Freeze-thaw soil conditioner as well as preparation method and application thereof
The freeze-thaw soil conditioner, which is a mixture of carbonized corn cobs and wheat straw, solves the problems of unstable soil structure and insufficient nutrients in freeze-thaw soil, improves the soil's water and fertilizer retention capacity and microbial activity, regulates pH value, and enhances soil fertility.
Patent Information
- Application Number
- CN202511676523.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies are insufficient to effectively improve freeze-thawed soils, especially in soybean-growing soils in Northeast China, where soil structure is unstable, water and fertilizer retention capacity is insufficient, pH adjustment is difficult, and microbial activity is low.
A freeze-thaw soil conditioner is made by mixing carbonized corn cob biochar and wheat straw biochar in a certain proportion. This conditioner is then mixed in situ into freeze-thaw soil to adjust soil pH and regulate soil nutrients.
It significantly improved the structure and aeration of freeze-thawed soils, enhanced water and fertilizer retention capacity, promoted microbial activity, regulated soil pH, and improved soil fertility.
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Figure CN121592352A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of freeze-thaw soil improvement technology, specifically relating to a freeze-thaw soil conditioner, its preparation method, and its application. Background Technology
[0002] Biochar is obtained by pyrolyzing various organic materials (such as crop residues, manure, sawdust, and sewage waste) and industrial waste (such as papermaking sludge and biomass) in a closed container under specific temperature and pressure conditions or under low-oxygen conditions. It can improve soil quality and crop yield, achieving waste resource recycling. It can also alter soil physicochemical properties, enhance soil water and fertilizer retention capacity, improve soil structure and aeration, and promote microbial activity. Summary of the Invention
[0003] The purpose of this invention is to provide a freeze-thaw soil conditioner that can effectively improve freeze-thaw soil, its preparation method, and its application.
[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a freeze-thaw soil conditioner, which is a mixed biochar made by mixing carbonized corn cob biochar and carbonized wheat straw biochar.
[0005] Furthermore, by mass ratio, corn cob biochar : wheat straw biochar = 1 : (1-3).
[0006] A method for preparing a freeze-thaw soil conditioner includes: washing corn cobs, air-drying them for 2-3 days, drying them at 70℃-80℃, and then carbonizing them under anaerobic conditions to obtain corn cob biochar; washing wheat straw, air-drying it for 2-3 days, drying it at 70℃-80℃, and then carbonizing it under anaerobic conditions to obtain wheat straw biochar; mixing the corn cob biochar and wheat straw biochar, and sterilizing them to obtain the freeze-thaw soil conditioner.
[0007] Furthermore, the corn cob biochar was obtained by carbonization at 450℃-550℃ for 4-5 hours under anaerobic conditions.
[0008] Furthermore, wheat straw biochar was obtained by carbonization at 250℃-350℃ for 4-5 hours under anaerobic conditions.
[0009] Furthermore, the sterilization process involves treating the food in an autoclave at 120℃-122℃ for 60-70 minutes.
[0010] The application of the freeze-thaw soil conditioner provided by this invention in improving freeze-thaw soil.
[0011] Further, the method is as follows: In freeze-thawed soil, the freeze-thawed soil conditioner is mixed in situ with the soil from the surface to a depth of 10cm-30cm.
[0012] Furthermore, the freeze-thaw soil conditioner is mixed in situ with the original soil at a mass percentage of 1%-5%.
[0013] Furthermore, the freeze-thawed soil refers to the soil used for soybean cultivation in Northeast China.
[0014] Compared with the prior art, the beneficial effects of the present invention are:
[0015] This invention produces biochar by carbonizing corn cobs and wheat straw separately. Corn cob biochar and wheat straw biochar have different physicochemical properties and structures. When the two are mixed into a certain proportion, their combined effect shows good results in regulating soil pH and controlling soil nutrients, effectively improving freeze-thawed soil. Attached Figure Description
[0016] Figure 1 Here is a SEM image of the corn cob biochar C500 prepared in Example 1 of this invention;
[0017] (a) is before freeze-thaw cycle (CK-C500); (b) is after freeze-thaw cycle (F-C500).
[0018] Figure 2 Here is a SEM image of wheat straw biochar B300 prepared in Example 1 of this invention;
[0019] (a) is before freeze-thaw cycle (CK-B300); (b) is after freeze-thaw cycle (F-B300).
[0020] Figure 3 This is a graph showing the changes in soil pH in the control area and the experimental area in Example 2 of this invention.
[0021] Figure 4 This is a graph showing the changes in available phosphorus content in the soil of the control area and the test area in Example 2 of this invention.
[0022] Figure 5 This is a graph showing the changes in available potassium content in the soil of the control area and the test area in Example 2 of this invention.
[0023] Figure 6 This is a graph showing the changes in nitrate nitrogen content in the soil of the control area and the test area in Example 2 of this invention. Detailed Implementation
[0024] The following examples are for illustrative purposes only and do not limit the scope of protection of the present invention.
[0025] Example 1: Freeze-thaw soil conditioner
[0026] (I) Preparation method of freeze-thaw soil conditioner
[0027] 1. Preparation of Corn Cob Biochar (C500)
[0028] Rinse the corn cobs three times with tap water, then rinse them twice with distilled water. Let them air dry naturally for two days, and then dry them in a 75℃ oven.
[0029] The dried corn cobs were packed into an iron can (10cm in diameter and 10cm in length), the biomass was compacted, and nitrogen gas was introduced until no oxygen was present. The iron can was then placed in a muffle furnace and heated to 500℃ at a rate of 10℃ / min. The mixture was then pyrolyzed at 500℃ for 4 hours. After cooling to room temperature, the mixture was removed to obtain corn cob biochar that had undergone anaerobic carbonization, labeled as C500.
[0030] 2. Preparation of wheat straw biochar (B300)
[0031] After rinsing the wheat straw three times with tap water, rinse it twice with distilled water, let it air dry naturally for two days, and then put it into a 75℃ oven to dry.
[0032] The dried wheat straw was packed into an iron can (10cm in diameter and 10cm in length), the biomass was compacted, and nitrogen gas was introduced until no oxygen was present. The can was then placed in a muffle furnace and heated to 300℃ at a rate of 10℃ / min. The mixture was pyrolyzed at 300℃ for 4 hours, cooled to room temperature, and removed to obtain wheat straw biochar treated under anaerobic conditions, labeled B300.
[0033] 3. Preparation of freeze-thaw soil conditioner
[0034] By mass ratio, C500:B300=1:2, corn cob biochar (C500) and wheat straw biochar (B300) are mixed and then placed in an autoclave and treated at 121℃ for 60 minutes to complete the sterilization process, obtaining mixed biochar, which is labeled as C500+B300.
[0035] (II) Effects of simulated freeze-thaw cycles on the structure and physicochemical properties of biochar
[0036] 1. The freeze-thaw cycle process of biochar was artificially simulated in a laboratory environment. The experimental steps for the freeze-thaw cycle are as follows:
[0037] 1.1) Select C500 and B300 biochar, pass them through a 2mm sieve, and weigh 5g of biochar into small PET round bottles. Mix ultrapure water and biochar at a ratio of 1:4, tighten the caps, and first age the samples at room temperature (25±2℃) for 12h to ensure uniform distribution and full diffusion of moisture. These are the samples before freeze-thaw cycles, and are labeled as CK-C500 and CK-B300.
[0038] 1.2) Freeze-thaw: The sample was transferred to a low temperature environment of -20℃ and frozen for 12 hours to simulate the severe winter conditions;
[0039] 1.3) Re-thawing: The sample was moved to a 0℃ environment for 12 hours to simulate the spring thawing situation in Northeast China.
[0040] 1.4) C500 and B300 biochar were freeze-thawed and re-thawed once a day for two months. The samples after the last re-thawed cycle were labeled as F-C500 and F-B300. The experiment was conducted in triplicate.
[0041] 2. Observation and determination of the physicochemical properties of biochar
[0042] 2.1) Observation of biochar surface structure
[0043] The microstructure and pore characteristics of biochar were observed using SEM. The morphology and structure of corn cob biochar and wheat straw biochar before and after freeze-thaw cycles were observed using scanning electron microscopy. The results are as follows: Figure 1 and Figure 2 .
[0044] from Figure 1 It can be seen that the surface structure of CK-C500 before freeze-thaw cycle is smooth, while the surface of F-C500 after freeze-thaw cycle is rougher and the number of wrinkles increases significantly, which increases the specific surface area of C500 biochar.
[0045] from Figure 2 It can be seen that the CK-B300 structure was relatively intact before the freeze-thaw cycle, while the F-B300 structure was obviously fractured after the freeze-thaw cycle, with some particles broken and falling off on the surface. The number of pores increased significantly, which can improve soil structure and aeration, and provide habitat for microorganisms.
[0046] Depend on Figure 1 and Figure 2It was found that the structures of C500 and B300 biochar were relatively intact before freeze-thaw cycles. However, with increasing freeze-thaw cycles, the surface structure of the biochar was gradually destroyed. These changes indicate that freeze-thaw cycles disrupt the existing structure of biochar, altering its particle size and thus changing its adsorption properties. Specifically, after freeze-thaw cycles, the specific surface area and particle size of the biochar increased. This change provides a favorable habitat for soil microorganisms, which is beneficial for activating soil ecology, enhancing the adsorption of pollutants, and remediating the soil.
[0047] 2.2) Determination of water absorption capacity of biochar
[0048] Weigh a certain mass of biochar sample (M0), mix it with ultrapure water at a mass ratio of 1:20, shake it thoroughly to disperse it evenly, place the mixed solution in an ultrasonic device for continuous treatment for 24 hours, then remove excess water, weigh the hydrous biochar (M1), calculate the water absorption, and the results are shown in Table 1.
[0049] Water absorption = (M1 - M0) / M0
[0050] Table 1 Water absorption capacity of biochar
[0051]
[0052] Note: Different lowercase letters indicate the significance of differences between different treatments (P<0.05).
[0053] As shown in Table 1, the water absorption capacity of both types of biochar increased after freeze-thaw cycles. Compared to before the freeze-thaw cycles, after a two-month freeze-thaw cycle, the water absorption of B300 increased by approximately 0.43 g / g, and the water absorption of C500 increased by approximately 0.45 g / g. Furthermore, the water absorption capacity of C500 was higher than that of B300 before and after multiple freeze-thaw cycles. Freeze-thaw cycles enhance the water absorption performance of biochar, which alters the surface functional groups and pore structure, improves the soil's water and fertilizer retention capacity, and provides a favorable habitat for microorganisms.
[0054] Example 3: Application of freeze-thaw soil conditioner in improving freeze-thaw soil
[0055] (a) The method is as follows:
[0056] The experiment was conducted using soil from soybean-growing areas in Shenyang.
[0057] 1. The test site was set up as a control area and a test area, separated by a beam pool. The beam pool was square (3m×3m). The control area was the blank area (CK) without any treatment, and the test area (BC) was where freeze-thaw soil conditioner was added.
[0058] 2. Test Area (BC): In the freeze-thawed soil, the freeze-thawed soil conditioner was mixed in situ with the soil from the surface to a depth of approximately 20 cm. The freeze-thawed soil conditioner was mixed in situ at a mass percentage of 2%.
[0059] 3. The experiment was launched in mid-May 2023 and ended in mid-April 2024. Topsoil samples (0-20cm) were collected in the middle of each month. Equal amounts of soil samples were taken from multiple points in both the control and experimental areas, mixed separately to form samples, sealed, and the sampling information was recorded. The samples were transported back to the laboratory, purified, and then placed in a well-ventilated, cool environment to air dry. After complete drying, the samples were sieved using a standard test sieve (2mm aperture) for analysis.
[0060] (ii) Soil pH measurement
[0061] Weigh 10.00 g of sieved, air-dried soil sample and place it in a 50 mL beaker. Add 25 mL of CO2-removed deionized water, with a water-to-soil ratio of 2.5:1 (mass ratio). Stir well and let stand for 30 min. Measure the pH of the supernatant using a pH meter (700 Bench Meter, Eutech Instruments). The results are as follows. Figure 3 .
[0062] Soil pH can be used to measure the effectiveness of soil amendment. Figure 3 The changes in pH values in the soil control and experimental areas were statistically analyzed. Figure 3 It can be seen that the original soil pH fluctuated significantly, reaching a maximum of 6.66 after about 9 months (January 2024), and then decreasing. In the experimental area, the soil pH increased significantly after the addition of mixed biochar treatment, reaching a maximum of 6.91 after 6 months of treatment (October 2023), then decreasing, and then gradually increasing again. The application of mixed biochar has a significant regulatory effect on soil pH and can promote the transformation of soil towards alkalinity.
[0063] (III) Determination of available phosphorus in soil
[0064] The available phosphorus content in the soil was determined using the 0.5 mol / L NaHCO3 extraction-molybdenum antimony colorimetric method. The results are as follows: Figure 4 .
[0065]
[0066] In the formula: —Soil available phosphorus content (mg / kg)
[0067] —The mass concentration of P (g / mL) obtained from the working curve.
[0068] V — Volume (mL) used for color development and final volume adjustment
[0069] ts — Dividend ratio (the ratio of the total volume of the extract to the volume of the extract taken for color development)
[0070] m — Mass of air-dried soil (g)
[0071] The available phosphorus content in the soil of the control and experimental areas in each month is as follows: Figure 4 As shown in the figure, the available phosphorus content in both treatment groups showed an increasing trend during the normal temperature period. In October 2023, the available phosphorus content in the original soil and the experimental soil reached its peak, with the available phosphorus content in the original soil and the soil with added mixed biochar being 79.53 mg / kg and 84.36 mg / kg, respectively.
[0072] (iv) Determination of available potassium in soil
[0073] The determination of available potassium in soil was performed using the ammonium acetate extraction-flame photometry method, and the results are as follows: Figure 5 .
[0074]
[0075] In the formula: —Soil available potassium content (mg / kg)
[0076] —The mass concentration of K (g / mL) obtained from the working curve.
[0077] V — Volume of extract (mL)
[0078] ts — Dividend ratio (the ratio of the total volume of the extract to the volume of the extract taken for color development)
[0079] m — Mass of air-dried soil (g)
[0080] The available potassium content in the soil of the control and experimental areas in each month is as follows: Figure 5 As shown, the available potassium content in the treatment group with added mixed biochar peaked at 186.23 mg / kg in September 2023, then decreased, reaching a low of 140.81 mg / kg in January 2024, before rising again. At the end of the remediation period, the addition of mixed biochar significantly increased the available potassium content in the soil, increasing it by 44.07% compared to the original soil available potassium content.
[0081] (v) Determination of soil nitrate nitrogen
[0082] Soil nitrate nitrogen was determined using the alkaline hydrolysis-diffusion method. The results are as follows: Figure 6 .
[0083]
[0084] In the formula: c — concentration of 0.005 mol / L (1 / 2 H2SO4) standard solution
[0085] V — Volume (mL) of 0.005 mol / L (1 / 2 H₂SO₄) standard solution used during sample titration.
[0086] V0 — Volume (mL) of 0.005 mol / L (1 / 2 H₂SO₄) standard solution used in the blank titration experiment.
[0087] 14.0 — Molar mass of nitrogen atom (g / mol)
[0088] M — Sample mass (g)
[0089] 10 3 ——Conversion factor
[0090] The monthly nitrate nitrogen content in the soil of the control and experimental areas is as follows: Figure 6 As shown in the figure, nitrate nitrogen content exhibited a trend of first increasing, then decreasing, and then increasing again throughout the remediation period, peaking in October 2023, with nitrate nitrogen contents of 161.84 mg / kg in the original soil and 165.37 mg / kg in the biochar-added soil. At the end of the remediation period, the addition of mixed biochar increased nitrate nitrogen content by 17.65% compared to the original soil. Nitrate nitrogen improves soil fertility and, as a nitrogen source, promotes microbial growth, increasing the abundance and diversity of soil microbial communities.
Claims
1. A freeze-thaw soil conditioner, characterized in that, The freeze-thaw soil conditioner is a mixed biochar made by mixing carbonized corn cob biochar and carbonized wheat straw biochar.
2. The freeze-thaw soil conditioner according to claim 1, characterized in that, By mass ratio, corn cob biochar : wheat straw biochar = 1 : (1-3).
3. The method for preparing the freeze-thaw soil conditioner according to claim 1 or 2, characterized in that, The preparation method includes: washing corn cobs, air-drying them for 2-3 days, drying them at 70℃-80℃, and then carbonizing them under anaerobic conditions to obtain corn cob biochar; washing wheat straw, air-drying it for 2-3 days, drying it at 70℃-80℃, and then carbonizing it under anaerobic conditions to obtain wheat straw biochar; mixing corn cob biochar and wheat straw biochar, sterilizing them, and obtaining a freeze-thaw soil conditioner.
4. The method for preparing the freeze-thaw soil conditioner according to claim 3, characterized in that, Corn cob biochar was obtained by carbonization at 450℃-550℃ for 4-5 hours under anaerobic conditions.
5. The method for preparing the freeze-thaw soil conditioner according to claim 3, characterized in that, Wheat straw biochar was obtained by carbonization at 250℃-350℃ for 4-5 hours under anaerobic conditions.
6. The method for preparing the freeze-thaw soil conditioner according to claim 3, characterized in that, The sterilization process involves treating the food in an autoclave at 120℃-122℃ for 60-70 minutes.
7. The application of the freeze-thaw soil conditioner according to claim 1 or 2 in improving freeze-thaw soil.
8. The application according to claim 7, characterized in that, The method is as follows: In freeze-thawed soil, the freeze-thawed soil conditioner described in claim 1 or 2 is mixed in situ with the soil from the surface to a depth of 10cm-30cm.
9. The application according to claim 8, characterized in that, The freeze-thaw soil conditioner is mixed in situ with the original soil at a weight percentage of 1%-5%.
10. The application according to claim 8 or 9, characterized in that, The freeze-thawed soil refers to the soil used for soybean cultivation in Northeast China.