Double-control nitrogen fertilizer synergistic preparation and preparation method thereof

Abstract

The invention discloses a double-control nitrogen fertilizer synergistic preparation and a preparation method thereof, and belongs to the technical field of agricultural preparations. The double-control nitrogen fertilizer synergistic preparation is prepared by the following steps: firstly dispersing DMPP in an isopropanol solution, adding a phenylalanine modified dopamine monomer to perform a polymerization reaction, performing centrifugal drying to obtain polydopamine coated DMPP, and then mixing the polydopamine coated DMPP with nano bentonite and water to obtain inner core slurry; adding a synergist into the chitosan solution to form a chitosan glue solution, and adding a sodium alginate aqueous solution and a glutaraldehyde aqueous solution to form a shell coating solution; and finally, adding the inner core slurry and the outer shell coating liquid into a device to form liquid drops, dropwise adding the liquid drops into a calcium chloride solution to form core-shell liquid drops, and curing in glutaraldehyde gas. The loss of the nitrogen fertilizer in the soil is reduced through the cooperation of chemical inhibition and physical prevention and control, DMPP molecules are effectively fixed by the dopamine layer through pi-pi stacking, the dissolution rate of DMPP is delayed, and the leaching loss rate of DMPP in the soil is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural formulations, and particularly relates to a double-control type nitrogen fertilizer synergistic agent and a preparation method thereof. BACKGROUND

[0002] Nitrogen fertilizer is the cornerstone of global food security, but its average utilization rate is only 30%-40%, and the nitrogen that is not absorbed by crops is lost through ammonia volatilization, nitrification-denitrification, leaching and other pathways, not only causing huge economic waste, but also leading to a series of serious environmental problems such as water eutrophication, soil acidification and greenhouse gas emissions. In response to this challenge, nitrogen fertilizer enhancers have emerged, and the core goal is to control nitrogen loss through technical means and improve fertilizer utilization efficiency.

[0003] The effect of the current nitrogen fertilizer enhancer is significantly affected by external environmental factors (such as water, climate, and soil characteristics), and the effect of nitrification / urease inhibitors is significantly different in different soil types, for example, the effect of nitrification inhibitors is more obvious in light soil; the volatilization characteristics, migration characteristics in soil, and decomposition rate of the inhibitor also affect its action time and effect, and the traditional DMPP inhibitor has problems such as high water solubility, short photolysis half-life, and high-temperature inactivation, which requires repeated application in the field, greatly increasing the labor cost.

[0004] In addition, the nitrogen fertilizer enhancer prepared by the traditional process often has problems such as poor environmental adaptability, unstable self-characteristics, uneven film layer, unstable performance, and low utilization efficiency, which restricts the full play of its synergistic potential. Therefore, it is necessary to propose a new nitrogen fertilizer synergistic agent. SUMMARY

[0005] Based on the deficiencies of the prior art, the purpose of the present application is to provide a double-control type nitrogen fertilizer synergistic agent and a preparation method thereof.

[0006] The first aspect of the present application is to provide a preparation method of a double-control type nitrogen fertilizer synergistic agent, comprising the following steps: S1: dispersing DMPP in an isopropyl alcohol solution, adding phenylalanine modified dopamine monomers to undergo polymerization, and obtaining polydopamine coated DMPP after centrifugal drying; S2: mixing the polydopamine coated DMPP, nano-bentonite and deionized water to obtain an inner core slurry; S3: dissolving chitosan in a solvent, and adding a synergist to form a chitosan glue solution; S4: adding sodium alginate aqueous solution and glutaraldehyde aqueous solution to the chitosan glue solution to form an outer shell coating liquid; S5: The core slurry and the outer shell coating liquid are added to the microfluidic device to form droplets, and the droplets are dropped into the calcium chloride solution to form core-shell droplets; S6: The core-shell droplets are transferred to a sealed container containing glutaraldehyde gas, and a gas-phase cross-linking reaction occurs to obtain a dual-controlled nitrogen fertilizer synergist.

[0007] In some embodiments, the phenylalanine-modified dopamine monomer is prepared by the following steps: mixing dopamine hydrochloride and phenylalanine in a molar ratio of 1:1, and adding a condensing agent to react.

[0008] In some embodiments, the isopropanol solution is obtained by mixing isopropanol and water at a volume ratio of 2-4:7; the mass ratio of DMPP to phenylalanine-modified dopamine monomer is 1:0.1-0.3; the condensing agent is EDC or EDCI, and the amount of condensing agent is 1.2-1.5 times the total molar number of dopamine hydrochloride and phenylalanine.

[0009] In some embodiments, the synergist is selected from at least one of nano zinc oxide and nano copper oxide, and the amount of synergist used is 5-8% of the amount of chitosan.

[0010] In some embodiments, the solvent is a 1% (w / w) aqueous solution of acetic acid, and the mass ratio of solvent to chitosan is 2-4:48-52.

[0011] In some embodiments, the mass concentration of sodium alginate aqueous solution is 1-2.5%; the mass concentration of glutaraldehyde aqueous solution is 0.5-1%; and the mass concentration of calcium chloride solution is 1.5-2.5%.

[0012] In some embodiments, the polymerization reaction in S1 takes 26-30 hours.

[0013] In some embodiments, in S3, the dissolution temperature is 40-45°C; in S6, the gas-phase crosslinking reaction temperature is 35-45°C, and the gas-phase crosslinking reaction time is 1.5-2 hours.

[0014] The second aspect of this invention is to provide a dual-control type nitrogen fertilizer synergist.

[0015] In some embodiments, the dual-control nitrogen fertilizer synergist comprises the following components in parts by weight: The composition consists of 40-60 parts polydopamine-coated DMPP, 10-20 parts nano-bentonite, 1-5 parts chitosan, 4-8 parts sodium alginate, 0.8-1.2 parts glutaraldehyde, and 30-40 parts deionized water.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs a core-shell structure of polydopamine-coated DMPP encapsulated by a sodium alginate-chitosan interpenetrating network, which synergistically reduces nitrogen fertilizer loss in soil through chemical inhibition and physical control. The core polydopamine layer effectively immobilizes DMPP molecules through π-π stacking. Phenylalanine hydrophobic modification enhances the hydrophobicity of polydopamine, making it difficult for water droplets to spread and effectively isolating soil moisture erosion. The high hydrophobicity also slows down the dissolution rate of DMPP, reducing its leaching rate in the soil. The UV shielding effect of polydopamine effectively prolongs the photolysis half-life of DMPP, enabling DMPP to better and more persistently inhibit ammonia monooxygenase of Nitrosomonas bacteria in the soil, blocking the conversion of ammonium nitrogen to nitrite. The process involves conversion, allowing nitrogen to remain in the soil in ammonium form. The outer shell is an interpenetrating network of sodium alginate and chitosan. Sodium alginate swells and expands with increasing soil moisture, matching the nitrification process of ammonium nitrogen fertilizer. It releases DMPP through enlarged pores to inhibit the activity of nitrifying bacteria and reduce the leaching rate of nitrate nitrogen. In the later stages of crop growth, acidic root exudates trigger the deacetylation of chitosan, which works synergistically with microbial enzymes to degrade sodium alginate, continuously releasing DMPP to block the denitrification loss of nitrate nitrogen fertilizer. This achieves a match between the inhibitor release curve and the crop's nutrient requirements.

[0017] 2. The dual-control nitrogen fertilizer synergist provided by this invention is a universal synergist suitable for nitrogen-containing fertilizers, capable of improving the utilization efficiency and duration of various nitrogen fertilizers in the soil. When used in combination with nitrogen fertilizers, this synergist can effectively reduce nitrogen fertilizer losses in the soil, such as volatilization, leaching, and denitrification, thereby significantly improving the efficacy of nitrogen fertilizers, extending their effective period, reducing the frequency of fertilization, increasing crop yield and quality, and simultaneously reducing negative environmental impacts. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Example 1 A dual-control nitrogen fertilizer synergist comprises the following components in parts by weight: The mixture consists of 50 parts polydopamine-coated DMPP, 15 parts nano-bentonite, 3 parts chitosan, 6 parts sodium alginate, 1 part glutaraldehyde, and 35 parts deionized water.

[0020] The above-mentioned dual-control nitrogen fertilizer synergist is prepared by the following steps: S1: DMPP was dispersed in an isopropanol solution (isopropanol and water were prepared at a volume ratio of 3:7), and phenylalanine-modified dopamine monomer was added to undergo a polymerization reaction for 28 hours. After centrifugation and drying, polydopamine-coated DMPP was obtained. The phenylalanine-modified dopamine monomer was prepared by the following steps: dopamine hydrochloride and phenylalanine were mixed in a molar ratio of 1:1, and condensing agent EDC was added to react. The amount of condensing agent EDC was 1.3 times the total molar amount of dopamine hydrochloride and phenylalanine. The mass ratio of DMPP to phenylalanine-modified dopamine monomer was 1:0.2. S2: A core slurry is obtained by mixing polydopamine-coated DMPP, nano-bentonite, and deionized water; S3: Chitosan is dissolved in a 1% (w / w) aqueous acetic acid solution at 45°C, and nano-zinc oxide is added to form a chitosan gel; wherein, the mass ratio of chitosan to aqueous acetic acid solution is 3:50, and the amount of nano-zinc oxide is 6% of the amount of chitosan. S4: Add a 1.5% sodium alginate aqueous solution and a 0.8% glutaraldehyde aqueous solution to the chitosan gel solution to form an outer shell coating solution; wherein, the sodium alginate aqueous solution is prepared by adding 6 parts of sodium alginate to deionized water to prepare a 1.5% sodium alginate aqueous solution, and the glutaraldehyde aqueous solution is prepared by adding 1 part of glutaraldehyde to deionized water to prepare a 0.8% glutaraldehyde aqueous solution; S5: The core slurry and the outer shell coating liquid are added to the microfluidic device to form droplets, and the droplets are dropped into a calcium chloride solution with a mass concentration of 2% to form core-shell droplets; S6: The core-shell droplet is transferred to a sealed container containing glutaraldehyde gas, and a gas-phase cross-linking reaction is carried out at 40°C for 1.5 h to obtain a dual-controlled nitrogen fertilizer synergist.

[0021] Example 2 A dual-control nitrogen fertilizer synergist comprises the following components in parts by weight: The mixture consists of 60 parts polydopamine-coated DMPP, 20 parts nano-bentonite, 5 parts chitosan, 8 parts sodium alginate, 1.2 parts glutaraldehyde, and 40 parts deionized water.

[0022] The above-mentioned dual-control nitrogen fertilizer synergist is prepared by the following steps: S1: DMPP was dispersed in an isopropanol solution (isopropanol and water were prepared at a volume ratio of 4:7), and phenylalanine-modified dopamine monomer was added to undergo a polymerization reaction for 30 hours. After centrifugation and drying, polydopamine-coated DMPP was obtained. The phenylalanine-modified dopamine monomer was prepared by the following steps: dopamine hydrochloride and phenylalanine were mixed in a molar ratio of 1:1, and condensing agent EDC was added to react. The amount of condensing agent EDC was 1.5 times the total molar amount of dopamine hydrochloride and phenylalanine. The mass ratio of DMPP to phenylalanine-modified dopamine monomer was 1:0.3. S2: A core slurry is obtained by mixing polydopamine-coated DMPP, nano-bentonite, and deionized water; S3: Chitosan is dissolved in a 1% (w / w) aqueous acetic acid solution at 45°C, and nano-copper oxide is added to form a chitosan gel; wherein, the mass ratio of chitosan to aqueous acetic acid solution is 4:52, and the amount of nano-copper oxide is 8% of the amount of chitosan. S4: Add a 2.5% sodium alginate aqueous solution and a 1% glutaraldehyde aqueous solution to the chitosan gel solution to form an outer shell coating solution; wherein, the sodium alginate aqueous solution is prepared by adding 8 parts of sodium alginate to deionized water to prepare a 2.5% sodium alginate aqueous solution, and the glutaraldehyde aqueous solution is prepared by adding 1.2 parts of glutaraldehyde to deionized water to prepare a 1% glutaraldehyde aqueous solution; S5: The core slurry and the outer shell coating liquid are added to the microfluidic device to form droplets, and the droplets are dropped into a calcium chloride solution with a mass concentration of 2.5% to form core-shell droplets; S6: The core-shell droplets were transferred to a sealed container containing glutaraldehyde gas and subjected to a gas-phase cross-linking reaction at 45°C for 2 hours to obtain a dual-controlled nitrogen fertilizer synergist.

[0023] Example 3 A dual-control nitrogen fertilizer synergist comprises the following components in parts by weight: The mixture consists of 40 parts polydopamine-coated DMPP, 10 parts nano-bentonite, 1 part chitosan, 4 parts sodium alginate, 0.8 parts glutaraldehyde, and 30 parts deionized water.

[0024] The above-mentioned dual-control nitrogen fertilizer synergist is prepared by the following steps: S1: DMPP was dispersed in an isopropanol solution (isopropanol and water were prepared at a volume ratio of 2:7), and phenylalanine-modified dopamine monomer was added to undergo a polymerization reaction for 26 hours. After centrifugation and drying, polydopamine-coated DMPP was obtained. The phenylalanine-modified dopamine monomer was prepared by the following steps: dopamine hydrochloride and phenylalanine were mixed in a molar ratio of 1:1, and condensing agent EDC was added to react. The amount of condensing agent EDC was 1.2 times the total molar amount of dopamine hydrochloride and phenylalanine. The mass ratio of DMPP to phenylalanine-modified dopamine monomer was 1:0.1. S2: A core slurry is obtained by mixing polydopamine-coated DMPP, nano-bentonite, and deionized water; S3: Chitosan is dissolved in a 1% (w / w) aqueous acetic acid solution at 40°C, and nano-zinc oxide is added to form a chitosan gel; wherein, the mass ratio of chitosan to aqueous acetic acid solution is 2:48, and the amount of nano-zinc oxide is 5% of the amount of chitosan. S4: Add a 1% sodium alginate aqueous solution and a 0.5% glutaraldehyde aqueous solution to the chitosan gel solution to form an outer shell coating solution; wherein, the sodium alginate aqueous solution is prepared by adding 4 parts of sodium alginate to deionized water to prepare a 1% sodium alginate aqueous solution, and the glutaraldehyde aqueous solution is prepared by adding 0.8 parts of glutaraldehyde to deionized water to prepare a 0.5% glutaraldehyde aqueous solution; S5: The core slurry and the outer shell coating liquid are added to the microfluidic device to form droplets, and the droplets are dropped into a calcium chloride solution with a mass concentration of 1.5% to form core-shell droplets; S6: The core-shell droplet is transferred to a sealed container containing glutaraldehyde gas, and a gas-phase cross-linking reaction is carried out at 35°C for 1.5 h to obtain a dual-controlled nitrogen fertilizer synergist.

[0025] Example 4 It is basically the same as Example 1, except that: The dual-control nitrogen fertilizer synergist includes the following components by weight: 45 parts polydopamine-coated DMPP, 12 parts nano-bentonite, 2 parts chitosan, 5 parts sodium alginate, 0.9 parts glutaraldehyde, and 32 parts deionized water.

[0026] Example 5 It is basically the same as Example 1, except that: The dual-control nitrogen fertilizer enhancement agent comprises the following components in parts by weight: 55 parts polydopamine-coated DMPP, 18 parts nano-bentonite, 4 parts chitosan, 7 parts sodium alginate, 1.1 parts glutaraldehyde, and 38 parts deionized water.

[0027] Comparative Example 1 It is basically the same as Example 1, except that the dual-control nitrogen fertilizer synergist is a non-core-shell structure, that is, polydopamine-coated DMPP, nano-bentonite, chitosan (powder), nano-zinc oxide, and sodium alginate (powder) are mixed evenly in a mixer.

[0028] Comparative Example 2 It is basically the same as Example 1, except that the polydopamine-coated DMPP is replaced with the same amount of DMPP.

[0029] The performance of the nitrogen fertilizer synergists prepared in Examples 1-5 and Comparative Examples 1-2 provided by this invention in agricultural fertilization processes was evaluated. Comparative Example 3 was a commercially available nitrogen fertilizer synergist (manufacturer: BASF, Entec® 26). The nitrogen fertilizer synergists prepared in Examples 1-5 and Comparative Examples 1-3 were applied to soils that had already been fertilized with the same amount of fertilizer. The cumulative ammonia volatilization, nitrate nitrogen leaching, ammonium nitrogen content, and nitrate nitrogen content of the soil were tested. The test data are shown in Table 1.

[0030] The amount of ammonia (NH3) volatilized from the soil surface was measured using a closed static chamber with an inlet and an outlet. Potted plants in fertilized soil were placed inside the chamber, and the outlet was connected to a series of Erlenmeyer flasks containing boric acid absorbent solution to absorb the volatilized ammonia. Ammonia-free air was introduced into the chamber at a constant flow rate (1 L / min) to carry the volatilized ammonia into the absorbent solution. The daily volatilization amount was calculated, and then the cumulative ammonia volatilization amount for the entire observation period (60 days) was obtained.

[0031] To assess the impact of nitrogen fertilizer treatment on nitrate nitrogen leaching loss, a typical farmland soil sample that was uniformly filled and sieved (2 mm) was compacted to a height of 30 cm according to a predetermined bulk density. An equal amount of nitrogen fertilizer synergist was uniformly mixed with the top 0-5 cm of soil. Simulated rainfall was used, with leaching occurring 1-2 times per week for a total of 8 weeks. After leaching, all filtrates were collected and measured, and the nitrate nitrogen concentration was determined by ultraviolet spectrophotometry.

[0032] To track the transformation process of ammonium nitrogen and nitrate nitrogen in the soil, soil samples were collected from 0-15 cm depth in each fertilized soil on the 30th day after fertilization. The nitrate nitrogen content was determined by ultraviolet spectrophotometry, and the ammonium nitrogen content was determined by indophenol blue colorimetry.

[0033] Table 1 As can be seen from Table 1, the dual-control nitrogen fertilizer synergist provided in the embodiments of the present invention can reduce the loss of nitrogen fertilizer in the soil and achieve long-term nitrification inhibition.

[0034] As can be seen from the comparative examples, Comparative Example 1, lacking a core-shell structure, resulted in DMPP and fertilizer being directly exposed to the soil environment. This led to rapid initial release and an inability to effectively control nitrification. Thirty days after fertilization, the nitrate nitrogen content reached a high of 115.7 mg / kg, indicating severely insufficient nitrification inhibition. Comparative Example 2, while retaining a core-shell structure, did not use PDA coating on the DMPP, making the inhibitor molecules susceptible to decomposition and loss due to environmental factors. Although its ammonia volatilization and nitrate nitrogen content were better than Comparative Example 1, its nitrate nitrogen leaching loss on day 60 was still significantly higher than in Example 1, and its ammonium nitrogen content on day 30 was much lower than in Example 1. This demonstrates that the absence of a PDA coating weakens the inhibitor's persistence and stability. Commercially available DMPP synergists... In the initial stage (day 25), the nitrate nitrogen leaching loss was lower than that of the control example 1, reflecting its basic inhibitory ability. However, due to the lack of a core-shell controlled release mechanism, the leaching loss soared to 315.8 mg at 60 days, and the nitrate nitrogen content reached as high as 142.5 mg / kg 30 days after fertilization, exposing its deficiency in inhibiting crop growth in the middle and late stages.

[0035] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-control type nitrogen fertilizer synergist, characterized in that, Includes the following steps: S1: DMPP was dispersed in isopropanol solution, phenylalanine-modified dopamine monomer was added to undergo polymerization reaction, and polydopamine-coated DMPP was obtained after centrifugation and drying. S2: Mix the polydopamine-coated DMPP, nano-bentonite, and deionized water to form a core slurry; S3: Dissolve chitosan in a solvent and add a synergist to form a chitosan gel solution; S4: Add sodium alginate aqueous solution and glutaraldehyde aqueous solution to the chitosan gel solution to form an outer shell coating solution; S5: The core slurry and the outer shell coating liquid are added to a microfluidic device to form droplets, and the droplets are dropped into a calcium chloride solution to form core-shell droplets; S6: The core-shell droplet is transferred to a sealed container containing glutaraldehyde gas to undergo a gas-phase cross-linking reaction to obtain the dual-controlled nitrogen fertilizer synergist.

2. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, The phenylalanine-modified dopamine monomer is prepared by the following steps: dopamine hydrochloride and phenylalanine are mixed in a molar ratio of 1:1, and a condensing agent is added to react.

3. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 2, characterized in that, The isopropanol solution is obtained by mixing isopropanol and water at a volume ratio of 2-4:7; the mass ratio of DMPP to the phenylalanine-modified dopamine monomer is 1:0.1-0.3; the condensing agent is EDC or EDCI, and the amount of condensing agent is 1.2-1.5 times the total molar number of dopamine hydrochloride and phenylalanine.

4. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, The synergist is selected from at least one of nano zinc oxide and nano copper oxide, and the amount of synergist used is 5-8% of the amount of chitosan used.

5. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, The solvent is a 1% (w / w) aqueous solution of acetic acid, and the mass ratio of the solvent to the chitosan is 2-4:48-52.

6. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, The sodium alginate aqueous solution has a mass concentration of 1-2.5%; the glutaraldehyde aqueous solution has a mass concentration of 0.5-1%; and the calcium chloride solution has a mass concentration of 1.5-2.5%.

7. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, In S1, the polymerization reaction takes 26-30 hours.

8. The preparation method of the dual-control nitrogen fertilizer synergist according to claim 1, characterized in that, In step S3, the dissolution temperature is 40-45℃; in step S6, the gas-phase crosslinking reaction temperature is 35-45℃, and the gas-phase crosslinking reaction time is 1.5-2h.

9. A dual-control nitrogen fertilizer synergist prepared by the preparation method of any one of claims 1-8.

10. The dual-control nitrogen fertilizer synergist according to claim 9, characterized in that, The dual-control nitrogen fertilizer synergist comprises the following components in parts by weight: The composition consists of 40-60 parts polydopamine-coated DMPP, 10-20 parts nano-bentonite, 1-5 parts chitosan, 4-8 parts sodium alginate, 0.8-1.2 parts glutaraldehyde, and 30-40 parts deionized water.

Images