A salt-alkali tolerant organic water-soluble fertilizer and its preparation method

Abstract

This application provides a salt-alkali tolerant organic water-soluble fertilizer and its preparation method. The salt-alkali tolerant organic water-soluble fertilizer comprises the following raw materials in parts by weight: 100 parts sulfonated-carboxymethylated humic acid Ca / K complex salt, 30-150 parts water-soluble potassium source, 10-100 parts water-soluble nitrogen source, 5-80 parts water-soluble phosphorus source, 5-50 parts compound amino acid powder, 0.1-3 parts water-soluble iron salt, 0.1-3 parts water-soluble manganese salt, 0.1-3 parts water-soluble zinc salt, 0.1-3 parts water-soluble copper salt, and 0.1-3 parts water-soluble boron source; wherein, the sulfonated-carboxymethylated humic acid Ca / K complex salt is obtained by first carboxylating and then sulfonating potassium humate, followed by ion exchange with calcium ions. The aforementioned salt- and alkali-tolerant organic water-soluble fertilizer can maintain the stable existence of trace metal elements in a saline-alkali environment, significantly improve the absorption efficiency of trace elements by plants, and further promote the utilization of macronutrients by plants, thereby improving the growth performance of crops under salt- and alkali stress.

Description

Technical Field

[0001] This application relates to the field of fertilizer technology, specifically to a salt-alkali tolerant organic water-soluble fertilizer and its preparation method. Background Technology

[0002] Saline-alkali soils are widely distributed and characterized by high soil pH, high soluble salt content, and unstable rhizosphere ion environment. Under these conditions, plant growth is often subjected to multiple stresses, among which the availability of trace metal elements (such as iron, manganese, zinc, and copper) in the rhizosphere is significantly reduced, which is one of the important reasons for slow crop growth, leaf chlorosis, and hindered root development.

[0003] Under high salinity and high pH conditions, trace metal elements such as iron, manganese, zinc, and copper readily react with carbonate, hydroxide, or phosphate ions in the soil to form insoluble precipitates, leading to a significant reduction in their effective concentration in the rhizosphere environment. For example, Fe... 3+ and Mn 2+ Hydroxide precipitation occurs significantly at pH levels above 8, Zn 2+ Cu 2+ Micronutrients are also affected by competitive adsorption and precipitation reactions of salt ions, making it difficult for plants to absorb these essential metal elements for maintaining metabolism and chlorophyll formation. Insufficient micronutrient supply further affects the absorption and utilization of macronutrients (nitrogen, phosphorus, and potassium). For example, under iron or zinc deficiency conditions, root respiration, energy metabolism, and membrane transport protein activity decrease, leading to a reduced rate of nitrogen absorption by the roots. Manganese deficiency inhibits electron transport in photosynthetic system II, reducing the plant's efficiency in utilizing phosphorus and potassium. Therefore, the inhibition of micronutrient absorption by saline-alkali soil will have a cascading effect on the overall nutrient utilization capacity of plants.

[0004] To address the problem of micronutrient failure under saline-alkali conditions, existing technologies mainly improve the situation through the following methods: First, applying large amounts of organic matter to improve soil structure and alleviate salt damage, but this is slow to take effect and requires high application rates; second, supplementing with inorganic salts of micronutrients such as iron, zinc, and manganese, but these are still prone to precipitation and failure under high pH conditions; and third, using chelated micronutrient fertilizers such as EDTA and DTPA to improve their water solubility and stability, but their stability under strongly alkaline conditions is still limited, and the chelating agents themselves cannot improve rhizosphere salt pressure.

[0005] Therefore, existing fertilizers for saline-alkali land still fall short in improving the availability of micronutrients. There is an urgent need for an organic water-soluble fertilizer that can stabilize the form of metal ions in a saline-alkali environment, improve the availability of micronutrients in the rhizosphere, and promote the absorption of various nutrients by plants, thereby improving the growth performance of crops in saline-alkali soil. Summary of the Invention

[0006] This application provides a salt- and alkali-tolerant organic water-soluble fertilizer and its preparation method, aiming to solve the problem that existing fertilizers are prone to the degradation of trace metal elements and have insufficient rhizosphere availability under high salt and high pH environments, thus affecting the absorption and utilization of various nutrients by plants.

[0007] In a first aspect, this application provides a salt- and alkali-resistant organic water-soluble fertilizer, comprising the following raw materials in parts by weight:

[0008] 100 parts sulfonated-carboxymethylated humic acid Ca / K double salt, 30-150 parts water-soluble potassium source, 10-100 parts water-soluble nitrogen source, 5-80 parts water-soluble phosphorus source, 5-50 parts compound amino acid powder, 0.1-3 parts water-soluble iron salt, 0.1-3 parts water-soluble manganese salt, 0.1-3 parts water-soluble zinc salt, 0.1-3 parts water-soluble copper salt, 0.1-3 parts water-soluble boron source;

[0009] The sulfonated-carboxymethylated humic acid Ca / K complex salt is obtained by first carboxymethylating and then sulfonating potassium humate, followed by ion exchange with calcium ions.

[0010] According to this application, the above-mentioned salt-alkali tolerant organic water-soluble fertilizer can maintain the stable existence of trace metal elements in a saline-alkali environment, significantly improve the absorption efficiency of plants for trace elements such as iron, manganese, zinc, and copper, and further promote the utilization of macronutrients such as nitrogen, phosphorus, and potassium by plants, thereby improving the growth performance of crops under salt-alkali stress.

[0011] Specifically, the sulfonated-carboxymethylated humic acid Ca / K double salt used in this application has a unique multi-coordination group structure, and its molecule simultaneously contains highly metal-philic functional groups such as sulfonic acid group, carboxyl group, carboxymethyl group, and phenolic oxygen group, and in Ca 2+ After exchange, a stable bridging dispersion structure is formed. This structure retains strong electronegativity and good solubility under high pH and high salt concentration conditions, avoiding the problem of flocculation and sedimentation of unmodified humic acid under alkaline conditions. The large number of hydrophilic anionic groups introduced after carboxymethylation and sulfonation can affect Fe... 2+ / Fe 3+ Mn 2+ Zn 2+ Cu 2+ This allows metal ions to form more stable multi-point complexes, ensuring that these trace elements remain in a soluble complex state at pH 8-10, reducing the risk of hydroxide precipitation. Compared to unmodified humic acid, this double salt exhibits higher solubility and ion stability in saline-alkali environments; it also has a synergistic effect in mitigating rhizosphere salt damage. (Ca...) 2+ The bridging structure can inhibit the coiling and shrinkage of humic acid molecules, making the complexation sites more easily exposed, which is conducive to the formation of a stable colloidal protective layer, thereby further preventing metal ions from instantaneously precipitating due to local high pH.

[0012] Meanwhile, water-soluble nitrogen, phosphorus, and potassium sources provide plants with essential macronutrients, and with the improved supply of micronutrients, they can be absorbed and utilized more efficiently by the roots. The compound amino acid powder can enhance root cell activity and promote the absorption of metal ions and macronutrients. The iron, manganese, zinc, and copper salts exhibit good compatibility with sulfonated-carboxymethylated humic acid Ca / K complex salts, maintaining stable dispersion in solution through complexation and adsorption, thus improving the efficiency of micronutrient supply. The boron source helps maintain cell wall structure and root tip growth, further enhancing the root system's ability to absorb nutrients.

[0013] Through the synergistic effect of the above-mentioned actions, the water-soluble fertilizer of this application can significantly improve the stability and availability of trace metal elements in saline-alkali environments, thereby improving the overall nutrient absorption efficiency of plants.

[0014] In some embodiments, the sulfonated-carboxymethylated humic acid Ca / K complex salt is prepared by the following steps:

[0015] S1: Disperse potassium humate and chloroacetate in water, so that some of the phenolic anions in potassium humate react with chloroacetate to undergo carboxymethylation reaction, and obtain carboxymethylated potassium humate aqueous solution;

[0016] S2: Add bisulfite to the aqueous solution of carboxymethylated potassium humate, so that the phenolic anion in the carboxymethylated potassium humate reacts with the bisulfite to produce an aqueous solution of sulfonated-carboxymethylated potassium humate.

[0017] S3: Add water-soluble calcium salt to the aqueous solution of the sulfonated-carboxymethylated potassium humate salt, so that the water-soluble calcium salt and the sulfonated-carboxymethylated potassium humate salt undergo cation exchange to obtain the sulfonated-carboxymethylated humic acid Ca / K double salt.

[0018] In some of the above embodiments, carboxymethylation, sulfonation, and Ca are performed sequentially. 2+ Ion exchange allows humic acid molecules to gradually incorporate more hydrophilic and charged groups, ultimately forming Ca2+. 2+A stable complex salt structure. Carboxymethylation improves the solubility and reactivity of humic acid, providing more reactive sites for subsequent sulfonation. Sulfonation significantly enhances the hydrophilicity and ionization of the molecule, maintaining good dispersion under alkaline conditions. Stepwise modification introduces or exposes more carboxyl groups on the humic acid molecule. The increased electron cloud density near the carboxyl groups facilitates sulfonation, creating more sulfonation sites. Improved water solubility and dispersibility fully expose embedded phenolic hydroxyl groups, further creating active sites. The introduction or exposure of more carboxyl groups also anchors sulfites through hydrogen bonding, leading to more sulfonation near the carboxyl groups. This further enhances the synergistic effect of carboxyl chelation of trace elements and soil improvement, while sulfonic acid groups improve water solubility and salt tolerance. Compared to simultaneous carboxymethylation and sulfonation, this application demonstrates superior performance in fertilizer application through precise molecular structure design. 2+ The introduction of [a specific ingredient] can form a more stable complex ionic structure, giving the resulting complex salt better solubility, structural stability, and salt resistance, making it more suitable for use in saline-alkali environments. The above stepwise structural control method ensures the controllability of the complex salt formation process and the consistency of product properties.

[0019] In some embodiments, step S1 includes:

[0020] Disperse 100 parts of potassium humate and 10-30 parts of chloroacetate in 300-500 parts of water, and react at pH 10-11 and 55-65℃ for 2-4 hours to obtain an aqueous solution of carboxymethylated potassium humate.

[0021] In some of the above embodiments, by controlling the pH at 10-11 and the reaction temperature at 55-65°C, the phenolic oxygen groups on the humic acid molecular chain can be more fully activated, which is beneficial for the selective nucleophilic substitution reaction of chloroacetate, thereby increasing the degree of carboxymethylation. The increased degree of carboxymethylation can increase the overall hydrophilicity and the number of anionic groups in the humic acid molecule, thus improving the subsequent sulfonation reaction and the final CaO reaction. 2+ The Ca / K double salt structure formed by the exchange is more stable. By comprehensively controlling the above conditions, carboxymethylated potassium humate with better solubility and more uniform structure can be obtained without increasing the reaction burden, providing a better reaction basis for subsequent sulfonation and calcium exchange steps.

[0022] In some implementations, step S2 includes:

[0023] Add 10-30 parts of bisulfite to the carboxymethylated potassium humate aqueous solution and react at pH 8-9 and 60-70℃ for 2-4 hours to obtain sulfonated-carboxymethylated potassium humate aqueous solution.

[0024] In some of the above embodiments, by controlling the reaction pH within a mild temperature range of 8-9 and maintaining it within 60-70°C, the nucleophilic substitution reaction of bisulfite on phenolic groups can be promoted, allowing the sulfonated groups to be introduced more uniformly and fully into the humic acid molecule, thereby increasing the hydrophilicity and anionic group density of the resulting sulfonated-carboxymethyl humic acid. An appropriate amount of bisulfite added can ensure the sulfonation reaction proceeds without excessive side reactions, contributing to the formation of a more stable high-charge-density humic acid structure, thus providing a foundation for subsequent Ca... 2+ The exchange and trace element complexation provide more coordination sites; at the same time, it can take into account the number of characteristic groups of sulfonic acid and carboxylic acid, thus achieving better synergistic effects.

[0025] In some implementations, step S3 includes:

[0026] Add 10-20 parts of water-soluble calcium salt to the aqueous solution of the sulfonated-carboxymethylated potassium humate, and perform ion exchange at pH 6-7 and 40-50℃ for 0.5-1 h to obtain the sulfonated-carboxymethylated humic acid Ca / K double salt.

[0027] In some of the above embodiments, by controlling the amount of water-soluble calcium salt added to 10-20 parts and conducting ion exchange at 40-50°C in a weakly acidic to neutral environment with pH=6-7, calcium ions can more fully replace potassium ions in humic acid molecules, thereby increasing the calcium content. 2+ This increases the exchange rate and reduces the content of unexchanged free potassium salts in the system. Appropriate temperature and pH conditions can prevent secondary condensation or partial precipitation of humic acid in acidic or alkaline environments, thus allowing Ca... 2+ The bridging structure forms more uniformly, resulting in a well-dispersed Ca / K double salt system. Furthermore, an exchange time of 0.5–1 hour is sufficient to essentially complete the Ca exchange at the complexation sites. 2+ Substitution helps to obtain structurally stable and highly soluble humic acid Ca / K complex salts, providing a more suitable basic system for the subsequent complexation and stabilization of trace elements.

[0028] In some embodiments, the water-soluble calcium salt includes a water-soluble organic calcium salt and a water-soluble inorganic calcium salt, wherein the mass ratio of the water-soluble organic calcium salt to the water-soluble inorganic calcium salt is 1:1 to 2.

[0029] In some of the above embodiments, the inventors discovered that when the water-soluble calcium salt simultaneously contains organic and inorganic calcium salts, and their mass ratio is controlled within the range of 1:1 to 2, a better plant growth-promoting effect can be obtained under salt-alkali stress conditions. This may be because organic calcium salts (such as calcium citrate and calcium gluconate) release Ca2+ in solution. 2+ The slower speed is beneficial to Ca 2+Uniform and gentle ion exchange occurs along the molecular chain segments of humic acid, maintaining a high degree of expansion of the humic acid molecules and thus exposing more sulfonic acid and carboxyl complexation sites. Meanwhile, inorganic calcium salts (such as calcium chloride and calcium nitrate) have high solubility and rapid ion dissociation rates, quickly providing a certain concentration of Ca in the initial stage of the reaction. 2+ Promote the K in the humic acid skeleton + Rapid exchange occurs, leading to the initial establishment of the Ca-bridged structure. The synergistic effect of both can form a relatively stable Ca / K double salt structure during the "rapid exchange-uniform rearrangement" process, allowing the humic acid molecular chain to be in a more extended state, reducing intra-chain association, and exposing the coordinating groups in the solution in a more accessible manner.

[0030] Based on this structure, Fe 2+ / Fe 3+ Mn 2+ Zn 2+ Cu 2+ Trace metal elements are more likely to form stable multi-point complexes in water-soluble fertilizer systems, making them less prone to hydroxide precipitation induced by localized high pH levels. Simultaneously, the Ca-bridged humic acid structure provides stronger colloidal protection for metal ions, slowing down the free aggregation and adsorption loss of trace elements, thereby increasing their stable existence time in saline-alkali environments. Due to the compounding of Ca... 2+ The system can enhance the uniformity of humic acid molecular structure and the effective exposure of metal complexation sites. Compared with single organic calcium salts or single inorganic calcium salts, it can further improve the stability and availability of trace metal elements in saline-alkali environments and improve the overall nutrient absorption efficiency of plants.

[0031] In some embodiments, the water-soluble organic calcium salt includes at least one of calcium citrate and calcium gluconate; the water-soluble inorganic calcium salt includes at least one of calcium chloride and calcium nitrate.

[0032] In some of the above embodiments, calcium citrate and calcium gluconate have high water solubility and certain coordination ability, enabling them to form stable temporary bonds with the multi-coordination groups in sulfonated-carboxymethylated humic acid during ion exchange, which is beneficial to Ca... 2+ The slow release allows it to enter the complex salt structure. Calcium chloride and calcium nitrate, on the other hand, have high solubility and provide Ca. 2+ Its high rate allows for a rapid increase in the Ca content of the system during the initial stages of the exchange reaction. 2+ The concentration allows for the rapid establishment of Ca-bridged structures. This, in turn, enables the resulting sulfonated-carboxymethylated humic acid Ca / K double salt to further enhance the absorption of micronutrients by plants in saline-alkali environments, thereby improving the overall nutrient absorption efficiency of plants.

[0033] In some embodiments, the salt-alkali resistant organic water-soluble fertilizer is a solid powder, granules, or liquid aqueous solution.

[0034] In some of the above embodiments, the diversification of product forms allows the water-soluble fertilizer to be suitable for different application methods and crop types. For example, solid powders and granules are easy to transport and store and can be used for basal application or fertigation; liquid aqueous solutions have better solubility and are suitable for drip irrigation or foliar spraying, and can provide available trace elements and organic nutrients to the rhizosphere more quickly in saline-alkali environments.

[0035] In some embodiments, the water-soluble potassium source includes at least one of potassium sulfate and potassium nitrate. Based on the above embodiments, potassium sulfate and potassium nitrate have high water solubility and can rapidly provide absorbable potassium ions in saline-alkali environments, which helps maintain rhizosphere osmotic pressure balance and enhances the plant's salt tolerance.

[0036] In some embodiments, the water-soluble nitrogen source includes at least one of ammonium nitrate and urea. Based on the above embodiments, both nitrate nitrogen and amide nitrogen can provide stable nitrogen sources for plants, enabling plants to utilize nitrogen sources more fully for growth under conditions of improved micronutrient supply.

[0037] In some embodiments, the water-soluble phosphorus source includes at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. Based on the above embodiments, these water-soluble phosphorus sources can maintain a higher effective phosphorus concentration in the presence of sulfonated-carboxymethylated humic acid Ca / K complex salts, which is beneficial to root energy metabolism and growth and development.

[0038] In some embodiments, the composite amino acid powder is derived from hydrolyzed animal hair keratin. Based on the above embodiments, this source of composite amino acids contains a variety of small molecule amino acids and peptides, which can promote root activity and improve the absorption of trace elements and macroelements.

[0039] In some embodiments, the water-soluble iron salt includes at least one of ferrous sulfate and ferric chloride. Based on the above embodiments, the water-soluble iron salt is more easily maintained in an absorbable form under the multi-point complexation of sulfonated-carboxymethylated humic acid Ca / K double salt, thereby reducing precipitation failure under saline-alkali conditions.

[0040] In some embodiments, the water-soluble manganese salt includes at least one of manganese sulfate and manganese chloride. Based on the above embodiments, the complexing and dispersing effects provided by the sulfonated-carboxymethylated humic acid Ca / K complex salt can maintain good stability of manganese ions under high pH conditions, avoiding premature formation of insoluble precipitates.

[0041] In some embodiments, the water-soluble zinc salt includes at least one of zinc sulfate and zinc chloride. Based on the above embodiments, since zinc ions readily precipitate in saline-alkali environments, their effective content in the rhizosphere can be increased by combining them with sulfonated-carboxymethylated humic acid Ca / K double salts.

[0042] In some embodiments, the water-soluble copper salt includes at least one of copper sulfate and copper chloride. Based on the above embodiments, the multi-point complexation of sulfonated-carboxymethylated humic acid Ca / K complex salts can improve the stability of copper ions, making them more easily maintained in an absorbable state under saline-alkali conditions.

[0043] In some embodiments, the water-soluble boron source includes at least one of boric acid and borax tetrahydrate. Based on the above embodiments, the water-soluble boron source can be released more stably under the buffering effect of the sulfonated-carboxymethylated humic acid Ca / K double salt system, which helps maintain healthy root tip elongation and plant cell wall structure.

[0044] Secondly, this application provides a method for preparing a salt- and alkali-tolerant organic water-soluble fertilizer, comprising:

[0045] Provide the raw materials according to any embodiment of the first aspect;

[0046] The raw materials are mixed to obtain a salt- and alkali-resistant organic water-soluble fertilizer.

[0047] According to this application, the above method can obtain an organic water-soluble fertilizer with good salt and alkali adaptability by directly mixing the raw materials. The overall process is simple and the conditions are mild, making it suitable for continuous industrial production.

[0048] In practical use, the obtained salt- and alkali-tolerant organic water-soluble fertilizer can be dissolved in water to achieve a solid content within a suitable range, such as 0.05% to 0.5%. This allows for the rapid formation of an effective complexed metal ion supply system in the rhizosphere environment. After dissolving in water, the trace elements complex with the multi-coordination groups (such as sulfonic acid groups, carboxyl groups, and carboxymethyl groups) in the sulfonated-carboxymethylated humic acid Ca / K complex salt, thus maintaining soluble stability even in high-salt and high-pH environments. This improves their absorption efficiency on plant roots, ultimately promoting plant growth.

[0049] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0050] This application constructs a sulfonated-carboxymethylated humic acid Ca / K complex salt as the core organic complexing-stabilizing system, enabling trace metal elements (such as iron, manganese, zinc, and copper) to exist in a stable complexed state under saline-alkali conditions. This significantly reduces the risk of them forming hydroxide, carbonate, or phosphate precipitation in high pH and high salt ionic strength environments. Compared to the problems of conventional humic acid water-soluble fertilizers, such as easy flocculation and sedimentation and insufficient complexing ability in alkaline environments, and the defects of traditional chelating agents such as EDTA and DTPA, such as easy disruption of complexation balance and possible dissociation and precipitation of some metals under strong alkaline conditions, the sulfonated-carboxymethylated humic acid Ca / K complex salt used in this application can maintain good solubility, strong multi-point synergistic complexing ability, and rhizosphere salt buffering capacity under high salt and high pH conditions, and can more effectively maintain the availability of metal ions. Therefore, the water-soluble fertilizer provided in this application can improve the absorption efficiency of micronutrients by plants under saline-alkali conditions, thereby promoting the absorption and utilization of macronutrients such as nitrogen, phosphorus, and potassium by the roots, and improving the overall growth performance of crops in saline-alkali land. Detailed Implementation

[0051] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0055] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0056] Potassium humate was purchased from Jinan Jiayang Chemical Co., Ltd.

[0057] The compound amino acid powder was purchased from Jinan Chaoyixing Chemical Co., Ltd., and is derived from hydrolyzed animal hair keratin.

[0058] Preparation Example 1

[0059] Preparation of sulfonated-carboxymethylated humic acid Ca / K double salts:

[0060] Add 400 parts of deionized water to a reaction vessel, start stirring, and slowly add 100 parts of potassium humate until it is completely dispersed into a homogeneous dark brown solution. Adjust the pH of the system to 10.5 at room temperature and add an appropriate amount of potassium hydroxide solution to maintain alkalinity. Then add 20 parts of sodium chloroacetate, raise the temperature to 60°C, and react for 3 hours under continuous stirring. After the reaction is completed, cool to below 40°C to obtain an aqueous solution of carboxymethylated potassium humate.

[0061] Add 20 parts of sodium bisulfite to the above carboxymethylated potassium humate solution and stir slowly until fully dissolved. Adjust the pH of the system to 8.5, raise the temperature to 65℃ and maintain the reaction for 3 hours; after the reaction is completed, cool to obtain an aqueous solution of sulfonated-carboxymethylated potassium humate.

[0062] Under stirring, the above-mentioned sulfonated-carboxymethylated potassium humate aqueous solution was heated to 45°C, and 15 parts of water-soluble calcium salt were slowly added. The water-soluble calcium salt was a mixture of calcium citrate and calcium chloride at a mass ratio of 1:1.5, so that Ca... 2+ It can undergo an ion exchange reaction with sulfonated-carboxymethylated potassium humate molecules, and the pH of the system is controlled in the range of 6 to 7. After the reaction continues for 1 hour, the system is naturally cooled to room temperature to obtain an aqueous solution of sulfonated-carboxymethylated humic acid Ca / K double salt.

[0063] The solution was concentrated under reduced pressure in a 55°C water bath, with the final solid content controlled at 30%–40%, to obtain a concentrated solution. The concentrated solution was then sent to a spray dryer and spray dried at an inlet air temperature of 170°C and an outlet air temperature of 85°C. The resulting brownish-black powder was collected and identified as sulfonated-carboxymethylated humic acid Ca / K double salt A.

[0064] Preparation Example 2

[0065] Preparation of sulfonated-carboxymethylated humic acid Ca / K double salts:

[0066] The preparation method is largely the same as in Example 1, except that all the water-soluble calcium salts are calcium citrate, and the final product is sulfonated-carboxymethylated humic acid Ca / K double salt B.

[0067] Preparation Example 3

[0068] Preparation of sulfonated-carboxymethylated humic acid Ca / K double salts:

[0069] The preparation method is largely the same as in Example 1, except that the water-soluble calcium salt is a mixture of calcium citrate and calcium chloride at a mass ratio of 1:0.5, and the final product is sulfonated-carboxymethylated humic acid Ca / K double salt C.

[0070] Preparation Example 4

[0071] Preparation of sulfonated-carboxymethylated humic acid Ca / K double salts:

[0072] The preparation method is largely the same as in Example 1, except that the water-soluble calcium salt is a mixture of calcium citrate and calcium chloride at a mass ratio of 1:2.5, and the final product is sulfonated-carboxymethylated humic acid Ca / K double salt D.

[0073] Preparation Example 5

[0074] Preparation of sulfonated-carboxymethylated humic acid Ca / K double salts:

[0075] The preparation method is largely the same as in Example 1, except that all water-soluble calcium salts are calcium chloride, and the final product is sulfonated-carboxymethylated humic acid Ca / K double salt E.

[0076] Comparative Preparation Example 1

[0077] Preparation of sulfonated-carboxymethylated potassium humate:

[0078] Add 400 parts of deionized water to a reaction vessel, start stirring, and slowly add 100 parts of potassium humate until it is completely dispersed into a homogeneous dark brown solution. Adjust the pH of the system to 10.5 at room temperature and add an appropriate amount of potassium hydroxide solution to maintain alkalinity. Then add 20 parts of sodium chloroacetate, raise the temperature to 60°C, and react for 3 hours under continuous stirring. After the reaction is completed, cool to below 40°C to obtain an aqueous solution of carboxymethylated potassium humate.

[0079] Add 20 parts of sodium bisulfite to the above carboxymethylated potassium humate solution and stir slowly until fully dissolved. Adjust the pH of the system to 8.5, raise the temperature to 65℃ and maintain the reaction for 3 hours; after the reaction is completed, cool to obtain an aqueous solution of sulfonated-carboxymethylated potassium humate.

[0080] The above aqueous solution was concentrated under reduced pressure in a water bath at 55°C, with the final solid content controlled at 30%~40%, to obtain a concentrated solution. The concentrated solution was then sent to a spray drying apparatus and spray dried at an inlet air temperature of 170°C and an outlet air temperature of 85°C. The resulting brownish-black powder was collected and identified as sulfonated-carboxymethylated potassium humate.

[0081] Comparative Preparation Example 2

[0082] Preparation of carboxymethylated humic acid Ca / K double salt:

[0083] Add 400 parts of deionized water to a reaction vessel, start stirring, and slowly add 100 parts of potassium humate until it is completely dispersed into a homogeneous dark brown solution. Adjust the pH of the system to 10.5 at room temperature and add an appropriate amount of potassium hydroxide solution to maintain alkalinity. Then add 40 parts of sodium chloroacetate, raise the temperature to 60°C, and react for 5 hours under continuous stirring. After the reaction is completed, cool to below 40°C to obtain an aqueous solution of carboxymethylated potassium humate.

[0084] Under stirring, the above carboxymethylated potassium humate aqueous solution was heated to 45°C, the pH was adjusted to 7, and 15 parts of water-soluble calcium salt were slowly added. The water-soluble calcium salt was a mixture of calcium citrate and calcium chloride at a mass ratio of 1:1.5, so that Ca... 2+ It can undergo an ion exchange reaction with carboxymethylated potassium humate molecules. The pH of the system is controlled within the range of 6 to 7. After the reaction continues for 1 hour, the system is naturally cooled to room temperature to obtain an aqueous solution of carboxymethylated humic acid Ca / K double salt.

[0085] The solution was concentrated under reduced pressure in a 55°C water bath, with the final solid content controlled at 30%–40%, to obtain a concentrated solution. The concentrated solution was then sent to a spray dryer and spray dried at an inlet air temperature of 170°C and an outlet air temperature of 85°C. The resulting brownish-black powder was collected and identified as carboxymethyl humic acid Ca / K double salt.

[0086] Comparative preparation example 3

[0087] Preparation of sulfonated humic acid Ca / K double salt:

[0088] Add 400 parts of deionized water to the reactor, start stirring, and slowly add 100 parts of potassium humate until it is completely dispersed into a homogeneous dark brown solution. Then add 40 parts of sodium bisulfite to adjust the pH of the system to 8.5, raise the temperature to 65°C and maintain the reaction for 5 hours. After the reaction is completed, cool to obtain an aqueous solution of sulfonated potassium humate.

[0089] Under stirring, the above-mentioned sulfonated potassium humate aqueous solution was heated to 45°C, and 15 parts of water-soluble calcium salt were slowly added. The water-soluble calcium salt was a mixture of calcium citrate and calcium chloride at a mass ratio of 1:1.5, so that Ca... 2+It can undergo an ion exchange reaction with potassium sulfonate molecules, and the pH of the system is controlled within the range of 6 to 7. After the reaction continues for 1 hour, the system is naturally cooled to room temperature to obtain an aqueous solution of sulfonated humic acid Ca / K double salt.

[0090] The solution was concentrated under reduced pressure in a 55°C water bath, with the final solid content controlled at 30%–40%, to obtain a concentrated solution. The concentrated solution was then sent to a spray dryer and spray dried at an inlet air temperature of 170°C and an outlet air temperature of 85°C. The resulting brownish-black powder was collected and identified as sulfonated humic acid Ca / K double salt.

[0091] Comparative preparation example 4

[0092] Preparation of carboxymethylated sulfonated humic acid Ca / K double salt:

[0093] Add 400 parts of deionized water to the reactor, start stirring, and slowly add 100 parts of potassium humate until it is completely dispersed into a homogeneous dark brown solution. Then add 20 parts of sodium bisulfite and 20 parts of sodium chloroacetate, and stir slowly until fully dissolved. Adjust the pH of the system to 9.5, raise the temperature to 65°C and maintain the reaction for 6 hours; after the reaction is completed, cool to obtain an aqueous solution of carboxymethylated sulfonated potassium humate.

[0094] Under stirring, the above carboxymethylated sulfonated potassium humate aqueous solution was heated to 45°C, and 15 parts of water-soluble calcium salt were slowly added. The water-soluble calcium salt was a mixture of calcium citrate and calcium chloride at a mass ratio of 1:1.5, so that Ca... 2+ It can undergo an ion exchange reaction with the aqueous solution of carboxymethyl sulfonated potassium humate. The pH of the system is controlled within the range of 6 to 7. After the reaction continues for 1 hour, the system is naturally cooled to room temperature to obtain an aqueous solution of carboxymethyl sulfonated humic acid Ca / K double salt.

[0095] The solution was concentrated under reduced pressure in a 55°C water bath, with the final solid content controlled at 30%–40%, to obtain a concentrated solution. The concentrated solution was then sent to a spray dryer and spray dried at an inlet air temperature of 170°C and an outlet air temperature of 85°C. The resulting brownish-black powder was collected and identified as carboxymethyl sulfonated humic acid Ca / K double salt.

[0096] Example 1

[0097] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0098] Salt-alkali tolerant organic water-soluble fertilizer is formulated according to the following mass parts: 100 parts sulfonated-carboxymethylated humic acid Ca / K double salt A, 80 parts potassium sulfate, 40 parts ammonium nitrate, 30 parts potassium dihydrogen phosphate, 20 parts compound amino acid powder, 1 part ferrous sulfate, 0.5 parts manganese sulfate, 0.5 parts zinc sulfate, 0.3 parts copper sulfate, and 0.3 parts boric acid;

[0099] All the above solid raw materials were added to the mixing tank in sequence, and an appropriate amount of deionized water was added to make the solid content of the system about 20%. The mixture was stirred for 30 minutes under high-speed shearing at room temperature to ensure that the components were fully dissolved and mixed evenly. The resulting mixture was then sent to a spray dryer and dried at an inlet air temperature of 150°C and an outlet air temperature of 80°C. The free-flowing light brown granular product was collected to obtain the salt-alkali resistant organic water-soluble fertilizer.

[0100] Example 2

[0101] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0102] Similar to Example 1, except that sulfonated-carboxymethylated humic acid Ca / K complex salt B is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0103] Example 3

[0104] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0105] Similar to Example 1, except that sulfonated-carboxymethylated humic acid Ca / K complex salt C is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0106] Example 4

[0107] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0108] Similar to Example 1, except that sulfonated-carboxymethylated humic acid Ca / K complex salt D is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0109] Example 5

[0110] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0111] Similar to Example 1, except that sulfonated-carboxymethylated humic acid Ca / K complex salt E is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0112] Comparative Example 1

[0113] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0114] Similar to Example 1, except that sulfonated-carboxymethylated potassium humate salt is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0115] Comparative Example 2

[0116] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0117] Similar to Example 1, except that sulfonated-carboxymethylated humic acid Ca / K complex salt A is replaced with carboxymethylated humic acid Ca / K complex salt.

[0118] Comparative Example 3

[0119] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0120] Similar to Example 1, except that sulfonated humic acid Ca / K complex salt is used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0121] Comparative Example 4

[0122] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0123] Similar to Example 1, except that the carboxymethylated sulfonated humic acid Ca / K complex salt of Comparative Preparation Example 4 was used instead of sulfonated-carboxymethylated humic acid Ca / K complex salt A.

[0124] Comparative Example 5

[0125] Preparation of salt-alkali tolerant organic water-soluble fertilizer:

[0126] Similar to Example 1, except that potassium humate is used instead of sulfonated-carboxymethylated humic acid Ca / K double salt A.

[0127] Test section

[0128] Hydroponic corn seedling growth experiment: Corn seedlings that are sensitive to trace elements were used in the experiment, and the same corn variety (Luyu No. 3) was selected as the test material. The seedlings were first raised in seedling trays in a conventional manner. When the seedlings grew to about 3 cm in root length and were growing uniformly, seedlings with consistent growth were selected and transferred to hydroponic containers.

[0129] Prepare a simulated saline-alkali mother liquor: the total salt concentration is about 0.45 wt% by mass-volume ratio, of which sodium chloride is 0.3 wt% and sodium carbonate is 0.15 wt%. Then adjust the pH to 9.0 with NaOH.

[0130] Preparation of hydroponic nutrient solution: The salt-tolerant organic water-soluble fertilizers obtained in each example and comparative example were added to the above simulated salt-alkali mother liquor at 0.1 wt% to obtain different hydroponic nutrient solutions.

[0131] The hydroponic nutrient solutions obtained in each of the embodiments and comparative examples were added to the hydroponic container. Each treatment was set up with 3 replicates, and 10 corn seedlings were placed in each replicate.

[0132] The hydroponic experiment was conducted in an artificial climate chamber, with daytime / nighttime temperatures set at 25℃ / 20℃, light / dark duration at 12h / 12h, and light intensity at 100% / 0%. The entire cultivation period was 15 days. The nutrient solution was changed every 3 days during the cultivation process. At the end of the experiment, the average plant height, average root length, average fresh weight, and average dry weight of the maize seedlings in each treatment were measured. The results are shown in Table 1.

[0133] Table 1

[0134]

[0135] According to Table 1, all examples showed higher plant height, root length, and fresh weight compared to Comparative Examples 1-4, indicating that the salt-alkali tolerant organic water-soluble fertilizer provided in this application can significantly improve the growth capacity of maize seedlings and improve the growth status of roots and aboveground parts under salt-alkali stress. This may be because, in Comparative Example 1, sulfonated-carboxymethylated potassium humate salt was used, which was not subjected to Ca... 2+ Exchange treatment, under high pH conditions, is more prone to chain coiling and local flocculation, and has limited ability to stabilize metal ions, resulting in partial precipitation of trace elements under saline-alkali conditions, and poor effect on promoting plant growth; in Comparative Example 2, carboxymethylated humic acid Ca / K double salt was used, without the introduction of sulfonic acid groups, thus lacking strong hydrophilic anionic groups, and the metal ion complexing ability in high salt systems is insufficient, easily leading to the precipitation of elements such as Fe and Mn in the rhizosphere, resulting in plant height and root length being lower than in the example; in Comparative Example 3, although sulfonated humic acid Ca / K double salt was used, carboxymethylation was not performed, resulting in a limited number of functional groups. The structure lacks sufficient complexation sites, resulting in weaker stability to metal elements compared to the dual-modified structure of this application. Its plant growth-promoting effect is also inferior to the examples. In Comparative Example 4, a carboxymethylated sulfonated humic acid Ca / K double salt was used. Although sulfonation and carboxymethylation were performed simultaneously, the sulfonation effect was limited and synergistically reduced with carboxymethylation. Therefore, its stability to metal elements is weaker than the double salt of this application with pre-carboxymethylation followed by carboxymethylation, and its plant growth-promoting effect is also inferior to the examples. In Comparative Example 5, ordinary potassium humate was used, lacking the dual-modified structure of sulfonation and carboxymethylation, and it was not treated with Ca... 2+ Ion exchange results in insufficient solubility and stability, and metal ion precipitation is more pronounced in saline-alkali environments, making it the worst performing comparative example.

[0136] As shown in Examples 1-5, the use of different Ca / K double salts has a significant impact on plant growth, indicating that the type of calcium salt and the ratio of organic to inorganic calcium affect the stability of the double salt structure and its ability to complex with metal ions. The calcium citrate:calcium chloride = 1:1.5 combination used in Example 1 was able to maintain the Ca / K ratio... 2+While improving exchange efficiency, it also ensures the most balanced Ca-bridge in the complex salt structure, thereby maintaining higher micronutrient stability and root absorption capacity in saline-alkali environments. Therefore, the plant height, root length, fresh weight, and dry weight of Example 1 are the highest among all groups, making it more suitable for promoting plant growth in saline-alkali environments.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A salt- and alkali-tolerant organic water-soluble fertilizer, characterized in that, Includes the following quantities of raw materials: 100 parts sulfonated-carboxymethylated humic acid Ca / K double salt, 30-150 parts water-soluble potassium source, 10-100 parts water-soluble nitrogen source, 5-80 parts water-soluble phosphorus source, 5-50 parts compound amino acid powder, 0.1-3 parts water-soluble iron salt, 0.1-3 parts water-soluble manganese salt, 0.1-3 parts water-soluble zinc salt, 0.1-3 parts water-soluble copper salt, 0.1-3 parts water-soluble boron source; The sulfonated-carboxymethylated humic acid Ca / K complex salt is prepared through the following steps: S1: Disperse 100 parts of potassium humate and 10-30 parts of chloroacetate in 300-500 parts of water, and react at pH 10-11 and 55-65℃ for 2-4 hours to obtain an aqueous solution of carboxymethylated potassium humate. S2: Add 10-30 parts of bisulfite to the carboxymethylated potassium humate aqueous solution and react at pH 8-9 and 60-70℃ for 2-4 hours to obtain sulfonated-carboxymethylated potassium humate aqueous solution. S3: Add 10-20 parts of water-soluble calcium salt to the aqueous solution of the sulfonated-carboxymethylated potassium humate, and perform ion exchange at pH 6-7 and 40-50℃ for 0.5-1 h to obtain the sulfonated-carboxymethylated humic acid Ca / K double salt.

2. The salt-alkali resistant organic water-soluble fertilizer according to claim 1, characterized in that, The water-soluble calcium salt includes water-soluble organic calcium salt and water-soluble inorganic calcium salt, and the mass ratio of the water-soluble organic calcium salt to the water-soluble inorganic calcium salt is 1:1~2.

3. The salt- and alkali-resistant organic water-soluble fertilizer according to claim 2, characterized in that, The water-soluble organic calcium salt includes at least one of calcium citrate and calcium gluconate; the water-soluble inorganic calcium salt includes at least one of calcium chloride and calcium nitrate.

4. The salt- and alkali-tolerant organic water-soluble fertilizer according to claim 1, characterized in that, The salt-alkali resistant organic water-soluble fertilizer is in the form of solid powder, granules, or liquid aqueous solution.

5. The salt- and alkali-tolerant organic water-soluble fertilizer according to any one of claims 1 to 4, characterized in that, The raw materials meet at least one of the following conditions: 1) The water-soluble potassium source includes at least one of potassium sulfate and potassium nitrate; 2) The water-soluble nitrogen source includes at least one of ammonium nitrate and urea; 3) The water-soluble phosphorus source includes at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; 4) The compound amino acid powder is derived from hydrolyzed animal hair keratin; 5) The water-soluble iron salt includes at least one of ferrous sulfate and ferric chloride; 6) The water-soluble manganese salt includes at least one of manganese sulfate and manganese chloride; 7) The water-soluble zinc salt includes at least one of zinc sulfate and zinc chloride; 8) The water-soluble copper salt includes at least one of copper sulfate and copper chloride; 9) The water-soluble boron source includes at least one of boric acid and borax tetrahydrate.

6. A method for preparing salt-alkali tolerant organic water-soluble fertilizer, characterized in that, include: Provide the raw materials according to any one of claims 1 to 5; The raw materials are mixed to obtain a salt- and alkali-resistant organic water-soluble fertilizer.

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