Agricultural modified humic acid-polyferric compound fertilizer for realizing high salt water content as well as preparation method and application of agricultural modified humic acid-polyferric compound fertilizer

Abstract

The invention discloses a preparation method and application of an agricultural modified humic acid-polyferric compound fertilizer for realizing high salt water content, and belongs to the technical field of agricultural resources and environment. The method mainly aims at solving the problem of utilization of high-salinity water such as brackish water and seawater which cannot be used for farmland irrigation due to over-high salinity or salinity. The method mainly comprises the following steps: firstly, dissolving humic acid in a KOH solution, adjusting the pH value, and catalyzing by using laccase to prepare a high-activity modified humic acid solution; then, adding a polyferric compound (such as polyferric phosphate) into the solution, reacting and drying to obtain a modified humic acid-polyferric compound fertilizer; and finally, adding the solid fertilizer into high-salinity water (such as brackish water and seawater), stirring, standing and filtering to obtain liquid, namely the irrigation nutritive water, which can be directly used for agricultural application such as irrigation, water culture and the like, so that'desalination and detoxification 'and'nutrition' are completed in one step.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of resources and environment, specifically relating to a method for the resource-based treatment of high-salinity water and its agricultural application, particularly a modified humic acid-polyferric compound fertilizer for high-salinity agricultural use, its preparation method, and its application. This invention aims to solve the bottleneck problem of severe water shortage for agricultural irrigation / hydroponics in freshwater-scarce regions, combining the attributes of environmental remediation technology and agricultural resource technology. Background Technology

[0002] Agricultural water use is the largest sector of global water consumption, accounting for approximately 70% of global freshwater consumption, and in some developing countries, this figure may even exceed 90%. Irrigation water constitutes the absolute majority of agricultural water use, typically accounting for over 70% of global agricultural water consumption, and even 60%-90% of total water consumption in some regions. Hydroponics is a highly efficient and cyclical form of agricultural water use, specifically referring to the use of nutrient solutions as a root growth medium and nutrient transport medium in soilless cultivation environments. Hydroponics has extremely high requirements for irrigation water quality. Conventional hydroponics requires the use of freshwater with low electrical conductivity to prepare nutrient solutions to avoid salt accumulation that could stress crop roots and to ensure accurate nutrient absorption. The scarcity of available freshwater resources for agriculture, including irrigation and hydroponics, is a significant bottleneck restricting the sustainable development of global agriculture.

[0003] On the one hand, agricultural production consumes a large amount of freshwater resources; on the other hand, there are vast amounts of highly saline water on Earth that cannot be directly used for irrigation. Highly saline water refers to water resources with excessively high salinity that are unusable, typically including brackish water and seawater. Brackish water is a naturally occurring, low-quality water resource, with a total dissolved solids (TDS) level typically exceeding 2000 mg / L and a sodium (Na+) concentration exceeding 100 mg / L. + Ca 2+ Cl - Mg 2+ High levels of certain chemical components make it unsuitable as a source of drinking water. In fact, highly saline water such as seawater and brackish water can be used for irrigation, but requires special processing or technology.

[0004] Currently, there are many technologies available, including distillation, electrodialysis, reverse osmosis, and nanofiltration. Currently, regarding the improvement of brackish water for irrigation, Chen Xueying et al. (application number: CN202410393367.8) developed a modular membrane distillation system, which uses solar photovoltaic panels and solar collectors to absorb solar energy to drive the membrane distillation system to treat brackish water. However, this system has many modules and a complex treatment process, which is not conducive to large-scale treatment and utilization. Li Yuan et al. (application number: CN201520311081.7) developed an agricultural brackish water treatment and irrigation system, which uses electrodialysis to desalinate brackish water and then adds fertilizer to achieve water and fertilizer integration. However, the electrodialysis method is costly and has low treatment efficiency. Zheng Hongfei et al. (CN201810358228.6) invented a solar-powered self-produced freshwater planting device that can be directly irrigated with seawater, but the investment cost is too high. Wang Shixiong et al. (application number: CN201810090107.8) used flocculants to purify water, but this is mainly aimed at removing arsenic and fluoride from drinking water, not high salinity. In addition, numerous studies have focused on crop selection and breeding. For example, Dai Yang et al. (CN201910686116.8) invented a hybrid rice breeding method to improve rice salt tolerance. However, this breeding method is time-consuming, difficult, applicable to only a limited range of crops, and prone to causing food security issues. In general, these traditional high-salinity desalination technologies have significant limitations: First, the equipment investment and operating energy consumption are high, resulting in huge processing costs, making it difficult to promote and apply in large-scale agricultural production; second, these technologies mainly focus on the extraction of pure water, while the resulting high-concentration waste brine or brines, if not properly treated, can cause secondary pollution; finally, these processes only remove salt from the water without imparting any additional fertility value to the water body.

[0005] Humic acid is a natural organic macromolecule extracted from weathered coal, lignite, or biomass, possessing excellent physiological activity and complexing ability. In agriculture, humic acid is often used as a soil conditioner and plant growth stimulant, improving soil structure, enhancing crop resistance, and promoting nutrient absorption. However, ordinary humic acid has a large molecular weight, poor water solubility, and few active functional groups, limiting its application. Modified humic acid obtained through various treatment techniques exhibits higher specific surface area, reactivity, and the number of surface functional groups, but its application in high-salinity treatment, particularly in simultaneous desalination and fertilizer efficiency conversion, has not yet been reported.

[0006] Therefore, there is an urgent need in this field to develop a new method that is low-cost, simple to operate, environmentally friendly, and capable of turning waste into valuable resources. This method aims to transform unusable high-salinity water into non-toxic, nutrient-rich agricultural water resources that promote plant growth. This approach is of great significance for alleviating agricultural water pressure, treating high-salinity wastewater, reducing agricultural irrigation costs, and achieving sustainable agricultural development. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing high-salinity water treatment technologies and the extreme shortage of agricultural freshwater resources, providing a modified humic acid-polyferric compound fertilizer for high-salinity agricultural use, its preparation method, and its application. The main objectives of this invention include: 1. Providing a low-energy-consumption, low-cost, and simple-to-operate method for modifying humic acid; 2. Simultaneously achieving desalination and fertilization of high-salinity water through the method, converting it into a nutrient solution suitable for agricultural irrigation / hydroponics; 3. Providing the application of the nutrient solution in agricultural irrigation / hydroponics, effectively alleviating osmotic stress and ion toxicity caused to plants by high-salinity environments, and significantly promoting plant growth, thereby realizing the agricultural resource utilization of brackish water, seawater, and other water resources.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing a modified humic acid-polyferric compound fertilizer for use in high-salinity agriculture, characterized by comprising the following steps:

[0010] S1: Preparation of modified humic acid solution: Humic acid is fully dissolved in alkaline solution, the pH of the system is adjusted to weakly acidic, laccase is added to carry out catalytic reaction, and modified humic acid solution is obtained.

[0011] S2: Preparation of modified humic acid-polyferric compound fertilizer: Add polyferric compound to the modified humic acid solution, and after sufficient reaction, obtain modified humic acid-polyferric compound fertilizer;

[0012] S3: Achieving agricultural use in high-salinity water: The prepared modified humic acid-polyferric compound fertilizer is added to high-salinity water, and after stirring, settling, and filtering, the resulting organic nutrient solution can be used for agricultural irrigation.

[0013] Preferably, in S1, the alkaline solution is a KOH solution with a concentration of 0.05–0.5 mol / L; the mass-to-volume ratio of humic acid to alkaline solution is 1 g:(1–50) mL; and the pH of the system is adjusted to weakly acidic, meaning a pH value of 5.0–7.0.

[0014] Preferably, in S1, the amount of laccase added is 0.01 to 1 wt.% of the mass of humic acid; the catalytic reaction is carried out at room temperature in air for 20 to 180 minutes.

[0015] Preferably, in S2, the polyferric compound is one or more of polyferric sulfate, polyferric chloride, polyferric phosphate, and ferric hydroxide; the dry weight ratio of the polyferric compound to humic acid is (0.1:1) to (1:1).

[0016] Preferably, in S2, the complete reaction refers to stirring at a constant temperature of 20-70°C until homogeneous, soaking and reacting for 0.5-2.5 hours, and then drying at 30-80°C by spray drying or vacuum drying.

[0017] Preferably, in step S3, the modified humic acid-polyferric compound fertilizer is added to high-salinity water at a mass-to-volume ratio of 0.1–5 g / L; the high-salinity water refers to brackish water, seawater, or other high-salinity water bodies with a total dissolved solids concentration of not less than 1000 mg / L, wherein Na… + Content greater than 1000 mg / L, Ca 2+ Content greater than 100 mg / L, Mg 2+ Content greater than 100 mg / L, K + Content greater than 50 mg / L, Cl - The content is greater than 2000 mg / L.

[0018] Preferably, in S3, the stirring refers to mechanical or manual stirring for 5-25 minutes to allow for a full reaction; the settling time is 0.5-3 hours; and the filtration refers to taking the supernatant and filtering it through a filter bag or microfiltration device.

[0019] Preferably, in S1, the humic acid is mineral-derived or bio-derived humic acid; the mass-to-volume ratio of the humic acid to the alkaline solution is 1g:2mL; and the amount of laccase added is 0.5wt.% of the mass of the humic acid.

[0020] In S2, the polyferric compound is polyferric phosphate; the dry weight ratio of the polyferric phosphate to humic acid is 0.1:1.

[0021] In S3, the mass-to-volume ratio of the modified humic acid-polyferric compound fertilizer to the high saline solution is (4±0.5) g / L.

[0022] The modified humic acid-polyferric compound fertilizer prepared by the method described in this invention.

[0023] The modified humic acid-polyferric compound fertilizer of the present invention is used in agricultural irrigation, hydroponics, and to promote crop growth.

[0024] The core principle of this invention lies in the synergistic effect of laccase catalysis and inorganic polymers to construct a modified humic acid-polyferric compound fertilizer that combines highly efficient flocculation and desalination functions with biostimulatory activity. This precipitant can react with harmful ions in high-salinity water and provide nutrients that can be utilized by plants, simultaneously achieving desalination and fertilization of high-salinity water. The specific principle is as follows:

[0025] 1. Polyferric sulfate and other polyferric substances are commonly used inorganic flocculants for treating high-salinity water, and in this invention, they mainly play the role of "high-efficiency flocculants." Polyferric sulfate hydrolyzes in water to generate various high-valence polynuclear hydroxyl metal complex ions. These positively charged complex ions can effectively neutralize negatively charged colloidal particles in the water (commonly present in high-salinity water), thereby rapidly removing suspended solids, colloids, and some colloidal pollutants from the water. This is its basic function as a water treatment agent. Furthermore, taking the most preferred polyferric sulfate as an example, it can react with Ca in high-salinity water... 2+ Mg 2+ Ions of equal hardness form insoluble calcium phosphate and magnesium phosphate precipitates, thus achieving ion precipitation removal. However, polyferric compounds alone are ineffective against high concentrations of Na. + and Cl - They have almost no removal capacity, and these two ions are the main culprits causing salt stress.

[0026] 2. Humic acid is an organic complex rich in functional groups, capable of effectively binding various anions and cations in water. However, high-salinity water has high mineralization and contains excessive sodium. + Cl - Various ions, including humic acid, are present in humic acids. Traditional humic acids have large molecular weights, poor solubility, and weak functional group binding capacity. Laccase, a polyphenol oxidase, catalyzes the oxidative polymerization or depolymerization of phenolic units in large humic acid molecules, reducing the particle size of humic acid and forming modified humic acid with higher specific surface area and reactivity. Simultaneously, the oxidation reaction may expose or generate more active functional groups such as carboxyl groups and phenolic hydroxyl groups, greatly enhancing its subsequent complexing ability. Therefore, modified humic acid will dissolve more effectively in water and more efficiently adsorb cations and anions from high-salt waters such as brackish water and seawater, reducing the total dissolved solids and salt content of high-salt waters.

[0027] 3. The compound fertilizer prepared using modified humic acid and polyferric sulfate is a novel material with complementary functions, mainly through ionic bonds (-COO). - Fe3 + The precipitant is bound by strong chemical bonds such as coordinating bonds, forming stable chemical bonds and a robust structure. Therefore, this precipitant can comprehensively, stably, and efficiently modify high-salt water, exhibiting a synergistic effect of 1+1>2. The compound fertilizer obtained by this invention not only possesses the rapid flocculation and sedimentation capabilities of polyferric sulfate, but also solves the problems of turbidity, colloidal particles, and Ca2+. 2+ Mg 2+ It addresses issues such as excessive plasma and also possesses highly efficient cation and anion exchange capabilities for modified humic acid, solving the problem of Na+. + and Cl - The main problem is that both methods produce humic acid-polyferric composite products that possess biostimulatory and nutritional functions.

[0028] 4. Compound fertilizers convert excess ions that are easily transferred in high saline water into organic complexed nutrients. The organic nutrient solution can be slowly utilized by plants, improving the rhizosphere soil environment and promoting plant growth.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. Synergistic Modification for Efficient Desalination and Fertilization: The compound fertilizer prepared in this invention cleverly integrates the biostimulating activity of modified humic acid with the efficient flocculation and precipitation function of polyferric compounds. Laccase is used for synergistic modification of humic acid, significantly increasing the content and reactivity of its active functional groups such as carboxyl, phenolic hydroxyl, and alcoholic hydroxyl groups. The modified humic acid-iron compound fertilizer can simultaneously and efficiently react with Na+ in high-salinity water. + Ca2 + Mg2 + Various harmful cations and anions, such as Cl-, undergo coordination complexation and ion exchange reactions to form stable organic complexes. This effectively reduces the salinity of salt water and eliminates salt stress, while simultaneously converting it into a nutrient source that crops can absorb, achieving the simultaneous completion of "desalination" and "fertilization".

[0031] 2. Dual Stress Resistance and Growth Promotion Effects: This invention not only fundamentally alleviates osmotic stress and ion toxicity in crops by removing harmful ions, but its rich content of active humic acid and complexed nutrients also stimulates root development, enhances the crop's own stress resistance, and continuously supplies nutrients, exhibiting a dual effect of stress inhibition and growth promotion. The final product, organic nutrient solution, is rich in modified humic acid-iron complex and potassium and other nutrients. Modified humic acid can significantly improve the root microenvironment and enhance the crop's salt stress resistance; iron exists in an easily absorbed organic complex form. The synergistic effect of these two factors jointly promotes crop growth and development in high-salt environments, achieving a triple effect of "water improvement-fertilization-stress resistance," which is unparalleled by traditional desalination technologies or ordinary fertilization methods.

[0032] 3. Green, efficient, and environmentally friendly: The entire process is carried out at normal temperature and pressure, requiring no high energy consumption or complex equipment. The main raw material, humic acid, is widely available and inexpensive, while polyferric compounds are common inorganic flocculants, conforming to green chemistry principles. The precipitate after the reaction can be used as a soil conditioner, without secondary pollution.

[0033] 4. Easy to apply and highly applicable: This method is simple to operate and suitable for decentralized field treatment. The filtered organic nutrient solution can be directly used for hydroponics or irrigation such as drip irrigation and sprinkler irrigation, which greatly expands the application scenarios of marginal water resources such as brackish water and seawater in the agricultural field. It is of great significance for ensuring food security and promoting the sustainable development of agriculture in arid and coastal areas. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the preparation method and application of a modified humic acid-polyferric compound fertilizer for use in high-salinity agriculture, as described in this invention.

[0035] Figure 2 Images of humic acid, modified humic acid, and modified humic acid-polyferric compound fertilizer.

[0036] Figure 3 SEM images of humic acid, modified humic acid, and modified humic acid-polyferric compound fertilizer.

[0037] Figure 4 Particle size distribution of humic acid, modified humic acid, and modified humic acid-polyferric compound fertilizer.

[0038] Figure 5 This is a comparison chart of the growth of wheat cultured in seawater for 14 days in Example 2.

[0039] Figure 6 This is a growth diagram of rice cultured in brackish water for 30 days in Example 3. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0041] Example 1

[0042] A method for preparing and applying a modified humic acid-polyferric compound fertilizer for use in high-salinity agriculture, the process is as follows: Figure 1 As shown. Specifically, it includes the following steps:

[0043] 10g of humic acid was dissolved in 20mL of 0.1mol / L KOH solution, and the pH was adjusted to approximately 6 using 0.05mol / L phosphoric acid solution. 0.05g of laccase was added to the solution, and the mixture was stirred thoroughly at room temperature for 60 minutes to obtain a modified humic acid solution. 1g of polyferric phosphate was added to the modified humic acid solution, and the mixture was stirred evenly at 30℃ and soaked for 1 hour. The solution was then dried under vacuum at 60℃ and pulverized to obtain 11.4g of modified humic acid-polyferric phosphate compound fertilizer. 2g of the compound fertilizer was added to 500mL of seawater (collected from the Pearl River Estuary, with a total dissolved solids of 8400mg / L, mainly consisting of Na+). + 2670 mg / L, Ca 2+ 210 mg / L, Mg 2+ 311 mg / L, K + 180 mg / L, Cl - In 4640 mg / L, stir for 10 minutes and let stand for 1 hour. Take the supernatant and filter it through a filter bag to obtain organic nutrient solution as seawater ①.

[0044] Meanwhile, only 0.18g of polyferric phosphate (equal to seawater ①) was added to 500mL of seawater, allowed to stand, and filtered to obtain seawater ②;

[0045] 1.76g of untreated commercial humic acid (equal to seawater ①) was added to 500mL of seawater, allowed to stand, and filtered to obtain seawater ③;

[0046] 1.82g of modified humic acid (equal to seawater ①) was added to 500mL of seawater, allowed to stand, and filtered to obtain seawater ④.

[0047] 0.18g of polyferric phosphate and 1.82g of modified humic acid were added to 500mL of seawater (simple physical mixing), allowed to stand, and filtered to obtain seawater ⑤;

[0048] 0.18g of conventional flocculant PFS (polyferric sulfate) was added to 500mL of seawater, allowed to stand, and then filtered to obtain seawater⑥.

[0049] The contents of elements such as Na, Ca, Mg, Cl, and K in different seawaters were determined using ICP-OES to compare desalination rates; the total organic carbon (TOC) content in seawater was measured using a TOC analyzer, and the humic acid content was estimated using the carbon coefficient to compare the relative content of humic acid in the water; at the same time, the electrical conductivity (EC) and pH of seawater were measured.

[0050] Table 1. Element content (mg / L) in different seawater samples

[0051]

[0052] Table 2. TOC, HA content (mg / L), EC (mS / cm), and pH in different seawater samples.

[0053]

[0054] Based on the measurement results, and considering both EC and ion concentration, the EC in seawater ② (polyferric sulfate only) decreased slightly, while the Ca... 2+ Mg 2+ The removal rate is extremely high (>95%), thanks to the phosphate precipitation effect of polyferric phosphate. However, it does not remove Na+. + The removal effect of Cl- is limited (<10%), proving that polyferric sulfate alone cannot solve the core sodium salt problem.

[0055] EC values ​​and Na of seawater ③ (humic acid only) and seawater ④ (modified humic acid only) +The Cl- concentration decreased only slightly, indicating that relying solely on the ion exchange effect of humic acid is inefficient and impractical. Modified humic acid (seawater ④) showed slightly better results than ordinary humic acid (seawater ③), demonstrating the advantages of modified humic acid, but it is still insufficient.

[0056] The effect of seawater (physical mixing) lies between that of individual components, and its effect on Ca... 2+ Mg 2+ The removal rate was significantly lower than that of the polyferric group alone, proving that simple physical mixing leads to mutual interference between components, resulting in a decrease in efficiency rather than an increase.

[0057] The values ​​for seawater ⑥ (traditional flocculation) are similar to those for seawater ②, indicating that the effects of traditional flocculants polyferric sulfate and polyferric phosphate are quite similar.

[0058] The EC value of seawater ① (in this invention) was significantly reduced to 7.2 mS / cm, the pH was as low as 7.1, and the Na+ content was significantly reduced. + It exhibited the highest Cl- removal rate, far surpassing any other group. Simultaneously, it maintained the removal of Ca... 2+ Mg 2+ The salt was almost completely removed. This proves that the modified humic acid-polyferric compound fertilizer synthesized in this invention produces a synergistic desalination effect of "1+1>>2".

[0059] The actual images of humic acid, modified humic acid, and modified humic acid-polyferric compound fertilizer used in the implementation case are as follows: Figure 2 As shown, their microstructures are as follows Figure 3 As shown, modified humic acid and compound fertilizer exhibit tortuous grooves, indicating a large specific surface area. This suggests that their application in high-salinity water will demonstrate adsorption and fixation effects, with the best desalination effect and the optimal reduction in mineralization. Particle size analysis was performed using a Malvern laser particle size analyzer (model number omitted). Figure 4 As shown, the modified humic acid and compound fertilizer have smaller particle sizes, which helps increase their solubility in water. This is consistent with the result that modified humic acid effectively increases the TOC and humic acid content in seawater. It is noteworthy that the particle size distribution of the compound fertilizer shows two ranges, indicating that some substances within it have formed complexes or bonded together, increasing the particle size.

[0060] Example 2: Hydroponics

[0061] The seawater samples ①, ②, ③, ④, ⑤, and ⑥ obtained in Example 1 were directly used for hydroponic wheat cultivation. Seven experimental groups were set up and hydroponically cultured for 14 days: seawater, seawater group ②, seawater group ③, seawater group ④, seawater group ⑤, seawater group ⑥, and seawater group ① (in this invention). Each group contained 50 wheat seeds. The germination rate and growth status of the wheat were observed and recorded, and the plant indicators were also recorded (Table 3).

[0062] like Figure 5 As shown, significant differences in wheat growth were observed after 14 days of cultivation. Based on growth and plant indicators, seawater had a clear stress effect on wheat growth. Regarding germination rate, the germination rate of wheat treated with seawater was only 45%. After adding polyferric sulfate, the germination rate of seawater treatments ② and ⑥ significantly increased to over 60%. Groups ③, ④, and ⑤ showed that humic acid could alleviate the germination rate caused by salt stress. Using modified humic acid-polyferric sulfate compound fertilizer, the germination rate of wheat in seawater could reach 100%, indicating its significant desalination efficiency and salt stress resistance, successfully converting high-salt water into a hydroponic organic nutrient solution. Simultaneously, data on plant height and root length showed that the organic nutrient solution obtained by this invention had the best effect on promoting wheat growth and provided good nutrition during the wheat's growing season. This proves that it not only alleviates salt stress but also serves as a nutrient source to promote crop growth.

[0063] Table 3. Germination rate, plant height, and root length of wheat under different hydroponic treatments

[0064]

[0065] In summary, raw high salinity has a strong inhibitory effect on crop growth. Neither desalination treatment (②, ⑥) nor biostimulation treatment (③, ④) can completely solve the problem of agricultural use of high salinity, and simple physical mixing (⑤) cannot reproduce the technical effects of this invention. Only seawater ① prepared using the technical solution of this invention can simultaneously achieve the triple effects of "efficient desalination," "nutrient supplementation," and "biostimulation." This fully demonstrates that the technology provided by this invention is a novel and effective technology, and its final technical effect is far superior to all comparative groups, providing reliable technical support for the safe agricultural utilization of marginal water resources such as brackish water and seawater.

[0066] Example 3: Irrigation

[0067] Different additives were added to brackish water (sampled from shallow groundwater in Hami City, Xinjiang, with a total dissolved solids concentration of 5700 mg / L, mainly including Na) according to the method in Example 1. + 1620 mg / L, Ca 2+ 190 mg / L, Mg 2+ 212 mg / L, K + 59 mg / L, Cl -Brackish water samples ①, ②, ③, ④, ⑤, and ⑥ (obtained from 2570 mg / L irrigation water) were added in equal amounts of nitrogen, phosphorus, and potassium fertilizer, and soil pot experiments were conducted. Seven experimental groups were set up and soil cultured for 30 days: brackish water group ②, irrigation water group ③, irrigation water group ④, irrigation water group ⑤, irrigation water group ⑥, and irrigation water group ① (this invention). Five rice plants were planted in each group and cultured continuously for 30 days. During this process, the growth of rice was observed, and its plant indicators were recorded (Table 4). After 30 days, the rice was harvested, and its plant height, root length, fresh weight, dry weight, and number of leaves were measured.

[0068] Table 4 Rice Indicators under Different Irrigation Treatments

[0069]

[0070]

[0071] like Figure 6 As shown, rice exhibited significant differences, with multiple leaves in the brackish water group showing signs of drying out. This was due to salt stress caused by excessively high mineralization in the irrigation water. According to the indicators (Table 4), the brackish water group suffered severe salt stress, and its growth was significantly inhibited. Adding polyferric sulfate (Fe2) and 6 slightly alleviated the stress, but the effect was limited due to incomplete desalination. Adding humic acid (Fe2) (Fe3), (Fe4), and (Fe5) showed a significant resistance effect, indicating that humic acid contributes to the resistance of rice growth, and that modified humic acid is even more effective. However, the organic nutrient solution obtained in this invention is more effective, showing an overwhelming advantage in both fresh and dry weight, as well as superior growth, demonstrating comprehensive superiority. This invention greatly promotes the accumulation of nutrients in crops and their overall healthy development, proving the significant synergistic effect of modified humic acid-polyferric sulfate compound fertilizer, transforming high-salt water into a highly efficient organic nutrient solution.

[0072] Summarize:

[0073] Examples demonstrate that the organic nutrient solution (treatment ①) prepared by this invention exhibits unprecedented and outstanding effects in both hydroponic and irrigation agricultural water. Physiologically, the crop germination rate reached 100%, completely eliminating the biotoxicity of high saline solution. Morphologically, crop height, root length, and leaf number were all significantly improved, exhibiting vigorous growth. In terms of biomass, the crop dry weight reached 1.59g, which is 196% of the control group and significantly superior to all other treatment groups. This fully demonstrates the significant advantages of this invention in promoting the synthesis and accumulation of organic matter in crops.

[0074] Furthermore, the effect of the treatment group (①) of the present invention is far superior to the simple sum of its individual components (②, ④), and even superior to the physical mixing group (⑤). This comparative result proves that the modified humic acid-polyferric compound fertilizer prepared by the present invention through a pre-compounding step produces a technical effect of mutual cooperation and functional synergy among its components, which is inventive and has outstanding substance.

[0075] In summary, this invention successfully transforms high-salinity water into a highly efficient organic nutrient solution that can be directly applied to agricultural irrigation / hydroponics, significantly promoting crop growth and increasing biomass, providing an economical, effective, and environmentally friendly new approach to solving the problem of agricultural water shortage.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified humic acid-polyferric composite fertilizer for high-salinity water agriculture, characterized by, The method comprises the following steps: S1: preparation of modified humic acid solution: humic acid is fully dissolved in alkali solution, the pH of the system is adjusted to weak acidity, laccase is added for catalytic reaction, and a modified humic acid solution is obtained; S2: preparation of modified humic acid-polyferric composite fertilizer: polyferric compounds are added to the modified humic acid solution, and after sufficient reaction, a modified humic acid-polyferric composite fertilizer is obtained; S3: realizing high-salt water agriculture: the prepared modified humic acid-polyferric composite fertilizer is put into high-salt water, and after stirring, standing and filtering, an organic nutrient solution is obtained, which can be used for agricultural irrigation.

2. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 1, characterized in that, In S1, the alkali solution is KOH solution with a concentration of 0.05-0.5 mol / L; the mass-volume ratio of humic acid to alkali solution is 1 g:(1-50) mL; and the pH of the system is adjusted to weak acidity, i.e. the pH value is 5.0-7.

0.

3. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 2, characterized in that, In S1, the laccase is added in an amount of 0.01-1 wt.% of the mass of humic acid; and the catalytic reaction is carried out at room temperature in air, and the reaction time is 20-180 minutes.

4. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 1, characterized in that, In S2, the polyferric compounds are one or more of polyferric sulfate, polyferric chloride, polyferric phosphate and hydroxyl ferric oxide; and the dry basis mass ratio of polyferric compounds to humic acid is (0.1:1)-(1:1).

5. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 4, characterized in that, In S2, the sufficient reaction means that the mixture is uniformly stirred at a constant temperature of 20-70°C for 0.5-2.5 hours, and then dried at 30-80°C by spray drying or vacuum drying.

6. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 1, characterized in that, In S3, the mass-volume ratio of the modified humic acid-polyferric composite fertilizer to the high-salinity water is 0.1-5 g / L. The high-salinity water refers to bitter-salty water, seawater or other high-salinity water bodies with total dissolved solids not less than 1000 mg / L, wherein Na + content is greater than 1000 mg / L, Ca 2+ content is greater than 100 mg / L, Mg 2+ content is greater than 100 mg / L, K + content is greater than 50 mg / L, Cl - content is greater than 2000 mg / L.

7. The method for preparing modified humic acid-polyferric composite fertilizer for high-salinity water agriculture according to claim 6, characterized in that, In S3, the stirring means mechanical or manual stirring for 5-25 minutes to make the mixture fully react; the standing time is 0.5-3 hours; and the filtering means taking the supernatant and filtering through a filter bag or a microfiltration device.

8. The method for preparing a modified humic acid-polyferric composite fertilizer for realizing high-salt water agriculture according to any one of claims 1-7, characterized in that, In S1, the humic acid is mineral or biological humic acid; the mass-volume ratio of humic acid to alkali solution is 1 g:2 mL; and the laccase is added in an amount of 0.5 wt.% of the mass of humic acid; In S2, the polyferric compounds are polyferric phosphate; and the dry basis mass ratio of polyferric phosphate to humic acid is 0.1:1; In S3, the mass-volume ratio of the modified humic acid-polyferric composite fertilizer to high-salt water is (4±0.5) g / L.

9. The modified humic acid-polyferric composite fertilizer prepared by the method of claims 1-8.

10. The application of the modified humic acid-polyferric composite fertilizer of claim 9 in agricultural irrigation, plant hydroponics and promoting crop growth.

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