Active desert microalgae biological fertilizer and application thereof

Abstract

The invention discloses an active desert microalgae biological fertilizer and application thereof, and belongs to the technical field of biological fertilizers. The active desert microalgae biological fertilizer is prepared from the following components in percentage by weight: 10 to 50 percent of cyanobacteria nitrogen fixation, 10 to 30 percent of microcoleus vasinatus, 10 to 50 percent of chlorella pyrenoidosa, 10 to 30 percent of Scenedesmus armatus, 10 to 50 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens, 10 to 30 percent of bacillus amyloliquefaciens and 10 to 30 percent of bacillus The microalgae in the desert microalgae biological fertilizer is in a living body state, can perform a series of life activities such as cell reproduction and metabolism, is vigorous in vitality and high in carbon fixation and nitrogen fixation efficiency, and can remarkably improve the soil fertility, provide nutrition for crop growth, prevent soil hardening and improve the stress resistance of crops.

Description

Technical Field

[0001] The invention belongs to the technical field of biological fertilizers, and in particular relates to an active desert microalgae biological fertilizer and application thereof. Background Art

[0002] As the world's population continues to grow, the demand for food is also rising. Although the large-scale use of fertilizers in the food production process has greatly increased the food supply, it has also brought a series of environmental problems, such as soil acidification, heavy metal pollution, soil compaction, nitrate pollution, etc., causing the soil fertility and crop quality to decline. Therefore, curbing the negative impact of the agricultural production process on the environment and reducing the use of fertilizers while ensuring food production have become issues that my country urgently needs to solve.

[0003] Microalgae are a type of low-level autotrophic organisms with tiny individuals, simple structures, and high photosynthetic utilization. They are widely distributed in different habitats such as soil, oceans, rivers, and lakes. The advantages of microalgae as a biological fertilizer are as follows: 1) Microalgae can prevent nutrient loss by slowly releasing nitrogen, phosphorus, and potassium to meet the growth needs of plants. 2) In addition to containing a large number of nutrients, microalgae also contain trace elements and substances that promote plant growth, such as plant hormones, vitamins, carotenoids, amino acids, and antifungal substances, which can promote crop growth and improve soil fertility. 3) Microalgae reproduce quickly and can be cultivated on a large scale. Its biomass can be directly used for soil inoculation without polluting the surrounding environment such as groundwater and soil. 4) It can repair damaged soil, such as desertified soil and saline-alkali land.

[0004] Biological nitrogen fixation is the main source of nitrogen in natural ecosystems. Nitrogen-fixing cyanobacteria are nitrogen-fixing organisms whose annual nitrogen fixation is second only to the symbiotic combination of leguminous plants and rhizobia on the earth, and are an important resource of available biological nitrogen fertilizer. Nitrogen-fixing cyanobacteria convert molecular nitrogen in the air into nitrogen compounds through heterocysts, thereby meeting the needs of animals and plants in the soil. At the same time, nitrogen-fixing cyanobacteria are the only organisms discovered that can carry out photosynthesis and nitrogen fixation at the same time. They do not compete with plants for nitrogen needs, and they will continuously secrete nitrogen-containing compounds and active substances such as amino acids, sugars, polypeptides and a small amount of hormones during their growth and reproduction, which promote the growth of other microorganisms and increase the concentration of effective nitrogen in the soil. Summary of the invention

[0005] The invention provides an active desert microalgae bio-fertilizer. The active desert microalgae bio-fertilizer comprises an active desert microalgae liquid. The desert microalgae comprise 10-50% of nitrogen-fixing Cyanospira capsulate, 10-30% of Microcoleus vaginatus, 10-50% of Chlorella pyrenoidosa and 10-30% of Scenedesmus armatus, wherein the above percentages are percentages in quantity.

[0006] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are: nitrogen-fixing spirulina 40%, sheathed microcoleus 20%, pyrenoid chlorella 20%, and armored scenedesmus 20%.

[0007] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are: 30% of nitrogen-fixing spirulina, 10% of sheathed microcoleus, 30% of pyrenoid chlorella, and 30% of armored scenedesmus.

[0008] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are: 30% of nitrogen-fixing spirulina, 20% of sheathed microcoleus, 30% of pyrenoid chlorella, and 20% of armored scenedesmus.

[0009] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are as follows: nitrogen-fixing spirulina 40%, sheathed microcoleus 30%, pyrenoid chlorella 15%, and armored scenedesmus 15%.

[0010] Preferably, the cell numbers of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are as follows: nitrogen-fixing spirulina 20%, sheathed microcoleus 10%, pyrenoid chlorella 40%, and armored scenedesmus 30%.

[0011] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are: nitrogen-fixing spirulina 50%, sheathed microcoleus 30%, pyrenoid chlorella 10%, and armored scenedesmus 10%.

[0012] Preferably, the cell number ratios of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella, and armored scenedesmus in the active desert microalgae bio-fertilizer are: nitrogen-fixing spirulina 10%, sheathed microcoleus 10%, pyrenoid chlorella 50%, and armored scenedesmus 30%.

[0013] The number of green algae cells in the active desert microalgae liquid is ≥ 1.0×10 7 Pieces / mL.

[0014] The wet weight of cyanobacteria biomass in the active desert microalgae liquid is ≥4.0 mg / mL.

[0015] The liquid matrix of the active desert microalgae liquid, the blue algae and the green algae, uses the same culture medium, namely, BG11 liquid culture medium.

[0016] The composition of BG11 liquid medium is as follows: NaNO3 1.5 g / L, K2HPO4 0.04 g / L, MgSO4.7H2O 0.075 g / L, CaCl2.2H2O 0.036 g / L, citric acid 0.006 g / L, ammonium ferric citrate 0.006 g / L, EDTANa2 0.001 g / L, Na2CO3 0.02 g / L, trace element A 51 mL;

[0017] The composition of trace elements A5 is as follows: H3BO3 2.860 g / L, MnCl2.4H2O 1.860 g / L, NaMoO4.2H2O 0.39 g / L, ZnSO4.7H2O 0.22 g / L, CuSO4.5H2O 0.08 g / L, Co(NO3)2.6H2O 0.05 g / L.

[0018] Cyanospira capsulate, Cyanobacteria, prokaryotic organism. The plant body is blue-green, with bead-shaped algae filaments, isopolar, unbranched, narrow cells at the top of the algae filaments, spherical cells that make up the algae filaments, 3-5μm wide, and spherical heterocysts in the algae cells, with a diameter of 4-5μm. Cyanospira capsulate reduces atmospheric nitrogen into nitrogen compounds that can be used by plants through the action of nitrogenase in its cells, and continuously secretes nitrogen-containing compounds and active substances such as amino acids and polypeptides during its growth and reproduction. After the death of nitrogen-fixing spirulina, it releases a large amount of ammonia nitrogen, which can increase soil organic matter and improve soil fertility.

[0019] Microcoleus vaginatus is a widely distributed terrestrial filamentous algae in the phylum Cyanobacteria and is also the dominant species of algal crusts in desert arid areas. Microcoleus vaginatus algae bundles are filamentous aggregates formed by multiple algal filaments gathered and interwoven in a common gelatinous sheath. The filaments are usually rope-like and entangled with sand particles and bonded together, becoming the main factor in increasing the cohesion of particles on the soil surface.

[0020] Chlorella pyrenoidosa, a chlorophyta and eukaryotic organism, is a spherical or elliptical single-cell algae with a diameter of 5-10um. Chlorella has strong environmental adaptability and contains a variety of active ingredients such as functional proteins, essential amino acids, polysaccharides, chlorophyll, polyunsaturated fatty acids, and unique Chlorella growth factors. Chlorella has a strong reproductive capacity and a strong ability to utilize sunlight. It can photosynthesize as long as it is in the state of visible light. Chlorella can be used as a microalgae biofertilizer in agriculture to increase soil nutrients, improve soil quality, and increase plant seed germination rate, yield, and fruit quality.

[0021] Scenedesmus armatus, a Chlorophyta, eukaryotic organism, has a true fixed group consisting of 2, 4, or 8 cells, and the cells are arranged in a straight line, even or slightly staggered. Scenedesmus cells are rich in protein and vitamins and have strong tolerance to organic pollutants. Studies have shown that Scenedesmus armatus can grow rapidly under a CO2 concentration of 60%.

[0022] The present invention also provides a preparation method of the above-mentioned active desert microalgae bio-fertilizer, comprising: respectively expanding the cultivation of nitrogen-fixing blue Spirulina, sheathed Microcoleus, protein-core Chlorella, and armored Scenedesmus, and mixing the obtained nitrogen-fixing blue Spirulina, sheathed Microcoleus, protein-core Chlorella, and armored Scenedesmus algae liquid to obtain the desert microalgae bio-fertilizer.

[0023] The nitrogen-fixing blue spirulina, sheathed microsheath, pyrenoid chlorella and armored scenedesmus are respectively expanded and cultured in BG11 liquid culture medium.

[0024] The composition of BG11 liquid medium is as follows: NaNO3 1.5 g / L, K2HPO4 0.04 g / L, MgSO4.7H2O 0.075 g / L, CaCl2.2H2O 0.036 g / L, citric acid 0.006 g / L, ammonium ferric citrate 0.006 g / L, EDTANa2 0.001 g / L, Na2CO3 0.02 g / L, trace element A 51 mL;

[0025] The composition of trace elements A5 is as follows: H3BO3 2.860 g / L, MnCl2.4H2O 1.860 g / L, NaMoO4.2H2O 0.39 g / L, ZnSO4.7H2O 0.22 g / L, CuSO4.5H2O 0.08 g / L, Co(NO3)2.6H2O 0.05 g / L.

[0026] During the expansion culture, when the number of green algae cells is ≥ 1.0×10 7 When the number of cells / mL reaches 40,000, the culture is expanded to the next level.

[0027] During the expansion culture, when the wet weight of the cyanobacterial biomass is ≥4.0 mg / mL, the next stage of expansion culture is entered.

[0028] The illumination intensity for the expanded culture of blue algae and green algae is 2700-3500 lux, more preferably 3000 lux.

[0029] The temperature for expanding the culture of the blue algae and green algae is 27-29°C, more preferably 28°C.

[0030] The light-dark ratio of the expanded culture of the blue algae and green algae is 16h:8h.

[0031] During the expansion culture process, purified air is continuously introduced into the algae liquid, and CO2 gas is intermittently introduced; the CO2 gas is aerated at intervals of 2-4 hours, and each aeration lasts 20-40 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The microalgae in the desert microalgae biofertilizer of the present invention are all in a living state, can carry out a series of life activities such as cell reproduction and metabolism, have strong vitality, and have high carbon and nitrogen fixation efficiency, can significantly improve soil fertility, provide nutrition for crop growth, prevent soil compaction, and improve crop stress resistance.

[0034] The microalgae biofertilizer of the present invention has an appropriate biomass of microalgae and high activity of microalgae. The various microalgae can have good compatibility and symbiosis with each other, and the number of living green algae cells in each 1 mL of algae liquid can reach 1.0×10 7 The wet weight of the living cytoplasm of cyanobacteria is more than 4.0 mg, and it can maintain vigorous vitality at room temperature.

[0035] All the microalgae contained in the desert microalgae biofertilizer of the present invention are beneficial algae, which can not only replenish soil organic matter after death, but also release organic matter during their life activities to enrich the soil. DETAILED DESCRIPTION

[0036] Example 1

[0037] An active desert microalgae biofertilizer, the preparation method of which comprises the following steps:

[0038] (1) Four algae liquids were obtained by expanding the culture of nitrogen-fixing Spirulina, Microcystis sp., Chlorella sp., and Scenedesmus sp.

[0039] The above-mentioned expansion culture process of blue algae and green algae liquid includes: preparing BG11 liquid culture medium, packaging, sealing with sealing film, sterilizing at high temperature and high pressure for 20 minutes at 121℃ → using an inoculation loop to take an appropriate amount of blue algae and green algae colonies under sterile conditions and inoculate them into the freshly prepared 20mL liquid BG11 culture medium, static culture for 12-15 days, and obtain 20mL algae liquid → inoculate into 80mL liquid BG11 culture medium and continue static culture for 12-15 days to obtain 100mL algae liquid → inoculate into 900mL liquid BG11 culture medium and continue aeration culture for 7-10 days to obtain 1L algae liquid → inoculate into 4L liquid BG11 culture medium and continue aeration culture for 7-10 days to obtain 5L algae liquid. During the culture process, 2ml samples were regularly taken from the culture medium every day, and the cell morphology, cell size, purity, cell number and other indicators were observed using an optical microscope. At the end of each stage of expansion culture, the number of active green algae cells in the microalgae solution was ≥1.0×10 7 / mL, the wet weight of cyanobacteria cytoplasm was ≥4mg / mL, and the number of living green algae cells in the algae solution was ≥1.0×10 7 / mL, and the wet weight of living cytoplasm of cyanobacteria was ≥4mg / mL.

[0040] When expanding the culture of blue algae and green algae, the light intensity is 3000 lux, the culture temperature is 28°C, and the light-dark ratio is 16h:8h. During the expansion culture process, purified air is continuously introduced into the algae liquid, and CO2 gas is intermittently introduced. The CO2 gas ventilation interval is 3h, and each ventilation lasts 30min. By adopting the above scheme, the introduced gas can not only promote the growth and reproduction of microalgae cells, but also play a role in stirring the algae liquid, so that the microalgae are evenly exposed to light, and improve the uniformity and consistency of microalgae growth and reproduction.

[0041] The four kinds of algae liquid were mixed to obtain active desert microalgae bio-fertilizer. According to the type of microalgae cells, the comprehensive ratio of blue algae and green algae was 6:4. The specific quantities were as follows: 40% nitrogen-fixing blue Spirulina, 20% sheathed Microcystis, 20% protein-nucleated Chlorella, and 20% armored Scenedesmus.

[0042] Example 2

[0043] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae to green algae is 4:6, and the specific proportions are: 30% nitrogen-fixing blue spirulina, 10% sheathed Microcoleus, 30% protein-core Chlorella, and 30% armored Scenedesmus.

[0044] Example 3

[0045] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae to green algae is 5:5, and the specific proportions are: 30% nitrogen-fixing blue spirulina, 20% sheathed Microcoleus, 30% protein-nucleated Chlorella, and 20% armored Scenedesmus.

[0046] Example 4

[0047] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae to green algae is 7:3, and the specific proportions are: 40% of nitrogen-fixing blue spirulina, 30% of sheathed Microcoleus, 15% of protein-core Chlorella, and 15% of armored Scenedesmus.

[0048] Example 5

[0049] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae and green algae is 3:7, and the specific proportions are: 20% nitrogen-fixing blue spirulina, 10% sheathed Microcoleus, 40% protein-core Chlorella, and 30% armored Scenedesmus.

[0050] Example 6

[0051] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae to green algae is 8:2, and the specific proportions are: 50% nitrogen-fixing blue spirulina, 30% sheathed Microcoleus, 10% protein-core Chlorella, and 10% armored Scenedesmus.

[0052] Example 7

[0053] The difference from Example 1 is that in the algae solution, the comprehensive ratio of blue algae and green algae is 2:8, and the specific proportions are: 10% nitrogen-fixing blue spirulina, 10% sheathed Microcoleus, 50% protein-core Chlorella, and 30% armored Scenedesmus.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that the active desert microalgae cell biofertilizer only contains cyanobacteria, and the specific proportions are: 60% of nitrogen-fixing cyanobacteria and 40% of sheathed Microcoleus.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that the active desert microalgae cell biofertilizer contains only green algae, and the specific proportions are: 50% of Chlorella pyrenoidosa and 50% of Scenedesmus armoredus.

[0058] Application Example 1

[0059] Experiment on the survival rate, compatibility and symbiosis of living algae cells in desert microalgae biofertilizer:

[0060] 9 portions of desert active microalgae bio-fertilizers prepared in Examples 1-7 and Comparative Examples 1 and 2 were stored at room temperature in a dark environment for 15 days, 30 days, 60 days, 90 days, and 120 days. The 9 portions of desert active microalgae cell bio-fertilizers were examined under a microscope, and the survival rate of the microalgae was calculated based on the ratio of the number of active microalgae cells during microscopic examination to the number of active microalgae cells at the initial time. The samples were shaken well before microscopic examination. The test results are shown in Tables 1 to 8.

[0061] Table 1 Results of the microalgae cell survival rate test in Example 1

[0062]

[0063] Table 2 Results of the microalgae cell survival rate test in Example 2

[0064]

[0065]

[0066] Table 3 Results of the microalgae cell survival rate test in Example 3

[0067]

[0068] Table 4 Results of the microalgae cell survival rate test in Example 4

[0069]

[0070] Table 5 Results of the microalgae cell survival rate test in Example 5

[0071]

[0072] Table 6 Results of the microalgae cell survival rate test in Example 6

[0073]

[0074] Table 7 Results of microalgae cell survival rate test in Example 7

[0075]

[0076]

[0077] Table 8 Results of the survival rate test of microalgae cells in Comparative Examples 1 and 2

[0078]

[0079] It can be seen from Tables 1 to 6 that in the desert active microalgae bio-fertilizer of Example 1, the preparation ratio of blue algae to green algae is 6:4, and the survival rate of all microalgae can still be maintained at more than 93% after 120 days, indicating that the blue algae and green algae of the present invention maintain cell activity for a long time, and the microalgae in this ratio coexist with each other and have good synergy.

[0080] In Examples 2, 5, and 7, the preparation ratios of blue algae and green algae are 4:6, 3:7, and 2:8, respectively. In Example 2, the survival rate of blue algae is 84.5% at 60 days, 72.5% at 90 days, and 60.5% at 120 days. In Example 5, the survival rate of blue algae is 67.5% at 60 days, 55% at 90 days, and only 47.5% at 120 days. In Example 7, the survival rate of blue algae is 55% at 60 days, 50% at 90 days, and only 40% at 120 days. It is proved that when green algae become the dominant population, the cell activity of blue algae is inhibited.

[0081] In Example 3, the ratio of blue algae to green algae is 5:5. The survival rate of blue algae in Example 3 is 96% at 60 days, 92.5% at 90 days, and 89% at 120 days. This proves that when the ratio of green algae to blue algae is the same, green algae inhibits the cell activity of blue algae but does not affect it.

[0082] In Examples 4 and 5, the preparation ratios of blue algae and green algae were 7:3 and 8:2 respectively. Since blue algae were more important and dominant, the survival rate of green algae in Example 4 was 88% at 60 days, 79% at 90 days, and 62.5% at 120 days. The survival rate of green algae in Example 6 was 62.5% at 60 days, 54% at 90 days, and only 42.5% at 120 days. It was proved that when blue algae became the dominant population, it had an inhibitory effect on green algae cells.

[0083] From the data in Table 8, it can be concluded that the activity of a single microalgae class was higher than 92% at 120 days.

[0084] Application Example 2

[0085] Experiment on improving farmland soil with desert active microalgae biofertilizer:

[0086] Nitrogen is one of the most important nutrients in the process of plant growth, and is mainly related to crop yield, and is of great significance in fertilization. The nitrogen-fixing blue spirulina in the active desert microalgae biofertilizer of the present invention has heterosexual cells, which supplement nitrogen for plant roots through nitrogen fixation. The large amount of extracellular polysaccharides secreted by the nitrogen-fixing blue algae during the growth and reproduction process are adhesives for forming soil aggregate structure and maintaining aggregate stability, which can overcome the soil compaction phenomenon caused by long-term excessive application of inorganic fertilizers, thereby promoting the long-term sustainable development of agricultural ecology.

[0087] In this experiment, plastic flower pots of the same specifications were selected and filled with 200g of farmland soil samples, and Examples 1-7, Comparative Example 1 single active blue algae, and Comparative Example 2 single active green algae were used for spraying, and the spraying amount was 40ml. A comparative test lasting 30 days was conducted, in which the active microalgae biological fertilizer liquid was sprayed onto the surface of the flower pots filled with farmland soil, and 3 parallels were set for each treatment. During the cultivation period, the sprayed plastic flower pots were placed on the balance every morning, and micro-spraying was used to supplement the test water requirement. After 30 days of cultivation, the total nitrogen content of the soil was determined by the Kjeldahl method. To reflect the nitrogen supply in the soil, the test results are shown in Table 9;

[0088] Table 9 Test results of soil total nitrogen content

[0089]

[0090] Note: Data are the mean ± standard deviation of 3 replicates.

[0091] It can be seen from Table 9 that the active microalgae biofertilizer prepared in Examples 1-7 can increase the total nitrogen content of the soil. The active microalgae cell biofertilizer has efficient nitrogen fixation and decomposition functions, can fix molecular nitrogen in the atmosphere into bound nitrogen, and further synthesize proteins and amino acids to increase soil fertility.

[0092] In summary, the present invention obtains active desert microalgae bio-fertilizer through scientific proportioning. Compared with conventional chemical fertilizers, the microalgae bio-fertilizer obtained by the present invention has the characteristics of safety, ecology, and environmental protection. The microalgae in the active desert microalgae bio-fertilizer of the present invention are all in a living state, with high carbon and nitrogen fixation efficiency, which improves soil fertility, provides nutrition for crop growth, prevents soil compaction, and improves crop stress resistance.

[0093] In summary, the present invention obtains active desert microalgae bio-fertilizer through scientific proportioning. Compared with conventional chemical fertilizers, the microalgae bio-fertilizer obtained by the present invention has the characteristics of safety, ecology, and environmental protection. The microalgae in the active desert microalgae bio-fertilizer of the present invention are all in a living state, with high carbon and nitrogen fixation efficiency, which improves soil fertility, provides nutrition for crop growth, prevents soil compaction, and improves crop stress resistance.

[0094] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An active desert microalgae biofertilizer, characterized in that: The active desert microalgae biofertilizer comprises 10-50% of nitrogen-fixing Cyanospira capsulate, 10-30% of Microcoleus vaginatus, 10-50% of Chlorella pyrenoidosa and 10-30% of Scenedesmus armatus, and the above percentages are percentages in terms of quantity.

2. The active desert microalgae biofertilizer according to claim 1, characterized in that: The cell numbers of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella and armored scenedesmus in the active desert microalgae biofertilizer are as follows: nitrogen-fixing spirulina 40%, sheathed microcoleus 20%, pyrenoid chlorella 20% and armored scenedesmus 20%.

3. The active desert microalgae biofertilizer according to claim 1, characterized in that: The cell numbers of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella and armored scenedesmus in the active desert microalgae biofertilizer are as follows: 30% of nitrogen-fixing spirulina, 10% of sheathed microcoleus, 30% of pyrenoid chlorella and 30% of armored scenedesmus.

4. The active desert microalgae biofertilizer according to claim 1, characterized in that: The cell numbers of nitrogen-fixing spirulina, sheathed microsheath, pyrenoid chlorella and armored scenedesmus in the active desert microalgae biofertilizer are as follows: 30% of nitrogen-fixing spirulina, 20% of sheathed microsheath, 30% of pyrenoid chlorella and 20% of armored scenedesmus.

5. The active desert microalgae biofertilizer according to claim 1, characterized in that: The cell numbers of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella and armored scenedesmus in the active desert microalgae biofertilizer are as follows: nitrogen-fixing spirulina 40%, sheathed microcoleus 30%, pyrenoid chlorella 15% and armored scenedesmus 15%.

6. The active desert microalgae biofertilizer according to claim 1, characterized in that: The cell numbers of nitrogen-fixing spirulina, sheathed microcoleus, pyrenoid chlorella and armored scenedesmus in the active desert microalgae biofertilizer are as follows: 20% of nitrogen-fixing spirulina, 10% of sheathed microcoleus, 40% of pyrenoid chlorella and 30% of armored scenedesmus.

7. A method for preparing the active desert microalgae biofertilizer according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: respectively expanding and culturing nitrogen-fixing blue spirulina, sheathed microsheathed algae, pyrenoid chlorella and armored scenedesmus, and mixing the obtained nitrogen-fixing blue spirulina, sheathed microsheathed algae, pyrenoid chlorella and armored scenedesmus algae liquid to obtain desert microalgae biofertilizer.

8. The preparation method according to claim 7, characterized in that: The nitrogen-fixing blue spirulina, sheathed microsheath, pyrenoid chlorella and armored scenedesmus are respectively expanded and cultured in BG11 liquid culture medium.

9. Use of the active desert microalgae biofertilizer according to any one of claims 1 to 6 in improving soil fertility.

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