Composite microalgae fertilizer for relieving soil compaction and preparation method thereof

Abstract

This invention provides a compound microalgae fertilizer for alleviating soil compaction and its preparation method. The compound microalgae fertilizer includes a compound algae component and a liquid dispersion medium. The compound algae component is formed by compounding Vischeria sp. WL1, Chlorella sp., and Nostoc flagelliforme in a dry weight ratio of (3-5):(2-4):(1-2). The compound microalgae fertilizer is a liquid suspension system with a total algal solids content of 2wt%-8wt%. The algal cells in the compound algae component are live algal cells. This invention uses Vischeria sp., Chlorella sp., and Nostoc flagelliforme to construct a compound microalgae fertilizer system, which can form a multi-algae synergistic effect during soil improvement, which is beneficial to improving the structural state of compacted soil, increasing soil porosity, water retention, and aeration, thus making it more suitable for the improvement of arid and mildly to moderately saline-alkali compacted soils.

Description

Technical Field

[0001] This invention relates to the field of microalgae fertilizer and soil improvement technology, and in particular to a compound microalgae fertilizer for relieving soil compaction and its preparation method. Background Technology

[0002] Soil compaction is a common soil degradation phenomenon in dryland agriculture and saline-alkali farmland, especially under conditions of long-term application of chemical fertilizers, frequent tillage disturbance, and insufficient organic matter replenishment. Once soil compaction occurs, it typically manifests as increased soil bulk density, poor aggregate structure, decreased porosity, reduced aeration and water permeability, and decreased water and fertilizer retention capacity. This restricts root development and nutrient absorption, affecting normal crop growth and leading to decreased soil fertility, reduced fertilizer utilization, and impaired yield and quality. In arid and mildly to moderately saline-alkali areas, these problems are often more pronounced, with the soil surface easily hardening and crusting, poor topsoil permeability, and persistent compaction. For compacted soil, existing technologies typically employ methods such as increasing the application of organic fertilizers, applying soil conditioners, combining with microbial inoculants, or adopting agronomic improvement measures. While these methods can replenish nutrients or improve local soil conditions to some extent, they still have the following shortcomings: First, most products mainly focus on nutrient supplementation or general soil improvement, lacking specificity for soil compaction, such as pore structure restoration, surface active system construction, and sustainable ecological regulation. Secondly, some soil improvement products have a weak ability to maintain activity in arid and mild to moderate saline-alkali environments, and their continuous effect after being applied to the soil is limited, making it difficult to simultaneously improve soil structure and enhance fertility. Third, existing single microbial or single algae preparations have relatively limited adaptability in complex farmland environments, making it difficult to simultaneously meet requirements such as drought resistance, salt and alkali resistance, surface planting, and stable application.

[0003] Therefore, a compound microalgae fertilizer for alleviating soil compaction and its preparation method are proposed. Summary of the Invention

[0004] In view of this, the present invention provides a compound microalgae fertilizer for alleviating soil compaction and a method for preparing the same, so as to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial option.

[0005] The technical solution of the present invention is implemented as follows: The first aspect of the present invention provides a compound microalgae fertilizer for alleviating soil compaction, comprising a compound algae component and a liquid dispersion medium, wherein the compound algae component is formed by compounding Vischeria sp. WL1, Chlorella sp. and Nostoc flagelliforme in a dry weight ratio of (3-5):(2-4):(1-2); the compound microalgae fertilizer is a liquid suspension system with a total algal solids content of 2wt%-8wt%, and the algal cells in the compound algae component are live algal cells.

[0006] Furthermore, the *Westlakeia* species mentioned is *Westlakeia* species with accession number CCTCC NO:M20211209.

[0007] Furthermore, the total algal solids content of the compound microalgae fertilizer is 3wt% to 6wt%, and the pH is 7.2 to 8.8.

[0008] Furthermore, the liquid dispersion medium is water, algal culture supernatant, or a mixture of the two.

[0009] Furthermore, the dry weight ratio of the *Westphalia wormi*, *Chlorella vulgaris*, and *Nostoc commune* is 4:3:1; the compound microalgae fertilizer also includes a stable dispersing component accounting for 0.05wt% to 0.20wt% of the total mass of the finished product, wherein the stable dispersing component is one or more of sodium alginate, xanthan gum, and sodium carboxymethyl cellulose.

[0010] A second aspect of this invention provides a method for preparing the above-mentioned compound microalgae fertilizer for alleviating soil compaction, comprising the following steps: S1. Activation and expansion culture were carried out on *Westbrook*, *Chlorella vulgaris*, and *Nostoc pubescens* to obtain the corresponding single algal culture solutions. S2. The single algae culture medium obtained in step S1 is subjected to outdoor aeration culture to obtain the corresponding single algae culture medium. S3. Concentrate the single algae liquid obtained in step S2 to obtain the corresponding high-concentration single algae slurry. S4. The high-concentration monoalgae slurry obtained in step S3 is mixed at a dry weight ratio of (3-5):(2-4):(1-2), and a liquid dispersion medium is added to prepare the compound microalgae fertilizer for relieving soil compaction.

[0011] Further, in step S1, when culturing *W. valera*, the concentration of NaNO3 in the culture system is 200 mg / L–400 mg / L, the concentration of NaCl is 15 g / L–20 g / L, the concentration of peptone is 100 mg / L–400 mg / L, the pH of the culture system is 7.5–8.5, the culture temperature is 25℃–30℃, and the light intensity is 40–60 μE / (m²).2 ·s).

[0012] Furthermore, the outdoor aerated culture in step S2 is carried out in a culture tank or aerated culture device, and mineral elements and nitrogen sources are added to the culture system as nutrient components.

[0013] Furthermore, the concentration in step S3 is achieved by one or more of the following methods: natural sedimentation, filtration concentration, membrane concentration, and centrifugal concentration, so that the solid content of the resulting high-concentration monoalgae slurry is 4wt% to 12wt%.

[0014] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. This invention uses *Westbrook*, *Chlorella vulgaris*, and *Nostoc commune* to construct a composite microalgae fertilizer system, which can form a multi-algae synergistic effect during soil improvement, which is beneficial to improving the structural state of compacted soil, increasing soil porosity, water retention and aeration, and thus is more suitable for the improvement of arid and mildly to moderately saline-alkali compacted soils.

[0015] Second, this invention combines three types of terrestrial microalgae to form a high-concentration liquid suspension system, which improves soil structure conditions while increasing soil organic carbon, microbial carbon, and nitrogen, phosphorus, and potassium content, thus achieving a synergistic unity of improving soil physicochemical properties and enhancing fertility.

[0016] Third, this invention selects terrestrial algae species suitable for growth in arid soils and uses separate activation culture, outdoor aeration culture, concentration pulping and compounding preparation methods to produce high-concentration liquid compound microalgae fertilizer. This not only helps to improve the product's adaptability to application in arid and mildly to moderately saline-alkali farmland, but also facilitates the product's preparation, storage, transportation and promotion.

[0017] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The present invention provides a flowchart for the preparation of a compound microalgae fertilizer that alleviates soil compaction. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, this embodiment of the invention provides a compound microalgae fertilizer for alleviating soil compaction. The compound microalgae fertilizer uses Vischeria sp. WL1, Chlorella sp., and Nostocflagelliforme as compound algae components. It is prepared by separately activating and cultivating, expanding cultivation, outdoor aerated cultivation, concentrating, and then compounding in a set ratio to obtain a high-concentration liquid suspension compound microalgae fertilizer. It is suitable for arid and mildly to moderately saline-alkali compacted soils. It can form a living algae colonization system on the soil surface and improve the soil physicochemical properties and fertility conditions through the algae themselves, the slow-release degradation products of the algae, and the synergistic effect of algae and soil microorganisms.

[0023] The basic raw materials are as follows: The strain of *Vischeria* sp. WL1 was obtained using the preservation number CCTCC NO:M20211209. Terrestrial Chlorella and Nostoc commune were prepared using terrestrial algal strains that were preserved in the laboratory and purified and rejuvenated. The activation culture conditions for *Westphalia wormini* were as follows: NaNO3 200–400 mg / L, NaCl 15–20 g / L, peptone 100–400 mg / L, pH 7.5–8.5, culture temperature 25–30℃, and light intensity 40–60 μE / (m²). 2 ·s). Terrestrial Chlorella and Nostoc commune were activated and expanded using conventional algal culture media suitable for their growth. The culture temperature was controlled at 24–30℃ and the pH was controlled at 7.0–8.5. Aeration or shaking culture methods were used. Outdoor cultivation is carried out in rectangular shallow culture tanks or aerated culture tanks with aeration devices. The depth of the culture medium is controlled at 20-45cm. Aeration is carried out continuously or intermittently, and the culture is carried out under natural light during the day. Mineral elements and nitrogen sources are added when necessary. The concentration step employs a combination of natural sedimentation and centrifugal concentration, or a combination of filtration concentration and membrane concentration, to obtain a high-concentration monoalgae slurry. The total algal solids content of the product obtained after compounding is controlled at 2wt% to 8wt%, and the target solids content is adjusted by adding water, algal culture supernatant or a mixture of the two; if necessary, a stabilizing and dispersing component is added.

[0024] Example 1 This embodiment is used to prepare a compound microalgae fertilizer with a preferred ratio for alleviating soil compaction.

[0025] Activation and scale-up of *W. wiltii*: *W. wiltii* was inoculated into 500mL Erlenmeyer flasks, with each flask containing 300mL of solution. The culture was carried out at 28℃, pH 8.0, and light intensity of 50μE / (m²). 2 Under the conditions of ·s), the algae were cultured for 6 days to obtain activated algal solution; then, at an inoculum rate of 10%, the algae were transferred to a 10L seed culture tank for further culture for 5 days to obtain the seed solution of *Westbrook*.

[0026] Activation and scale-up culture of terrestrial Chlorella: Terrestrial Chlorella was inoculated into a 500mL Erlenmeyer flask and cultured at 26℃ and pH 7.4 for 5 days. Then, it was transferred to a 10L seed culture tank at an inoculation rate of 8% for scale-up culture for 4 days to obtain terrestrial Chlorella seed solution.

[0027] Activation and scale-up culture of Nostoc pubescens: Nostoc pubescens was inoculated into a 500mL Erlenmeyer flask and cultured at 25℃ and pH 7.8 for 7 days. Then, it was transferred to a 10L seed culture tank at a 10% inoculum and cultured for 6 days to obtain Nostoc pubescens seed solution.

[0028] Outdoor aerated culture: The three seed cultures were inoculated into a 300L outdoor culture tank, with the culture depth controlled at 30cm. Continuous micro-aeration was carried out, and culture was conducted under natural light during the day, with aeration stopped for 8 hours at night. During the culture period, pH was measured every 2 days, and mineral elements and nitrogen sources were supplemented to maintain continuous algal growth. After 8-10 days of culture, three single-algae cultures were obtained.

[0029] Concentration and pulping: First, the monoalgal liquid was allowed to stand and settle for 12 hours. After discarding the supernatant, it was centrifuged at 3000 r / min for 10 min for a second concentration to obtain a high-concentration monoalgal slurry. The solid content of the *Westbrook* slurry was controlled at 10.2 wt%, the solid content of the *Chlorella vulgaris* slurry was 9.6 wt%, and the solid content of the *Nostoc commune* slurry was 8.9 wt%.

[0030] Compounding and preparation: The compound was prepared according to the dry weight ratio of *Westphalia vegetans*: *Chlorella vulgaris*: *Nostoc commune* = 4:3:1. A mixture of water and the supernatant of the algal culture solution was added as a liquid dispersion medium to make the total algal solids content of the finished product 5.0 wt%. 0.10 wt% sodium alginate was added as a stabilizing and dispersing component. After stirring evenly, it was filled into the container to obtain the compound microalgae fertilizer of Example 1.

[0031] Example 2 This embodiment is used to prepare a compound microalgae fertilizer with a low solids content.

[0032] The preparation steps are basically the same as in Example 1, except that: (1) The three types of single algal slurry were compounded according to the dry weight ratio of *Westbrook*: *Chlorella terrestrialis*: *Nostoc commune* = 3:2:1; (2) The liquid dispersion medium is the supernatant of algal culture medium; (3) The total algal solids content of the finished product is adjusted to 3.0 wt%; (4) No additional stabilizing and dispersing components are added; The final product was the compound microalgae fertilizer of Example 2.

[0033] Example 3 This embodiment is used to prepare a compound microalgae fertilizer with a high solids content.

[0034] The preparation steps are basically the same as in Example 1, except that: (1) The three single algal slurries were compounded according to the dry weight ratio of Algae Widmanstätten: Chlorella vulgaris: Nostoc commune = 5:4:2; (2) The solid content of monoalgae slurry was increased by combining membrane concentration and centrifugal concentration, with the solid content of *Westbrook* slurry being 11.5 wt%, *Chlorella vulgaris* slurry being 11.2 wt%, and *Nostoc commune* slurry being 10.8 wt%. (3) The total algal solids content of the finished product is adjusted to 8.0 wt%; (4) Add 0.15 wt% sodium carboxymethyl cellulose as a stabilizing and dispersing component; The final product was the compound microalgae fertilizer of Example 3.

[0035] Example 4 This embodiment is used to prepare composite microalgae fertilizers using different liquid dispersion media.

[0036] The preparation steps are basically the same as in Example 1, except that: (1) The three single algal slurries were compounded according to the dry weight ratio of *Westbrook*: *Chlorella terrestrialis*: *Nostoc commune* = 4:3:1; (2) The liquid dispersion medium is a mixture of deionized water and algal culture supernatant at a mass ratio of 1:1; (3) The total algal solids content of the finished product is adjusted to 6.0 wt%; (4) Add 0.08 wt% xanthan gum as a stabilizing and dispersing component; The final product was the compound microalgae fertilizer of Example 4.

[0037] Comparative Example 1 The product was prepared using the same method as in Example 1, except that only *W. w ...

[0038] Comparative Example 2 The product was prepared using the same method as in Example 1, except that only *W. w. erinaceus* and *Chlorella vulgaris* were used in a dry weight ratio of 4:3, and *Nostoc commune* was not added. The total algal solids content of the finished product was 5.0 wt%.

[0039] Comparative Example 3 The product was prepared using the same method as in Example 1, except that only *Nostoc wildina* and *Nostoc commune* were used in combination at a dry weight ratio of 4:1, and no *Chlorella vulgaris* was added. The total algal solids content of the finished product was 5.0 wt%.

[0040] Comparative Example 4 The product was prepared using the same method as in Example 1, except that three types of algae were used in combination, but the dry weight ratio of the combination was adjusted to 6:1:1, which is outside the preferred combination range of the present invention. The total algal solids content of the finished product was 5.0 wt%.

[0041] Comparative Example 5 The product was prepared using the same method as in Example 1, except that after compounding, the product was treated in a 70°C water bath for 30 minutes to inactivate the main algal cells, resulting in a non-live algal control product. The total algal solids content of the finished product was 5.0 wt%.

[0042] Test Example 1: Soil Physicochemical Properties and Fertility Improvement Test Test soil: Topsoil (0–20 cm) from a typical dry, slightly compacted farmland in Shaanxi Province was collected. After removing impurities, it was air-dried and sieved through a 2 mm sieve. The initial properties of the test soil were: pH 8.18, bulk density 1.46 g / cm³. 3 Total porosity 44.9%, maximum water holding capacity 24.8%, organic carbon 7.6 g / kg, microbial carbon 128 mg / kg, alkaline nitrogen 52.4 mg / kg, available phosphorus 8.6 mg / kg, available potassium 96.3 mg / kg. Experimental design: Each pot contained 5 kg of soil, with nine treatments in total: Examples 1-4 and Comparative Examples 1-5. A control (CK) was also included. Each treatment had three replicates. All treatments were mixed with soil at a rate of 0.50 g / kg dry matter of algae before potting, and the same watering and management conditions were maintained. Soil parameters were measured after 45 days of treatment. Test results: Table 1: Effects of different treatments on soil physicochemical properties

[0043] Table 2: Effects of different treatments on soil fertility indicators

[0044] As shown in Tables 1 and 2, all embodiments of the present invention can significantly reduce soil bulk density, increase porosity, water retention and air permeability, and increase the content of organic carbon, microbial carbon and nitrogen, phosphorus and potassium. Among them, the comprehensive effect of Example 1 is the best, indicating that the three algae, when compounded within the proportion range of the present invention, have a good synergistic effect on improving compacted soil and enhancing fertility.

[0045] Test Example 2: Wheat Seed Germination and Seedling Growth Test Experimental Methods: Plump and uniform wheat seeds were selected and soaked for 4 hours after being diluted to 25% (v / v) with the compound microalgae fertilizer stock solution of Examples 1-4 and Comparative Examples 1-5, respectively. The control group was soaked in water. Each treatment contained 50 seeds in 3 replicates, and germination tests were conducted in an artificial climate chamber. Germination rate, average root length, and average shoot length were measured 7 days after germination. Test results: Table 3 Effects of different treatments on wheat germination and seedling growth

[0046] The results in Table 3 show that the embodiments of the present invention have a better promoting effect on wheat seed germination and seedling growth, especially Embodiment 1, which is superior to the other embodiments in terms of germination rate, root length and shoot length.

[0047] Test Example 3: Test of Wheat Growth and Yield Indicators under Pot Conditions Experimental Methods: A potted plantation method was used to simulate a dryland planting environment. Each pot contained 8 kg of soil and 20 wheat seeds were sown. After emergence, seedlings were thinned to 12 plants per pot. All treatments were treated with 0.60 g / kg soil of algal dry matter. Half of the application was mixed with the soil before sowing, and the other half was diluted and sprayed onto the soil surface at the three-leaf stage. Water and basic nutrient management were consistent throughout the entire growth period. At maturity, the number of effective spikes, the number of grains per spike, the thousand-grain weight, and the yield per pot were measured. Test results: Table 4. Effects of different treatments on wheat yield composition

[0048] As shown in Table 4, all embodiments of the present invention can improve the wheat yield composition indicators. Among them, Embodiment 1 showed the best performance in terms of effective spike number, spike grain number, thousand grain weight and yield per pot, indicating that the three algae compound system of the present invention can not only improve soil conditions, but also further promote wheat growth and development and yield formation.

[0049] Test Example 4: Product Storage Stability Test Experimental method: The compound microalgae fertilizers prepared in Examples 1 to 4 were respectively placed in 1L light-proof polyethylene bottles and left to stand at 25℃ for 30 days. The appearance was observed every 5 days, and the stratification rate, redispersibility and retention of live algae were tested at 30 days. Test results: Table 5 Storage stability of products from different embodiments

[0050] The results show that, within the total algal solids range defined in this invention, the composite microalgae fertilizer prepared by rationally selecting the liquid dispersion medium and stable dispersion components has good storage stability and the ability to retain live algae.

[0051] Implementation Conclusion Based on the above embodiments, comparative examples, and test examples, it can be seen that the present invention, by compounding *Westphalia wormi*, *Chlorella vulgaris*, and *Nostoc commune* in a specific ratio and preparing a high-concentration liquid suspension compound microalgae fertilizer, can improve the pore structure, water retention, and air permeability of compacted soil while maintaining the product's adaptability to storage and transportation. It can also increase soil organic carbon, microbial carbon, and nitrogen, phosphorus, and potassium levels, and promote wheat germination, growth, and yield. This demonstrates that the present invention has good application value for soil improvement and yield increase.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A compound microalgae fertilizer for alleviating soil compaction, characterized in that: The product comprises a complex algal component and a liquid dispersion medium. The complex algal component is formed by combining Vischeria sp. WL1, Chlorella sp., and Nostoc flagelliforme in a dry weight ratio of (3-5):(2-4):(1-2). The complex microalgal fertilizer is a liquid suspension system with a total algal solids content of 2wt%-8wt%. The algal cells in the complex algal component are live algal cells.

2. The compound microalgae fertilizer for alleviating soil compaction according to claim 1, characterized in that: The *Westbrook* species in question is *Westbrook* with accession number CCTCC NO:M20211209.

3. The compound microalgae fertilizer for alleviating soil compaction according to claim 1, characterized in that: The total algal solids content of the compound microalgae fertilizer is 3wt% to 6wt%, and the pH is 7.2 to 8.

8.

4. The compound microalgae fertilizer for alleviating soil compaction according to claim 1, characterized in that: The liquid dispersion medium is water, algal culture supernatant, or a mixture of the two.

5. The compound microalgae fertilizer for alleviating soil compaction according to claim 1, characterized in that: The dry weight ratio of the *Westbrook*, *Chlorella vulgaris*, and *Nostoc pubescens* is 4:3:1; the compound microalgae fertilizer also includes a stable dispersing component accounting for 0.05wt% to 0.20wt% of the total mass of the finished product, wherein the stable dispersing component is one or more of sodium alginate, xanthan gum, and sodium carboxymethyl cellulose.

6. The method for preparing the compound microalgae fertilizer for alleviating soil compaction according to any one of claims 11 to 5, characterized in that, Includes the following steps: S1. Activation and expansion culture were carried out on *Westbrook*, *Chlorella vulgaris*, and *Nostoc pubescens* to obtain the corresponding single algal culture solutions. S2. The single algae culture medium obtained in step S1 is subjected to outdoor aeration culture to obtain the corresponding single algae culture medium. S3. Concentrate the single algae liquid obtained in step S2 to obtain the corresponding high-concentration single algae slurry. S4. The high-concentration monoalgae slurry obtained in step S3 is mixed at a dry weight ratio of (3-5):(2-4):(1-2), and a liquid dispersion medium is added to prepare the compound microalgae fertilizer for relieving soil compaction.

7. The preparation method according to claim 6, characterized in that: In step S1, when culturing *W. valera*, the concentration of NaNO3 in the culture system is 200 mg / L–400 mg / L, the concentration of NaCl is 15 g / L–20 g / L, the concentration of peptone is 100 mg / L–400 mg / L, the pH of the culture system is 7.5–8.5, the culture temperature is 25℃–30℃, and the light intensity is 40–60 μE / (m²). 2 ·s).

8. The preparation method according to claim 6, characterized in that: The outdoor aerated culture in step S2 is carried out in a culture tank or aerated culture device, and mineral elements and nitrogen source are added to the culture system as nutrient components.

9. The preparation method according to claim 6, characterized in that: The concentration in step S3 is achieved by one or more of the following methods: natural sedimentation, filtration concentration, membrane concentration, and centrifugal concentration, so that the solid content of the resulting high-concentration monoalgae slurry is 4wt% to 12wt%.

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