A nitrogen-fixing algal floc active phosphorus bio-soil conditioner for saline-alkali land and a preparation method thereof

Abstract

The application belongs to the technical field of agricultural biological fertilizer, and particularly relates to a nitrogen-fixing algal flocculent active phosphorus biological soil improver for saline-alkali soil and a preparation method thereof. The improver comprises, by weight, 10-120 parts of nitrogen-fixing blue algae, and 2-30 parts of auxiliary agents; the nitrogen-fixing blue algae comprises small monomer and nitrogen-fixing fishy algae; the nitrogen-fixing blue algae is algal liquid or algal powder, and the auxiliary agent is phosphorus-solubilizing bacteria and phosphorus-accumulating bacteria, or the auxiliary agent is a filler and an adhesive. The active biological improver is prepared based on the optimized recombination of the nitrogen-fixing blue algae, can be used to improve nitrogen source and phosphorus source in saline-alkali soil, so as to improve the nitrogen and phosphorus available for plant absorption in the saline-alkali soil, reduce the loss of nitrogen and phosphorus in the soil, improve the land hardening condition, and enhance the utilization rate of the soil; meanwhile, the active biological improver has multiple functional advantages such as green, environmental protection, and economy; and can be used to prepare nitrogen-phosphorus biological active composite fertilizer for saline-alkali paddy fields and rape, so as to meet the diversified demand of agricultural production for fertilizer functions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural biological fertilizer, and particularly relates to a nitrogen-fixing algal floc active phosphorus biological soil improver for saline-alkali land and a preparation method thereof. BACKGROUND

[0002] When the salt content in the soil is greater than the normal growth level of plants, it is called saline-alkali land. When the saline-alkali content is more than 0.6%, it is called heavy saline-alkali land. Data shows that the world's saline-alkali land area is 12.495 billion mu, and China has 1.5 billion mu of saline-alkali land, of which 86.53 million mu is heavy saline-alkali land, accounting for more than 20% of the total saline-alkali land area; the harm of soil salinization is very great, and has adverse effects on the natural growth of trees and agricultural productivity, and the ecological benefits decrease sharply. Therefore, it is imperative to effectively and practically improve the heavy saline-alkali land.

[0003] The large-scale and long-term use of chemical fertilizers and pesticides pollutes the soil, water and agricultural products, and at the same time, the microorganisms on which plants rely for survival in the soil are also killed, leading to the imbalance of farmland ecology in many high-yield crop areas, more and more diseases and pests, and increasingly serious problems such as farmland pollution, water pollution and decline in agricultural product quality, which also have irreversible effects on the environment. Some people have studied the influence of microbial fertilizer on the soil of kiwi fruit orchard and the quality of fruit through experiments, which has a certain improvement effect, but the participation of microorganisms is single, the improvement speed is slow, and part of the bacteria has inhibitory effect on the nature of the soil.

[0004] The use of active microalgae fertilizer can improve the microbial ecosystem of the soil, improve the fertility, reduce the use of chemical fertilizers, and help crops to maximize the absorption and utilization of nutrients. Microalgae have strong ability to utilize ammonia nitrogen, can utilize ammonia nitrogen to synthesize amino acids in the body without energy consumption, and the amino acids are absorbed into the plant body by the root system to synthesize proteins. At the same time, the extracellular secretion of microalgae can help the growth of soil bacteria.

[0005] About 30% of the global farmland is deficient in phosphorus. The productivity of crops in saline-alkali soils depends more on phosphorus than on other nutrients or environmental factors. It is important to enhance the recycling of phosphorus. However, the excessive application of traditional phosphorus fertilizers has adverse effects on the soil, including the following aspects: (1) excessive phosphorus nutrition can greatly enhance the respiration of crops, thus consuming the sugar and energy stored in the crops. (2) After excessive application of calcium superphosphate, a large amount of insoluble zinc phosphate salt is formed in the soil, and the crops show obvious zinc deficiency symptoms; after excessive application of alkaline phosphorus fertilizers such as calcium magnesium phosphate, the soil is alkalized, the availability of zinc is reduced, and the absorption of zinc by crops is affected. (3) Excessive application of phosphorus can cause crops to lose silicon. Silicon has a very positive effect on the growth and high yield of many crops. Sometimes, the silicon deficiency of rice is caused by excessive application of phosphorus. (4) Excessive application of phosphorus fertilizers often causes the "strong phosphorus and weak molybdenum" phenomenon between phosphorus and molybdenum, so that the crops cannot absorb and utilize phosphorus and molybdenum. (5) Phosphorus fertilizers are mainly derived from phosphate rock, which contains many impurities, including harmful elements such as cadmium, lead and fluorine. Therefore, excessive application of phosphorus fertilizers can cause the accumulation of harmful elements in the soil. SUMMARY

[0006] In view of the problems existing in the prior art, the purpose of the present application is to provide a method for preparing a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali soils, which can effectively fix nitrogen and capture phosphorus, thereby improving the nitrogen and phosphorus in the soil and promoting the absorption of nutrient components by crops.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] A nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali soils, comprising, by weight, 10-120 parts of nitrogen-fixing blue-green algae and 2-30 parts of auxiliary agents; the nitrogen-fixing blue-green algae comprises small Scytonema and nitrogen-fixing Anabaena;

[0009] The nitrogen-fixing blue-green algae is algal liquid or algal powder; the auxiliary agents are divided into first auxiliary agents and second auxiliary agents; the first auxiliary agents are phosphorus-solubilizing bacteria and phosphorus-accumulating bacteria; and the second auxiliary agents are fillers and adhesives.

[0010] I. Liquid preparation

[0011] (1) When the soil conditioner is a liquid preparation, the nitrogen-fixing blue-green algae is small Scytonema culture solution and nitrogen-fixing Anabaena culture solution; the auxiliary agents are selected from the first auxiliary agents, which are phosphorus-solubilizing bacteria and phosphorus-accumulating bacteria; the small Scytonema culture solution and the nitrogen-fixing Anabaena culture solution both refer to algal liquid cultured to the logarithmic phase, and the concentration of the small Scytonema culture solution and the nitrogen-fixing Anabaena culture solution is 0.3g / L-0.5g / L;

[0012] 10-20 parts by weight of Tolypothrix tenuis culture solution, 10-20 parts by weight of Anabaena azotica culture solution, 1-10 parts by weight of phosphorus-dissolving bacteria, and 1-5 parts by weight of phosphorus-accumulating bacteria;

[0013] Further, the phosphorus-dissolving bacteria include one or more of Bacillus megaterium, Bacillus mucilaginosus and Bacillus azotoformans.

[0014] The Bacillus megaterium can degrade insoluble phosphorus-containing compounds in the soil, and has a synergistic effect of nitrogen fixation when mixed with Bacillus sphaericus, so as to improve soil fertility and increase yield and income; the Bacillus mucilaginosus can promote the transformation of ineffective phosphorus and potassium in the soil, increase the supply of phosphorus and potassium in the soil, and improve crop yield, and can also produce carbonic anhydrase and has a certain effect on carbon dioxide fixation. The Bacillus azotoformans has strong nitrogen fixation ability and strong competitive adaptability.

[0015] Further, the Tolypothrix tenuis contains rich nitrogenase in heteromorphous cells, which is the place for nitrogen fixation of cyanobacteria; the Anabaena azotica can not only dissolve phosphorus in the soil to increase the effective phosphorus in the soil, but also reduce the demand of plants for additional phosphorus.

[0016] Further, the phosphorus-accumulating bacteria include one or more of Acinetobacter sp., Aeromonas sp. and Pseudomonas sp.

[0017] The Acinetobacter sp. can form polyphosphate in cells, and then degrade the intracellular polyphosphate to release phosphorus under anaerobic conditions during the vigorous metabolism period; the Aeromonas sp. can not only form polyphosphate inclusions, but also degrade organic matter; the Pseudomonas sp. can increase the content of polyphosphate from the logarithmic growth phase to the stationary growth phase under aerobic conditions.

[0018] Further, the culture solution of the Tolypothrix tenuis and the culture solution of the Anabaena azotica are both culture solutions cultured to the logarithmic phase, and the culture medium is BG11-N culture medium; the culture time of the Tolypothrix tenuis is 10-14 days, and the culture time of the Anabaena azotica is 7-12 days; the culture conditions are as follows: 120 r / min, temperature maintained at 25℃, light intensity of 2500 lux, and full light.

[0019] (2) The application provides a preparation method of the active phosphorus biological soil conditioner for saline-alkali soil.

[0020] The mixed cyanobacterial solution is obtained by mixing the Anabaena azotica culture solution and the Nostoc commune culture solution, and the phosphorus solubilizing bacteria and the phosphate accumulating bacteria are added after pH adjustment, thereby obtaining the active phosphorus biological soil conditioner for saline-alkali soil.

[0021] Further, the pH of the mixed cyanobacterial solution is adjusted to 7-7.5.

[0022] II. Solid preparation

[0023] (1) When the soil conditioner is a solid preparation, the nitrogen-fixing cyanobacteria are algal powder of Anabaena azotica and Nostoc commune; the second auxiliary agent is selected as the filler and the binder;

[0024] According to weight parts, the algal powder of Anabaena azotica is used in an amount of 20-40 parts, the algal powder of Nostoc commune is used in an amount of 50-80 parts, the filler is 10-20 parts, and the binder is 5-10 parts;

[0025] Further, the filler is one or more of bentonite, diatomite, vermiculite and kaolin.

[0026] Further, the algal powder of the nitrogen-fixing cyanobacteria is Anabaena azotica and Nostoc commune.

[0027] Further, the binder is one or more of hydroxymethyl cellulose, sodium hydroxymethyl cellulose, methyl cellulose, ethyl cellulose and gum arabic.

[0028] Further, the algal powder of Anabaena azotica and the algal powder of Nostoc commune are both Anabaena azotica and Nostoc commune cultured to the logarithmic phase; the culture medium is BG11-N culture medium; the culture time of Anabaena azotica is 10-14 days, and the culture time of Nostoc commune is 7-12 days; and the culture conditions are all 120 r / min, temperature of 25 DEG C, light intensity of 2500 lux and full light.

[0029] (2) The application provides a preparation method of the active phosphorus biological soil conditioner for saline-alkali soil.

[0030] The dried Anabaena azotica and Nostoc commune are ground into powder, the powder is put into a coating machine, the binder and the filler are added, and the adhesive is added in an amount of 15-20% of the weight of the filler, so that the filler uniformly wraps the algal powder, thereby obtaining the pelletized algal powder, which is the active phosphorus biological soil conditioner for saline-alkali soil.

[0031] Application: The nitrogen-fixing algal floc active phosphorus biological soil conditioner prepared in this invention can be used to enhance nitrogen and phosphorus sources in saline-alkali soils.

[0032] Furthermore, the growth cycle of rice during rice cultivation includes the seedling stage, the greening stage, the tillering stage, the panicle growth stage, and the grain filling stage. The phosphorus-capturing and nitrogen-fixing dual-effect algal floc active bio-fertilizer needs to be added at one of the stages after the tillering stage.

[0033] After planting, the cyanobacteria do not need to be harvested. They die naturally and are released into the soil, which can increase the soil's organic matter content.

[0034] Compared to traditional fertilizers, this application has at least the following effective effects:

[0035] (1) The nitrogen-fixing algae added contains nitrogenase, which can fix nitrogen in the atmosphere and then synthesize amino acids and proteins, thereby increasing the plant's demand for nitrogen. Its nitrogen fixation principle is N2 + 8e - +16Mg ATP +8H + →2NH3 + H2 + 16MgADP + 16P i It can also dissolve phosphorus in the soil, increasing the available phosphorus in the soil and reducing the plant's need for additional phosphorus. Its phosphorus-dissolving principle is Ca3(PO4)2 + C. n O n H = H + +2PO4 3- +C n O n - +3Ca 2+ Furthermore, its extracellular matrix contains abundant extracellular polymeric substances (EPS), mainly polysaccharides, which can adsorb heavy metals in the soil, thereby improving the soil's physical and chemical properties and enhancing its ability to retain fertilizer and water.

[0036] (2) The *Monophora indicum* added in this invention is a filamentous cyanobacterium containing a special metamorphic vegetative cell—the heterocyst. The heterocyst contains abundant nitrogenase, serving as the site of nitrogen fixation for cyanobacteria. During differentiation, the heterocyst must form a coating layer outside its original cell wall to block oxygen entry, ensuring a microaerobic environment inside the heterocyst to protect the nitrogenase from inactivation. This allows it to directly absorb atmospheric nitrogen in an oxygen-rich environment and reduce it to NH4. + .

[0037] Therefore, the preparation method of the nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land provided in this application can improve soil fertility (nitrogen and phosphorus sources), increase soil organic matter content, reduce dependence on traditional chemical fertilizers and the pollution they cause; and provide an effective method for improving the yield and quality of grain (rice). Attached Figure Description

[0038] Figure 1 This is a comparison chart of available phosphorus in soil under different treatment groups.

[0039] Figure 2 This is a comparison chart of soil ammonium nitrogen under different treatment groups.

[0040] Figure 3 This is a comparison diagram of the inorganic phosphorus forms in the soil under different treatment groups, where (a) represents Al-P; (b) represents Fe-P; and (c) represents Ca-P.

[0041] Figure 4 This is a comparison diagram of soil organic phosphorus speciation under different treatment groups, where (a) represents active organic phosphorus, (b) represents moderately active organic phosphorus, (c) represents moderately stable organic phosphorus, and (d) represents highly stable organic phosphorus. Detailed Implementation

[0042] The features, specific objectives, and functions of the present invention are further illustrated below through embodiments, and the content and advantages of the present invention are analyzed. It should be noted that the following embodiments and accompanying drawings are merely further detailed descriptions of the above-mentioned content of the present invention, but do not limit the present invention to the scope of the embodiments. Without departing from the core of the present invention, any simple modifications, similar alterations, or similar substitutions made by those skilled in the art without creative effort within the spirit and principles of the present invention should fall within the protection scope of the present invention.

[0043] In the following implementation examples:

[0044] The *Monifocybe spp.* (FACHB-185) and *Anabaena spp.* (FACHB-119) were purchased from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences; the phosphate-solubilizing bacteria (*Bacillus megaterium* ACCC 04314) and polyphosphate-accumulating bacteria (*Acinetobacter spp.* ACCC 60234) were purchased from the China Culture Collection Center for Microbial Cultures.

[0045] The BG11-N medium formulation consists of 6 mg / L citric acid, 6 mg / L ferric ammonium citrate, 36 mg / L CaCl2·2H2O, 40 mg / L K2HPO4·3H2O, 75 mg / L MgSO4·7H2O, 20 mg / L Na2CO3, 1 mg / L Na2EDTA·2H2O, and 1 mL / L trace metal solution (H3BO3 2.86 g / L, MnCl2·4H2O 1.86 g / L, ZnSO4·7H2O 0.22 g / L, Na2MoO4·2H2O 0.39 g / L, CuSO4·5H2O 0.08 g / L, Co(NO3)2·6H2O 0.05 g / L), with the pH adjusted to 7.1 using 1 mol / L NaOH or HCl solution.

[0046] Example 1:

[0047] (1) Activation of *Monoflagellates*: Under aseptic conditions, *Monoflagellates* purchased from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences was inoculated into a 100 mL Erlenmeyer flask containing 50 mL of liquid BG11-N medium. The flask was placed on a shaker and shaken at 120 r / min, with the temperature maintained at 25℃ and the light intensity at 2500 lux, and the flask was kept under continuous illumination. The dry weight was measured to determine the concentration change. After 14 days of cultivation, the flask grew to the logarithmic growth phase. Then, it was inoculated into a 500 mL Erlenmeyer flask containing 250 mL of BG11-N medium at a concentration of 0.3 g / L. The flask was placed on a shaker and shaken at 120 r / min, with the temperature maintained at 25℃ and the light intensity at 2500 lux, and the flask was kept under continuous illumination. The flask was cultivated for another 14 days until the logarithmic growth phase was reached, thus obtaining activated *Monoflagellates*.

[0048] (2) Column aeration culture of *Monoflagellates*: The activated *Monoflagellates* was transferred to a column containing 500 mL of BG11-N medium for large-scale culture. The inoculum concentration was 0.3 g / L. The column was placed in a light incubator and cultured for 10 days at a temperature of 25°C, a light intensity of 2500 lux, and an air flow rate of 0.6 L / min to obtain the final *Monoflagellates* culture solution grown to the logarithmic growth phase required for the experiment, with a concentration of 0.3 g / L.

[0049] (3) Activation of nitrogen-fixing Anabaena: Under sterile conditions, the nitrogen-fixing Anabaena strain purchased from the Freshwater Algae Culture Bank of the Chinese Academy of Sciences was inoculated into a 100 mL Erlenmeyer flask containing 50 mL of liquid BG11-N medium. The flask was placed on a shaker and shaken at 120 r / min. The temperature was maintained at 25℃ and the light intensity at 2500 lux. The biomass growth was detected by measuring the dry weight. After 12 days of culture, when the nitrogen-fixing Anabaena reached the logarithmic growth phase, it was inoculated into a 500 mL Erlenmeyer flask containing 250 mL of BG11-N medium at a concentration of 0.4 g / L. The temperature was maintained at 25℃ and the light intensity at 2500 lux. The flask was cultured for another 12 days to obtain activated nitrogen-fixing Anabaena.

[0050] (4) Nitrogen-fixing Anabaena column aeration culture: The nitrogen-fixing Anabaena activated in step (3) was inoculated into a column containing 500 mL of BG11-N medium for large-scale culture. The inoculation concentration was 0.4 g / L. The column was placed in a light incubator for 7 days with a light setting of 2500 lux and an air flow rate of 0.6 L / min to obtain the final nitrogen-fixing Anabaena culture solution grown to the logarithmic phase required for the experiment, with a concentration of 0.4 g / L.

[0051] This invention provides a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land, comprising the following raw materials by weight: 10 parts of Bacillus megaterium, 20 parts of nitrogen-fixing Anabaena culture medium, 20 parts of Monofibrillaria culture medium, and 5 parts of Acinetobacter bacillus.

[0052] (5) A method for preparing a liquid formulation of nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land, comprising the following steps: mixing a culture medium of *Monifocybe simulans* and a culture medium of nitrogen-fixing *Anabaena* to obtain a mixed cyanobacterial solution, adjusting the pH to 7, and then adding *Bacillus megaterium* and *Acinetobacter* to obtain the phosphorus-capturing and nitrogen-fixing dual-effect algal floc active liquid conditioner.

[0053] Set up a comparative experiment: A) Apply distilled water; B) Apply BG11-N medium; C) Apply liquid modifier;

[0054] Soil property testing: Equal masses of air-dried topsoil from paddy fields were placed in glass jars. Then, distilled water, BG11-N culture medium, and liquid soil conditioner were applied at 25% of the soil mass, respectively. Distilled water was applied every 3 days.

[0055] From the start of the experiment, the inorganic phosphorus form, organic phosphorus form, available phosphorus, and ammonium nitrogen in the soil were tested every 5 days. The testing methods can be found in "Soil Agricultural Chemical Analysis Methods" edited by Lu Rukun.

[0056] Results analysis: From Figures 1-2It can be seen that, compared with applying distilled water and BG11-N medium, applying the liquid amendment increased the available phosphorus and ammonium nitrogen content in the soil. Specifically, from... Figure 3 It can be seen that the inorganic phosphorus forms mainly increased in Al-P and Fe-P content, with Fe-P being the main inorganic phosphorus component. This may be due to the climate of the experimental site and the slightly acidic soil, resulting in a higher content of iron and aluminum ions in the soil. After phosphate fertilizer is applied to the soil, it is first converted into Fe-P and Al-P, with some Al-P further converted into Fe-P. The Ca-P content increases slowly, possibly because residual plant roots in the soil directly absorb some Ca-P. Figure 4 As can be seen, for organic phosphorus components, phosphorus application increases the organic phosphorus content of each component, mainly increasing the content of active and moderately active organic phosphorus. This is mainly because phosphorus application increases the activity of soil microorganisms, thereby increasing their fixation and leading to an increase in organic phosphorus content.

[0057] Example 2:

[0058] Following the steps (1)-(4) of Example 1, nitrogen-fixing Anabaena and Monofibrillaria were activated and cultured respectively to obtain a Monofibrillaria culture solution with a concentration of 0.3 g / L and a nitrogen-fixing Anabaena culture solution with a concentration of 0.4 g / L; then the nitrogen-fixing Anabaena and Monofibrillaria were taken out, air-dried, and ground into powder to obtain nitrogen-fixing Anabaena powder and Monofibrillaria powder.

[0059] This invention provides a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land, comprising the following raw materials by weight: 80 parts of nitrogen-fixing algae powder, 30 parts of algae powder of small monofibrillated algae, 10 parts of kaolin, and 5 parts of binder hydroxymethyl cellulose.

[0060] A method for preparing solid pelletized algal powder, a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land, includes the following steps: putting algal powder of nitrogen-fixing fish algae and algal powder of small monofibrillar into a coating machine, adding hydroxymethyl cellulose as an adhesive to bind them together, continuing to add kaolin as a filler at a uniform speed, and adding an adhesive at 20% of the weight of the filler to make the filler evenly coat the algal powder, thus obtaining pelletized algal powder.

[0061] Three sets of experiments were set up: A) applying distilled water; B) applying BG11-N medium; C) applying pelleted algae powder.

[0062] Soil property testing: Equal mass of air-dried topsoil from paddy fields was placed in glass jars, and then the following components were added at 25% of the soil mass: A. Distilled water; B. BG11-N culture medium; C. Granulated algae powder.

[0063] From the start of the experiment, the inorganic phosphorus form, organic phosphorus form, available phosphorus, and ammonium nitrogen in the soil were tested every 5 days; the testing methods were based on "Soil Agricultural Chemical Analysis Methods" edited by Lu Rukun.

[0064] Results analysis: Compared with the application of distilled water and BG11-N medium, the effect of applying pelleted algae powder on soil nitrogen and phosphorus was consistent with the trend of the results of applying liquid amendment in Example 1, significantly increasing the nitrogen and phosphorus content of the soil; however, the content was slightly lower than that of liquid amendment, which may be because dry algae powder needs time to absorb water before it becomes active, thereby increasing the nitrogen and phosphorus content of the soil.

[0065] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, 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 present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land, characterized in that, The product, by weight, is composed of nitrogen-fixing cyanobacteria and excipients, wherein the nitrogen-fixing cyanobacteria are *Monifocobala* and *Anabaena*; the nitrogen-fixing cyanobacteria are algal liquid or algal powder; the excipients are either a first excipient or a second excipient; the first excipient is *Bacillus megaterium* and *Acinetobacter*; the second excipient is kaolin and hydroxymethyl cellulose. (1) Liquid formulation: When nitrogen-fixing cyanobacteria are in the form of algal solution, the first adjuvant is selected; the nitrogen-fixing cyanobacteria are Monofibrillaria var. microcarpa culture medium and Anabaena var. microcarpa culture medium, wherein the Anabaena var. microcarpa culture medium is the logarithmic phase Anabaena var. microcarpa culture medium with a concentration of 0.4 g / L; the Monofibrillaria var. microcarpa culture medium is the logarithmic phase Monofibrillaria var. microcarpa culture medium with a concentration of 0.3 g / L; By weight, 20 parts of Monofibrillaria cirrhosa culture medium, 20 parts of Anabaena nitrogen-fixing culture medium, 10 parts of Bacillus megaterium, and 5 parts of Acinetobacter bacillus. (2) Solid preparation: When nitrogen-fixing cyanobacteria are in the form of algal powder, a second excipient is selected; the nitrogen-fixing cyanobacteria are algal powders of *Monoflagellates* and *Anabaena*; the algal powder is prepared by: firstly taking the culture medium of *Anabaena* in the logarithmic phase with a concentration of 0.4 g / L; and the culture medium of *Monoflagellates* in the logarithmic phase with a concentration of 0.3 g / L; then naturally air-drying *Anabaena* and *Monoflagellates* and grinding them into powder to obtain algal powders of *Anabaena* and *Monoflagellates*. By weight, the amount of algal powder from *Monoflagellates* is 30 parts, the amount of algal powder from *Anabaena* is 80 parts, the amount of kaolin is 10 parts, and the amount of hydroxymethyl cellulose is 5 parts.

2. The nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land according to claim 1, characterized in that, Both *Monoflagellates* and *Anabaena* were cultured on BG11-N medium. *Monoflagellates* was cultured for 10 days, and *Anabaena* was cultured for 7 days. The culture conditions were: 120 r / min, temperature maintained at 25℃, light intensity 2500 lux, and continuous illumination.

3. The method for preparing a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land according to claim 1, characterized in that, The preparation method of the liquid preparation in step (1) is as follows: mix the culture medium of *Monifocybe simulans* and the culture medium of nitrogen-fixing *Anabaena* to obtain a mixed cyanobacterial solution, adjust the pH to 7, and then add *Bacillus megaterium* and *Acinetobacter* to obtain a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land.

4. The method for preparing a nitrogen-fixing algal floc active phosphorus biological soil conditioner for saline-alkali land according to claim 1, characterized in that, The solid preparation method in step (2) is as follows: dry nitrogen-fixing algae and small monofibrillary algae are ground into powder, the powder is put into a coating machine, then hydroxymethyl cellulose and kaolin are added, and an adhesive is added at 20% of the weight of the filler, so that the filler is evenly coated on the algae powder to obtain granulated algae powder, which is the nitrogen-fixing algae floc active phosphorus biological soil conditioner for saline-alkali land.

5. The use of the nitrogen-fixing algal floc active phosphorus biological soil conditioner according to any one of claims 1-2 for enhancing nitrogen and phosphorus sources in saline-alkali soils.

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