the organic matter content is 1.7 - 4.1 g / kg, the humic acid content is 6.3 - 10.5 g / kg, and the humic acid content is 2.5 - 3.9 g / kg.

[0009] Preferably, the dry weight ratio of the livestock and poultry manure to the saline-alkali soil is (6 - 8):(2 - 4).

[0010] Preferably, the raw materials further include straw.

[0011] Preferably, the livestock and poultry manure includes one or more of cow dung, chicken manure, and pig manure.

[0012] The present invention also provides a preparation method of the matured fertilizer described in the above technical solution, including the following steps: performing aerobic composting on the raw materials for 35 - 120 d to obtain the matured fertilizer.

[0013] Preferably, after the aerobic composting is completed, it further includes: standing the materials obtained from the aerobic composting for ≤ 120 d.

[0014] The present invention also provides an application of the matured fertilizer described in the above technical solution in the remediation of saline-alkali soil.

[0015] Preferably, the pH of the saline-alkali soil is 9.9 - 10.5, the electrical conductivity is 1.1 - 1.5 ds / m, the organic matter content is 1.7 - 4.1 g / kg, the humic acid content is 6.3 - 10.5 g / kg, and the humic acid content is 2.5 - 3.9 g / kg.

[0016] The present invention also provides a method for remediating saline-alkali soil, applying the matured fertilizer described in the above technical solution at 0 - 30 cm of the saline-alkali soil to be remediated and mixing evenly.

[0017] Preferably, the application amount of the matured fertilizer is 50 - 300 t / hm 2 .

[0018] Beneficial effects:

[0019] The present invention provides a matured fertilizer, and the raw materials of the matured fertilizer include livestock and poultry manure and saline-alkali soil; the C / N of the raw materials is (20-40):1, the water content is 40-70%, and the pH is 6-9; the pH of the saline-alkali soil is 9.9-10.5, the electrical conductivity is 1.1-1.5 ds / m, the organic matter content is 1.7-4.1 g / kg, the humic acid content is 6.3-10.5 g / kg, and the humic acid content is 2.5-3.9 g / kg. The present invention uses livestock and poultry manure and saline-alkali soil as raw materials, and by controlling the C / N, water content and pH of the raw materials, as well as the properties of the saline-alkali soil, the obtained matured fertilizer has a low pH and electrical conductivity, and a high nutrient content; when the obtained matured fertilizer is applied back to the saline-alkali soil, it can not only significantly improve the salinization degree of the saline-alkali soil, but also increase the humic acid content in the saline-alkali soil, improve the nutrient structure of the saline-alkali soil, and restore the soil ecosystem in the saline-alkali area. And the preparation method of the matured fertilizer is simple, the fermentation period is short, no secondary pollution will be caused, and the saline-alkali soil can be repaired at low cost. Detailed implementation manners

[0020] The present invention provides a matured fertilizer, and the raw materials of the matured fertilizer include livestock and poultry manure and saline-alkali soil;

[0021] The C / N of the raw materials is (20-40):1, the water content is 40-70%, and the pH is 6-9;

[0022] The pH of the saline-alkali soil is 9.9-10.5, the electrical conductivity is 1.1-1.5 ds / m, the organic matter content is 1.7-4.1 g / kg, the humic acid content is 6.3-10.5 g / kg, and the humic acid content is 2.5-3.9 g / kg.

[0023] As an implementation manner, the C / N of the raw materials of the present invention is (25-35):1; as another implementation manner, the C / N of the raw materials of the present invention is 30:1. As an implementation manner, the porosity of the raw materials of the present invention is 40%-70%; as another implementation manner, the porosity of the raw materials of the present invention is 50%-60%.

[0024] The raw materials of the present invention include livestock and poultry manure and saline-alkali soil. As an embodiment, the raw materials of the present invention further include straw. As an embodiment, the straw of the present invention can be rice straw. The straw of the present invention is used as a regulator to adjust the C / N, moisture content, pH and porosity of the raw materials. As an embodiment, the dry weight ratio of the livestock and poultry manure to the saline-alkali soil is (6-8):(2-4); as another embodiment, the dry weight ratio of the livestock and poultry manure to the saline-alkali soil is 7:3. Adjusting the dry weight ratio of the livestock and poultry manure and the saline-alkali soil in the present invention helps to promote the microbial activities in the compost pile, while accelerating the decomposition of the livestock and poultry manure, reducing the degree of soil salinization, improving the soil structure, enhancing the soil fertility, and realizing the dual treatment of the livestock and poultry manure and the saline-alkali soil.

[0025] As an embodiment, the livestock and poultry manure of the present invention includes granular and / or powdered livestock and poultry manure; as another embodiment, the livestock and poultry manure of the present invention is granular livestock and poultry manure. The livestock and poultry manure of the present invention includes one or more of cow dung, chicken manure and pig manure; as another embodiment, the livestock and poultry manure of the present invention is cow dung. Defining the specific type of the livestock and poultry manure in the present invention helps to reasonably select and match it in the subsequent implementation stage to optimize the carbon-nitrogen ratio and microbial activity of the compost, and improve the composting efficiency and quality.

[0026] As an embodiment, the pH of the saline-alkali soil of the present invention is 10.2, the electrical conductivity is 1.3 ds / m, the organic matter content is 2.9 g / kg, the humic acid content is 8.4 g / kg, and the humic acid content is 3.2 g / kg. In the present invention, the pH and electrical conductivity of the saline-alkali soil are the pH and electrical conductivity of the saturated mud extract of the saline-alkali soil. As an embodiment, the saturated mud extract of the saline-alkali soil of the present invention is prepared with reference to GB 20205107-T-326 (Classification and Grading of Soils for Agricultural Use in Saline and Alkaline Lands). Defining the specific properties of the saline-alkali soil in the present invention helps to specifically improve the soil repair properties of the saline soil or alkaline soil.

[0027] The present invention also provides a preparation method of the matured fertilizer according to the above technical solution, including the following steps: performing aerobic composting on the raw materials for 35 d to 120 d to obtain the matured fertilizer.

[0028] As an embodiment, the temperature of the aerobic composting of the present invention is 15-70 °C; as another embodiment, the temperature of the aerobic composting of the present invention is 25-60 °C. As an embodiment, the turning method of the aerobic composting of the present invention is manual turning.

[0029] As an embodiment, the time of the aerobic composting of the present invention is 40-100 d; as another embodiment, the time of the aerobic composting of the present invention is 50-80 d; as an embodiment, the time of the aerobic composting of the present invention is 55 d.

[0030] As an implementation manner, after the aerobic composting of the present invention is completed, it further includes: standing the material obtained from the aerobic composting for ≤ 120 d. As an implementation manner, the standing time of the present invention is 80 d. Standing the material obtained from the aerobic composting after the aerobic composting of the present invention is completed helps the ripening of the compost product, reduces potential harmful substances, helps nutrients to be further released and transformed in the soil, and thus improves the repair effect on saline-alkali soil.

[0031] The preparation method of the mature fertilizer of the present invention is also a preliminary method for repairing saline-alkali soil. Using saline-alkali soil and livestock manure as raw materials for aerobic composting can stimulate the activities of microorganisms in the raw materials and improve the distribution of beneficial microorganisms in saline-alkali soil; it can also use the humic acid substances formed during aerobic composting to chelate saline-alkali ions, change the properties of saline-alkali soil, and perform harmless treatment on saline-alkali soil to achieve the preliminary treatment of saline-alkali soil. And while preliminarily treating saline-alkali soil, the obtained mature fertilizer can be used for in-situ repair of saline-alkali soil to perform secondary treatment on saline-alkali soil.

[0032] The present invention also provides the application of the mature fertilizer described in the above technical solution in the repair of saline-alkali soil. As an implementation manner, the pH of the saline-alkali soil is 9.9 - 10.5, the electrical conductivity is 1.1 - 1.5 ds / m, the organic matter content is 1.7 - 4.1 g / kg, the humic acid content is 6.3 - 10.5 g / kg, and the humic acid content is 2.5 - 3.9 g / kg; as another implementation manner, the pH of the saline-alkali soil of the present invention is 10.2, the electrical conductivity is 1.3 ds / m, the organic matter content is 2.9 g / kg, the humic acid content is 8.4 g / kg, and the humic acid content is 3.2 g / kg. In the present invention, the pH and electrical conductivity of the saline-alkali soil are the pH and electrical conductivity of the saturated mud extract of the saline-alkali soil. As an implementation manner, the saturated mud extract of the saline-alkali soil of the present invention is prepared with reference to GB20205107-T-326 (Soil Classification and Grading for Agricultural Use of Saline-alkali Land).

[0033] The present invention also provides a method for repairing saline-alkali soil, applying the mature fertilizer described in the above technical solution at 0 - 30 cm of the saline-alkali soil to be repaired and mixing evenly.

[0034] As an implementation manner, the application rate of the mature fertilizer of the present invention is 50 - 300 t / hm 2 ; as an implementation manner, the application rate of the mature fertilizer of the present invention is 80 - 250 t / hm 2 ; as another implementation manner, the application rate of the mature fertilizer of the present invention is 100 - 200 t / hm 2 ; as an implementation manner, the application rate of the mature fertilizer of the present invention is 150 t / hm2 As an implementation manner, the time for uniform mixing in the present invention is 30 to 120 days; as another implementation manner, the time for uniform mixing in the present invention is 40 to 100 days; as another implementation manner, the time for uniform mixing in the present invention is 60 to 80 days; as another implementation manner, the time for uniform mixing in the present invention is 70 days.

[0035] As an implementation manner, the present invention performs rotary tillage on the saline-alkali soil to be repaired at a depth of 0 to 30 cm by applying the decomposed fertilizer described in the above technical solution, so as to achieve uniform mixing of the saline-alkali soil to be repaired and the decomposed fertilizer. The present invention has no strict requirements on the way of rotary tillage, and the conventional way in the art can be adopted, such as using a rotary tiller.

[0036] Although the raw materials of the decomposed fertilizer provided by the present invention contain saline-alkali soil, due to being mixed and decomposed with livestock and poultry manure, they have reached a harmless state. Applying the obtained decomposed fertilizer back to the saline-alkali soil can significantly increase the organic matter content in the saline-alkali soil, and reduce the pH and conductivity. The repair method provided by the present invention is actually a secondary treatment method for saline-alkali soil. By preparing the decomposed fertilizer, the saline-alkali soil is preliminarily repaired to achieve harmless treatment; the obtained decomposed fertilizer is used to backfill the saline-alkali soil, and by activating various beneficial microorganisms (Flavobacterium, Saprospiraceae) in the saline-alkali soil, the content of humic acid in the soil is increased to improve the soil condition, restore the soil ecosystem in the saline-alkali area, and enhance the fertilizer retention and water storage capacity of the saline-alkali soil. The present invention combines the harmless treatment and repair treatment of saline-alkali soil and acts together, which can effectively improve the soil fertility.

[0037] In order to further illustrate the present invention, the following examples are used to describe in detail a decomposed fertilizer for saline-alkali soil repair provided by the present invention, its preparation method and application, but they cannot be understood as limiting the protection scope of the present invention.

[0038] Example 1

[0039] Determination of soil properties

[0040] (1) Determination of pH and conductivity

[0041] Prepare the soil saturated mud extract according to GB 20205107-T-326 (Soil Classification and Grading for Agricultural Use of Saline-alkali Land). Specifically: Weigh the dried surface soil sample (soil from Du'erbert Mongol Autonomous County, Daqing City, Heilongjiang Province) into a container, then add deionized water to the container and continuously stir until the soil mud reaches a saturated state (the surface of the saturated soil mud is shiny and can flow slowly when the container is tilted, and can quickly return to its original state when the container is slapped or shaken); After placing the saturated mud for at least 4 hours, ensure that the soil mud remains in a saturated state. If there is excess deionized water accumulated on the mud surface, appropriate soil samples can be added again and remixed. If the soil hardens or the texture becomes rough, add deionized water again for mixing; Finally, vacuum filter the soil mud to obtain the soil saturated mud extract. Measure the pH of the soil saturated mud extract to be 10.2 ± 0.3, and the conductivity to be 1.3 ± 0.2 ds / m.

[0042] (2) Determination of organic matter content

[0043] Adopt the ignition method. Take the air-dried surface soil sample and calcine it in a muffle furnace at 550 °C for 4 hours. Measure the organic matter content to be 2.9 ± 1.2 g / kg.

[0044] (3) Determination of humic acid content

[0045] Adopt the Na 4 P 2 O 7 -NaOH extraction method. Take the air-dried surface soil sample into a container, add 0.1 mol / L Na 4 P 2 O 7 -NaOH mixed solution according to the solid-liquid ratio of 1 g:20 mL. After extracting at 180 r / min on a shaker at room temperature for 24 hours, use a vacuum pump to filter under reduced pressure to obtain humic acid. Measure the humic acid concentration to be 8.4 ± 2.1 g / kg.

[0046] (4) Determination of fulvic acid content

[0047] Adjust the pH value of a part of the humic acid in step (3) to 1.0, then let it stand for 12 hours and centrifuge. Filter the supernatant through a 0.45 μm filter membrane to obtain the fulvic acid part. Measure the fulvic acid concentration to be 3.8 ± 0.8 g / kg.

[0048] (5) Determination of humic acid content

[0049] Adjust the pH value of a part of the humic acid in step (3) to 1.0, then let it stand for 12 hours and centrifuge. Dissolve the precipitate in NaOH, centrifuge for purification, then readjust the pH value to 1.0 and let it stand for 12 hours and centrifuge. Wash the precipitate 2 times, then dissolve it in NaHCO 3The humic acid fraction was obtained from the solution, and the humic acid concentration was determined to be 3.2 ± 0.7 g / kg.

[0050] From steps (1) to (5), it can be seen that the soil pH was 10.2 ± 0.3, the electrical conductivity was 1.3 ± 0.2 ds / m, the organic matter content was 2.9 ± 1.2 g / kg, the humic acid content was 8.4 ± 2.1 g / kg, the humic acid content was 3.2 ± 0.7 g / kg, and the humic acid to fulvic acid ratio (humic acid / fulvic acid) was 0.8 ± 0.04. It indicates that the soil in Du'erbert Mongol Autonomous County, Daqing City, Heilongjiang Province is an alkaline soil with a high degree of salinization and low soil nutrient content, which is recorded as the soil to be repaired.

[0051] Example 2

[0052] Cow dung was mixed with the soil to be repaired in Example 1 at a dry weight ratio of 8:2, and rice straw was used to adjust the porosity to 50% - 60%, C / N to 30:1, water content to 40% - 70%, and pH to 8.7 ± 0.12; coupled composting was carried out for 55 days, and after the composting materials were left standing for 80 days, matured fertilizer 1 was obtained.

[0053] Example 3

[0054] Cow dung was mixed with the soil to be repaired in Example 1 at a dry weight ratio of 7:3, and rice straw was used to adjust the porosity to 50% - 60%, C / N to 30:1, water content to 40% - 70%, and pH to 8.8 ± 0.03; coupled composting was carried out for 55 days, and after the composting materials were left standing for 80 days, matured fertilizer 2 was obtained.

[0055] Comparative Example 1

[0056] Same as Example 2, the only difference is that the soil to be repaired in Example 1 was not added, and rice straw was directly used to adjust the porosity to 50% - 60%, C / N to 30:1, water content to 40% - 70%, and pH to 8.6 ± 0.2; coupled composting was carried out for 55 days, and after the composting materials were left standing for 80 days, matured fertilizer 3 was obtained.

[0057] Comparative Example 2

[0058] Same as Example 2, the only difference is that rice straw was used to adjust the porosity to 50% - 60%, C / N to 25:1, water content to 40% - 70%, and pH to 8.8 ± 0.11, matured fertilizer 4.

[0059] Comparative Example 3

[0060] Same as Example 2, the only difference is that coupled composting was carried out for 45 days, and after being left standing for 135 days, matured fertilizer 5 was obtained.

[0061] Comparative Example 4

[0062] Same as Example 2, the only difference is that cow dung is replaced by chicken dung to obtain matured fertilizer 6.

[0063] Comparative Example 5

[0064] Same as Example 2, the only difference is that after the coupled composting is completed, it is not left standing to obtain matured fertilizer 7.

[0065] Comparative Example 6

[0066] Same as Example 2, the only difference is that after the coupled composting is completed, the composting materials are left standing for 45 days to obtain matured fertilizer 8.

[0067] Test Example 1

[0068] Referring to the method of Example 1, the pH, electrical conductivity, organic matter content, humic acid content, fulvic acid content, and humic acid to fulvic acid ratio of matured fertilizers 1 - 8 in Examples 2 - 3 and Comparative Examples 1 - 6 were detected respectively, and the results are shown in Table 1.

[0069] Table 1 Detection results of the properties of different matured fertilizers

[0070] Composted fertilizer pH Electrical conductivity (ds / m) Organic matter (g / kg) Humic acid (g / kg) Humic acid (g / kg) Ratio of humic acid to fulvic acid Composted fertilizer 1 7.9±0.07c 0.45±0.03d 19.9±2.2abc 96.4±2.1abc 53.9±1.1a 1.83±0.1a Composted fertilizer 2 8.1±0.07ab 0.61±0.02ab 18.5±1.2bcd 95.9±4.8bc 47.4±4.3cd 1.6±0.08b Composted fertilizer 3 7.6±0.09d 0.65±0.01a 22.1±2.7a 104.8±9.5a 52.9±2.1ab 1.81±0.05a Composted fertilizer 4 8.0±0.05bc 0.52±0.02bcd 17.4±0.3cd 96.1±1.8bc 49.1±1.2bcd 1.67±0.04ab Composted fertilizer 5 8.2±0.02a 0.57±0.06abc 16.8±0.5d 88.1±1.4c 43.2±0.8e 1.53±0.08bc Composted fertilizer 6 8.2±0.12a 0.51±0.07cd 21.3±1.6ab 94.8±3.3bc 45.3±2.2de 1.61±0.12b Composted fertilizer 7 8.0±0.13bc 0.46±0.08d 21.1±1.4ab 98.2±2.7ab 50.3±0.5abc 1.41±0.09c Composted fertilizer 8 8.0±0.09bc 0.48±0.05cd 20.5±1.1ab 97.3±1.1ab 50.1±1.7abc 1.69±0.07ab

[0071] Note: Different lowercase letters indicate P < 0.05, the same below.

[0072] Since saline - alkali soil is not mixed in matured fertilizer 3, it can be conventionally inferred that the pH and electrical conductivity of matured fertilizer 3 will be lower than those of matured fertilizers 1 and 2, and the organic matter and humic acid contents will also be relatively higher. However, according to Table 1, the electrical conductivity of matured fertilizers 1 and 2 is lower than that of matured fertilizer 3, and the pH value is equivalent to that of matured fertilizer 3. Fulvic acid is an important part of humic acid that enhances soil fertility and is an important indicator for measuring soil remediation. According to Table 1, the fulvic acid content of matured fertilizer 1 is higher than that of matured fertilizers 2 and 3, indicating that the dry weight ratio of the composting materials (cow dung) to the soil to be remediated during the coupled composting process affects the remediation effect. When the dry weight ratio of cow dung to the soil to be remediated is 8:2 for the coupled composting experiment, the highest fulvic acid content is obtained, and the best soil remediation effect is achieved.

[0073] Application Example 1

[0074] In - situ remediation of saline - alkali soil

[0075] At 50 t / hm 2The application rates of the composted fertilizers 1-8 in Examples 2-3 and Comparative Examples 1-6 were applied to the surface layer of 0-10 cm of the soil to be repaired in Example 1, and then rotary tillage was carried out to mix evenly. After natural placement for 30 days, in the same way as in Example 1, the pH, electrical conductivity, organic matter content, humic acid content, fulvic acid content and H / F ratio of the soil after cultivation were detected. The results are shown in Table 2.

[0076] Table 2 Repair effects of different composted fertilizers on saline-alkali soil

[0077]

[0078]

[0079] It can be seen from Table 2 that when the composted fertilizer produced by coupling the saline-alkali soil to be repaired with cow dung is applied back to the saline-alkali soil, it can not only significantly improve the degree of soil salinization, but also increase the humic acid content in the soil, improve the soil nutrient structure, and restore the soil ecosystem in the saline-alkali area.

[0080] It can be seen from the above that the technical solution provided by the present invention can not only significantly improve the degree of soil salinization, but also increase the humic acid content in the saline-alkali soil, improve the nutrient structure of the saline-alkali soil, and restore the soil ecosystem in the saline-alkali area.

[0081] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. People can also obtain other embodiments without creative efforts based on this embodiment, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A decomposed fertilizer, characterized in that: The raw materials of the decomposed fertilizer include livestock and poultry excrement and saline-alkali soil; The C / N of the raw material is (20-40):1, the moisture content is 40-70%, and the pH is 6-9; The saline-alkali soil has a pH value of 9.9 to 10.5, an electrical conductivity of 1.1 to 1.5 ds / m, an organic matter content of 1.7 to 4.1 g / kg, a humic acid content of 6.3 to 10.5 g / kg, and a humic acid content of 2.5 to 3.9 g / kg.

2. The decomposed fertilizer according to claim 1, characterized in that: The dry weight ratio of livestock and poultry manure to saline-alkali soil is (6-8):(2-4).

3. The decomposed fertilizer according to claim 1, characterized in that: The raw materials also include straw.

4. The decomposed fertilizer according to claim 1 or 2, characterized in that: The livestock and poultry manure includes one or more of cow manure, chicken manure and pig manure.

5. The method for preparing the decomposed fertilizer according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: aerobic composting of raw materials for 35 to 120 days to obtain decomposed fertilizer.

6. The preparation method according to claim 5, characterized in that: After the aerobic composting is completed, the further step includes: allowing the aerobic composted material to stand for ≤120 days.

7. Use of the decomposed fertilizer according to any one of claims 1 to 4 or the decomposed fertilizer obtained by the preparation method according to claim 5 or 6 in saline-alkali soil remediation.

8. The use according to claim 7, characterized in that: The saline-alkali soil has a pH value of 9.9 to 10.5, an electrical conductivity of 1.1 to 1.5 ds / m, an organic matter content of 1.7 to 4.1 g / kg, a humic acid content of 6.3 to 10.5 g / kg, and a humic acid content of 2.5 to 3.9 g / kg.

9. A method for repairing saline-alkali soil, characterized in that: Apply the decomposed fertilizer according to any one of claims 1 to 4 or the decomposed fertilizer obtained by the preparation method according to claim 5 or 6 at 0 to 30 cm on the saline-alkali soil to be repaired and mix well.

10. The repair method according to claim 9, characterized in that: The application amount of the decomposed fertilizer is 50-300t / hm 2 .

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