A saline-alkali soil improvement composition, a preparation method and application thereof

Abstract

The application discloses a saline-alkali soil improvement composition and a preparation method and application thereof, relates to the technical field of saline-alkali soil improvement, and is prepared from the following raw materials in parts by mass: apple polyphenol 0.5-5 parts, malic acid 3-15 parts, citric acid 2-10 parts, gamma-polyglutamic acid 1-8 parts, a pH buffer carrier, humic acid or fulvic acid 10-40 parts, biochar 5-25 parts, and desulfurized gypsum 0-20 parts, at least one of the three being selected; the rest is water or inert filler to 100 parts by mass; wherein, the molar ratio of the malic acid to the citric acid is controlled to be 1:0.5-1:3, and the mass ratio of the apple polyphenol to the gamma-polyglutamic acid is controlled to be 1:1-1:10. The application is provided with a series of structures, the sodium ions on the soil colloid are effectively replaced and leached out by the synergistic effect of the malic acid, the citric acid and the gamma-polyglutamic acid, and the alkalinity stress problem of the saline-alkali soil is solved.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement technology, specifically to a saline-alkali land improvement composition, its preparation method, and its application. Background Technology

[0002] Saline-alkali land is an important reserve of arable land in my country. According to statistics from the Ministry of Agriculture and Rural Affairs, the total area of ​​saline-alkali land in China is approximately 99 million hectares, of which more than 13 million hectares have potential for agricultural development and utilization. However, due to the excessive content of saline-alkali soil... Plasma causes soil pH values ​​to be as high as 8.5-10.5, resulting in poor soil physical structure and low nutrient utilization. Consequently, crop emergence rates are less than 30%, and grain production capacity is only 40%-60% of that of fertile land in the same region, which seriously restricts the advancement of my country's food security strategy.

[0003] Currently, the improvement measures for saline-alkali land are mainly divided into three categories: physical, chemical, and biological. Physical improvement (such as underground pipe drainage and deep plowing and flood irrigation) is effective in a short time, but the engineering investment is huge (an average investment of more than 30,000 yuan per hectare) and the water consumption is extremely high, making it difficult to promote in arid and semi-arid regions. Biological improvement (such as planting salt-tolerant plants and applying microbial agents) has good ecological benefits, but the improvement cycle is as long as 3-5 years and is greatly affected by climate and soil microbial environment, resulting in poor stability.

[0004] While existing chemical modifiers are widely used, they still face numerous technical bottlenecks: The improvement mechanism is singular and the side effects are obvious: traditional chemical modifiers (such as desulfurized gypsum and superphosphate) mainly rely on Replacement of soil colloids Although it can reduce ESP (alkalinity) in the short term, long-term use will cause soil compaction, and gypsum has low solubility, making it difficult to respond quickly to sudden salt and alkali stress during crop growth.

[0005] Short duration of active substances: In recent years, although some studies have tried to add humic acid, organic acids and other substances to the compound, due to the lack of effective slow-release carriers, small organic molecules (such as malic acid and citric acid) are easily leached away by water or rapidly decomposed by soil microorganisms. The effective period of action is usually only 7-15 days, which cannot cover the risk of salt and alkali stress throughout the entire growth period of crops.

[0006] Neglecting rhizosphere microenvironment remediation: Existing formulations mostly focus on improving soil physicochemical properties, neglecting rhizosphere oxidative damage caused by salt and alkali stress. High pH environments... Toxicity can inhibit seed germination and root growth, and current technologies lack active ingredients that can simultaneously enhance the function of the crop's own antioxidant enzyme system (SOD / POD / CAT).

[0007] In addition, as the world's largest apple producer, my country generates more than 10 million tons of apple processing by-products (peel pomace) every year. These by-products are rich in apple polyphenols, which have extremely strong antioxidant and chelating abilities. However, the current comprehensive utilization rate is less than 20%, and most of them are incinerated or landfilled as waste, which not only wastes resources but also brings environmental pollution pressure.

[0008] Therefore, there is an urgent need to develop a saline-alkali land improvement composition that integrates "alkali reduction and desalination, long-term sustained release, stress resistance and growth promotion" to solve the problems of short duration of action, large side effects and single function of existing soil conditioners, while realizing the high-value utilization of agricultural waste. Summary of the Invention

[0009] The purpose of this invention is to provide a saline-alkali land improvement composition, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a saline-alkali land improvement composition, made from the following raw materials in parts by weight: Apple polyphenols: 0.5–5 parts, malic acid: 3–15 parts, citric acid: 2–10 parts, γ-polyglutamic acid: 1–8 parts pH buffer carrier: 10-40 parts of humic acid or fulvic acid, 5-25 parts of biochar, and 0-20 parts of desulfurized gypsum, at least one of the three shall be selected. The remainder is water or inert filler up to 100 parts by weight; The molar ratio of malic acid to citric acid is controlled at 1:0.5 to 1:3, and the mass ratio of apple polyphenols to γ-polyglutamic acid is controlled at 1:1 to 1:10.

[0011] Preferably, the apple polyphenols are derived from apple processing byproducts through ethanol extraction or separation and purification using macroporous resin, and the total phenolic equivalent, calculated as gallic acid, is ≥40%.

[0012] Preferably, the total amount of organic acids, namely malic acid and citric acid, is 5 to 20 parts by mass, and the molar ratio of the total amount of organic acids to the carboxyl functional group of γ-polyglutamic acid is 0.3:1 to 3:1.

[0013] Preferably, it also includes a sustained-release encapsulation structure, specifically: a cross-linked network or microcapsule formed by γ-polyglutamic acid and a portion of malic acid / citric acid to encapsulate apple polyphenols inside, thereby extending the effective release period of apple polyphenols in the soil to 20-45 days.

[0014] The preparation method of the saline-alkali land improvement composition includes the following steps: Step 1: Extraction of apple polyphenols: Crush apple peel and pulp, extract with 50%–75% ethanol at a material-to-liquid ratio of 1:8–1:15, and extract by ultrasonication or reflux at 40–60°C for 1–3 hours. Filter, concentrate, and purify with resin to obtain concentrated apple polyphenols. Step 2: Prepare the organic acid phase: Dissolve malic acid and citric acid in water, and use citric acid / malic acid together to pre-adjust the pH to 3.0-4.5 to obtain an organic acid solution; Step 3: Disperse γ-polyglutamic acid: Add γ-polyglutamic acid in aqueous solution or powder form to the organic acid solution, and stir and disperse at 25-40℃ for 20-60 min to form a polymer-organic acid mixture; Step 4: Composite carrier slurry: Mix humic acid or fulvic acid, biochar, optional desulfurized gypsum and water to prepare a carrier slurry; Step 5: Blending / Encapsulation: Add apple polyphenol concentrate to a polymer-organic acid mixture, then blend with carrier slurry, and adjust the final solid content to 5%–30% (m / v) to obtain a liquid modifier; or obtain solid granules by spray drying / granulation.

[0015] Preferably, in step 3, the mass concentration of γ-polyglutamic acid in the mixture is 0.5% to 3%, and ultrasonic dispersion at 50 to 200 W is applied for 5 to 15 minutes while stirring to promote the stretching of γ-polyglutamic acid chains and the formation of a hydrogen bond / ionic bond synergistic network with organic acids.

[0016] The application of a saline-alkali land improvement composition in the remediation or improvement of saline-alkali land includes: Before crop planting or during fallow periods, the composition is applied to the topsoil layer at a rate of 150–600 kg / hm² or diluted 200–800 times and applied by irrigation to a depth of 0–25 cm. The application method is one or a combination of drip irrigation, strip application mixed with soil, and surface spraying and covering. After application, perform a shallow leaching with water equivalent to 80%–120% of field capacity to displace the water. They migrate downwards out of the rhizosphere; Apply organic base fertilizer within 7 to 15 days after application to increase soil organic matter by no less than 0.2% to 0.5%.

[0017] Preferably, the saline-alkali land is a soda-type / sulfate-chloride-type saline-alkali soil with a pH of 8.0 to 10.5 and a total salt content of 0.3% to 1.5%. The improvement target is to reduce the pH of the topsoil to ≤8.0 and reduce the ESP by ≥20%.

[0018] Preferably, the apple polyphenols in the composition exist in the form of free phenolic acid components and / or complex phenolic systems composed of proanthocyanidins, and their synergistic effect with citric acid / malic acid is as follows: Lower soil Alkalinity stress caused by alkalinity; Promoted by synergistic chelation of phenolic hydroxyl and carboxyl groups Replacement of soil colloids ; It enhances the activity of rhizosphere antioxidant enzyme systems and alleviates salt-alkali induced oxidative damage.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This saline-alkali land improvement composition, its preparation method, and its application, through the synergistic effect of malic acid, citric acid, and γ-polyglutamic acid, precisely regulates the soil acid-base balance. Within 90 days, it can reduce the pH of the topsoil to below 8.0 and decrease ESP by more than 20%, effectively replacing sodium ions on soil colloids and promoting their leaching and discharge, thus solving the problem of alkalinity stress in saline-alkali land.

[0020] This saline-alkali land improvement composition, its preparation method, and its application utilize a cross-linked network constructed from γ-polyglutamic acid and organic acids to encapsulate apple polyphenols, achieving slow release of active ingredients and extending the effective release period to 20-45 days. This avoids the shortcomings of traditional soil conditioners, such as easy loss and short duration of effect, and reduces the frequency of application and cost.

[0021] This saline-alkali land improvement composition, its preparation method, and its application: The composite system of apple polyphenols and organic acids can improve the physical and chemical properties of the soil, activate the activity of antioxidant enzymes such as SOD and POD in the rhizosphere, alleviate saline-alkali induced oxidative damage, promote the absorption of calcium by crop roots, and achieve multiple benefits of "soil improvement-root protection-yield increase". Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] Example 1: Preparations before implementation Raw material screening and pretreatment Apple polyphenol raw materials: Apple processing byproducts (such as Fuji apple peel and pomace, moisture content ≤12%) are selected, pulverized to a particle size of 0.5-1mm by air jet milling, and stored in a 4℃ cold storage for later use; ethanol (analytical grade, 95% by volume), macroporous resin (AB-8 type, pretreatment: first soaked in 95% ethanol for 24 hours, washed with deionized water until no alcohol odor remains, then...) and 5% Alternating activation).

[0026] Organic acids and polymers: malic acid (food grade, purity ≥99%), citric acid (anhydrous, food grade, purity ≥99.5%); γ-polyglutamic acid (molecular weight 500,000-1,000,000 Da, produced by fermentation, purity ≥90%, carboxyl content ≥15 mmol / g).

[0027] pH buffering carriers: humic acid (mineral source, organic matter ≥65%, pH 4.5-5.5), biochar (corn straw charcoal, 500℃ oxygen-limited pyrolysis, specific surface area ≥200m² / g, pH 8.0-8.5), desulfurization gypsum (power plant waste, Content ≥85%, fineness 200 mesh).

[0028] Auxiliary reagents: deionized water (conductivity ≤10μS / cm), inert filler (attapulgite clay, 200 mesh, dried at 105℃ for 2h).

[0029] Example 2: Core Preparation Process Apple polyphenol extraction and purification Extraction process: Weigh 100g of apple peel pomace, add 60% ethanol solution at a material-to-liquid ratio of 1:12 (m / V), place in an ultrasonic cell disruptor (power 300W, frequency 40kHz), and extract at a constant temperature of 45℃ for 2h (stirring once every 30min); centrifuge the extract at 8000r / min for 15min, collect the supernatant, and concentrate it to 1 / 5 of the original volume using a rotary evaporator (60℃, vacuum degree -0.08MPa) to obtain crude extract.

[0030] Resin purification: The crude extract was loaded onto an AB-8 macroporous resin column (column diameter × column height = 2.5 cm × 30 cm, flow rate 2 BV / h). Impurities were first eluted with 4 BV of deionized water, and then the polyphenol components were eluted with 5 BV of 70% ethanol. The eluent was collected, concentrated under reduced pressure (55 °C, vacuum degree -0.09 MPa) to dryness, and redissolved with a small amount of deionized water to obtain apple polyphenol concentrate (total phenol equivalent based on gallic acid ≥ 45%, corresponding to claim 2).

[0031] Organic acid phase modulation and γ-polyglutamic acid dispersion Organic acid molar ratio control: Weigh the raw materials (e.g., 13.4g of malic acid and 19.2g of citric acid) according to the ratio of malic acid to citric acid = 1:1.5 (molar ratio), dissolve them in 200mL of deionized water, and stir magnetically (500r / min) until completely dissolved; finely adjust the pH to 3.8±0.2 with citric acid / malic acid.

[0032] γ-Polyglutamic acid dispersion and network construction: 8g of γ-polyglutamic acid powder was slowly added to an organic acid solution and stirred at 25°C (300r / min) for 40min to dissolve, while simultaneously being ultrasonically dispersed at 100W for 10min (corresponding to claim 6); at this time, the mass concentration of γ-polyglutamic acid was 2%, the total amount of its carboxyl functional groups was 1.2mmol (based on a carboxyl content of 15mmol / g), the total amount of organic acid was 3.6mmol, and the molar ratio of the two was 3:1.

[0033] Construction of sustained-release encapsulation structures The above-mentioned concentrated apple polyphenol solution (containing 5g of polyphenols) was slowly added dropwise to a mixture of γ-polyglutamic acid and organic acid. The mixture was stirred (200r / min) in a 40℃ water bath for 30min to allow the apple polyphenols and γ-polyglutamic acid to form a cross-linked network through hydrogen bonding / hydrophobic interaction. Dynamic light scattering characterization showed that the encapsulated apple polyphenols had a particle size of 200-500nm. In vitro simulated soil solution release experiments showed that the cumulative release rate was ≤40% after 72h and the effective release period reached 35d (meeting the 20-45d requirement in claim 4).

[0034] Preparation and blending of composite carrier slurry Carrier slurry preparation: Weigh the raw materials according to the following ratio: 25 parts humic acid, 15 parts biochar, and 10 parts desulfurized gypsum. Add 200 mL of deionized water and emulsify at high speed (10000 r / min) for 5 min to prepare a uniform slurry (solid content 20%).

[0035] Blending molding: The γ-polyglutamic acid-organic acid mixture loaded with apple polyphenols is mixed with the carrier slurry at a volume ratio of 1:1 and stirred (400 r / min) for 20 min. The solid content is adjusted to 15% (m / V) to obtain a liquid modifier. A portion of the liquid modifier is spray-dried (inlet air temperature 180℃, outlet air temperature 80℃, feed flow rate 5 mL / min) to obtain solid granules (particle size 0.5-1 mm, moisture content ≤5%).

[0036] Example 3: Field Application Implementation Plan Applicable land parcel selection Typical soda-type saline-alkali land (pH 9.2, total salt content 0.8%, ESP 35%, soil texture clay loam) was selected, with sunflower (salt-tolerant variety, yield ≤1500kg / hm²) as the previous crop. The experimental area was 10hm², with 3 replicates and randomized block design.

[0037] Application method and dosage Application period: 15 days before crop planting (mid-April, with an average daily temperature ≥10℃), combined with spring plowing.

[0038] Application dosage and method: Liquid soil conditioner: Apply at 300 kg / hm² (converted to solid form), diluted 500 times, and then applied evenly to the topsoil layer of 0-25 cm through the field drip irrigation system. The drip irrigation duration is 4 hours, and the irrigation volume is 450 m³ / hm² (equivalent to 100% of field capacity).

[0039] Solid granules: Apply at a depth of 15cm in furrows at a rate of 200kg / hm², followed by rotary tillage to mix with the soil (tillage depth 20cm).

[0040] Supporting measures: 7 days after application, apply 3000 kg of well-rotted sheep manure organic fertilizer per mu (organic matter ≥45%), and plant salt-tolerant green manure (sesbania, seeding rate 15 kg / hm²) to promote soil organic matter improvement.

[0041] Effect monitoring and verification Soil physicochemical indicators: Soil samples from 0-20 cm depth were collected before application and at 30, 60, and 90 days after application. pH (potential method), ESP (ammonium acetate exchange method), and total salt content (conductivity method) were measured. The results showed that after 90 days, the pH of the topsoil layer decreased to 7.8 (a decrease of 15.2%), ESP decreased to 26% (a decrease of 25.7%), and total salt content decreased to 0.4% (a decrease of 50%), which met the target of "pH≤8.0 and ESP reduction≥20%" in claim 8.

[0042] Crop response: Maize (Zhengdan 958) was planted, and yield and quality were measured at harvest. The results showed that the grain yield reached 7500 kg / hm² (68% increase compared to the control), and the leaf SOD activity increased by 42% and POD activity increased by 55%.

[0043] Example 4: Key Points of Quality Control Raw material testing: Each batch of apple polyphenols must be tested for total phenolic equivalent (Folin-Ciocalteu method) to ensure ≥40%; the molecular weight distribution of γ-polyglutamic acid (GPC method) deviation ≤10%.

[0044] Process monitoring: The pH of organic acids is controlled between 3.0 and 4.5 (precision pH meter calibration), the ultrasonic power error during γ-polyglutamic acid dispersion is ≤10W, and the inlet air temperature fluctuation during spray drying is ≤5℃.

[0045] Finished product inspection: Liquid amendments need to be tested for solid content (drying method) and pH (3.5-5.0); solid granules need to be tested for moisture content (≤5%) and disintegration time (≤30min, simulating soil environment).

[0046] Incompatibilities: Avoid mixing with strongly alkaline fertilizers (such as wood ash) to prevent the organic acids from neutralizing and degrading the fertilizer. Environmental compatibility: Double the dosage is required for heavily saline-alkali land with pH > 10.5, and it should be used in conjunction with a concealed drainage system. Storage conditions: Liquid products should be stored at 4°C away from light for 6 months; solid products should be sealed and protected from moisture for 12 months.

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composition for improving saline-alkali land, characterized in that: Made from the following parts by weight of raw materials: Apple polyphenols: 0.5-5 parts, malic acid: 3-15 parts, citric acid: 2-10 parts, γ-polyglutamic acid: 1-8 parts; pH buffer carrier: 10-40 parts of humic acid or fulvic acid, 5-25 parts of biochar, and 0-20 parts of desulfurized gypsum, at least one of the three shall be selected. The remainder is water or inert filler up to 100 parts by weight; The molar ratio of malic acid to citric acid is controlled at 1:0.5 to 1:3, and the mass ratio of apple polyphenols to γ-polyglutamic acid is controlled at 1:1 to 1:

10.

2. The saline-alkali land improvement composition according to claim 1, characterized in that: The apple polyphenols are derived from apple processing byproducts through ethanol extraction or separation and purification using macroporous resin, with a total phenolic equivalent of ≥40% calculated as gallic acid.

3. The saline-alkali land improvement composition according to claim 1, characterized in that: The total amount of organic acids, including malic acid and citric acid, is 5 to 20 parts by mass, and the molar ratio of the total amount of organic acids to the carboxyl functional group of the γ-polyglutamic acid is 0.3:1 to 3:

1.

4. The saline-alkali land improvement composition according to claim 1, characterized in that: It also includes a sustained-release encapsulation structure, specifically: a cross-linked network or microcapsule formed by γ-polyglutamic acid and some malic acid / citric acid to encapsulate apple polyphenols inside, thereby extending the effective release period of apple polyphenols in the soil to 20-45 days.

5. The method for preparing the saline-alkali land improvement composition according to claims 1-4, characterized in that: Includes the following steps: Step 1: Extraction of apple polyphenols: Crush apple peel and pulp, extract with 50%–75% ethanol at a material-to-liquid ratio of 1:8–1:15, and extract by ultrasonication or reflux at 40–60°C for 1–3 hours. Filter, concentrate, and purify with resin to obtain concentrated apple polyphenols. Step 2: Prepare the organic acid phase: Dissolve malic acid and citric acid in water, and use citric acid / malic acid together to pre-adjust the pH to 3.0-4.5 to obtain an organic acid solution; Step 3: Disperse γ-polyglutamic acid: Add γ-polyglutamic acid in aqueous solution or powder form to the organic acid solution, and stir and disperse at 25-40℃ for 20-60 min to form a polymer-organic acid mixture; Step 4: Composite carrier slurry: Mix humic acid or fulvic acid, biochar, optional desulfurized gypsum and water to prepare a carrier slurry; Step 5: Blending / Encapsulation: Add apple polyphenol concentrate to a polymer-organic acid mixture, then blend with carrier slurry, and adjust the final solid content to 5%–30% (m / v) to obtain a liquid modifier; or obtain solid granules by spray drying / granulation.

6. The method for preparing the saline-alkali land improvement composition according to claim 5, characterized in that: In step 3, the mass concentration of γ-polyglutamic acid in the mixture is 0.5% to 3%. While stirring, ultrasonic dispersion at 50 to 200 W is applied for 5 to 15 minutes to promote the extension of γ-polyglutamic acid chains and the formation of a hydrogen bond / ionic bond synergistic network with organic acids.

7. The application of the saline-alkali land improvement composition according to any one of claims 1-4 in the remediation or improvement of saline-alkali land soil, characterized in that, include: Before crop planting or during fallow periods, the composition is applied to the topsoil layer at a rate of 150–600 kg / hm² or diluted 200–800 times and applied by irrigation to a depth of 0–25 cm. The application method is one or a combination of drip irrigation, strip application mixed with soil, and surface spraying and covering. After application, perform a shallow leaching with water equivalent to 80%–120% of field capacity to move the displaced Na⁺ downwards out of the rhizosphere. Apply organic base fertilizer within 7 to 15 days after application to increase soil organic matter by no less than 0.2% to 0.5%.

8. The application of the saline-alkali land improvement composition according to claim 7 in the remediation or improvement of saline-alkali land soil, characterized in that: The saline-alkali land is a soda-type / sulfate-chloride-type saline-alkali soil with a pH of 8.0 to 10.5 and a total salt content of 0.3% to 1.5%. The improvement target is to reduce the pH of the topsoil to ≤8.0 and reduce the ESP by ≥20%.

9. The saline-alkali land improvement composition according to claims 1-4, characterized in that: The apple polyphenols in the composition exist in the form of free phenolic acid components and / or complex phenolic systems composed of proanthocyanidins, and their synergistic effect with citric acid / malic acid is as follows: Lower soil Alkalinity stress caused by alkalinity; Promoted by synergistic chelation of phenolic hydroxyl and carboxyl groups Replacement of soil colloids ; It enhances the activity of rhizosphere antioxidant enzyme systems and alleviates salt-alkali induced oxidative damage.

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