Organic selenium fertilizer as well as preparation method and application thereof

Abstract

The invention relates to an organic selenium fertilizer and a preparation method and application thereof, and belongs to the technical field of organic fertilizers. The preparation method comprises the following steps: firstly, preparing selenium-containing inorganic salt sodium selenite / sodium selenate into a solution, and then carrying out chelation reaction on the solution and specific organic complexing agents such as humic acid, amino acid and alginic acid to generate a stable selenium-organic matter complexing solution; and then uniformly spraying the solution onto an adsorption carrier in a rolling state in a spraying manner, and finally drying to obtain the solid organic selenium fertilizer. According to the invention, through organic complexing and carrier adsorption processes, uniform fixation of the selenium element at the carrier particle level is realized, and agglomeration and segregation are fundamentally prevented. The prepared organic selenium fertilizer is high in mixing uniformity and good in stability, selenium in an organic complex state is more easily absorbed and converted by plants, meanwhile, the complexing agent and the carrier have the synergistic interaction effect of promoting plant growth and improving soil, the complexing agent and the carrier can be used independently or mixed with basic fertilizer for use, and the selenium content and quality of agricultural products are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic fertilizer, in particular to an organic selenium fertilizer, a preparation method and application thereof. BACKGROUND

[0002] Plant selenium nutrition strengthening is a key agricultural technology to cope with global soil selenium deficiency and improve human selenium intake. The core is to make crops effectively absorb and convert into organic selenium beneficial to human body by applying selenium fertilizer. In actual agricultural production, in order to facilitate application and reduce cost, it is usually necessary to add a small amount of selenium element to a large amount of base fertilizer to prepare selenium-rich compound fertilizer.

[0003] However, uniform mixing of a small amount of selenium and a large amount of fertilizer is a basic engineering technical problem that has long plagued those skilled in the art. As a trace element essential for plants, the addition amount of selenium in fertilizer is usually at a low level, generally measured in milligrams per kilogram (mg / kg) or parts per million (ppm) concentration. It is almost impossible to achieve ideal uniform mixing effect by relying on conventional mechanical mixing means. Moreover, a small amount of selenium raw material is prone to agglomeration due to its own characteristics and electrostatic action, forming small particle clumps that are difficult to break up, resulting in uneven distribution of selenium in the fertilizer.

[0004] At present, to solve this problem, the prior art usually adopts simple mechanical methods such as prolonging stirring time or adding liquid selenium source. However, the former has high energy consumption and low efficiency, and cannot fundamentally solve the problem of segregation; the latter faces new problems such as more difficult dispersion of liquid in solid and easy caking. Therefore, developing a preparation method that can fundamentally ensure long-term stable and uniform distribution of a small amount of selenium in a large amount of fertilizer has become a technical bottleneck that needs to be broken through in the field of selenium-rich fertilizer. SUMMARY

[0005] To solve the above technical problems, the present application provides a preparation method of an organic selenium fertilizer, comprising the following steps: Step S1: providing a selenium-containing inorganic salt solution, wherein the selenium-containing inorganic salt is sodium selenite and / or sodium selenate.

[0006] Step S2: providing an organic complexing agent, wherein the organic complexing agent is at least one of humic acid, fulvic acid, amino acid, polyaspartic acid and alginic acid.

[0007] Step S3: carrying out chelation reaction of the selenium-containing inorganic salt solution and the organic complexing agent under a predetermined reaction condition to generate a stable selenium-organic complex solution; Step S4: spraying the selenium-organic complex solution on an adsorption carrier to make the selenium-organic complex solution be fully adsorbed by the adsorption carrier, and then drying to obtain an organic selenium fertilizer; the adsorption carrier is at least one of diatomite, bentonite and zeolite powder.

[0008] Moreover, the amino acid is at least one of methionine, cysteine and glycine; and the mass concentration of the selenium-containing inorganic salt solution is 10%-15%.

[0009] Moreover, in step S3, the preset reaction condition comprises: the reaction temperature is 50-80℃, the reaction time is 2-3 hours, and the stirring is continuously performed.

[0010] Moreover, in step S3, the pH value of the chelation reaction system is 6.0-8.0; and the pH value of the system is adjusted by using citric acid or sodium hydroxide and ammonia solution.

[0011] Moreover, in step S3, the mass ratio of selenium in the selenium-containing inorganic salt to the organic complexing agent is 1:30-1:40.

[0012] Moreover, the drying is performed at 60-80℃ until the moisture content is less than 5%.

[0013] Moreover, in step S4, the particle size of the adsorption carrier is 150-300 mesh.

[0014] Moreover, in step S4, the specific method for spraying the selenium-organic complex solution on the adsorption carrier is: the selenium-organic complex solution is diluted by adding 2-3 times of deionized water (in large-scale production, in order to save cost, pure water can also be used) (the standard is that the solution can flow down like water or milk in a continuous line, without obvious stringing or dropping), and then the solution is uniformly sprayed on the adsorption carrier in a rolling state by using a spraying device; in order to improve the absorption efficiency, the carrier can be heated to a certain temperature, for example, 30-40℃.

[0015] In a second aspect, the application provides an organic selenium fertilizer prepared by the preparation method.

[0016] In a third aspect, the application provides an application of the organic selenium fertilizer, which is used alone or after being uniformly mixed with a base fertilizer.

[0017] Compared with the prior art, the application has the following beneficial effects: 1. Traditional methods involve mechanically mixing trace amounts of solid selenium powder with large quantities of solid fertilizer, which struggles to achieve ideal, uniform mixing. Furthermore, selenium raw materials are prone to agglomeration, forming granular clumps and further contributing to uneven selenium distribution. This invention first chelates a selenium-containing inorganic salt solution with an organic complexing agent to generate a stable selenium-organic complex solution. This solution is then uniformly sprayed onto a tumbling adsorption carrier with a high specific surface area, thus preparing organic selenium fertilizer. Through the chelation reaction, inorganic selenium ions are converted into organically complexed selenium, fundamentally eliminating the agglomeration of inorganic selenium caused by electrostatic interactions. Spraying the organically complexed selenium onto the tumbling, high-specific-surface-area adsorption carrier allows the selenium-organic complex solution to penetrate and firmly adsorb into the micropores of the adsorption carrier, achieving uniform distribution of selenium at the carrier particle level. This also avoids segregation and clumping problems caused by vibration and moisture absorption during transportation and storage. The organic selenium fertilizer made in this way can be mixed with a large amount of basic fertilizer to achieve uniformity of selenium content in the final fertilizer product.

[0018] 2. The preparation method provided by this invention involves first chelating a selenium-containing inorganic salt solution with an organic complexing agent to generate a stable selenium-organic complex solution. Organically complexed selenium is generally more easily absorbed and transported within plant roots than inorganic selenates or selenites, helping plants to more efficiently convert inorganic selenium into beneficial organic selenium. The organic complexing agents used (such as humic acid, alginic acid, amino acids, etc.) are themselves high-quality plant growth stimulants, capable of promoting root development, improving soil structure, and enhancing crop resistance. Simultaneously, the adsorbent carrier (such as diatomaceous earth, bentonite, etc.) possesses water and fertilizer retention capabilities, extending the effective time of selenium fertilizer in the plant rhizosphere. In this invention, the organic combination of selenium, the organic complexing agent, and the adsorbent carrier collectively endows the fertilizer with comprehensive agronomic value in nutrient fortification, plant growth stimulation, and soil improvement. Detailed Implementation Example

[0019] A method for preparing an organic selenium fertilizer includes the following steps: Step S1: Provide a selenium-containing inorganic salt solution, wherein the selenium-containing inorganic salt is sodium selenite and sodium selenate.

[0020] Step S2: Provide an organic complexing agent, wherein the organic complexing agent is alginate.

[0021] Step S3: The selenium-containing inorganic salt solution and the organic complexing agent are subjected to a chelation reaction under preset reaction conditions to generate a selenium-organic complex solution; Step S4: Spray the selenium-organic complex solution onto the adsorption carrier, so that the selenium-organic complex solution is adsorbed by the adsorption carrier, and then dry it to obtain organic selenium fertilizer; the adsorption carrier is diatomaceous earth.

[0022] Preferably, in step S3, the preset reaction conditions include: a reaction temperature of 50°C, a reaction time of 2 hours, and continuous stirring.

[0023] Preferably, in step S3, the pH value of the chelation reaction system is 6.0; the pH of the system is adjusted using citric acid and sodium hydroxide solution.

[0024] Preferably, in step S3, the mass ratio of selenium in the selenium-containing inorganic salt to the organic complexing agent is 1:30.

[0025] Preferably, in step S4, the product is dried at 60°C until the moisture content is less than 5%.

[0026] Preferably, in step S4, the particle size of the adsorption carrier is 150 mesh to 300 mesh.

[0027] Preferably, in step S4, the specific method for spraying the selenium-organic complex solution onto the adsorption carrier is as follows: the selenium-organic complex solution is diluted with twice the volume of deionized water (until the solution can flow continuously in a linear fashion like water or milk, without obvious stringing or dripping), and then evenly sprayed onto the adsorption carrier in a tumbling state using a spraying device. In order to improve the absorption efficiency, the carrier can be heated to 30°C. Example

[0028] A method for preparing an organic selenium fertilizer includes the following steps: Step S1: Provide a selenium-containing inorganic salt solution, wherein the selenium-containing inorganic salt is sodium selenite.

[0029] Step S2: Provide an organic complexing agent, wherein the organic complexing agent is humic acid.

[0030] Step S3: The selenium-containing inorganic salt solution and the organic complexing agent are subjected to a chelation reaction under preset reaction conditions to generate a selenium-organic complex solution; Step S4: Spray the selenium-organic complex solution onto the adsorption carrier, so that the selenium-organic complex solution is adsorbed by the adsorption carrier, and then dry it to obtain organic selenium fertilizer; the adsorption carrier is diatomaceous earth.

[0031] Preferably, in step S3, the preset reaction conditions include: a reaction temperature of 80°C, a reaction time of 3 hours, and continuous stirring.

[0032] Preferably, in step S3, the pH value of the chelation reaction system is 8.0; the pH of the system is adjusted using citric acid and ammonia solution.

[0033] Preferably, in step S3, the mass ratio of selenium in the selenium-containing inorganic salt to the organic complexing agent is 1:40.

[0034] Preferably, in step S4, the product is dried at 80°C until the moisture content is less than 5%.

[0035] Preferably, in step S4, the particle size of the adsorption carrier is 150 mesh to 300 mesh.

[0036] Preferably, in step S4, the specific method for spraying the selenium-organic complex solution onto the adsorption carrier is as follows: the selenium-organic complex solution is diluted with 3 times its volume of deionized water (the solution can flow continuously in a linear fashion like water or milk, without obvious stringing or dripping), and then evenly sprayed onto the adsorption carrier in a tumbling state through a spraying device. In order to improve the absorption efficiency, the carrier can be heated to 40°C. Example

[0037] A method for preparing an organic selenium fertilizer includes the following steps: Step S1: Provide a selenium-containing inorganic salt solution, wherein the selenium-containing inorganic salt is sodium selenate.

[0038] Step S2: Provide an organic complexing agent, wherein the organic complexing agent is fulvic acid or amino acid.

[0039] Step S3: The selenium-containing inorganic salt solution and the organic complexing agent are subjected to a chelation reaction under preset reaction conditions to generate a selenium-organic complex solution; Step S4: Spray the selenium-organic complex solution onto the adsorption carrier, so that the selenium-organic complex solution is adsorbed by the adsorption carrier, and then dry it to obtain organic selenium fertilizer; the adsorption carrier is bentonite.

[0040] Preferably, the amino acid is methionine; and the mass concentration of the selenium-containing inorganic salt solution is 15%.

[0041] Preferably, in step S3, the preset reaction conditions include: a reaction temperature of 80°C, a reaction time of 3 hours, and continuous stirring.

[0042] Preferably, in step S3, the pH value of the chelation reaction system is 6.0-8.0; the pH of the system is adjusted using citric acid and ammonia solution.

[0043] Preferably, in step S3, the mass ratio of selenium in the selenium-containing inorganic salt to the organic complexing agent is 1:35.

[0044] Preferably, in step S4, the product is dried at 70°C until the moisture content is less than 5%.

[0045] Preferably, in step S4, the particle size of the adsorption carrier is 150 mesh to 300 mesh.

[0046] Preferably, in step S4, the specific method for spraying the selenium-organic complex solution onto the adsorption carrier is as follows: the selenium-organic complex solution is diluted with 2.5 times its volume of deionized water (the solution can flow continuously in a linear fashion like water or milk, without obvious stringing or dripping), and then evenly sprayed onto the adsorption carrier in a tumbling state through a spraying device. In order to improve the absorption efficiency, the carrier can be heated to 35°C.

[0047] Unlike Example 1, this comparative example directly mixes powdered sodium selenite with the same type of diatomaceous earth carrier using a mechanical dry method to obtain selenium fertilizer.

[0048] Unlike Example 1, in this comparative example, sodium selenite was prepared into an aqueous solution by adding water and then sprayed directly onto a tumbling diatomaceous earth carrier and dried.

[0049] Test samples: organic selenium fertilizers prepared in Examples 1, 2, and 3, and selenium fertilizers prepared in Comparative Examples 1 and 2.

[0050] Test crops: selenium-enriched model plants (such as Chinese cabbage or rapeseed), of the same variety.

[0051] Test soil: Collect farmland soil, air dry, sieve, and mix well for later use.

[0052] Ten test points were randomly selected from each sample, and the selenium content at each point was determined by atomic fluorescence spectrometry. The relative standard deviation (RSD, %) of the selenium content at the ten test points was calculated, and the results are shown in Table 1.

[0053] Table 1. Relative standard deviation of selenium content in samples Sample name Selenium content relative standard deviation (RSD, %) Example 1 3.1% Example 2 2.8% Example 3 3.5% Comparative Example 1 18.6% Comparative Example 2 9.2% As shown in Table 1, the RSDs of Examples 1-3 of this invention are 2.8%, 3.1%, and 3.5%, respectively, which are all relatively low, proving that the selenium products prepared by this invention have significantly high uniformity. This is because this invention converts inorganic selenium into a uniformly dispersed complex by reacting selenium-containing inorganic salts with an organic complexing agent through an organic complexation reaction, eliminating agglomeration caused by electrostatic effects. Subsequently, through spraying, the selenium solution is brought into full and uniform contact with and fixed in the form of microdroplets with carrier particles that are in a rolling state and have a high specific surface area. The synergistic effect between each step produces the same result.

[0054] Comparative Example 1 (RSD=18.6%) exhibited the worst uniformity, demonstrating that traditional mechanical mixing methods cannot solve the technical challenges of trace component agglomeration and uneven distribution. Comparative Example 2 (RSD=9.2%) showed better uniformity than Comparative Example 1, indicating that adsorption after preparing selenium as a solution does indeed improve the mixing effect. However, the RSD value of Comparative Example 2 remained high, which may be due to uneven distribution of the inorganic selenium solution on the carrier surface or migration during the drying process.

[0055] Potted Chinese cabbage was used in six treatment groups: Example 1, Example 2, Example 3, blank control group (no fertilizer), Comparative Example 1, and Comparative Example 2, with at least five replicates per group. All selenium fertilizer treatment groups received the same total selenium application (approximately 1.0 mg selenium per soil layer), applied one week after emergence. The fresh weight of the above-ground parts of the Chinese cabbage was measured 30 days later, and the results are shown in Table 2.

[0056] Table 2 Effects of different treatments on the biomass of Chinese cabbage Treatment group Average fresh weight (g / plant) Example 1 group 57.1 Example 2 group 54.9 Example 3 group 53.9 Blank control group 43.2 Comparative Example 1 group 45.0 Comparative Example 2 group 47.8 As shown in Table 2, the fresh weight of all example groups and comparative groups was higher than that of the blank group, indicating that the application of selenium fertilizer had a certain basic promoting effect on crops under the experimental conditions. The example groups showed better results than the comparative groups, proving that the organic selenium fertilizer provided by this invention can significantly promote crop growth, and its effect is significantly better than that of selenium fertilizer prepared by traditional methods.

Claims

1. A method for preparing an organic selenium fertilizer, characterized in that, Includes the following steps: Step S1: Provide a selenium-containing inorganic salt solution, wherein the selenium-containing inorganic salt is sodium selenite and / or sodium selenate. Step S2: Provide an organic complexing agent, wherein the organic complexing agent is at least one selected from humic acid, fulvic acid, amino acids, polyaspartic acid, and alginic acid. Step S3: Perform a chelation reaction between the selenium-containing inorganic salt solution and the organic complexing agent under preset reaction conditions to generate a selenium-organic complex solution. Step S4: Spray the selenium-organic complex solution onto an adsorption carrier, allowing the selenium-organic complex solution to be adsorbed by the adsorption carrier, followed by drying to obtain organic selenium fertilizer; wherein the adsorption carrier is at least one selected from diatomaceous earth, bentonite, and zeolite powder.

2. The preparation method according to claim 1, characterized in that, The amino acid is at least one of methionine, cysteine, and glycine; the mass concentration of the selenium-containing inorganic salt solution is 10%-15%.

3. The preparation method according to claim 1, characterized in that, In step S3, the preset reaction conditions include: a reaction temperature of 50℃-80℃, a reaction time of 2-3 hours, and continuous stirring.

4. The preparation method according to claim 3, characterized in that, In step S3, the pH value of the chelation reaction system is 6.0-8.0; the pH of the system is adjusted using citric acid or sodium hydroxide or ammonia solution.

5. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of selenium in the selenium-containing inorganic salt to the organic complexing agent is 1:30-1:

40.

6. The preparation method according to claim 1, characterized in that, In step S4, the product is dried at 60℃-80℃ until the moisture content is less than 5%.

7. The preparation method according to claim 1, characterized in that, In step S4, the particle size of the adsorption carrier is 150 mesh to 300 mesh.

8. The preparation method according to claim 1, characterized in that, In step S4, the specific method for spraying the selenium-organic complex solution onto the adsorption carrier is as follows: after diluting the selenium-organic complex solution with 2-3 times its volume of deionized water, it is evenly sprayed onto the adsorption carrier at 30-40°C in a tumbling state using a spraying device.

9. An organic selenium fertilizer prepared by any one of claims 1 to 8.

10. The application of the organic selenium fertilizer according to claim 9, characterized in that, The organic selenium fertilizer can be used alone or mixed evenly with base fertilizer.