Biochar-based compound fertilizer with slow release performance and preparation method thereof

Abstract

The invention relates to the technical field of biochar compound fertilizers, and discloses a biochar-based compound fertilizer with slow release performance and a preparation method thereof. The invention relates to a biochar-based compound fertilizer with slow release performance. The biochar-based compound fertilizer is prepared from the following raw materials in percentage by mass: 40% of fertilizer, 10-30% of biochar and the balance of binder. The biochar-based compound fertilizer with the slow release performance has the good fertilizer slow release performance, and a new thought is provided for application of the biochar-based compound fertilizer in the soil performance improvement process.

Description

Technical Field

[0001] This invention relates to the field of biochar compound fertilizer technology, and more specifically, to a biochar-based compound fertilizer with slow-release properties and its preparation method. Background Technology

[0002] The widespread use of chemical fertilizers, while increasing crop yields and effectively alleviating pressure on food production, has also caused a series of negative effects. Excessive application of chemical fertilizers leads to high nutrient leaching and low utilization rates, while also causing serious environmental problems such as eutrophication of water bodies and soil salinization. Biochar, as a widely available and environmentally friendly material, possesses many excellent properties, such as a large specific surface area, abundant porous structure, and surface functional groups. Studies have shown that applying biochar to soil can not only improve soil water retention capacity and fertilizer utilization efficiency, reduce greenhouse gas emissions and phosphate leaching, but also improve soil physicochemical properties, promote plant growth, and increase crop yields.

[0003] Therefore, providing a biochar-based compound fertilizer with slow-release properties has significant application value and practical significance. Summary of the Invention

[0004] The purpose of this invention is to provide a biochar-based compound fertilizer with slow-release properties and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention: A biochar-based compound fertilizer with slow-release properties comprises the following raw materials by mass fraction: Fertilizer 40%, biochar 10%–30%, and the remainder is binder.

[0006] Furthermore, the fertilizer is composed of urea, diammonium phosphate, and potassium nitrate mixed in a ratio of N:P2O5:K2O=15:10:15.

[0007] Furthermore, the biochar is pyrolytic char.

[0008] Furthermore, the adhesive is a starch solution with a concentration of 5% to 15%.

[0009] The second technical solution of this invention: The preparation method of the above-mentioned biochar-based compound fertilizer with slow-release properties includes the following steps: Fertilizer, biochar, and binder are mixed and pressed into shape to obtain the biochar-based compound fertilizer with slow-release properties.

[0010] Furthermore, the mixing method is as follows: first, the fertilizer is dissolved in deionized water, then biochar and binder are added, stirred and mixed evenly, equilibrated for 24 hours, and then heated and dried.

[0011] Furthermore, the molding pressure of the pressure molding is 4 to 8 MPa.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The biochar-based compound fertilizer with slow-release properties provided by this invention has good slow-release performance, providing a new approach for the application of biochar-based compound fertilizer in the process of soil performance improvement. Attached Figure Description

[0013] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 The image shows a physical sample of the biochar-based compound fertilizer provided in the embodiments of the present invention. Figure 2 This is an electron microscope scan image of BC provided in an embodiment of the present invention; Figure 3 This is an electron microscope scan image of BCF-2 provided in an embodiment of the present invention; Figure 4 The FTIR plots of BCF-2 and BC provided in the embodiments of the present invention; Figure 5 The nitrogen spectra of BCF-2 and BC provided in the embodiments of this invention; Figure 6 The phosphorus spectra of BCF-2 and BC provided in the embodiments of the present invention; Figure 7 The potassium spectra of BCF-2 and BC provided in the embodiments of this invention; Figure 8 A diagram of the soil column leaching device provided in an embodiment of the present invention; Figure 9 This is a graph showing the cumulative total nitrogen release rate of BCF-2 and CF provided in the embodiments of the present invention; Figure 10 This is a graph showing the cumulative total phosphorus release rate of BCF-2 and CF provided in the embodiments of the present invention; Figure 11 This is a graph showing the cumulative release rate of total phosphorus and potassium from BCF-2 and CF provided in the embodiments of the present invention. Figure 12The diagram shows the release pattern of nitrogen nutrients in soil columns of BCF-2, CF, and BC+CF provided in the embodiments of the present invention.

[0014] Figure 13 The diagram shows the release pattern of phosphorus nutrients in soil columns of BCF-2, CF, and BC+CF provided in the embodiments of the present invention.

[0015] Figure 14 The diagram shows the release pattern of potassium nutrients in soil columns of BCF-2, CF, and BC+CF provided in the embodiments of the present invention. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0017] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0019] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] like Figure 1 As shown, in some embodiments of this application, the biochar-based compound fertilizer with slow-release properties comprises the following raw materials by mass fraction: Fertilizer 40%, biochar 10%–30%, and the remainder is binder.

[0022] Preferably, the mixture consists of 40% fertilizer, 30% biochar, and the remainder is a binder. In some embodiments of this application, the fertilizer is a mixture of urea, diammonium phosphate and potassium nitrate in the ratio of N:P2O5:K2O=15:10:15.

[0023] In some embodiments of this application, the biochar is pyrolytic char. Specifically, the elemental analysis of the pyrolytic carbon used is shown in Table 1; Table 1 Elemental analysis of pyrolytic carbon

[0024] The nutrient element content of the pyrolytic char used is shown in Table 2. Table 2. Nutrient content of pyrolytic char

[0025] In some embodiments of this application, a method for preparing a biochar-based compound fertilizer with slow-release properties includes the following steps: The fertilizer, biochar, and binder are mixed according to the following mass fraction: 40% fertilizer, 10% to 30% biochar, and the remainder is binder. The mixture is then pressed and molded to obtain the biochar-based compound fertilizer with slow-release properties. The fertilizer is composed of urea, diammonium phosphate and potassium nitrate mixed in the ratio of N:P2O5:K2O=15:10:15; The biochar is pyrolytic char. The adhesive is a starch solution with a concentration of 5% to 15%, preferably 5%; The specific mixing method is as follows: first, the fertilizer is dissolved in deionized water, then biochar and binder are added, stirred and mixed evenly, equilibrated for 24 hours, and then heated and dried. The molding pressure of the pressure molding is 4 to 8 MPa, preferably 8 MPa.

[0026] To investigate the effects of biochar type, biochar content (biochar mass fraction), binder concentration and molding pressure on the molding effect of carbon-based compound fertilizer, an orthogonal experiment was conducted based on four factors: biochar content, biochar type, binder concentration and molding pressure. The orthogonal experimental design is shown in Table 2. Table 3 Orthogonal Experimental Design

[0027] The orthogonal experimental results of pyrolytic carbon (BC)-based compound fertilizer with slow-release properties obtained by using pyrolytic carbon as biochar are shown in Table 4. Table 4. Results of the orthogonal experiment on pyrolysis carbon-based compound fertilizer

[0028] One-way ANOVA was performed on the above orthogonal experimental results to explore the differences in the effects of carbon content, binder concentration, and molding pressure on resistance to breakage, water permeability, and density. Use response indicators ( ) and the average value of the response index ( ( ) to characterize the quality of the experimental results; Average response index ( The formula for calculating ) is: ; To further determine the magnitude of the influence among the factors, the range (R) is introduced. Factors with larger ranges are considered primary factors, and vice versa. The formula for calculating the range (R) is: ; Finally, the most suitable preparation scheme was selected using a comprehensive balance method; The results of the one-way ANOVA of the adsorption-type pyrolysis carbon-based compound fertilizer are shown in Table 5. Table 5. Results of one-way ANOVA for adsorption-type pyrolysis carbon-based compound fertilizer

[0029] As shown in Table 4, the differences in the effects of molding pressure, carbon content, and binder concentration on resistance to crushing force, water permeability, and density were analyzed using a one-way ANOVA. The statistical model R0... 2 The values ​​were 0.998, 0.929, and 0.973, respectively, meaning that molding pressure, carbon content, and binder concentration could explain 99.80% of the changes in fracture resistance, 92.90% of the changes in water permeability, and 97.30% of the changes in density. Further analysis showed that molding pressure and carbon content had a very significant effect on fracture resistance (p<0.01), while binder concentration did not have a significant effect on fracture resistance. However, molding pressure, carbon content, and binder concentration did not have a significant effect on water permeability and density.

[0030] The range analysis results of the adsorption-type pyrolysis carbon-based compound fertilizer are shown in Table 6. Table 6. Range analysis results of adsorption-type pyrolysis carbon-based compound fertilizer

[0031] Table 5 shows that the influence of each factor on the three indicators varies, with the order of importance of the factors being BAC. For fracture resistance, the theoretically optimal combination is A2B2C2; for impermeability, the theoretically optimal combination is A3B3C1 / A3B3C3; and for density, the theoretically optimal combination is A3B1C3. A comprehensive balance method is used to select the scheme suitable for all three evaluation indicators. For factor A, impermeability and density are best at level A3; for factor B, the three indicators are best at levels B1, B2, and B3 respectively, and since it is the primary factor, referring to the selection of the secondary factor A, B3 is chosen; similarly, for factor C, C3 is chosen.

[0032] In summary, as the molding pressure increases, the crush resistance, water permeability resistance, and density of biochar-based compound fertilizer gradually increase. This is because as the molding pressure increases, the particles of biochar-based compound fertilizer become more compact, thus increasing their crush resistance, water permeability resistance, and density. As the amount of char added increases, the crush resistance of biochar-based compound fertilizer gradually decreases or tends to stabilize. This is because the increased content of powdered char leads to poorer adhesion between biochar-based compound fertilizer particles, making the particles more prone to breakage. As a binder that binds nutrients and biochar, an increase in its content leads to a trend of first increasing and then decreasing the crush resistance of biochar-based compound fertilizer particles. Excessive binder addition reduces the contact area between solid particles and decreases the interlocking between particles, thus reducing the crush resistance.

[0033] Based on the results of the above one-way ANOVA and range analysis, the optimal process for adsorption-type pyrolysis carbon-based compound fertilizer BCF-2 is: molding pressure 8MPa, carbon content 30%, and binder concentration 15%.

[0034] Effect test: 1. The surface morphology of BCF-2 and pyrolytic carbon BC was analyzed by scanning electron microscopy, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the surface of BCF-2 material is covered with a substance, indicating that there is a significant nutrient adsorption phenomenon. Moreover, the adsorbed particle size is small and relatively uniform, which is consistent with the adsorption results of carbon materials in nutrient solution.

[0035] 2. The structural characteristics of BCF-2 and BC were tested. The structural characteristics of BCF-2 and pyrolytic carbon (BC) are shown in Table 7. Table 7 Structural properties of BCF-2 and pyrolytic carbon (BC)

[0036] As shown in Table 5, the specific surface area of ​​BCF-2 is relatively small and differs significantly from that of the carrier, indicating that the binding of nutrients has been improved.

[0037] 3. The surface functional groups of BCF-2 and BC were qualitatively displayed using Fourier transform infrared spectroscopy, and the results are as follows: Figure 4 As shown, the functional group peaks of BCF-2 are significantly more pronounced compared to BC. (Figure 3208 cm⁻¹) -l ~3450 cm -l The broad absorption peak originates from the stretching vibration of the hydroxyl group -OH, at 2396 cm⁻¹. -l The peaks at 1684 cm⁻¹ represent the asymmetric and symmetric stretching vibrations of adipose CH₂, respectively. -l The absorption peak at 1624 cm⁻¹ is mainly due to the C=O stretching vibration of carboxylic acids. -l The peak at 1454 cm⁻¹ represents the C=C or C=O stretching vibration of the aromatic ring. -l and 1389cm -l The absorption peaks at 1076 cm⁻¹ are the vibrational peaks of aromatic C=C and OH, respectively. -l The vibrational absorption peak of CO is at 959 cm⁻¹. -l and 823 cm -l The vibrational absorption peak of Si-O is located at 549 cm⁻¹. -l The peak at this location represents the vibrational absorption peak of CH.

[0038] 4. X-ray photoelectron spectroscopy was used to analyze the nitrogen, phosphorus, and potassium spectra of BCF-2 and BC. Characteristic peaks were observed in the spectral results, including C1s, K2p, N1s, O1s, and P2p. The peak areas of the nitrogen, phosphorus, and potassium spectra of BCF-2 and BC are shown in Table 8. Table 8. Peak areas of nitrogen, phosphorus, and potassium spectra

[0039] For the N1s spectrum, from Figure 5 It was found that BC exhibited three peaks at 399.0 eV, 399.9 eV, and 400.6 eV, corresponding to the nitrogen forms present on its surface: NC pyridine nitrogen, NC pyrrole nitrogen, and NO, respectively. BCF-2 showed a significant increase in peak area compared to BC, with the peak area of ​​NC pyridine nitrogen increasing by 14.6 times. The total peak area of ​​nitrogen-containing functional groups increased by 8.6 times compared to BC. The study indicates that pyridine nitrogen is more stable and relatively more difficult to release than pyrrole nitrogen, resulting in better sustained-release performance.

[0040] For the P2p spectrum, from Figure 6It can be seen that BC has two peaks at 131.8 eV and 133.0 eV. Literature and energy dispersive spectroscopy library information indicate that the two peaks correspond to the forms of phosphorus on its surface, namely CPO and PO. The binding energy of the two functional groups of the pyrolytic carbon-based fertilizer is increased compared with the carrier carbon, and the peak area is also significantly improved, indicating that different forms of phosphorus are adsorbed and fixed on the surface of pyrolytic carbon in large quantities during the preparation process.

[0041] For the K2p spectrum, from Figure 7 It is known that BC has two peaks at 293.7 eV and 296.5 eV. Literature and energy dispersive spectroscopy library information indicate that the KO functional group is located at 293.7 eV. The binding energy of the functional group of the pyrolytic carbon-based fertilizer is increased compared with that of the carrier carbon, and the peak area is also significantly improved, indicating that potassium elements in different forms are adsorbed and immobilized on the surface of the pyrolytic carbon in large quantities during the preparation process. The peak area of ​​the KO functional group is 17.48 times larger than that of BC.

[0042] 5. Conduct nutrient leaching tests and nutrient release tests from soil columns. Experimental Design: (1) Nutrient leaching test The nutrient release of BCF-2 in water was measured to observe the slow-release effect. The experimental design and operation steps are as follows: Weigh out BCF-2 and place it into a small bag made of 100-mesh nylon mesh, then seal it. Slowly place the bag into a 250 mL Erlenmeyer flask containing 200 mL of distilled water, seal it with plastic wrap, and place it in a biochemical incubator at 25 ℃. Take samples every 24 hours. When taking samples, invert the flask three times to ensure a consistent liquid concentration, transfer the samples to a 250 mL volumetric flask, cool to room temperature, and then bring the volume to a final volume. Repeat this process seven times. Then, add another 200 mL of water to the flask containing the sample bag, seal it, and place it in the biochemical incubator for further incubation. The experiment was set up with four replicates, with the fertilizer used to prepare BCF-2 (hereinafter referred to as CF) serving as the control group.

[0043] (2) Nutrient column release test BCF-2 was uniformly mixed into a soil column and leached to observe the nutrient release of different types of carbon-based fertilizers in the soil. Based on the nutrient release of BCF-2 in water, the slow-release performance of BCF-2 applied to the soil was further verified.

[0044] The leaching device is a PVC pipe 25 cm high and 7.5 cm inner diameter, sealed at the bottom with 200-mesh mesh. It is filled with a soil-fertilizer mixture (approximately 20 cm high) of BCF-2 and air-dried soil that has passed through a 1 mm sieve, and finally covered with a layer of filter paper. The leaching device uses a plastic bottle assembly with an adjustable flow rate dripper to maintain a consistent leaching speed and minimize disturbance to the soil layer during leaching. A soil column device is also included. Figure 8 As shown in the figure. The experiment included a BCF-2 group, a control group without fertilizer, and control groups with added fertilizer (CF) and pyrolytic char + fertilizer (BC + CF).

[0045] Experimental results: (1) The 24-hour nutrient dissolution rate of BCF-2 and CF was detected, and the results are shown in Table 9: Table 9 Nutrient dissolution rate over 24 hours

[0046] As can be seen from the table, in the initial stage of nutrient release, BCF-2 showed a more obvious slow-release effect compared to pure fertilizer CF.

[0047] The total nitrogen, total phosphorus, and total potassium contents of BCF-2 and CF were collected and determined. The results are as follows: Figure 9-10 As shown: Depend on Figure 9 As can be seen from the cumulative total nitrogen release rate graph, both charcoal-based fertilizers and chemical fertilizers exhibit rapid total nitrogen release rates in the initial stages, gradually slowing down over time. Regarding release days, chemical fertilizers are fully released by day 3, while BCF-2's release period reaches 6 days. The 7-day cumulative total nitrogen release rate of BCF-2 is 87.45%. Depend on Figure 10 As can be seen from the cumulative total phosphorus release rate graph, the release pattern of total phosphorus from both charcoal-based fertilizers and chemical fertilizers is quite similar to that of total nitrogen, showing a rapid release rate in the initial stage of nutrient release, which gradually slows down over time. Furthermore, the number of days for total phosphorus release from charcoal-based fertilizers is also consistent with that of total nitrogen. The 7-day cumulative total phosphorus release rate of BCF-2 is 85.45%.

[0048] Depend on Figure 11 As can be seen from the cumulative total potassium release rate graph, the total potassium release pattern and release days of carbon-based fertilizers and chemical fertilizers are basically consistent with the above trends. The cumulative total potassium release rate of BCF-2 over 7 days is 85.09%.

[0049] (2) Results of soil column release characteristics of BCF-2 and CF nutrients, such as Figure 12-14 As shown: Depend on Figure 12It can be seen that although there are numerical differences between the cumulative nitrogen release rate in the soil column and the release rate in water, the general patterns are the same. The release rate of nutrients in all treatments was relatively fast in the initial stage. As the number of leaching cycles increased, the slope of the release curve of the charcoal-based fertilizer showed varying degrees of stability, indicating that compared to the rapid initial release and subsequent decline and stabilization of nutrients in chemical fertilizers, the nutrient release of charcoal-based fertilizers during leaching is more stable. The changes in the slope show that the nutrients in the charcoal-based fertilizer were not completely released after six leaching cycles, indicating that the nutrients were released slowly and gradually.

[0050] Depend on Figure 13-14 It can be seen that the cumulative release of phosphorus and potassium in the soil column is similar to that in water, and also has a certain similarity with the release pattern of nitrogen. Both show a trend of rapid release rate in the early stage of nutrient release, which gradually slows down over time.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A biochar-based compound fertilizer with slow-release properties, characterized in that, Including the following raw materials by mass fraction: Fertilizer 40%, biochar 10%–30%, and the remainder is binder.

2. The biochar-based compound fertilizer with slow-release properties according to claim 1, characterized in that, The fertilizer is a mixture of urea, diammonium phosphate and potassium nitrate in the ratio of N:P2O5:K2O=15:10:

15.

3. The biochar-based compound fertilizer with slow-release properties according to claim 1, characterized in that, The biochar is pyrolytic char.

4. The biochar-based compound fertilizer with slow-release properties according to claim 1, characterized in that, The adhesive is a starch solution with a concentration of 5% to 15%.

5. A method for preparing a biochar-based compound fertilizer with slow-release properties according to any one of claims 1 to 4, characterized in that, Includes the following steps: Fertilizer, biochar, and binder are mixed and pressed into shape to obtain the biochar-based compound fertilizer with slow-release properties.

6. The preparation method according to claim 5, characterized in that, The mixing method involves first dissolving the fertilizer in deionized water, then adding biochar and binder, stirring and mixing thoroughly, equilibrating for 24 hours, and then heating and drying.

7. The preparation method according to claim 5, characterized in that, The molding pressure for the pressure molding process is 4–8 MPa.

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