Method for rapid in-situ treatment of cadmium-polluted cultivated land through relay intercropping of corn and green soy beans

Abstract

The invention discloses a method for rapid in-situ treatment of cadmium-polluted farmland by relay intercropping of corn and green soy beans, which comprises the following steps: S1, selecting the cadmium-polluted farmland in a strict management and control area, replacing polluted soil at different depths, and exchanging heavily polluted soil on the surface layer and clean soil on the middle layer; s2, applying an organic fertilizer to the cadmium-polluted farmland treated in the step S1, and performing rapid fertilization treatment; and S3, performing a corn and green soy bean intercropping mode in the cadmium-polluted farmland treated in the S2, and carrying out conventional field management measures to ensure normal growth and development of crops. According to the technical scheme, polluted soil and relatively clean soil are replaced in situ, farming production operation can be carried out immediately after remediation treatment, safe utilization of polluted cultivated land is achieved by applying organic fertilizer for rapid fertilization and utilizing a corn and green soy bean relay intercropping mode, and the economic benefit is increased. And edible parts of the planted crops meet the national food safety standard.

Description

Technical Field

[0001] The invention relates to the technical field of soil heavy metal pollution control and restoration, and in particular to a method for rapid in-situ control of cadmium-contaminated farmland through intercropping of corn and edamame. Background Art

[0002] At present, heavy metal pollution in cultivated soil has become a major problem affecting human health, regional environment and food safety. Heavy metal pollution in soil is characterized by concealment, irreversibility, long-term and serious consequences. Among them, heavy metal cadmium is a non-essential nutrient element that is highly toxic to plants and animals at low concentrations. It is often enriched in the human body through the food chain, causing chronic poisoning, affecting the metabolism of calcium and phosphorus in the body, causing pathological changes in the kidneys, bones and liver, inducing a variety of diseases of the bones, digestive system and urinary system, and can lead to malignant tumors. Cadmium heavy metal pollution in the environment is characterized by long-term, concealed and irreversible. Its pollutants have poor mobility in the medium, long retention time, cannot be degraded by microorganisms, and can also affect environmental quality and endanger human health through the food chain. Therefore, it is of great practical significance to study new cadmium-contaminated soil remediation technologies.

[0003] At present, there has been extensive research on soil heavy metal remediation technology, which can be roughly divided into the following measures: (1) Engineering measures, mainly including soil addition, soil replacement and deep plowing; (2) Physical and chemical remediation, mainly including electric remediation, electric heat remediation and soil leaching; (3) Chemical remediation, adding amendments to the soil to reduce the biological effectiveness of heavy metals through adsorption, redox, antagonism or precipitation of heavy metals; (4) Bioremediation, a new method of using biotechnology to treat contaminated soil, using organisms to reduce and purify heavy metals in the soil or reduce the toxicity of heavy metals. According to the difference in organisms and remediation mechanisms, bioremediation is divided into phytoremediation technology and microbial remediation technology.

[0004] Among them, in terms of bioremediation, the patent application with publication number CN 118527468 A discloses a method for repairing cadmium-contaminated soil based on the pepper-corn intercropping model. In the acidic soil in the south, peppers with a high Cd enrichment coefficient are first planted and then corn with a low Cd enrichment coefficient is intercropped. Double-film measures are taken, and 100 mg / L nano-selenium is sprayed during the pepper budding period and corn jointing period to further control the absorption of Cd by pepper and corn grains. At the same time, fertilization management is combined with the entire growth period to repair Cd-contaminated soil. This method is green, high-yield, efficient and sustainable. However, spraying nano-selenium increases the difficulty of field management and increases Increased costs; Jiang Chengai et al., in "The Effect of Mixed Cropping of Sedum Southeast and Different Plants on Soil Heavy Metal Absorption", disclosed the performance of using super-enriched Sedum Southeast for enrichment of Cd, Zn and Pb, and mixed cropping with corn and soybeans can significantly increase the absorption of Zn by the aboveground part of Sedum Southeast, and mixed cropping with Sedum Southeast significantly reduced the absorption of Cd and Zn by corn and ryegrass. However, Sedum Southeast has a small biomass and grows slowly, making it impossible to quickly repair and manage cultivated land in strictly controlled areas, and it is difficult to dispose of harvested agricultural and sideline products, affecting the recovery of agricultural production. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame, through the method of in-situ soil replacement and organic rapid fertilization, combined with the planting mode of intercropping corn and edamame, safe crops can be harvested.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] A method for rapidly treating cadmium-contaminated farmland in situ by intercropping corn and edamame, comprising the following steps:

[0008] S1. Select cadmium-contaminated farmland in the strictly controlled area, replace soil contaminated at different depths, and exchange the heavily contaminated surface soil with clean soil in the middle layer;

[0009] S2, applying organic fertilizer to the cadmium-contaminated farmland treated by S1 for rapid fertilization;

[0010] S3. Implement intercropping of corn and edamame in the cadmium-contaminated farmland treated with S2, and carry out routine field management measures to ensure the normal growth and development of crops.

[0011] Preferably, in S1, the 0-20 cm surface layer of heavily contaminated soil is exchanged with a 20-40 cm layer of clean soil.

[0012] As a preferred method, in S2, the amount of organic fertilizer used is 30t / hm 2 ~37.5t / hm 2The organic fertilizer has an organic matter content of ≥30%, and the sum of N, P2O5 and K2O in the total nutrients is not less than 4.0%. After the organic fertilizer is applied, the field is plowed and the land is prepared.

[0013] Preferably, in S3, the corn variety is Meiyu No. 27 and the edamame variety is Daliqing No. 3.

[0014] As a preferred method, deep furrows and high ridges were used in S3. The intercropping corn row was 130 cm wide and the narrow row was 45 cm. Two rows of soybeans were sown in the wide rows of corn when the corn was in the trumpet stage. The intercropping soybean row spacing was 30 cm, and the spacing between corn and soybean was 50 cm. The hole spacing between corn and soybean was 18 cm. One corn plant was left in the hole, and the density was 58,500 plants / hm2. 2 ; Leave 2 soybean plants in each hole, density 117,000 plants / hm 2 .

[0015] As a preferred method, in S3, corn fertilizer is applied twice, namely corn base fertilizer and topdressing during the flaring period, wherein the corn base fertilizer is 150kg / hm2 of nitrogen, phosphorus and potassium compound fertilizer. 2 , nitrogen fertilizer urea 225kg / hm2 in the big bell mouth period 2 At the same time, soybeans were sown and nitrogen, phosphorus and potassium compound fertilizers were applied at 150kg / hm2. 2 Use it as base fertilizer and do not apply top dressing afterwards.

[0016] Preferably, in S3, field management includes the following: early planting and replanting, first intertillage and weeding during the 5-6 leaf period of corn, second intertillage and weeding during the 13-15 leaf period, intertillage and weeding during the 5-6 leaf period of soybean, and directional spraying of 25% fomesafen aqueous solution 1200-1500g / hm2 between soybean rows. 2 .

[0017] As a preference, the method further comprises the following steps:

[0018] S4. After corn is harvested, the corn stalks obtained as a by-product of the crop are carbonized in the field to obtain biochar products.

[0019] Preferably, in S4, the carbonization treatment method of corn straw is: heating the corn straw at 300°C in an oxygen-free environment for 90 minutes to obtain corn straw biochar, naturally cooling to room temperature, and then placing the carbonized product in an oven at 80°C for 24 hours, grinding and passing through a 100-mesh sieve to obtain a biochar product.

[0020] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0021] 1. The present invention replaces the contaminated soil with relatively clean soil in situ, so that agricultural production operations can be carried out immediately after restoration and treatment. By applying organic fertilizers for rapid fertilization and using the intercropping mode of corn and edamame, the safe utilization of contaminated cultivated land can be achieved, and the edible parts of the crops planted meet the national food safety standards;

[0022] 2. In the present invention, the harvested crop byproduct corn stalks can be used to prepare biochar. On the one hand, a portion of heavy metals can be removed from the soil through plant adsorption. On the other hand, the prepared biochar has a good effect on sewage purification, realizing resource utilization, avoiding secondary pollution of the soil, realizing resource utilization, and having good economic and ecological effects;

[0023] 3. The method for treating cadmium-contaminated farmland provided by the present invention has a short restoration and treatment time, good results, relatively small investment, low technical requirements, relatively safe economic benefits, and certain prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of in-situ soil replacement in the present invention;

[0025] Figure 2 Schematic diagram of the effects of different amounts of organic fertilizer on soil (a) pH, (b) organic matter, (c) total nitrogen, (d) alkaline nitrogen, (e) available potassium and (f) available phosphorus in the present invention;

[0026] Figure 3 Schematic diagram of the changes in (a) available cadmium, (b) total cadmium, and (c) pH of soil at different depths in the modified area and the unmodified area in the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0028] Embodiment 1:

[0029] The invention discloses a method for rapidly treating cadmium-contaminated farmland in situ by intercropping corn and edamame, comprising the following steps:

[0030] S1. Select cadmium-contaminated farmland in the strictly controlled area, replace soil contaminated at different depths, and exchange the heavily contaminated surface soil with clean soil in the middle layer;

[0031] S2, applying organic fertilizer to the cadmium-contaminated farmland treated by S1 for rapid fertilization;

[0032] S3. Implement intercropping of corn and edamame in the cadmium-contaminated farmland treated with S2, and carry out routine field management measures to ensure the normal growth and development of crops.

[0033] Embodiment 2:

[0034] This example optimizes the method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame in Example 1 through a single factor experiment.

[0035] 2.1. Vertical distribution of heavy metal content in contaminated soil

[0036] The site selected by the present invention is a piece of cadmium-contaminated farmland in the strictly controlled cultivated land area, with an area of ​​about 2 mu. In S1, the vertical distribution of heavy metal content in the contaminated soil is obtained through profile soil analysis as shown in Table 1 below.

[0037] Table 1: Vertical distribution of heavy metals in soil of a cadmium-contaminated farmland in the strictly controlled cultivated land area

[0038] Soil Depth Cr(mg / kg) Cd(mg / kg) Pb(mg / kg) Hg(mg / kg) As (mg / kg) Stone 0-10cm 54.33 5.6 47.27 0.12 6.95 Stone 10-20cm 50.41 2.95 35.84 0.1 6.27 Stone 20-30cm 53.66 0.29 22.56 0.06 5.38 Stone Fu 30-40cm 51.19 0.08 19.25 0.03 5.2 Stone 40-50cm 50.17 0.11 17.92 0.03 4.35 Stone 50-70cm 51.01 0.18 19.73 0.02 3.39 Stone 70-100cm 54.38 0.16 19.02 0.03 5.01 Stone 100-120cm 63.11 0.04 18.49 0.03 5.29 Coefficient of variation % 8％ 169％ 43％ 72％ 21％

[0039] As shown in Table 1, except for cadmium, all other heavy metal elements are lower than the risk control value (Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial) (GB 15618-2018)), but the vertical spatial variation coefficient of cadmium, lead and mercury is relatively high, and there may be surface pollution. In a cadmium-contaminated farmland in the cultivated land area of ​​the strict control zone, the contaminated soil with heavy metal cadmium concentration higher than 0.3 mg / kg is mainly concentrated in the 0-20 cm tillage layer, which belongs to the cultivated land with serious surface soil pollution and no deep soil pollution. Therefore, if Figure 1 As shown, the 0-20 cm topsoil and the 20-40 cm middle soil can be replaced by engineering equipment such as excavators.

[0040] The physical and chemical properties of the surface soil before and after the in-situ soil layer replacement were tested, and the results are shown in Table 2.

[0041] Table 2: Effects of in-situ soil replacement on surface soil properties

[0042] Soil physical and chemical indicators Before renovation After transformation pH 7.54 8.49 Alkaline nitrogen (mg / kg) 51.21 42.34 Organic matter (%) 4.35 1.38 Total nitrogen (g / kg) 2.59 0.58 Available potassium (mg / kg) 50.11 37.48 Available phosphorus (mg / kg) 156.72 16.51 Cadmium (mg / kg) 5.60 1.92

[0043] As shown in Table 2 above, according to the nutrient classification standards of the second national soil survey, the surface soil was alkaline before the transformation, with medium and low content of organic matter, available phosphorus and available potassium, and lack of total nitrogen and alkaline nitrogen. According to the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018), the content of heavy metal Cd in the soil seriously exceeded the standard. After the in-situ soil layer replacement, the Cd content in the soil was significantly reduced from 5.6 mg / kg to 1.92 mg / kg, a decrease of 65.72%, and the soil pH increased by 0.95 units, but at the same time it also reduced the content of total nitrogen and available potassium in the soil, making the soil nutrient classification reach the fifth level, which is a nutrient-deficient soil and needs to be further transformed by certain measures.

[0044] 2.2 Effect of organic fertilizer application on total cadmium and available cadmium content in soil

[0045] In the transformation area, 0 tons / hm 2 , 22.5 tons / hm 2 、30.0 tons / hm 2 and 37.5 tons / hm 2 The commercial organic fertilizer is fertilized and the field is tilled. The organic matter content of the organic fertilizer is ≥30%, and the sum of N, P2O5 and K2O in the total nutrients is not less than 4.0%. The main raw materials are decomposed livestock and poultry manure, straw, and fungus residue. The physical and chemical properties of the surface soil are tested, and the test results are shown in Table 3 below:

[0046] Table 3: Effects of different organic fertilizer dosages on soil physical and chemical properties

[0047]

[0048] As shown in Table 3 and Figure 2 As shown in the figure, different amounts of organic fertilizers had no significant effect on soil pH, with a difference of 0.12 units between the maximum and minimum values. The application of organic fertilizers can effectively increase the content of organic matter, available phosphorus, available potassium, total nitrogen and alkaline nitrogen in the soil, with increases of 19.49% to 45.99%, 97.48% to 227.44%, 48.68% to 161.57%, 34.48% to 68.97% and 12.14% to 80.44%, respectively. With the increase of organic fertilizer application, the soil nutrient content increased significantly. Different amounts of organic fertilizers had no significant effect on total cadmium and available cadmium in the soil, but could reduce the content of total cadmium in the soil to a certain extent.

[0049] 2.3 Effect of organic fertilizer application on cadmium accumulation in edamame and corn

[0050] In the transformation area, 0 tons / hm 2 , 22.5 tons / hm 2、30.0 tons / hm 2 and 37.5 tons / hm 2 After that, the fields were tilled and prepared, and corn and edamame were intercropped in the prepared fields. The corn variety was Meiyu 27, and the edamame variety was Daliqing 3. The specific steps were as follows: deep furrows and high ridges were used for planting, the intercropping corn row was 130 cm wide and the narrow row was 45 cm. Two rows of soybeans were sown in the wide rows of corn when the corn was in the trumpet stage. The intercropping soybean row spacing was 30 cm, and the spacing between corn and soybean was 50 cm. Among them, the hole spacing of corn and soybean was 18 cm, and one corn plant was left in the corn hole, with a density of 58,500 plants / hm2. 2 ; Leave 2 soybean plants in each hole, density 117,000 plants / hm 2 In S3, corn fertilizer was applied twice, namely corn base fertilizer and topdressing during the flaring period. The base fertilizer of corn was 150kg / hm2 of nitrogen, phosphorus and potassium compound fertilizer. 2 , nitrogen fertilizer urea 225kg / hm2 in the big bell mouth period 2 At the same time, soybeans were sown and nitrogen, phosphorus and potassium compound fertilizers were applied at 150kg / hm2. 2 As base fertilizer, no topdressing is done afterwards; the nitrogen, phosphorus and potassium compound fertilizer is a three-element compound fertilizer of nitrogen, phosphorus and potassium (15-15-15). Carry out conventional field management measures, plant seedlings and replant in the early stage, carry out the first intertillage and weeding when the corn has 5 to 6 leaves, carry out the second intertillage and weeding when the corn has 13 to 15 leaves, carry out intertillage and weeding when the soybean has 5 to 6 leaves, and spray 25% fomesafen aqueous solution 1200-1500g / hm2 between the soybean rows. 2 , be aware that soybeans are sensitive during the 2-3 compound leaf stage and are very likely to be harmed by pesticides, so do not spray them. In pest control, we must strictly adhere to the principle of "prevention first, comprehensive control". Ensure that crops can grow and develop normally, harvest them when they are mature, and test the cadmium content in the edible parts of corn and edamame and the straw. The test results are shown in Table 4 below:

[0051] Table 4: Effects of different organic fertilizer dosages on cadmium accumulation in edamame and corn

[0052]

[0053] As shown in Table 4 above, the cadmium content in the edible parts of corn and edamame is different under different organic fertilizer application rates. According to the National Food Safety Standard Limits of Contaminants in Food (GB2762-2017), the limit value of Cd content in beans is 0.2 mg / kg. Therefore, the application rate of organic fertilizer is between 22.5 and 37.5 tons / hm2. 2 The Cd content of edible parts of soybeans meets the national food safety standards. The limit value of Cd content in corn is 0.1 mg / kg. Therefore, the application rate of organic fertilizer is 30.0-37.5 tons / hm2. 2In general, to meet the conditions of rapid fertilization and safe production, it is recommended that the application rate of organic fertilizer be 30.0-37.5 tons / hm2. 2 within the range.

[0054] Embodiment 3:

[0055] In order to further solve the secondary pollution caused by crop by-products to the environment, after the corn is harvested, the corn stalks obtained as a crop by-product are moved to the field for carbonization treatment to obtain biochar products.

[0056] Corn straw was heated at 300, 500 and 700℃ for 90min in an oxygen-free environment to obtain corn straw biochar. After naturally cooling to room temperature, the carbonized product was placed in an oven at 80℃ for 24h, ground and passed through a 100-mesh sieve, and then transferred to a plastic bag for storage and marked as 300℃, 500℃ and 700℃, respectively. The prepared biochar was used for a wastewater purification simulation test. The specific steps are as follows:

[0057] Weigh 0.1g of biochar prepared at different temperatures, add 100mL of simulated sewage (weigh 0.3g glucose, 0.085g NH4Cl, 0.0175g KH2PO4, dilute to 1L with deionized water), put into 250mL conical flasks, set 3 replicates for each group, oscillate at 180r / min at 25℃ for 24h, centrifuge at 3800r / min for 10min, determine the concentrations of COD, ammonia nitrogen and total phosphorus in the supernatant, analyze the nitrogen and phosphorus removal effect of biochar, and the test results are shown in Table 5 below:

[0058] Table 5: Adsorption effect of corn straw biochar

[0059]

[0060] As shown in Table 5, the biochar prepared at a carbonization temperature of 700°C has the weakest adsorption effect, followed by 500°C and the best at 300°C. It can be seen that straw carbonized at 300°C can effectively adsorb nitrogen, phosphorus and COD in water, with removal rates of 42.57%, 55.5% and 90.56%, respectively.

[0061] In order to understand the risk assessment of the treatment plan, 1.5 years after the experiment, soil samples at depths of 0-10cm, 10-20cm, 20-30cm, 30-40cm, 40-50cm, 50-60cm, 60-80cm and 80-100cm were collected in the transformed and unmodified areas to comprehensively analyze the changes in soil nutrients and heavy metal cadmium and understand the follow-up situation of restoration and treatment.

[0062] Sampling and testing were carried out on the physical and chemical vertical distribution of soil in the transformed and unmodified areas. The results are shown in Table 6.

[0063] Table 6: Vertical distribution of soil physicochemical properties in the transformed and unmodified areas

[0064]

[0065]

[0066] After nearly 1.5 years of treatment, sampling and analysis of the renovated and unrenovated areas revealed that Figure 3 As shown, compared with the original area, the total cadmium and effective cadmium contents in the soil of the cultivated layer in the transformed area decreased from 7.6 mg / kg and 4.2 mg / kg to 2.1 mg / kg and 0.9 mg / kg, respectively, with a decrease of 72.4% and 79.3%, respectively, which greatly reduced the risk of cadmium absorption by crop planting. The cadmium content in the soil of the cultivated layer in the transformed area did not change significantly and was relatively stable.

[0067] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Ordinary technicians in the field can change, modify, replace, modify, delete some features, add features or re-combine features to form a technical solution in the above embodiments without departing from the principles and purpose of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the innovative principles of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame, characterized in that: The steps include: S1. Select cadmium-contaminated farmland in the strictly controlled area, replace soil contaminated at different depths, and exchange the heavily contaminated surface soil with clean soil in the middle layer; S2, applying organic fertilizer to the cadmium-contaminated farmland treated by S1 for rapid fertilization; S3. Implement intercropping of corn and edamame in the cadmium-contaminated farmland treated with S2, and carry out routine field management measures to ensure the normal growth and development of crops.

2. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: In S1, the top layer of heavily contaminated soil (0-20 cm) is exchanged with the clean soil (20-40 cm).

3. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: In S2, the amount of organic fertilizer is 30t / hm 2 ~37.5t / hm 2 The organic fertilizer has an organic matter content of ≥30%, and the sum of N, P2O5 and K2O in the total nutrients is not less than 4.0%. After the organic fertilizer is applied, the field is plowed and the land is prepared.

4. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: In S3, the corn variety is Meiyu No. 27 and the edamame variety is Daliqing No.

3.

5. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: In S3, deep furrows and high ridges were used for planting. The intercropping maize row was 130 cm wide and the narrow row was 45 cm. Two rows of soybeans were sown in the wide maize row when the maize was in the trumpet stage. The intercropping soybean row spacing was 30 cm, and the spacing between maize and soybean was 50 cm. The hole spacing between maize and soybean was 18 cm. One maize plant was left in the hole, and the density was 58,500 plants / hm2. 2 ; Leave 2 soybean plants in each hole, density 117,000 plants / hm 2 .

6. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 5, characterized in that: In S3, corn fertilizer was applied twice, namely corn base fertilizer and topdressing during the flaring period. The base fertilizer of corn was 150kg / hm2 of nitrogen, phosphorus and potassium compound fertilizer. 2 , nitrogen fertilizer urea 225kg / hm2 in the big bell mouth period 2 At the same time, soybeans were sown and nitrogen, phosphorus and potassium compound fertilizers were applied at 150kg / hm2. 2 Use it as base fertilizer and do not apply top dressing afterwards.

7. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: In S3, field management includes the following: In the early stage of planting and replanting, the first intertillage and weeding should be carried out when the corn has 5 to 6 leaves, and the second intertillage and weeding should be carried out when the soybean has 5 to 6 leaves. The intertillage and weeding should be carried out when the soybean has 5 to 6 leaves, and 25% fomesafen aqueous solution 1200-1500g / hm2 should be sprayed between the soybean rows. 2 .

8. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 1, characterized in that: The following steps are also included: S4. After corn is harvested, the corn stalks obtained as a by-product of the crop are carbonized in the field to obtain biochar products.

9. The method for rapid in-situ treatment of cadmium-contaminated farmland by intercropping corn and edamame according to claim 8, characterized in that: In S4, the carbonization treatment method of corn straw is as follows: the corn straw is heated at 300°C in an oxygen-free environment for 90 minutes to obtain corn straw biochar, and after naturally cooling to room temperature, the carbonized product is placed in an oven at 80°C for 24 hours, ground and sieved through a 100-mesh sieve to obtain a biochar product.

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