Phyllostachys edulis soda-saline soil repairing agent and preparation method thereof

Abstract

The present application relates to the technical field of soil pollution treatment, in particular to a bamboo-based soda saline soil remediation agent and a preparation method thereof, the bamboo-based soda saline soil remediation agent is composed of the following components in parts by weight: 46-50 parts of mature bamboo-based organic matter, 31-36 parts of modified bamboo charcoal, 10-13 parts of potassium humate, 5-6 parts of desulfurized gypsum, and 1-3 parts of iron-zinc-manganese chelate; the mature bamboo-based organic matter is bamboo-based organic material treated by aerobic fermentation; the modified bamboo charcoal is obtained by modifying bamboo charcoal with citric acid and phytic acid, and has carboxyl and phosphoric acid functional groups grafted on the surface. The present application can significantly improve the physicochemical properties of soda saline soil, achieve the multiple goals of desalination, alkali reduction and soil fertilization by converting bamboo raw materials into mature bamboo-based organic matter and modified bamboo charcoal, and combining the synergistic effect of potassium humate, desulfurized gypsum and iron-zinc-manganese chelate.

Description

Technical Field

[0001] This invention relates to the field of soil pollution remediation technology, specifically to a bamboo-based soda saline soil remediation agent and its preparation method. Background Technology

[0002] Soda saline soil refers to saline soil containing a high amount of alkaline substances such as sodium carbonate and sodium bicarbonate. It is a type of alkalized soil, also known as soda saline-alkali soil. The soil colloids in soda saline soil carry a large number of negative charges. These negative charges adsorb sodium ions from the soil solution, creating a sodium-saturated state. Due to the hydrolysis of sodium ions, the soil colloid particles disperse, the soil structure is damaged, becoming compacted and hardened, with extremely poor aeration and permeability, thus affecting the growth and development of plant roots.

[0003] Chinese invention patent CN119081704B discloses a novel high-efficiency soil conditioner, its preparation method, and its application. This invention adds bamboo powder to the formula to increase soil organic matter content, but it has the following shortcomings: 1. Bamboo powder is mainly composed of lignin and cellulose. However, in the highly alkaline environment of soda saline soil, the activity of functional microorganisms such as cellulose-decomposing bacteria and lignin-degrading bacteria is significantly inhibited, making it difficult for bamboo powder to be effectively degraded, unable to quickly release active organic matter, and unable to improve the soil pore structure in a timely manner, resulting in low overall remediation efficiency. 2. The carbon-nitrogen ratio of dried bamboo powder is about 50:1. Under this high carbon-nitrogen ratio, microorganisms will consume a large amount of the limited available nitrogen in the soil to meet their own metabolic needs. This causes crops to suffer from both salt and alkali damage, as well as nitrogen stress, which can easily lead to problems such as decreased germination rate, yellowing of plants and root necrosis. 3. Uncomposted bamboo powder contains fewer active functional groups (such as carboxyl and hydroxyl groups), which has a limited effect on improving the soil cation exchange capacity. Although bamboo powder contains a small amount of divalent cations such as calcium and magnesium, the content is insufficient to achieve the core goal of desalination and alkali reduction in soda saline soil. Summary of the Invention

[0004] The purpose of this invention is to provide a bamboo-based soda saline soil remediation agent and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, on the one hand, the present invention provides the following technical solution: a bamboo-based soda saline soil remediation agent, wherein the bamboo-based soda saline soil remediation agent is composed of the following components in parts by weight: 46-50 parts of decomposed bamboo-based organic matter, 31-36 parts of modified bamboo charcoal, 10-13 parts of potassium humate, 5-6 parts of desulfurized gypsum, and 1-3 parts of iron-zinc-manganese chelate; The decomposed bamboo-based organic matter is a moso bamboo-derived organic material that has undergone aerobic fermentation treatment, with a carbon-to-nitrogen ratio of 21–23:1. When mixed with water at a mass ratio of 1:10, the pH is 7.8–8.0, and the seed germination index (GI) is not less than 80%. The modified bamboo charcoal is prepared by synergistic modification of bamboo charcoal with citric acid and phytic acid, and its surface is grafted with carboxyl and phosphate functional groups, with a cation exchange capacity of 38-45 cmol. + / kg.

[0006] Optionally, the preparation method of the decomposed bamboo-based organic matter includes the following steps: mixing 100 parts of bamboo powder, 10-15 parts of soybean meal, 5-8 parts of phosphogypsum powder, 1-2 parts of urea, and 0.5-1.0 parts of alkali-resistant compound fermentation agent evenly to obtain a mixture; adding deionized water to the mixture to adjust the moisture content to 65%-70%; subjecting the mixture to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and turning it over once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days to obtain the decomposed bamboo-based organic matter.

[0007] Optionally, the bamboo powder is obtained by drying, crushing and sieving the bamboo culms of 3-5 year old healthy moso bamboo (Phyllostachys edulis), with a particle size ≤2 mm and a moisture content ≤10%.

[0008] Optionally, the alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of (2-3):(1-2):1, with a total viable count of not less than 5×10^8 CFU / g.

[0009] Optionally, the preparation method of the modified bamboo charcoal includes the following steps: placing bamboo processing residue in a nitrogen atmosphere tube furnace and pyrolyzing it at 480–520℃ for 1.0–2.5 h; after naturally cooling to room temperature, pulverizing and sieving to collect bamboo charcoal with a particle size of 0.5–2.0 mm; dissolving citric acid and phytic acid in deionized water at a mass ratio of (2–6):1 to prepare a mixed aqueous solution with a total organic acid concentration of 8–12 wt%; mixing the bamboo charcoal and the mixed aqueous solution at a solid-liquid ratio of 1:(3–4) kg / L, ultrasonically treating it at 58–65℃ for 0.8–1.2 h, then raising the temperature to 88–95℃ and stirring at 300–400 rpm for 2.5–3.5 h; after the reaction, separating the solid and liquid phases, collecting the solid product, vacuum drying it at 58–65℃ for 6–8 h, and then heat-treating it in air at 190–205℃ for 1.0–2.5 h. h, after cooling, the modified bamboo charcoal is obtained.

[0010] Optionally, the iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citrate, and manganese chelate citrate, with a mass ratio of (2-3):1:1.

[0011] On the other hand, the present invention also provides the following technical solution: the preparation method of the above-mentioned bamboo-based soda saline soil remediation agent includes the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 15-25 rpm for 20-30 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in 3 to 5 times its total mass of deionized water to prepare a chelation solution. Under stirring at 15 to 25 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 10 to 15 minutes. Then, ventilate and dry at 40 to 45°C until the moisture content is not higher than 12% to obtain the moso bamboo-based soda saline soil remediation agent.

[0012] In addition, the present invention provides the following technical solution: the above-mentioned bamboo-based soda saline soil remediation agent is applied after the autumn crop harvest and before the soil freezes, or before spring land preparation. The remediation agent is first evenly spread on the surface of the soda saline soil at a dosage of 300-500 kg / mu, and then a rotary tiller is used to perform rotary tillage to mix the bamboo-based soda saline soil remediation agent into the soil layer of ≤20 cm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention converts raw bamboo into decomposed bamboo-based organic matter and modified bamboo charcoal, and combines the synergistic effects of potassium humate, desulfurized gypsum and iron-zinc-manganese chelate to significantly improve the physicochemical properties of soda saline soil, achieving multiple goals of desalination, alkali reduction and fertilization. 2. Field trials have demonstrated that the application of bamboo-based soda saline soil remediation agent can simultaneously and significantly reduce soil salinity and pH, and greatly increase organic matter content. Pot experiments have also shown that the bamboo-based soda saline soil remediation agent can effectively stabilize the heavy metal cadmium in the soil while promoting rice yield. This achieves a synergistic effect of saline-alkali soil remediation, heavy metal passivation, and crop yield increase. Furthermore, the raw materials used are bamboo and its processing waste, which has resource utilization value. The preparation process parameters are clear and the process is controllable. The resulting product has good biocompatibility and high environmental safety. Attached Figure Description

[0014] Figure 1 This is a line graph showing the change in soil organic matter content over remediation time in Experiment Example 2; Figure 2 This is a line graph showing the change in soil pH over remediation time in Experiment Example 2; Figure 3 This is a line graph showing the change in organic matter content over remediation time in Experiment Example 2; Figure 4 This is a bar chart showing the grain yield in Experiment Example 3.

[0015] Figure 5 This is a bar chart showing the cadmium content of rice grains in Experiment Example 3. Detailed Implementation

[0016] 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.

[0017] Example 1 This embodiment provides a bamboo-based soda saline soil remediation agent, which is composed of the following components in parts by weight: 48 parts of decomposed bamboo-based organic matter, 34 parts of modified bamboo charcoal, 11 parts of potassium humate, 5.5 parts of desulfurized gypsum, and 1.5 parts of iron-zinc-manganese chelate.

[0018] The preparation method of decomposed bamboo-based organic matter includes the following steps: 100 parts of bamboo powder, 12 parts of soybean meal, 6 parts of phosphogypsum powder, 1.5 parts of urea, and 0.8 parts of alkali-resistant compound fermentation agent are mixed evenly to obtain a mixture; deionized water is added to the mixture to adjust the moisture content to 68%; the mixture is subjected to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days to obtain decomposed bamboo-based organic matter.

[0019] The alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of 2.5:1.5:1.

[0020] The preparation method of modified bamboo charcoal includes the following steps: bamboo processing residue is placed in a tube furnace under nitrogen atmosphere and pyrolyzed at 500℃ for 2.0 h. After natural cooling to room temperature, it is crushed and sieved to collect bamboo charcoal with a particle size of 0.5-2.0 mm. Citric acid and phytic acid are dissolved in deionized water at a mass ratio of 4:1 to prepare a mixed aqueous solution with a total organic acid concentration of 10 wt%. The bamboo charcoal and the mixed aqueous solution are mixed at a solid-liquid ratio of 1:3.5 kg / L and ultrasonically treated at 62℃ for 1.0 h. Then, the temperature is raised to 92℃ and stirred at 350 rpm for 3.0 h. After the reaction is completed, the solid and liquid phases are separated, the solid product is collected, vacuum dried at 60℃ for 7 h, and then heat-treated in air at 200℃ for 2.0 h. After cooling, modified bamboo charcoal is obtained.

[0021] The iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citric acid, and manganese chelate citric acid, with a mass ratio of 2.5:1:1.

[0022] This embodiment also provides a method for preparing the above-mentioned bamboo-based soda saline soil remediation agent, including the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 20 rpm for 25 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in four times its total mass of deionized water to prepare a chelation solution. Under stirring at 20 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 12 minutes. Then, air dry at 42°C until the moisture content is no more than 12% to obtain the bamboo-based soda saline soil remediation agent.

[0023] Example 2 This embodiment provides a bamboo-based soda saline soil remediation agent, which is composed of the following components in parts by weight: 50 parts of decomposed bamboo-based organic matter, 31 parts of modified bamboo charcoal, 12 parts of potassium humate, 6 parts of desulfurized gypsum, and 1 part of iron-zinc-manganese chelate.

[0024] The preparation method of decomposed bamboo-based organic matter includes the following steps: 100 parts of bamboo powder, 10 parts of soybean meal, 5 parts of phosphogypsum powder, 1 part of urea, and 0.5 parts of alkali-resistant compound fermentation agent are mixed evenly to obtain a mixture; deionized water is added to the mixture to adjust the moisture content to 65%; the mixture is subjected to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days to obtain decomposed bamboo-based organic matter.

[0025] The alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of 2:1:1.

[0026] The preparation method of modified bamboo charcoal includes the following steps: bamboo processing residue is placed in a tube furnace under nitrogen atmosphere and pyrolyzed at 480℃ for 2.5 h. After natural cooling to room temperature, it is crushed and sieved to collect bamboo charcoal with a particle size of 0.5-2.0 mm. Citric acid and phytic acid are dissolved in deionized water at a mass ratio of 6:1 to prepare a mixed aqueous solution with a total organic acid concentration of 8 wt%. The bamboo charcoal and the mixed aqueous solution are mixed at a solid-liquid ratio of 1:4 kg / L and ultrasonically treated at 60℃ for 0.8 h. Then, the temperature is raised to 95℃ and stirred at 400 rpm for 2.5 h. After the reaction is completed, the solid and liquid phases are separated, the solid product is collected, vacuum dried at 65℃ for 6 h, and then heat-treated in air at 205℃ for 1.0 h. After cooling, modified bamboo charcoal is obtained.

[0027] The iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citric acid, and manganese chelate citric acid, with a mass ratio of 2:1:1.

[0028] This embodiment also provides a method for preparing the above-mentioned bamboo-based soda saline soil remediation agent, including the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 15 rpm for 30 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in three times its total mass of deionized water to prepare a chelation solution. Under stirring at 15 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 15 min. Then, ventilate and dry at 40℃ until the moisture content is no more than 12% to obtain the moso bamboo-based soda saline soil remediation agent.

[0029] Example 3 This embodiment provides a bamboo-based soda saline soil remediation agent, which is composed of the following components in parts by weight: 46 parts of decomposed bamboo-based organic matter, 32 parts of modified bamboo charcoal, 13 parts of potassium humate, 6 parts of desulfurized gypsum, and 3 parts of iron-zinc-manganese chelate.

[0030] The preparation method of decomposed bamboo-based organic matter includes the following steps: 100 parts of bamboo powder, 15 parts of soybean meal, 8 parts of phosphogypsum powder, 2 parts of urea, and 1.0 part of alkali-resistant compound fermentation agent are mixed evenly to obtain a mixture; deionized water is added to the mixture to adjust the moisture content to 70%; the mixture is subjected to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and turning it over once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days to obtain decomposed bamboo-based organic matter.

[0031] The alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of 3:2:1.

[0032] The preparation method of modified bamboo charcoal includes the following steps: bamboo processing residue is placed in a tube furnace under nitrogen atmosphere and pyrolyzed at 520℃ for 1.0 h. After natural cooling to room temperature, it is crushed and sieved to collect bamboo charcoal with a particle size of 0.5-2.0 mm. Citric acid and phytic acid are dissolved in deionized water at a mass ratio of 2:1 to prepare a mixed aqueous solution with a total organic acid concentration of 12 wt%. The bamboo charcoal and the mixed aqueous solution are mixed at a solid-liquid ratio of 1:3 kg / L and ultrasonically treated at 65℃ for 1.2 h. Then, the temperature is raised to 88℃ and stirred at 300 rpm for 3.5 h. After the reaction, the solid and liquid phases are separated, the solid product is collected, vacuum dried at 58℃ for 8 h, and then heat-treated in air at 190℃ for 2.5 h. After cooling, modified bamboo charcoal is obtained.

[0033] The iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citric acid, and manganese chelate citric acid, with a mass ratio of 3:1:1.

[0034] This embodiment also provides a method for preparing the above-mentioned bamboo-based soda saline soil remediation agent, including the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 25 rpm for 20 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in 5 times its total mass of deionized water to prepare a chelation solution. Under stirring at 25 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 10 min. Then, ventilate and dry at 45℃ until the moisture content is no more than 12% to obtain the bamboo-based soda saline soil remediation agent.

[0035] Example 4 This embodiment provides a bamboo-based soda saline soil remediation agent, which is composed of the following components in parts by weight: 47 parts of decomposed bamboo-based organic matter, 36 parts of modified bamboo charcoal, 10 parts of potassium humate, 5 parts of desulfurized gypsum, and 2 parts of iron-zinc-manganese chelate.

[0036] The preparation method of decomposed bamboo-based organic matter includes the following steps: 100 parts of bamboo powder, 13 parts of soybean meal, 7 parts of phosphogypsum powder, 1.8 parts of urea, and 0.9 parts of alkali-resistant compound fermentation agent are mixed evenly to obtain a mixture; deionized water is added to the mixture to adjust the moisture content to 67%; the mixture is subjected to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days to obtain decomposed bamboo-based organic matter.

[0037] The alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of 3:2:1.

[0038] The preparation method of modified bamboo charcoal includes the following steps: bamboo processing residue is placed in a tube furnace under nitrogen atmosphere and pyrolyzed at 500℃ for 1.7 h. After natural cooling to room temperature, it is crushed, sieved, and bamboo charcoal with a particle size of 0.5-2.0 mm is collected. Citric acid and phytic acid are dissolved in deionized water at a mass ratio of 5:1 to prepare a mixed aqueous solution with a total organic acid concentration of 10.5 wt%. The bamboo charcoal and the mixed aqueous solution are mixed at a solid-liquid ratio of 1:3.2 kg / L and ultrasonically treated at 63℃ for 1.0 h. Then, the temperature is raised to 90℃ and stirred at 360 rpm for 3.2 h. After the reaction is completed, the solid and liquid phases are separated, the solid product is collected, vacuum dried at 60℃ for 7 h, and then heat-treated in air at 200℃ for 1.8 h. After cooling, modified bamboo charcoal is obtained.

[0039] The iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citric acid, and manganese chelate citric acid, with a mass ratio of 2.8:1:1.

[0040] This embodiment also provides a method for preparing the above-mentioned bamboo-based soda saline soil remediation agent, including the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 22 rpm for 22 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in four times its total mass of deionized water to prepare a chelation solution. Under stirring at 22 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 12 minutes. Then, ventilate and dry at 43°C until the moisture content is no more than 12% to obtain the bamboo-based soda saline soil remediation agent.

[0041] In Examples 1-4, the bamboo powder was obtained by drying, crushing and sieving the bamboo culms of 3-5 year old healthy bamboo (Phyllostachys edulis), with a particle size ≤2 mm and a moisture content ≤10%. The raw material for modified bamboo charcoal—bamboo processing residues—mainly came from the production process of decomposed bamboo-based organic matter, realizing the recycling of resources. The total viable count of the alkali-resistant compound fermentation agent was not less than 5×10^8 CFU / g.

[0042] Compare with Example 1 The preparation of the repair agent is basically the same as that in Example 1, except that bamboo powder is used to replace the organic matter of decomposed bamboo base.

[0043] Compare with Example 2 The preparation of the repair agent is basically the same as in Example 1, except that the modified bamboo charcoal is replaced with bamboo charcoal.

[0044] Test Example 1: Physicochemical Properties Test 1. Test sample Examples 1-4 show the preparation of decomposed bamboo-based organic matter and modified bamboo charcoal.

[0045] 2. Experimental Content and Methods (1) Determination of the physicochemical properties of decomposed bamboo-based organic matter Carbon-to-nitrogen ratio (C / N): The total carbon and total nitrogen were determined using an elemental analyzer, and the C / N ratio was calculated. pH value: Mix decomposed bamboo-based organic matter with deionized water at a mass ratio of 1:10, shake for 30 min and let stand for 30 min, then use a pH meter to measure the pH of the supernatant. Seed germination index (GI): Measured according to the test method disclosed in NY / T 525-2021, using the seeds of Chinese cabbage (Brassica rapa) as the indicator plant.

[0046] (2) Determination of the physicochemical properties of modified bamboo charcoal Cation exchange capacity (CEC): Measured by the test method disclosed in HJ 889-2017; Content of surface acidic functional groups: Quantitative analysis of surface acidic functional groups of modified bamboo charcoal was carried out by Boehm titration method. The specific method is as follows: React the sample with 0.1 mol / L NaHCO3, Na2CO3 and NaOH solutions respectively, and determine the consumed alkali content by back titration. Classify the types of acidic sites according to the following rules: Acidic groups neutralizable by NaHCO3 (pKa < 5): Mainly contributed by carboxyl groups; Groups neutralizable by Na2CO3 but not by NaHCO3 (5 < pKa < 10): Include the second dissociation state of phosphate groups and some strong phenolic hydroxyl groups; Groups neutralizable by NaOH but not by the former two (pKa > 10): Mainly weak phenolic hydroxyl groups and lactone groups.

[0047] The data results are recorded in Table 1.

[0048] Table 1

[0049] As can be seen from Table 1, the carbon-nitrogen ratio of the examples is between 21.37 and 22.89, indicating that the decomposed bamboo-based organic matter has been fully decomposed, which is beneficial to subsequent stable application and nutrient release in the soil. The pH values of the examples are between 7.82 and 7.97, showing weak alkalinity, which is within the suitable range of soil pH for most crops and will not cause significant acidification or alkalization effects on the soil. The seed germination indices of the examples are all higher than 80%, meeting the standards of non-plant toxicity and safe application to agriculture, indicating that the decomposed bamboo-based organic matter has no inhibitory effect on plant growth and has good biocompatibility.

[0050] The cation exchange capacity of the examples is between 38.42 and 44.63 cmol + / kg, indicating that it has strong fertilizer retention capacity and to K + 、Ca 2+ 、Mg 2+ 、NH4 +The adsorption and fixation capacity of soil cations helps to improve soil fertility. Boehm titration results showed that the total acidic functional group content of modified bamboo charcoal was 1.52–1.64 mmol / g (i.e., the sum of NaHCO3 titration amount + Na2CO3 titration increment + NaOH titration increment). Among them, the content of strongly acidic sites (mainly contributed by carboxyl groups) was 0.76–0.90 mmol / g, while the content of moderately strong acidic sites (corresponding to Na2CO3 titration increment) estimated from the titration difference reached 0.42–0.54 mmol / g. Given that phytic acid was clearly introduced during the modification process, and its molecular structure is rich in multiple phosphate groups, it can be confirmed that the moderately strong acidic sites mainly originate from the phosphate functional groups successfully grafted onto the surface of bamboo charcoal. Therefore, the synergistic modification process of citric acid and phytic acid effectively constructed carboxyl and phosphate groups on the surface of bamboo charcoal.

[0051] In summary, the decomposed bamboo-based organic matter prepared by this invention is obtained through aerobic fermentation for 7 days using an alkali-resistant composite fermentation agent under strict control of moisture content and turning regime. This aerobic fermentation-treated bamboo-derived organic material exhibits a carbon-to-nitrogen ratio reduced to 21–23:1, significantly alleviating excessive nitrogen consumption by microorganisms in the soil and preventing nitrogen stress in crops. Furthermore, when mixed with water at a mass ratio of 1:10, its pH value remains stable at 7.8–8.0, and its seed germination index is ≥80%, indicating thorough decomposition and lack of phytotoxicity. It can rapidly improve soil pore structure and provide slow-release nutrients. The modified bamboo charcoal prepared by this invention, through synergistic modification with citric acid and phytic acid, successfully grafts a large number of acidic functional groups such as carboxyl and phosphate groups onto the surface of the bamboo charcoal, increasing its cation exchange capacity to 38–45 cmol. + / kg, significantly enhances the resistance to Na + The ability to substitute for K + Ca 2+ Mg 2+ NH4 + It has the ability to retain beneficial cations, thereby efficiently achieving desalination and alkali reduction in soda saline soil.

[0052] Experimental Example 2: Field Trial 1. Test sample The bamboo-based soda saline soil remediation agents prepared in Examples 1-4, and the remediation agents prepared in Comparative Examples 1-2.

[0053] 2. Experimental Content and Methods A field remediation experiment was conducted on six adjacent soda-saline-alkali land plots in Yuanzhou District, Yichun City, Jiangxi Province. The specific process is as follows: (1) Before the experiment, the topsoil (0-20 cm) of each plot was collected using the five-point sampling method. The salt content, pH value and organic matter content were measured, and the plot average value of each index was calculated as the initial value. (2) Apply the test sample evenly to the surface of each test plot at a rate of 500 kg / mu, and then use a rotary tiller to perform rotary tillage to ensure that the test sample is fully mixed with the 0-20 cm soil layer. (3) Starting from the date of application, sampling and measurement were repeated every 5 days for 45 days, resulting in dynamic monitoring data at 10 time points. Based on this, line graphs were plotted showing the changes in soil salinity, pH value, and organic matter content over remediation time. Figures 1 to 3 .

[0054] Depend on Figures 1 to 3 It can be seen that all embodiments significantly improved the physicochemical properties of soda-saline soil. Compared with before treatment, after treatment with the bamboo-based soda-saline soil remediation agents prepared in Examples 1-4, the soil salinity was significantly reduced, the pH value was significantly decreased, and the organic matter content was significantly increased, fully demonstrating that the bamboo-based soda-saline soil remediation agents have a good synergistic effect in desalination, alkalinity reduction, and fertility improvement. Among them, the bamboo-based soda-saline soil remediation agent prepared in Example 4 showed the most outstanding effect: after treatment, the soil salinity was reduced to the lowest level, the pH value was reduced to near neutral, and the organic matter content was the highest, indicating that it can efficiently achieve multiple remediation goals of salt reduction, alkalinity mitigation, and soil fertility improvement in a short period of time, demonstrating excellent application potential. In contrast, the remediation effects of Comparative Examples 1 and 2 were significantly weaker than those of Example 1, further confirming that decomposed bamboo-based organic matter and modified bamboo charcoal are the key functional components for achieving efficient improvement in this remediation system.

[0055] Experimental Example 3: Pot Experiment 1. Test soil and crops The tested soil samples were collected from the surface layer (0–20 cm) of soda-saline farmland in Yuanzhou District, Yichun City, Jiangxi Province. Its basic physicochemical properties are as follows: pH 9.2, electrical conductivity (EC) 1.8 dS / m, organic matter content 12.3 g / kg, DTPA-extractable cadmium 0.85 mg / kg, and total cadmium content 1.62 mg / kg, classifying it as lightly to moderately cadmium-contaminated soda-saline soil. The tested rice variety was Nanjing 9108.

[0056] 2. Experimental Content and Methods This experiment used a pot experiment method, with each pot containing 5 kg of air-dried and sieved soil. The experiment consisted of 8 treatment groups, with 4 replicates per group. The specific treatment protocols are as follows: CK group: No fertilizer was applied; CF group: NPK 15-15-15 compound fertilizer was used as base fertilizer, with an application rate of 50 kg / mu (calculated based on the soil mass of the pots). Groups T1 to T8: The bamboo-based soda saline soil remediation agent prepared in Example 4 was applied at amounts of 0.15%, 0.30%, 0.60%, 0.90%, 1.20%, 1.80%, 2.40%, and 3.00% of the soil mass, respectively.

[0057] Except for the base fertilizer, the topdressing and water management were the same for all treatments.

[0058] All treatment groups maintained the same topdressing method and water management conditions, except for the basal fertilizer application scheme. Rice was harvested after maturity, and grain yield was measured (converted to the standard value at 14% moisture content). The cadmium content in rice grains was determined according to the method in GB 5009.15-2023 National Food Safety Standard for the Determination of Cadmium in Food. The experimental data are as follows: Figure 4 and Figure 5 As shown.

[0059] Depend on Figure 4 Data shows that when the bamboo-based soda saline soil remediation agent prepared in Example 4 was used as a base fertilizer, the rice grain yield exceeded that of the CF group when the application rate reached 0.60% of the soil mass. Furthermore, the application of low-dose bamboo-based soda saline soil remediation agent did not reduce rice yield, showing no significant difference from the CF group. With the increase in the application rate of the bamboo-based soda saline soil remediation agent prepared in Example 4, the rice yield showed a synchronous upward trend, indicating that this bamboo charcoal organic fertilizer has a significant promoting effect on rice yield. The rice grain yield reached its peak when the application rate was 2.40% of the soil mass.

[0060] Depend on Figure 5 Data shows that applying different concentrations of bamboo-based soda ash soil remediation agent can significantly reduce cadmium content in rice grains, demonstrating good heavy metal stabilization effects on lightly and moderately polluted soils. The most significant reduction was observed when the ratio of bamboo-based soda ash soil remediation agent application rate to soil mass was 0.90%, with a cadmium content in rice grains reduced by approximately 40% compared to the control group (CK). Furthermore, a relatively significant reduction was also observed when the ratio of bamboo-based soda ash soil remediation agent application rate to soil mass was 0.15%.

[0061] In summary, the application of this bamboo charcoal organic fertilizer can simultaneously achieve the dual effects of significantly reducing the cadmium content in rice grains and promoting rice yield. Specifically, the highest rice yield was observed when the application rate was 2.4% of the soil mass, significantly higher than that of the CF group; the lowest cadmium content in rice grains was observed when the application rate was 1.2% of the soil mass, demonstrating the optimal cadmium reduction effect.

[0062] The aforementioned synergistic effect is mainly attributed to the synergistic effect of the two core components in the bamboo-based soda saline soil remediation agent: On the one hand, the well-rotted bamboo-based organic matter has a moderate carbon-nitrogen ratio and a near-neutral pH, effectively avoiding the soil nitrogen fixation problem caused by unrotted materials with a high carbon-nitrogen ratio, and providing a stable and slow-release nutrient environment for crops; at the same time, its rich humic substances can react with Cd 2+ This forms a stable organometallic complex, reducing the solubility and bioavailability of cadmium. On the other hand, modified bamboo charcoal exhibits a high concentration of 38–45 cmol. + With a cation exchange capacity of / kg, and through surface-grafted carboxyl and phosphate functional groups, it efficiently adsorbs and immobilizes free Cd in the soil. 2+ It significantly reduces its migration and accumulation to plant roots.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bamboo-based soda-based saline soil remediation agent, characterized in that, The bamboo-based soda saline soil remediation agent is composed of the following components in parts by weight: 46-50 parts of decomposed bamboo-based organic matter, 31-36 parts of modified bamboo charcoal, 10-13 parts of potassium humate, 5-6 parts of desulfurized gypsum, and 1-3 parts of iron-zinc-manganese chelate. The decomposed bamboo-based organic matter is a moso bamboo-derived organic material that has undergone aerobic fermentation treatment, with a carbon-to-nitrogen ratio of 21–23:

1. When mixed with water at a mass ratio of 1:10, the pH is 7.8–8.0, and the seed germination index (GI) is not less than 80%. The modified bamboo charcoal is prepared by synergistic modification of bamboo charcoal with citric acid and phytic acid, and its surface is grafted with carboxyl and phosphate functional groups, with a cation exchange capacity of 38-45 cmol. + / kg.

2. The bamboo-based soda-based saline soil remediation agent according to claim 1, characterized in that, The preparation method of the decomposed bamboo-based organic matter includes the following steps: 100 parts of bamboo powder, 10-15 parts of soybean meal, 5-8 parts of phosphogypsum powder, 1-2 parts of urea, and 0.5-1.0 parts of alkali-resistant compound fermentation agent are mixed evenly to obtain a mixture; deionized water is added to the mixture to adjust the moisture content to 65%-70%; the mixture is subjected to aerobic decomposition fermentation, maintaining the center temperature of the pile at 55-62℃, turning it over once every 12 hours for the first 3 days, and once every 24 hours from the 4th to the 7th day, with a fermentation cycle of 7 days, to obtain the decomposed bamboo-based organic matter.

3. The bamboo-based soda-based saline soil remediation agent according to claim 2, characterized in that, The preparation of the bamboo powder includes the following steps: taking healthy bamboo aged 3-5 years and cutting it into bamboo segments; placing the bamboo segments in a citric acid aqueous solution with a mass fraction of 0.5%-1.0% and extracting it for 2-3 hours under ultrasonic power of 200 W-300 W, frequency of 35 kHz-45 kHz, and temperature of 40℃-50℃; taking out the extracted bamboo segments, rinsing them with deionized water until the surface pH value is 6.5-7.5, and then drying them at 60℃ until the moisture content is ≤10%; pulverizing and sieving the dried bamboo segments to obtain bamboo powder with a particle size ≤2 mm.

4. The bamboo-based soda-based saline soil remediation agent according to claim 2 or 3, characterized in that, The alkali-resistant compound fermentation agent is composed of alkali-resistant nitrogen-fixing bacteria (Azotobacter alkalitolerans), alkaliphilus cellulolytic bacteria (Alkaliphilus cellulolyticus), and Bacillus mucilaginosus in a mass ratio of (2-3):(1-2):1, with a total viable count of not less than 5×10^8 CFU / g.

5. The bamboo-based soda-based saline soil remediation agent according to claim 1, characterized in that, The method for preparing the modified bamboo charcoal includes the following steps: placing bamboo processing residue in a nitrogen atmosphere tube furnace and pyrolyzing it at 480–520℃ for 1.0–2.5 h; after naturally cooling to room temperature, pulverizing and sieving to collect bamboo charcoal with a particle size of 0.5–2.0 mm; dissolving citric acid and phytic acid in deionized water at a mass ratio of (2–6):1 to prepare a mixed aqueous solution with a total organic acid concentration of 8–12 wt%; mixing the bamboo charcoal and the mixed aqueous solution at a solid-liquid ratio of 1:(3–4) kg / L, ultrasonically treating it at 58–65℃ for 0.8–1.2 h, then raising the temperature to 88–95℃ and stirring at 300–400 rpm for 2.5–3.5 h; after the reaction, separating the solid and liquid phases, collecting the solid product, vacuum drying it at 58–65℃ for 6–8 h, and then heat-treating it in air at 190–205℃ for 1.0–2.5 h. h, after cooling, the modified bamboo charcoal is obtained.

6. The bamboo-based soda-based saline soil remediation agent according to claim 1, characterized in that, The iron-zinc-manganese chelate is a mixture of sodium iron ethylenediaminetetraacetate, zinc chelate citric acid, and manganese chelate citric acid, with a mass ratio of (2-3):1:

1.

7. A method for preparing a bamboo-based soda-based saline soil remediation agent as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Add decomposed bamboo-based organic matter, modified bamboo charcoal, potassium humate, and desulfurized gypsum into a mixer and mix at 15-25 rpm for 20-30 minutes at room temperature to obtain a dry mixture. S2. Dissolve the iron-zinc-manganese chelate in 3 to 5 times its total mass of deionized water to prepare a chelation solution. Under stirring at 15 to 25 rpm, spray the chelation solution evenly into the dry mixture and continue mixing at the same speed for 10 to 15 minutes. Then, ventilate and dry at 40 to 45°C until the moisture content is not higher than 12% to obtain the bamboo-based soda saline soil remediation agent.

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