Northeast black soil acidification improvement method

Abstract

The invention relates to the technical field of agricultural planting, in particular to a Northeast black soil acidification improvement method, which realizes efficient and lasting soil remediation through the synergistic effect of humic acid-calcium complex targeted application, microbial agent activation and green manure planting. According to the technical scheme, the method comprises the steps that soil is partitioned, a first acidification area and a second acidification area are divided according to pH values, humic acid-calcium complexes are applied in a differentiated mode, and pH responsiveness is used for releasing # imgabs 0 # for neutralizing # imgabs 1 # and passivating # imgabs 2 #. The fungus fungicide is applied in furrows, and # imgabs3 is transported to a root system through a hypha network, so that the calcium utilization rate is increased. Soybeans are sown, citric acid is sprayed, mineral calcium is activated through root exudates, and organic matter input is increased. The humic acid-calcium complex is preferentially precipitated in the acidification area. Hypha-root systems cooperatively construct an anti-acidification micro-ecology, so that the yield of crops is increased. The method is suitable for rapid restoration and sustainable management of the severely acidified soil in the northeast black soil area.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural planting, and particularly relates to a method for improving soil acidification of Northeast black soil. Background Art

[0002] As an important commodity grain base in China, the Northeast black soil area has given birth to rich crop resources with its fertile soil conditions and plays an irreplaceable role in ensuring national food security. However, in recent years, the Northeast black soil is facing the problem of acidification. Long-term unreasonable agricultural production methods, such as overuse of chemical fertilizers and single planting patterns, have led to the breakdown of the acid-base balance in the soil and the gradual increase in soil acidity. After the acidification of the black soil, its physical, chemical, and biological properties have changed significantly, the soil fertility has declined, the aggregate structure has been damaged, and the water and fertilizer retention capacity has weakened, seriously affecting the growth and development of crops.

[0003] In the past, for the problem of soil acidification, traditional improvement methods were mainly adopted, such as applying alkaline substances like lime. Although these methods can neutralize soil acidity to a certain extent and increase the soil pH value, there are many drawbacks. On the one hand, the functions of substances such as lime are relatively single, and they can only simply adjust the soil acidity and alkalinity, and cannot fundamentally improve the soil ecological environment and fertility status. On the other hand, traditional methods lack precision and are difficult to effectively control the hot spots of soil acidification. They are often blindly applied over a large area, which not only causes waste of resources but also may have a negative impact on the soil ecosystem. In addition, the effect of traditional methods lasts for a short time. As time goes by and agricultural production activities continue, the soil acidity is likely to rise again, making it difficult to achieve long-term control of the soil acidification problem. Summary of the Invention

[0004] (I) Technical Problems to be Solved In view of the technical problem of how to precisely and effectively control the hot spots of soil acidification on the basis of improving the soil ecological environment and fertility in the prior art, and the treatment result is long-term effective.

[0005] (II) Technical Solutions For this reason, the present invention mentions a method for improving soil acidification of Northeast black soil, including: Dividing the target soil into a first acidification area and a second acidification area according to the parameters of the target soil; Differentially applying humic acid-calcium complex to the target soil; Applying microbial inoculum by strip application to the target soil; Sowing soybean seeds into the target soil.

[0006] Further, the improvement method includes: measuring the parameters of the target soil, classifying the area with pH < 5.0 in the target soil as the first acidification area, and classifying the area with pH of 5.0 - 5.5 as the second acidification area; Applying the humic acid-calcium complex at 2 - 3 tons per hectare in the first acidification area of the target soil, and applying the humic acid-calcium complex at 1.5 - 2 tons per hectare in the second acidification area; Applying the microbial inoculant by strip application to the target soil at 150 - 250 kg per hectare; Broadcasting soybean seeds onto the target soil at 25 - 35 kg per hectare.

[0007] Further, the preparation steps of the humic acid-calcium complex include: Mixing according to the molar ratio of humic acid:calcium gluconate of 1:(1.5 - 2.5), and dissolving in deionized water according to the solid-liquid mass ratio of 1:(6 - 8); Performing ultrasonic chelation on the deionized water, controlling the temperature at 40 - 50 °C, the power at 250 - 35 W, the frequency at 30 - 40 kHz, controlling the pH at 5.5 - 6.0, and performing ultrasonic chelation for 25 - 35 min to obtain a chelated solution; Mixing the chelated solution and biochar according to the volume ratio of (3 - 5):1, oscillating, and then performing vacuum drying to obtain the humic acid-calcium complex.

[0008] Further, the preparation steps of the microbial inoculant include: Adding malic acid to a humic acid solution with a concentration of 0.08% - 0.1% and a pH of 6 - 6.5; Mixing and culturing the spores with the humic acid solution to obtain an activated spore solution; After culturing, mixing the activated spore solution and sterilized bentonite according to the volume ratio of 1:(3 - 4) to obtain a spore suspension; Adding 2% - 3% of sodium alginate to the spore suspension, and dropping it into a 2% - 3% solution for curing, performing microcapsule embedding, and then drying to obtain the microbial inoculant.

[0009] Further, after the soybeans grow, spraying a citric acid solution on the leaves.

[0010] Further, after sowing the soybean seeds, assist in watering and add trehalose to the water to enhance the metabolic activity of the hyphae.

[0011] Further, the parameters of the target soil include at least one of pH, exchangeable , and organic matter content.

[0012] Further, the size of the mesopores of the biochar is 2 - 50 nm.

[0013] Further, before applying the microbial inoculant, soil parameters are measured. If the pH of the first acidified area is < 4.8, lime is applied at a rate of 0.3 - 0.5 tons per hectare to raise the pH to 4.8 - 5.0. After 6 - 8 days, the microbial inoculant is applied.

[0014] (III) Beneficial effects The beneficial effects of the present invention are as follows: The present invention mentions a method for improving soil acidification of Northeast black soil, including: dividing the target soil into a first acidified area and a second acidified area according to the parameters of the target soil; differentially applying humic acid-calcium complex to the target soil; strip-applying the microbial inoculant to the target soil; and sowing soybean seeds into the target soil.

[0015] The present invention realizes the efficient repair of the acidification problem of Northeast black soil by constructing an intelligent improvement system with humic acid as an ion transport promoter. Through the establishment of a targeted migration mechanism, the humic acid-calcium complex precisely locates the acidification hot spots through the dual effects of carboxyl protonation precipitation in the low pH area and soil microdomain electric field guidance. Citric acid is used to activate the release of , and the hyphal network constructs a "biological ion channel" to form a three-dimensional coordination of roots-hyphae-humic acid. Through the mesoporous loading of biochar to achieve slow release, after the pH is increased by 1.5 units, the fluctuation is less than ±0.2. This application has the characteristics of both rapid response and continuous stability, achieving a 37% increase in corn yield and a 91% aluminum toxicity elimination rate in the application in the Jilin black soil area, providing a new idea for the treatment of acidified soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of a method for improving soil acidification of Northeast black soil mentioned in this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to better explain the present invention for easy understanding, the present invention will be described in detail below with reference to the accompanying drawings through specific embodiments.

[0018] Refer to Figure 1 , this application mentions a method for improving soil acidification of Northeast black soil, including: Step S100: Classify the target soil into a first acidified area and a second acidified area.

[0019] First, measure the parameters of the target soil, list the area with pH < 5.0 in the target soil as the first acidified area, and list the area with pH of 5.0 - 5.5 as the second acidified area.

[0020] Among them, the parameters of the target soil include at least one of pH, exchangeable , and organic matter content.

[0021] For example, in the first acidification zone (pH < 5.0), the exchange >2cmol / kg, organic matter <2.5%, crop root development is hindered. The key to its improvement is to quickly neutralize active acid ions, such as , , and then rebuild the calcium store.

[0022] In the second acidification zone (pH: 5.0-5.5), there is a potential risk of acidification and the buffering capacity decreases. The key to its improvement is to stabilize the pH value and enhance the activity of microorganisms.

[0023] Step S200: applying humic acid-calcium complex at 2-3 tons / hectare in the first acidification zone of the target soil, and applying humic acid-calcium complex at 1.5-2 tons / hectare in the second acidification zone.

[0024] In the low pH region, i.e. the first acidification region, carboxyl protonation and selective precipitation occur. The concentration is high. The carboxyl groups in the humic acid-calcium complex It has strong nucleophilicity and will react with Protonation reaction occurs, destroying Chelate bond, i.e. Combination Converted to -COOH. The protonation of the carboxyl group changes the polarity of the humic acid-calcium complex, and the interaction between its molecules also changes accordingly. The complex, which originally has good water solubility due to the ionization of the carboxyl group, has a lower solubility after protonation.

[0025] Selective precipitation allows the humic acid-calcium complex to be preferentially enriched in the acidified zone. When the complex is precipitated in the acidified zone, the dissociated humic acid (-COOH) is re-adsorbed , forming HA-Al complexes, passivating aluminum toxicity, thus improving soil acidification. At the same time, the precipitated complex can also improve the physical structure of the soil, increase soil agglomeration and porosity, and facilitate soil ventilation and water penetration.

[0026] In a low pH environment, the quinone group (C=O) in humic acid has a strong oxidizing property and will accept electrons to be reduced to hydroquinone (-OH). The quinone group takes electrons from the surrounding environment and consumes the The chemical reaction can be simply expressed as: The reduction process of quinone groups will produce electron transfer, thus forming an electron gradient, which is manifested as a redox potential difference. Microorganisms can use the electron gradient to perform respiration and obtain energy.

[0027] In the second acidification zone (pH: 5.0-5.5), the The concentration is relatively low. The carboxyl groups (-COOH) in the humic acid-calcium complex will dissociate, releasing , and transforming into . As the pH increases, the degree of dissociation of the carboxyl groups increases. After the carboxyl groups dissociate, the humic acid-calcium complex carries more negative charges, enhancing its solubility in water. At this time, the complex can diffuse along with the movement of water in the soil. Due to the lower pH in the acidified area, a pH gradient is formed. Driven by this gradient, the dissolved humic acid-calcium complex will diffuse from the weakly acidic area with a higher pH to the acidified area with a lower pH, thus achieving targeted migration and continuous improvement of the acidified area, automatically guiding the complex to enrich in the acidified area and avoiding ineffective dispersion.

[0028] In this technical solution, the preparation steps of the humic acid-calcium complex include: Mix according to the molar ratio of humic acid to calcium gluconate of 1:(1.5 - 2.5), and dissolve in deionized water according to the solid-liquid mass ratio of 1:(6 - 8), ensuring that the humic acid and calcium gluconate react fully to avoid free causing local pH fluctuations; Humic acid contains a large number of active functional groups such as carboxyl groups and phenolic hydroxyl groups, which can chelate with calcium ions to form humic acid-calcium complexes, reducing the electrostatic repulsion with soil colloids. This complex has stability and a special structure, providing a basis for subsequent ion transport and migration.

[0029] Perform ultrasonic chelation on deionized water, control the temperature at 40 - 50 °C, the power at 250 - 350 W, the frequency at 30 - 40 kHz, control the pH at 5.5 - 6.0, and perform ultrasonic chelation for 25 - 35 min to obtain a chelated solution.

[0030] During the ultrasonic chelation process, controlling the temperature at 40 - 50 °C, the power at 250 - 350 W, the frequency at 30 - 40 kHz, and the pH at 5.5 - 6.0, and performing ultrasonic chelation for 25 - 35 min can make the humic acid and calcium gluconate chelate fully to form a stable humic acid-calcium complex, which can better play the role of neutralizing acidic substances and improving soil structure.

[0031] Mix the chelated solution and biochar in a volume ratio of (3 - 5):1, oscillate, and then perform vacuum drying. Biochar has a large specific surface area and pore structure, and the humic acid-calcium complex realizes sustained release through a multi-stage slow-release mechanism, which can not only quickly neutralize soil acidity but also avoid calcium waste or local alkalization caused by short-term excessive release.

[0032] Biochar has certain alkalinity and buffering properties. When acting together with the humic acid-calcium complex, it can buffer the drastic changes in soil pH. When the soil is affected by external acidic substances, biochar and the complex can neutralize some of the acidic substances and maintain the relative stability of soil pH. The combination of biochar and the humic acid-calcium complex can improve the soil microenvironment and promote the growth and activities of beneficial microorganisms. The metabolic activities of microorganisms can further regulate the soil acidity and accelerate the decomposition and transformation of acidic substances in the soil, thus achieving the long-term improvement of acidic soil.

[0033] The obtained humic acid-calcium complex was subjected to a slow-release test. In a buffer solution with a pH of 4.5, release half-life hours. By restricting the diffusion of HA-Ca through the mesopores of biochar, the release half-life was extended. HA-Ca gradually dissociated in the mesopores and was synchronized with the consumption rate of the soil to maintain continuous supply, enabling to be slowly and continuously released into the soil, allowing the soil pH value to gradually increase and remain within a relatively stable range, which is beneficial to maintaining the soil acid-base balance and the microbial ecological environment.

[0034] The humic acid-calcium complex was applied at 2 - 3 tons per hectare in the first acidified area and at 1.5 - 2 tons per hectare in the second acidified area. The calcium in the humic acid-calcium complex can neutralize the active acid in the soil and rebuild the soil calcium pool. The first acidified area has a high degree of soil acidification and requires more calcium to neutralize acidic substances, so the application rate is larger; the second acidified area has relatively weaker soil acidity, and an appropriate reduction in the application rate can achieve the effect of stabilizing the pH.

[0035] Step S300: The microbial inoculant was applied in strips to the target soil at 150 - 250 kg per hectare. The concentration released by the previously applied humic acid-Ca can drop to the safe threshold for spore germination after 6 - 8 days. Applying the humic acid-calcium complex in advance provides a stable and humic acid carbon source for the subsequent microorganisms, avoiding the direct inhibition of spore germination by high concentrations of.

[0036] Among them, the preparation steps of the microbial inoculant include: adding malic acid to a humic acid solution with a concentration of 0.08 - 0.1% and a pH of 6 - 6.5; mixing the spores with the humic acid solution for cultivation to obtain an activated spore solution; after cultivation, mixing the activated spore solution with sterilized bentonite at a volume ratio of 1:(3 - 4) to obtain a spore suspension.

[0037] Low-concentration humic acid (80 - 100 mg / L) is used as a microbial slow-release carbon source to promote spore germination and avoid inhibition at high concentrations. The carboxyl groups of humic acid can complex to reduce the damage of metal toxicity to spores.

[0038] Adding malic acid induces hyphal branching. Malic acid can mimic plant root exudates and activate the strigolactone receptor signaling pathway of AM fungi, increasing the hyphal branching frequency by 3 times. Additionally, malic acid competitively chelates the in the humic acid-calcium complex, which can accelerate its targeted release. Among them, AM fungi are arbuscular mycorrhizal fungi (Arbuscular Mycorrhizal Fungi).

[0039] The spores in the activated spore liquid are usually in a dormant state. By mixing and culturing with a humic acid solution containing nutrients, the metabolic activities of the spores can be activated, causing them to transform from a dormant state to an active growth state. The dissociation of the humic acid-calcium complex induces the expression of spore acid-resistant genes in advance to pre-adapt to the acidified environment.

[0040] After culturing, the activated spore liquid is mixed with sterilized bentonite at a volume ratio of 1:(3 - 4) to obtain a spore suspension. After being sterilized, bentonite can be used as a carrier for microbial spores. When the activated spore liquid is mixed with bentonite, the spores can adhere to the surface of bentonite particles and be protected. Bentonite can prevent spores from being affected by external environmental factors and extend the survival time of spores.

[0041] The water holding rate of bentonite > 150% can provide a stable slightly moist environment for spore germination. Additionally, bentonite gradually releases to support the early growth of hyphae.

[0042] In this technical solution, it is applied in a band below the seed side at 5 cm to ensure efficient connection between the hyphal network and the roots. Compared with broadcast application, band application improves the utilization rate of the microbial agent.

[0043] It should be noted that in this application, a hyphal network is established to enhance calcium transport and organic matter transformation.

[0044] Humic acid contains easily degradable components, providing a carbon source for the spores of fungi. It provides the necessary energy and material basis for spore germination, promoting the spore germination rate to increase by more than 50%, enabling the spores to enter the growth stage faster. The released can activate microbial calmodulin, increasing the hyphal branching frequency.

[0045] It should be noted that humic acid forms a chemical gradient field by precipitation in the acidified area. Due to the chemotactic response of hyphae, they will be induced to move towards the high The concentration zone extends. The hyphae will grow along the surface of the humic acid-calcium complex, resulting in an increased contact area. This directional growth helps the hyphae to expand more purposefully in the soil, gradually forming a network structure.

[0046] The hyphal diameter (2 - 10 μm) is much smaller than the soil pores, enabling the humic acid-calcium complex to be transported to micro-domains inaccessible to the roots. During this process, the hyphae continuously extend and branch in the soil, interacting with the surrounding humic acid-calcium complex, further promoting the formation and expansion of the hyphal network.

[0047] The humic acid-calcium complex can quickly neutralize the active acid in the soil and release , and in the soil to undergo an exchange reaction, reducing the soil acidity and improving the soil's acid-base environment.

[0048] After the hyphal network is formed, it can transport to the plant roots, providing the necessary calcium nutrition for the plants and promoting the growth and development of the plants.

[0049] Apply the microbial inoculant in bands to the target soil at a rate of 150 - 250 kg / ha. Waiting for 6 - 8 days allows sufficient time for the humic acid-calcium complex to fully react with the soil, improving the soil's chemical properties. The beneficial microorganisms in the microbial inoculant can decompose the organic matter in the soil, release nutrients, enhance the soil microbial activity, and promote the balance and stability of the soil ecosystem. The band application method can make the microbial inoculant more concentrated in the soil, improving its effectiveness.

[0050] For the first acidification zone (pH < 4.5), apply a small amount of lime (0.5 tons / ha) one week in advance to raise the pH to 4.8 - 5.0, and then operate in the above order to avoid inactivation of the fungi caused by direct inoculation.

[0051] Step S400: Sow soybean seeds at a rate of 25 - 35 kg / ha into the target soil.

[0052] After the soybeans grow, spray a citric acid solution on the leaves.

[0053] Activate mineral calcium through root exudates and increase organic input. Exemplarily, sow soybean seeds, cover them with a shallow layer of soil 2 cm thick, and spray a 0.05% humic acid solution during this period to promote germination. Sow the seeds after the complex and the inoculant are initially located to avoid seed competition , and the roots of the green seedlings develop synchronously with the hyphal network, forming a symbiotic system with the complex and the inoculant in the soil, ultimately achieving the goals of activating mineral calcium, increasing organic input, and improving the soil.

[0054] Sow after 6 - 8 days to avoid premature sowing of the seeds, competing with the complex and the inoculant for in the soil. Equal nutrients are provided to ensure a good germination and growth environment for the seeds. After the soybeans grow, a citric acid solution is sprayed on the leaves. Citric acid has a certain acidity and can enter the plant through leaf absorption, affecting the plant's physiological metabolism process. On the one hand, citric acid helps regulate the pH value in the plant and enhance the plant's stress resistance; on the other hand, it promotes the production of root exudates, which can activate mineral calcium in the soil and improve the availability of calcium, thus providing more calcium nutrition for plant growth.

[0055] Furthermore, the natural water-holding property of the Northeast black soil enables the humic acid-calcium complex to reach the acidification hotspots in the soil. At the same time, the appropriate water content helps maintain the stability of the humic acid-calcium complex, preventing it from precipitating or aggregating due to insufficient water and affecting its function.

[0056] The natural water-holding property of the Northeast black soil provides a suitable living and functioning environment for the humic acid-calcium complex and microorganisms. The humic acid-calcium complex can efficiently carry out targeted migration under appropriate water conditions, accurately locate the acidification hotspots, and play a role in improving the soil. Microorganisms can grow and metabolize vigorously in such a water environment and jointly construct a dynamic synergistic system with the humic acid-calcium complex. In this system, the activities of microorganisms can promote the decomposition and transformation of the humic acid-calcium complex, releasing more calcium ions and further improving the soil pH value. At the same time, the humic acid-calcium complex can also provide certain nutrients and living space for microorganisms, promoting the growth and reproduction of microorganisms. The water-holding property of the Northeast black soil highly matches the needs of the humic acid-calcium complex and microorganisms, providing a strong guarantee for the efficient restoration of the acidification problem of the Northeast black soil.

[0057] Furthermore, spraying a 0.05% humic acid solution during this period promotes germination. Humic acid contains various nutrients and active substances, such as easily degradable glucuronic acid, etc. It can provide nutrients such as carbon sources for soybean seeds, promoting seed germination and early growth. At the same time, humic acid can also improve the soil structure and enhance the water and fertilizer retention capacity of the soil, further optimizing the growth environment of soybeans.

[0058] The humic acid-calcium complex and the microbial agent applied to the soil have formed a certain mycelial network. During the growth process, the roots of soybean green seedlings interact with the mycelial network to form a symbiotic relationship. This symbiont can achieve resource sharing and functional complementarity. The mycelial network can help soybean roots better absorb nutrients and water in the soil, while the root exudates of soybean roots can provide substances such as carbon sources for the mycelium, promoting the growth and metabolism of the mycelium, and thus jointly promoting soil improvement and plant growth.

[0059] The present invention achieves efficient repair of the acidification problem of Northeastern black soil by constructing an intelligent improvement system with humic acid as an ion transport promoter. Its core advantage lies in: establishing a targeted migration mechanism, the humic acid-calcium complex accurately locates the acidification hotspot through the dual effects of pH-responsive chemical chemotaxis and soil micro-domain electric field guidance, so that The enrichment efficiency in the pH < 5.0 region is 85%, which is 3 times higher than the traditional method. Dynamic synergistic system: using citric acid to activate the complex release The AM fungus hyphae network constructs a "biological ion channel" to form a three-dimensional synergy of roots, hyphae and humic acid. Slow release, combined with Northeastern black soil, increases the pH by 1.5 units and the fluctuation is less than ±0.2.

[0060] This solution combines the characteristics of rapid response and sustained stability. In its application in the black soil area of ​​Jilin Province, it achieved a 37% increase in corn yield and a 91% aluminum toxicity elimination rate, providing an innovative solution for acidified soil management.

[0061] The improved system proposed in the present invention, which uses humic acid as an ion transport promoter, can achieve efficient repair of the acidification problem of Northeast China black soil by establishing a targeted migration mechanism and exerting a dynamic synergistic system. It can not only accurately locate the acidification hotspots, but also improve The enrichment efficiency can also improve the soil ecological environment by forming a three-dimensional synergy of roots, hyphae and humic acid. The slow release of the chlorine and the stable improvement of soil pH value provide new ideas and methods for the acidification control of Northeast China black soil, and are expected to play an important role in ensuring the sustainable development of agriculture in the Northeast China black soil region.

[0062] In order to better understand the technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. Soil acidification improvement verification experiment.

[0063] The test site was set up in an experimental field in Jilin. The climate characteristics of the test site are shown in Table 1, and the physical and chemical properties of the test soil are shown in Table 2.

[0064] ; ; This experiment adopted plot experiments, with a total of 4 experimental cases. The fertilizer application rates for each treatment were in line with local fertilization habits. The experiment started from April 2022 to October 2023, and materials were applied in mid-to-late April every spring. Each plot contained 6 ridges, each ridge was 6 m long, and there was a 2 m interval between each plot. The nutrient application amount for each plot was phosphorus: , potassium: , nitrogen: . Each example / control example was set with 3 replicates. Example 1

[0065] Treatment method: After the spring snowmelt (early May): After deep plowing 20 cm in the first acidification area, apply 2.8 tons / ha of humic acid-calcium complex.

[0066] Perform film mulching for heat preservation, with a thickness of 0.01 mm, to increase the ground temperature by 2 - 3 °C.

[0067] Before the rainy season (June): Inoculate cold-tolerant AM fungi (220 kg / ha), sow soybeans (25 kg / ha), and spray 0.05% citric acid + 0.02% humic acid after sowing and emergence.

[0068] Growth season management: Foliar spray 0.05% citric acid (at intervals of 15 days, for a total of 3 times). Example 2

[0069] Treatment method: After the spring snowmelt (early May): After deep plowing 20 cm in the second acidification area, apply humic acid-calcium complex (1.8 tons / ha).

[0070] Perform film mulching for heat preservation, with a thickness of 0.01 mm, to increase the ground temperature by 2 - 3 °C.

[0071] Before the rainy season (June): Inoculate cold-tolerant AM fungi (150 kg / ha), sow soybeans (25 kg / ha), and spray 0.05% citric acid + 0.02% humic acid after sowing and emergence.

[0072] Growth season management: Foliar spray 0.05% citric acid (at intervals of 15 days, for a total of 3 times). Control Example 1

[0073] Treatment method: After the spring snowmelt (early May): Base-apply the conditioner, apply well-rotted cow dung (4 tons / ha, organic matter content 35%), and mix with agricultural lime (2 tons / ha, fineness 80 mesh).

[0074] Perform film mulching for heat preservation, with a thickness of 0.01 mm, to increase the ground temperature by 2 - 3 °C.

[0075] Sowing management:: Plant corn (variety: Xianyu 335).

[0076] Field management: Conventional irrigation throughout the growth period (total irrigation volume of 300 mm), and topdressing with urea (150 kg / ha, in two applications). Comparative Example 2

[0077] Treatment method: After snowmelt in spring (early May): Apply biochar (2.5 tons / ha, not compounded with humic acid-Ca).

[0078] Perform film mulching for heat preservation, with a thickness of 0.01 mm, to increase the soil temperature by 2-3°C.

[0079] Sowing management:: Plant corn (variety: Xianyu 335).

[0080] Field management: Topdress with urea (150 kg / ha, in two applications). Based on the comparative analysis of the improvement effects of soil active acidity and buffering performance.

[0081] ; Refer to Table 3, which shows the active acidity neutralization efficiency of the above experiments. The continuous neutralization ability of Example 1 is the strongest, and the humic acid-calcium complex dissociates selectively in the acidification zone (pH < 5.0). The initial efficiency of Comparative Example 1 is high but rebounds severely because after the lime is exhausted , hydrolysis and regeneration .

[0082] ; Refer to Table 4. The buffering capacity of Example 1 is optimal in the pH range of 5.0 - 6.0 (β = 48.3), while the buffering capacity of Comparative Example 1 decays rapidly with the dissolution of lime, and the β value decreases by 60% after 12 months.

[0083] ; Refer to Table 5. Example 1 significantly reduces activity through the complexation of humic acid-Ca-Al (logK = 10.2), while reducing regeneration. The of Comparative Example 1 redissolves at pH < 5.5, resulting in unstable improvement effects.

[0084] ; Refer to Table 6. The root exudates of soybeans in Example 1 promote the formation of humic acid, and its carboxyl density (4.5 mmol / g) provides the main buffering sites. The cow dung in Comparative Example 1 is mainly fulvic acid (H / F = 1.3), and the buffering capacity is limited.

[0085] Example 1 exhibits the optimal performance in terms of active acid neutralization and buffering properties. Due to its pH-responsive release, the humic acid-calcium complex targets the acidified region. The dual buffering of humic acid and biochar further facilitates the transport of AM fungi , and the activation of organic matter by root exudates realizes biological synergy.

[0086] The basic principles, main features, and advantages of the present invention have been described above. However, the above are only specific embodiments of the present invention, and the technical features of the present invention are not limited thereto. Any other embodiments obtained by those skilled in the art without departing from the technical solution of the present invention should be covered within the patent scope of the present invention.

[0087] In the description of the present invention, each embodiment focuses on the differences from other embodiments, and the same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

Claims

1. A method for improving soil acidification of Northeastern black soil, characterized in that: include: Dividing the target soil into a first acidification zone and a second acidification zone according to the parameters of the target soil; Differentiated application of humic acid-calcium complex in target soils; Apply the microbial inoculant strips to the target soil; Sow soybean seeds into target soil.

2. The method for improving soil acidification of Northeastern black soil according to claim 1, characterized in that: include: Determine the parameters of the target soil, and classify the area with pH < 5.0 in the target soil as the first acidification zone, and the area with pH 5.0-5.5 as the second acidification zone; Apply humic acid-calcium complex at 2-3 tons / ha in the first acidification zone of the target soil, and 1.5-2 tons / ha in the second acidification zone; Apply microbial inoculant strips to the target soil at 150-250 kg / ha; Sow soybean seeds at 25-35kg / hectare into the target soil.

3. The method for improving soil acidification of Northeastern black soil according to claim 2, characterized in that: The preparation steps of humic acid-calcium complex include: Mix humic acid and calcium gluconate at a molar ratio of 1:(1.5-2.5), and dissolve in deionized water at a solid-liquid mass ratio of 1:(6-8); Performing ultrasonic chelation on deionized water, controlling the temperature to 40-50°C, the power to 250-35W, the frequency to 30-40kHz, the pH to 5.5-6.0, and performing ultrasonic chelation for 25-35min to obtain a chelated liquid; The chelating liquid and biochar were mixed and shaken in a volume ratio of (3-5):1 and then vacuum dried to obtain a humic acid-calcium complex.

4. The method for improving soil acidification of Northeastern black soil according to claim 2, characterized in that: The preparation steps of the microbial agent include: Add malic acid to a humic acid solution having a concentration of 0.08%-0.1% and a pH of 6-6.5; The spores are mixed and cultured with a humic acid solution to obtain an activated spore solution; After the culture, the activated spore solution is mixed with sterilized bentonite at a volume ratio of 1:(3-4) to obtain a spore suspension; Add 2%-3% sodium alginate to the spore suspension and drop 2%-3% The solution is solidified, embedded in microcapsules and then dried to obtain the microbial agent.

5. The method for improving soil acidification of Northeastern black soil according to claim 1, characterized in that: After soybeans grow, spray the leaves with a citric acid solution.

6. The method for improving soil acidification of Northeastern black soil according to claim 1, characterized in that: After sowing the soybean seeds, watering is performed and trehalose is added to the water to enhance the metabolic activity of the mycelium.

7. The method for improving soil acidification of Northeastern black soil according to claim 2, characterized in that: Target soil parameters include: pH, exchangeability , organic matter content.

8. The method for improving soil acidification of Northeastern black soil according to claim 3, characterized in that: The size of biochar mesopores is 2-50nm.

9. The method for improving soil acidification of Northeastern black soil according to claim 2, characterized in that: Before applying the microbial agent, measure the soil parameters. If the pH of the first acidified zone is less than 4.8, apply lime at a rate of 0.3-0.5 tons / hectare to raise the pH to 4.8-5.

0. After 6-8 days, apply the microbial agent.

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