Microalgae biofertilizer for promoting growth of transplanted pepper and preparation and application method thereof

Abstract

The present application belongs to the technical field of microalgae fertilizer, and particularly relates to a microalgae bio-fertilizer for promoting the growth of pepper after transplanting, and a preparation and application method thereof. The microalgae bio-fertilizer is composed of reticulate pseudococcomyxa and a special liquid medium, and the algal body concentration is 0.5-2 g / L. The special liquid medium uses urea, glycine and sodium nitrate as a composite nitrogen source, and is matched with glycerol-2-phosphate sodium, lysine chelated magnesium, citric acid chelated calcium and other components. Through screening verification, the growth promotion effect and soil colonization ability of the reticulate pseudococcomyxa are better than those of various common microalgae. The special medium can improve the growth rate and active maintenance time of the algal body, and the combination of the two can significantly improve the plant height, stem diameter, chlorophyll content, root activity and biomass of the pepper, and shorten the seedling period. The present application is simple to prepare, is applied to root irrigation after the pepper is transplanted, is used once a week for four times in succession, and is suitable for rapid seedling and growth promotion of the pepper after transplanting.

Description

Technical Field

[0001] This invention belongs to the field of microalgae fertilizer technology, specifically relating to a microalgae bio-fertilizer that promotes the growth of chili peppers after transplanting, and its preparation and application methods. Background Technology

[0002] Chili peppers (Capsicum spp.) are an important vegetable and economic crop widely cultivated globally, holding a significant position in terms of cultivated area and economic output among vegetable crops. In large-scale chili pepper production systems, seedling transplanting is a core production link. The speed of seedling recovery after transplanting, the recovery ability of the root system after damage, and the vegetative growth status of the above-ground parts directly determine the plant's early fruit-setting ability, final yield, and fruit marketability. Therefore, shortening the seedling recovery period after transplanting and promoting rapid recovery growth of chili peppers after transplanting are important technical needs that have long been a focus in the field of chili pepper cultivation.

[0003] Currently, technical solutions for promoting seedling establishment and early growth of chili peppers after transplanting can be mainly divided into three categories: The first category is fast-acting chemical fertilizer solutions. In production, fast-acting fertilizers containing nitrogen, phosphorus, and potassium, or water-soluble fertilizers containing trace elements, are often applied to quickly replenish the nutrient needs of chili peppers in the early stages of transplanting. However, these traditional fertilizer formulations often use nitrate nitrogen or ammonium nitrogen as the main nitrogen source, phosphorus is mostly produced using orthophosphate systems, and the potassium source ratio is usually high. Under the condition of root damage and drastic fluctuations in the rhizosphere microenvironment after transplanting, these fertilizers are prone to causing drastic changes in rhizosphere pH, salt stress, and antagonistic effects between metal ions, and their effect on the restoration of the rhizosphere microecology is very limited, ultimately leading to unstable effects on promoting growth and seedling establishment.

[0004] The second category is biostimulant-based solutions. Current technologies often employ biostimulants such as seaweed extracts, humic acid, Bacillus subtilis, phosphate-solubilizing bacteria, and nitrogen-fixing bacteria, focusing on enhancing plant stress resistance or improving rhizosphere nutrient availability. While these products can shorten the seedling recovery period to some extent under specific soil and climatic conditions, they generally have significant limitations: the colonization effect of microbial agents in the soil is heavily influenced by environmental conditions; their functional targets are not focused on the rapid recovery of chlorophyll synthesis and photosynthetic systems in leaves after transplanting; and the product formulation is not well-matched with mineral nutrient supply, making it difficult to fully meet the comprehensive growth needs of peppers after transplanting.

[0005] The third category is research and products related to microalgae biofertilizers. Some research and products have attempted to prepare microalgae such as Chlorella and Spirulina into biofertilizers or foliar spray materials, hoping to promote plant growth through the bioactive substances secreted by microalgae. However, existing microalgae preparations still have many shortcomings: on the one hand, most use general algae strains and general culture medium systems, lacking special formulas and algae strain screening and optimization tailored to the physiological characteristics of peppers after transplanting; on the other hand, the design of the algal concentration and the ratio of the accompanying nutrient system lacks specificity, resulting in a short duration of algal activity after application to the soil, a mismatch between metabolic activity and rhizosphere nutrient requirements, and large fluctuations in actual application effects.

[0006] At the level of culture medium and carrier systems for microalgae biofertilizers, existing liquid microalgae fertilizers often directly borrow general-purpose microalgae culture media such as BG-11 and BBM, or directly adopt modified water-soluble fertilizer systems. The composition of their nitrogen, phosphorus, and metal ion sources does not fully match the physiological recovery needs of peppers after transplanting. Specifically, this manifests in the following ways: First, the nitrogen source structure is too simple. A single form of nitrate or ammonium nitrogen supply easily causes pH fluctuations in the rhizosphere environment and leads to nitrogen metabolism imbalance in pepper seedlings, which is detrimental to physiological recovery under transplant stress. Second, the phosphorus source has poor availability. When orthophosphate is combined with a high-potassium buffer system, it easily forms precipitates or produces ion antagonisms with trace elements such as iron and magnesium, significantly reducing the bioavailability of trace elements. Third, the supply of trace elements is unreasonable. Magnesium, as a core component of chlorophyll synthesis, often plays a crucial role, and the existing supply methods are not conducive to the rapid absorption and utilization of nutrients by seedlings. At the same time, the synergistic supply relationship between magnesium, calcium, and trace elements in the early stages of transplanting has not been fully considered, making it difficult to simultaneously support chlorophyll synthesis, cell wall and membrane system stability, and osmotic regulation processes, thus affecting the repair speed of the photosynthetic system and cell structure.

[0007] Furthermore, the stability and function of microalgae carriers are closely related to the chemical composition of the culture medium. Current technologies lack systematic optimization of nitrogen source compounding, stable phosphorus source supply, and efficient magnesium and calcium coordination supply, ultimately resulting in insufficient maintenance of microalgae activity in the rhizosphere, weak synergistic effect between algal metabolic activity and mineral nutrient release, and difficulty in significantly improving the growth vigor and leaf quality of pepper plants in a short period of time after transplanting.

[0008] In summary, there is an urgent need to develop a specialized microalgae bio-fertilizer technology solution that addresses the physiological characteristics of chili peppers after transplanting. By screening suitable algae strains and optimizing the formulation of a specialized culture medium, a synergistic match between maintaining microalgae activity and supplying mineral nutrients can be achieved, effectively promoting chlorophyll synthesis and cell structure recovery in chili peppers after transplanting, ultimately leading to rapid seedling establishment and enhanced early growth. Summary of the Invention

[0009] The purpose of this invention is to provide a microalgae bio-fertilizer that promotes the growth of chili peppers after transplanting, as well as its preparation and application methods. This invention can effectively accelerate the seedling recovery process after transplanting, enhance the early growth vigor of seedlings, and lay a solid growth foundation for the later fruit setting and yield formation of chili peppers.

[0010] The objective of this invention is achieved through the following technical solution: This invention provides a microalgae bio-fertilizer that promotes the growth of chili peppers after transplanting, comprising *Pseudomonas reticulata* and a special liquid culture medium, wherein the preservation number of *Pseudomonas reticulata* is CGMCC No. 46977.

[0011] Furthermore, the concentration of the *Reticulitermes oocystis* in the microalgae bio-fertilizer is 0.5-2 g / L.

[0012] Furthermore, each liter of the dedicated liquid culture medium contains the following components: 50-60 mg urea, 80-100 mg glycine, 80-100 mg sodium nitrate, 150-170 mg sodium glycero-2-phosphate, 200-350 mg lysine chelated magnesium, 120-450 mg citrate chelated calcium, 50 mg potassium chloride, and 100-150 mg sodium bicarbonate.

[0013] Furthermore, each liter of the dedicated liquid culture medium contains the following components: 50 mg urea, 80 mg glycine, 80 mg sodium nitrate, 150 mg sodium glycero-2-phosphate, 200 mg lysine chelated magnesium, 120 mg citrate chelated calcium, 50 mg potassium chloride, and 100 mg sodium bicarbonate.

[0014] Furthermore, the solvent for the special liquid culture medium is tap water.

[0015] This invention also provides a method for preparing the microalgae bio-fertilizer that promotes the growth of chili peppers after transplanting, comprising the following steps: (1) Expand the culture and collect the thallus of *Reticulitermes oocystis*; (2) Prepare the special liquid culture medium; (3) Mix the collected Reticulata oocysts with the special liquid culture medium and adjust the volume to the target algal concentration.

[0016] Further, step (1) specifically involves inoculating *Reticulata oocystis* into BG11 liquid medium for expanded culture. The culture conditions are: temperature 27℃, light intensity 2700±50lx, light-dark cycle 16h:8h, and cultured with full aeration until the late logarithmic growth stage. The algal cells are then collected by centrifugation.

[0017] Furthermore, in step (2), the components of the special liquid culture medium are dissolved in tap water and stirred until completely dissolved to obtain the special liquid culture medium; in step (3), the concentration of the reticulate oocyst after volume adjustment is 0.5-2 g / L.

[0018] The present invention also provides a method for promoting the growth of chili peppers after transplanting, wherein the microalgae bio-fertilizer is applied to the roots of the transplanted chili pepper plants by root irrigation.

[0019] Furthermore, the microalgae bio-fertilizer is applied once a week for four consecutive weeks, with each application amount being 1-2 L / acre.

[0020] The beneficial effects of this invention are as follows: This invention addresses the problems of root damage, prolonged seedling establishment period, and weak early growth in chili peppers after transplanting, as well as the issues of existing fast-acting fertilizers easily causing fluctuations in the rhizosphere environment, the strong universality of algae strains and formulations in conventional microalgae preparations, unstable growth-promoting effects, and insufficient rhizosphere colonization capacity. By screening suitable algae strains and optimizing the formulation of a dedicated liquid culture medium, this invention achieves a synergistic effect between microalgal bioactivity and mineral nutrient supply, significantly shortening the seedling establishment period after chili pepper transplanting and effectively promoting plant vegetative growth and biomass accumulation. Comparative verification with multiple microalgae strains shows that the selected *Pseudomonas reticulata* has a significantly better promoting effect on chili pepper growth after transplanting than common microalgae such as *Emerson's Lipnocarpus*, *Chlorella proteoglycans*, and *Scenedesmus*, exhibiting the highest improvement in plant height, stem diameter, plant fresh weight, and root vitality. Furthermore, this algae strain has a stronger colonization and survival capacity in the soil, maintaining biological activity for a longer period by increasing the chlorophyll a content in the rhizosphere soil, and continuously exerting its rhizosphere regulatory and growth-promoting effects.

[0021] The specialized liquid culture medium of this invention employs a composite nitrogen source system of urea, glycine, and sodium nitrate, replacing traditional single-form nitrogen sources. This system provides a stable supply of nitrogen in different forms, adapting to the nitrogen metabolism characteristics of peppers in the initial post-transplanting stage. It avoids the drastic fluctuations in rhizosphere pH and nitrogen metabolism imbalances caused by relying solely on nitrate or ammonium nitrogen, reducing the risk of salt stress and providing a stable rhizosphere nitrogen environment for plant recovery and microalgae colonization. The phosphorus source uses sodium glycerol-2-phosphate as a stable phosphorus supply system, replacing traditional orthophosphates. This effectively reduces the probability of phosphorus antagonism and precipitation with metal ions such as magnesium and calcium, improving the bioavailability of phosphorus and related micronutrients, achieving a continuous and gradual phosphorus supply that matches the nutrient absorption rhythm of the gradually recovering pepper root system after transplanting.

[0022] This invention employs a chelated medium-quantity element supply scheme using lysine-chelated magnesium and citrate-chelated calcium to replace conventional inorganic salt forms of magnesium and calcium sources, significantly improving the absorption and utilization efficiency of magnesium and calcium. The chelated magnesium efficiently participates in the chlorophyll synthesis process in leaves, and with the synergistic effect of a composite nitrogen source and a stable phosphorus source, rapidly increases the SPAD value and total chlorophyll content of leaves, enhancing the plant's photosynthetic assimilation ability and providing material and energy support for rapid recovery after transplanting. The chelated calcium effectively strengthens the cell wall structure and cell membrane system stability of plants, alleviating root damage and environmental stress caused by transplanting, reducing the inhibitory effect of transplanting stress on seedling growth, and improving seedling resistance and recovery speed.

[0023] The specialized liquid culture medium of this invention is highly compatible with *Pseudomonas reticulata*, and compared to the general BG11 medium, it can more efficiently support the growth and reproduction of *Pseudomonas reticulata*, allowing the algae to enter the logarithmic growth phase more quickly and maintain activity for a longer period, providing a good carrier environment for the preparation and storage of microalgae biofertilizer. After field application, this specialized culture medium can simultaneously provide suitable nutritional conditions for *Pseudomonas reticulata* in the rhizosphere, further enhancing the colonization ability and survival time of the algae in the soil. This ensures a precise match between the biostimulatory effect of the microalgae and the mineral nutrient supply of the culture medium in terms of timing and dosage, allowing them to work synergistically and avoiding the problems of rapid algal activity decay and mismatch between nutrient supply and algal needs found in general microalgae preparations.

[0024] Applying this invention's microalgae bio-fertilizer to transplanted chili peppers via root irrigation simultaneously promotes above-ground growth and root system recovery, resulting in significant improvements in morphological indicators such as plant height, stem diameter, leaf length, and leaf width, effectively expanding the plant's photosynthetic area. It also significantly enhances root vitality, strengthening the plant's water and nutrient absorption capacity, ultimately leading to a substantial increase in both fresh and dry weight. The overall solution is simple to prepare, convenient to apply, and provides stable and significant growth-promoting effects. It effectively accelerates the recovery process of transplanted chili peppers, enhances early seedling growth, and lays a solid foundation for later fruit setting and yield formation. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a comparison of the plant morphology of pepper seedlings in each treatment group after the experiment in Example 1 of the present invention. Figure 2 This is a comparison chart of the plant height of chili pepper plants in each treatment group in Example 1 of the present invention; Figure 3 This is a comparison diagram of the stem diameter of pepper plants in each treatment group in Example 1 of the present invention; Figure 4 This is a comparison diagram of leaf length of chili pepper plants in different treatment groups in Example 1 of the present invention; Figure 5 This is a comparison diagram of leaf width of pepper plants in different treatment groups in Example 1 of the present invention; Figure 6 This is a comparison chart of the SPAD values ​​of leaves of pepper plants in different treatment groups in Example 1 of the present invention; Figure 7 This is a comparison chart of the total chlorophyll content of leaves of pepper plants in different treatment groups in Example 1 of the present invention; Figure 8 This is a comparison diagram of root activity of pepper plants in different treatment groups in Example 1 of the present invention; Figure 9 This is a comparison chart of the fresh weight of chili pepper plants in each treatment group in Example 1 of the present invention; Figure 10 This is a comparison chart of the dry weight of chili pepper plants in each treatment group in Example 1 of the present invention; Figure 11 This is a comparison chart of the plant height of chili pepper plants under different microalgae strains in Example 2 of the present invention; Figure 12 This is a comparison diagram of the stem diameter of pepper plants under different microalgae strains in Example 2 of the present invention; Figure 13 This is a comparison chart of the fresh weight of chili plants under different microalgae strains in Example 2 of the present invention. Figure 14 This is a comparison diagram of root activity of pepper plants under different microalgae strains in Example 2 of the present invention. Figure 15 This is a comparison chart of soil chlorophyll a content under different microalgae strains in Example 2 of the present invention; Figure 16 This is a growth curve of *Pseudomonas reticulata* under different culture medium formulations in Example 3 of the present invention; Figure 17 This is a comparison diagram of the plant height of chili pepper plants under different treatment combinations in Example 4 of the present invention; Figure 18 This is a comparison diagram of the stem diameter of chili plants under different treatment combinations in Example 4 of the present invention; Figure 19 This is a comparison chart of the fresh weight of chili plants under different treatment combinations in Example 4 of the present invention; Figure 20 This is a comparison chart of the total chlorophyll content of chili pepper leaves under different treatment combinations in Example 4 of the present invention; Figure 21 This is a comparison diagram of root activity of chili plants under different treatment combinations in Example 4 of the present invention; Figure 22 This is a comparison chart of soil chlorophyll a content under different treatment combinations in Example 4 of the present invention. Detailed Implementation

[0027] 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.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to 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 in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Example 1: Preparation of the microalgae bio-fertilizer of the present invention and its effect on promoting the growth of chili peppers after transplanting. 1.1 Preparation of Microalgae Bio-fertilizer (1) Microalgae Culture and Collection: The algae species used in this embodiment is classified as *Scotiellopsis reticulata*, which was deposited on July 6, 2026, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, with accession number CGMCC No. 46977. Under aseptic conditions, the algae species was inoculated into standard BG11 liquid medium for large-scale culture. The culture conditions were: temperature 27℃, light intensity 2700±50 lx, light-dark cycle 16h:8h, and aeration throughout the culture. When the algae reached the late logarithmic growth stage, the algal cells were collected by centrifugation to obtain wet algal sludge for later use.

[0033] (2) Preparation of special liquid culture medium: Weigh out 50mg of urea, 80mg of glycine, 80mg of sodium nitrate, 150mg of sodium glycero-2-phosphate, 200mg of lysine chelated magnesium, 120mg of citrate chelated calcium, 50mg of potassium chloride and 100mg of sodium bicarbonate per liter of culture medium. Dissolve the above components in 1L of tap water in sequence and stir until completely dissolved to obtain special liquid culture medium.

[0034] (3) Microalgae bio-fertilizer compounding: The wet algae mud collected in step (1) is thoroughly mixed with the special liquid culture medium prepared in step (2), and after adjusting the volume, the final concentration of Reticulatae oocystis is 1.5 g / L, thus obtaining the microalgae bio-fertilizer of this embodiment.

[0035] 1.2 Pepper Transplanting Treatment and Experimental Design Select plump, uniformly sized chili seeds and treat them in a 50℃ water bath for 15 minutes. Afterward, soak them in sterile water at room temperature for 8 hours. Then, transfer the seeds to a 27℃ incubator for germination, keeping them in a humid environment. Once the seeds show white sprouts, select seeds with uniform sprout length and sow them in seedling trays. The seedling substrate is a mixture of peat moss, perlite, and vermiculite in a 2:1:1 ratio. When the chili seedlings reach the three-leaf stage, select seedlings with uniform growth for transplanting. An experimental group and a control group were established, with biological replicates for each group.

[0036] The experimental group was treated with the above-mentioned microalgae bio-fertilizer by root irrigation, with 25 mL applied per plant each time; the control group was treated with the same amount of water. The application frequency was once a week for 4 consecutive weeks.

[0037] 1.3 Measurement Indicators and Result Analysis After the experiment, ten indicators of pepper plants were measured, including plant height, stem diameter, leaf length, leaf width, leaf SPAD value, total chlorophyll content, root activity, plant fresh weight, and plant dry weight. The results are as follows: like Figure 1As shown, after the experiment, the overall plant morphology of the pepper seedlings in the experimental group was significantly better than that in the control group. The plants were taller, the stems were thicker, and there were more leaves with a darker green color. The difference in growth vigor was clearly visible.

[0038] like Figure 2 As shown, the plant height of the experimental group of pepper plants increased by 20.58% compared with the control group, demonstrating a significant advantage in longitudinal growth and effectively shortening the plant height recovery period after seedling establishment.

[0039] like Figure 3 As shown, the stem diameter of the pepper plants in the experimental group increased by 10.07% compared with that in the control group, and the stems were more robust, which is beneficial to improving the plant's resistance to adverse conditions and its ability to bear fruit in the later stages.

[0040] like Figure 4 As shown, the leaf length of the pepper plants in the experimental group increased by 15.90% compared with that in the control group, the leaves developed fully longitudinally, and the photosynthetic area of ​​each plant was effectively expanded.

[0041] like Figure 5 As shown, the leaf width of the pepper plants in the experimental group increased by 13.83% compared with the control group, and the lateral growth of the leaves also increased simultaneously, further expanding the photosynthetic effective area.

[0042] like Figure 6 As shown, the SPAD value of the leaves of the pepper plants in the experimental group increased by 6.80% compared with that of the control group, and the greenness of the leaves was significantly improved, which directly reflects the improvement of the chlorophyll level of the leaves.

[0043] like Figure 7 As shown, the total chlorophyll content of the pepper plants in the experimental group increased by 33.75% compared with the control group, and the accumulation of photosynthetic pigments increased significantly, providing the core material basis for improving photosynthetic efficiency.

[0044] like Figure 8 As shown, the root activity of the pepper plants in the experimental group was 52.97% higher than that in the control group, and the root physiological activity and water and nutrient absorption capacity were significantly enhanced, which is an important support for the rapid growth of the above-ground parts.

[0045] like Figure 9 As shown, the fresh weight of the pepper plants in the experimental group increased by 65.89% compared with the control group, and the overall biomass accumulation of the plants was significantly improved, demonstrating a good growth-promoting effect.

[0046] like Figure 10 As shown, the dry weight of the pepper plants in the experimental group increased by 76.72% compared with the control group, and the dry matter accumulation efficiency was significantly higher than that of the control group, indicating that the plant's ability to synthesize and accumulate assimilates was significantly enhanced.

[0047] The results of this embodiment show that the microalgae bio-fertilizer of the present invention can significantly promote the vegetative growth of peppers after transplanting, effectively improve the accumulation of plant biomass and photosynthetic capacity, enhance root activity, and lay a material foundation for rapid seedling establishment and high yield of peppers after transplanting.

[0048] Example 2: Comparison of the effects of different microalgae strains on the growth of chili peppers after transplanting. This embodiment aims to screen the microalgae strains that have the best effect on promoting the growth of chili peppers after transplanting, and to provide experimental basis for the selection of microalgae strains for microalgae biofertilizers.

[0049] 2.1 Experimental Materials and Processing Emerson's Lipochrysis, Chlorella proteoglycans, Pseudomonas reticulata, and Scenedesmus were cultured in BG11 liquid medium. After each algal strain reached the logarithmic growth phase, the algal cells were collected by centrifugation. The four algal species were then mixed with BG11 medium to a final concentration of 1.5 g / L, and used as the treatment solutions for experimental group 1 (Emerson's Lipochrysis), experimental group 2 (Chlorella proteoglycans), experimental group 3 (Pseudomonas reticulata), and experimental group 4 (Scenedesmus). An equal volume of BG11 medium served as the control group.

[0050] The seedling raising, transplanting and application methods for chili peppers are the same as in Example 1. Each plant is irrigated with 25 mL of the treatment solution once a week for 4 consecutive weeks.

[0051] 2.2 Measurement Indicators and Result Analysis After the experiment, the plant height, stem diameter, fresh weight, root activity, and chlorophyll a content in the rhizosphere soil (reflecting the colonization and survival ability of microalgae in the soil) of each group of pepper plants were measured. The results are as follows: like Figure 11 As shown, all four microalgae treatments increased the plant height of chili peppers. Among them, experimental group 3 (Reticulata oocystis) showed the greatest increase, with a height increase of 15.50% compared to the control group. The plant heights of experimental groups 1, 2, and 4 increased by 7.14%, 8.66%, and 10.79% respectively compared to the control group.

[0052] like Figure 12 As shown, in terms of stem diameter, experimental group 3 (Reticulate Oocystis) also showed the best improvement effect, increasing by 8.43% compared with the control group; the stem diameters of experimental groups 1, 2 and 4 increased by 4.58%, 6.83% and 5.62% respectively compared with the control group.

[0053] like Figure 13 As shown, in terms of plant fresh weight, experimental group 3 (Reticulate Oocystis) increased by 30.94% compared with the control group, which was significantly higher than the other three groups; the fresh weight of experimental groups 1, 2 and 4 increased by 9.16%, 15.71% and 12.53% compared with the control group, respectively.

[0054] like Figure 14 As shown, among the root activity indicators, experimental group 3 (Reticulitermes oocystis) showed a 37.24% increase compared to the control group, demonstrating the most significant root-promoting effect; the root activity of experimental groups 1, 2, and 4 increased by 12.14%, 20.69%, and 19.31% respectively compared to the control group.

[0055] like Figure 15 As shown, soil chlorophyll a content can reflect the colonization and survival ability of microalgae in the rhizosphere. The soil chlorophyll a content of experimental group 3 (Reticulate Oocystis) increased by 572.41% compared with the control group, and its colonization ability was significantly stronger than other algal strains. The soil chlorophyll a content of experimental groups 1, 2 and 4 increased by 258.62%, 372.41% and 386.21% respectively compared with the control group.

[0056] The results of this embodiment show that all four tested microalgae have certain growth-promoting and soil colonization capabilities. Among them, *Pseudocystis reticulata* showed the best performance in all indicators and is the preferred algae strain for preparing microalgae bio-fertilizer for chili transplanting.

[0057] Example 3: Effects of different culture medium formulations on the growth performance of *Reticulitermes urticatus* This embodiment aims to optimize the culture medium formulation for *Pseudomonas reticulata* and verify the promoting effect of the special liquid culture medium on algal growth and activity maintenance.

[0058] 3.1 Experimental Design Seven culture medium treatments were set up, namely: Control group: Standard BG11 liquid culture medium; Experimental group 1: Each liter of culture medium contained 110.24 mg of urea, 181.5 mg of dipotassium hydrogen phosphate, 76 mg of magnesium sulfate, 41 mg of calcium chloride, 50 mg of potassium chloride, and 100 mg of sodium bicarbonate, with tap water as the solvent; Experimental Group 2: Each liter of culture medium contains 50 mg of urea, 80 mg of glycine, 80 mg of sodium nitrate, 181.5 mg of dipotassium hydrogen phosphate, 76 mg of magnesium sulfate, 41 mg of calcium chloride, 50 mg of potassium chloride, and 100 mg of sodium bicarbonate. The solvent is tap water. Experimental Group 3: Each liter of culture medium contains 50 mg of urea, 80 mg of glycine, 80 mg of sodium nitrate, 150 mg of sodium glycero-2-phosphate, 76 mg of magnesium sulfate, 41 mg of calcium chloride, 50 mg of potassium chloride, and 100 mg of sodium bicarbonate. The solvent is tap water. Experimental group 4: Each liter of culture medium contains 50 mg of urea, 80 mg of glycine, 80 mg of sodium nitrate, 181.5 mg of dipotassium hydrogen phosphate, 200 mg of lysine chelated magnesium, 41 mg of calcium chloride, 50 mg of potassium chloride, and 100 mg of sodium bicarbonate. The solvent is tap water. Experimental group 5: Each liter of culture medium contains 50mg urea, 80mg glycine, 80mg sodium nitrate, 181.5mg dipotassium hydrogen phosphate, 76mg magnesium sulfate, 120mg calcium citrate chelate, 50mg potassium chloride, and 100mg sodium bicarbonate, with tap water as the solvent; Experimental group 6: Each liter of culture medium contained 110.24 mg of urea, 150 mg of sodium glycero-2-phosphate, 200 mg of lysine chelated magnesium, 120 mg of citrate chelated calcium, 50 mg of potassium chloride, and 100 mg of sodium bicarbonate. The solvent was tap water.

[0059] After sterilizing the culture media of each group, *Pseudocystis reticulata* was inoculated into each group at an initial inoculation density of 1 × 10⁻⁶. 5 The algal cell density was measured daily using a hemocytometer, and growth curves were plotted continuously.

[0060] 3.2 Results Analysis like Figure 16 As shown, the growth rate of *Pseudomonas reticulata* differed significantly under different culture medium formulations. Among them, *Pseudomonas reticulata* in experimental group 6 culture medium showed the fastest growth rate, entered the logarithmic growth phase earlier, and maintained algal cell activity for a longer period, which was significantly better than the control group BG11 culture medium and the formulations of the other experimental groups.

[0061] The results of this embodiment show that the synergistic ratio of organic phosphorus source and chelated calcium and magnesium can more efficiently support the growth and activity maintenance of *Pseudomonas reticulata*, providing a culture medium system basis for the long-term effect of microalgae biofertilizer.

[0062] Example 4: Comparison of the effects of different treatment combinations on the growth of chili peppers and algal colonization after transplanting. This embodiment aims to verify the synergistic growth-promoting effect of *Reticulitermes urticaria* and the special liquid culture medium, and to clarify the contribution of each component.

[0063] 4.1 Experimental Design Two experimental groups and three control groups were set up, and the specific treatments were as follows: Experimental group 1: *Pseudomonas reticulata* + BG11 medium, algal concentration 1.5 g / L; Experimental group 2: Reticulate oocystis + the special liquid culture medium of this invention, algae concentration 1.5g / L, i.e. the microalgae bio-fertilizer of this invention; Control group 1: Equal volume of water; Control group 2: Equal volume of BG11 culture medium; Control group 3: An equal volume of the special liquid culture medium of this invention (excluding algae).

[0064] The cultivation of *Pseudomonas reticulata*, the preparation of the special culture medium, the transplanting of pepper seedlings, and the application methods were all the same as in Example 1. Each plant was irrigated with 25 mL of the solution once a week for 4 consecutive weeks.

[0065] 4.2 Measurement Indicators and Result Analysis After the experiment, the plant height, stem diameter, fresh weight, total chlorophyll content of leaves, root activity, and soil chlorophyll a content of each group of pepper plants were measured. The results are as follows: like Figure 17 As shown, in terms of plant height, experimental group 1 increased by 15.04% compared with control group 1, and experimental group 2 increased by 21.98% compared with control group 1. The combination of special culture medium and algae further enhanced the growth promotion effect.

[0066] like Figure 18 As shown, in terms of stem diameter, experimental group 1 increased by 8.53% compared with control group 1, and experimental group 2 increased by 11.15% compared with control group 1, indicating that the stems developed more robustly under the synergistic effect.

[0067] like Figure 19 As shown, in terms of plant fresh weight, experimental group 1 increased by 32.52% compared with control group 1, and experimental group 2 increased by 63.70% compared with control group 1, with the synergistic gain effect of biomass accumulation being the most significant.

[0068] like Figure 20 As shown, the total chlorophyll content in the leaves increased by 22.83% in experimental group 1 compared to control group 1, and by 32.63% in experimental group 2 compared to control group 1. The chelated magnesium and compound nitrogen source in the special culture medium further enhanced the chlorophyll synthesis effect.

[0069] like Figure 21 As shown, in terms of root activity index, experimental group 2 increased by 36.38% compared with control group 1, and experimental group 1 increased by 51.50% compared with control group 1. The root activity improvement was greater under synergistic treatment.

[0070] like Figure 22 As shown, the chlorophyll a content in the soil was 539.34% higher in experimental group 1 than in control group 1, and 670.82% higher in experimental group 2 than in control group 1. This indicates that the special culture medium can significantly enhance the colonization and survival ability of *Pseudomonas reticulata* in the soil and prolong the duration of action.

[0071] The results of this embodiment show that there is a significant synergistic effect between *Pseudomonas reticulata* and the special liquid culture medium of this invention. The combination of the two is significantly better than the combination of a single algal strain and a general culture medium in terms of promoting pepper growth, activating the root system and colonizing the algae, thus verifying the scientific nature and superiority of the formulation of this invention.

[0072] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A microalgae bio-fertilizer that promotes the growth of chili peppers after transplanting, characterized in that, It includes *Pseudomonas reticulata* and a special liquid culture medium, wherein the preservation number of *Pseudomonas reticulata* is CGMCC No. 46977.

2. The microalgae bio-fertilizer according to claim 1, characterized in that, The concentration of *Reticulitermes oocystis* in the microalgae bio-fertilizer is 0.5-2 g / L.

3. The microalgae bio-fertilizer according to claim 1, characterized in that, Each liter of the dedicated liquid culture medium contains the following components: urea 50-60 mg, glycine 80-100 mg, sodium nitrate 80-100 mg, sodium glycero-2-phosphate 150-170 mg, lysine chelated magnesium 200-350 mg, citrate chelated calcium 120-450 mg, potassium chloride 50 mg, and sodium bicarbonate 100-150 mg.

4. The microalgae bio-fertilizer according to claim 3, characterized in that, Each liter of the dedicated liquid culture medium contains the following components: 50 mg urea, 80 mg glycine, 80 mg sodium nitrate, 150 mg sodium glycero-2-phosphate, 200 mg lysine chelated magnesium, 120 mg citrate chelated calcium, 50 mg potassium chloride, and 100 mg sodium bicarbonate.

5. The microalgae bio-fertilizer according to claim 1, characterized in that, The solvent for the special liquid culture medium is tap water.

6. A method for preparing the microalgae bio-fertilizer for promoting the growth of chili peppers after transplanting as described in claim 1, characterized in that, Includes the following steps: (1) Expand the culture and collect the thallus of *Reticulitermes oocystis*; (2) Prepare the special liquid culture medium; (3) Mix the collected Reticulata oocysts with the special liquid culture medium and adjust the volume to the target algal concentration.

7. The preparation method according to claim 6, characterized in that, Step (1) is as follows: Inoculate *Reticulata oocystis* into BG11 liquid medium for large-scale culture. The culture conditions are: temperature 27℃, light intensity 2700±50lx, light-dark cycle 16h:8h, and culture with full aeration until the late logarithmic growth stage. Collect algal cells by centrifugation.

8. The preparation method according to claim 6, characterized in that, In step (2), the components of the special liquid culture medium are dissolved in tap water and stirred until completely dissolved to obtain the special liquid culture medium; in step (3), the concentration of the reticulate oocyst after volume adjustment is 0.5-2 g / L.

9. A method for promoting the growth of chili peppers after transplanting, characterized in that, The microalgae bio-fertilizer described in claim 1 is applied to the roots of transplanted chili plants through root irrigation.

10. The application method according to claim 9, characterized in that, The microalgae bio-fertilizer is applied once a week for four consecutive weeks, with each application amount being 1-2 L / acre.

Images