Microorganism-mineral based composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of agriculture, and discloses a microorganism-mineral based composite material as well as a preparation method and application thereof. The microorganism-mineral-based composite material comprises the following components: iron phosphate powder and dissimilatory iron reduction microorganisms, wherein the dissimilatory iron reducing microorganisms comprise at least one of shewanella, geobacter, desulfurization vibrio, clostridium butyricum, geoacidophilus and iron-rich bacteria. The microorganism-mineral-based composite material provided by the invention comprises the mineral component iron phosphate and dissimilatory iron reduction microorganisms, and the dissimilatory iron reduction microorganisms can actively reduce the iron phosphate which is originally stable in chemical property and insoluble into Fe (II) with relatively high solubility, so that the crystal structure of the iron phosphate is destroyed; the phosphate fertilizer can release free PO4 < 3-> which can be absorbed and utilized by plants, the effect of the mineral reduction dissolution process driven by microorganisms is far better than that of simple addition when minerals or microorganisms are independently used, and an efficient phosphorus activation mechanism is formed.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and in particular to a microbial-mineral-based composite material, its preparation method, and its application. Background Technology

[0002] Phosphorus is an essential macronutrient for plant growth and a key limiting factor in global food production. However, as a non-renewable strategic resource, global reserves of phosphorus are facing depletion. Predictions indicate that at current consumption rates, global economically recoverable phosphate rock reserves could be exhausted within 50 years. Therefore, improving phosphorus utilization efficiency is crucial for sustainable agricultural development.

[0003] In rice-growing areas of southern China, paddy soils are generally acidic and rich in iron. This soil chemical environment makes it easy for applied phosphate fertilizers to be fixed in the soil, forming iron phosphate (FePO4) minerals with extremely low solubility. This results in low availability and makes it difficult for crop roots to absorb and utilize the fertilizer. This phenomenon severely restricts rice growth and grain filling, leading to reduced yields and a huge waste of fertilizer resources. Traditional water-soluble phosphate fertilizers, such as superphosphate, generally have a utilization efficiency of less than 20%. The vast majority of phosphorus that is not absorbed and utilized by crops often remains in the soil, causing not only economic losses to farmers but also triggering a series of environmental pollution problems, especially eutrophication of surface water bodies.

[0004] To address this challenge, existing technologies primarily offer two solutions: the use of phosphate-solubilizing microbial agents and slow-release mineral fertilizers. Phosphate-solubilizing microorganisms can dissolve fixed phosphates in the soil by secreting organic acids or enzymes. However, the effectiveness of these agents in actual field applications is highly unstable, as their activity is highly dependent on complex environmental factors such as soil type, pH, and organic matter content, making their growth-promoting effects unpredictable and unreliable. Slow-release mineral fertilizers reduce nutrient loss by directly applying phosphate rock or synthesizing slow-release phosphate fertilizers (such as iron phosphate itself). The core drawback of these fertilizers is that their nutrient release rate is difficult to synchronize with crop nutrient requirements. During peak nutrient demand periods, the release amount is insufficient, while during periods of lower demand, it continues to release nutrients slowly, ultimately resulting in low fertilizer utilization. Therefore, although their loss is less than that of readily soluble chemical fertilizers, their low bioavailability limits their effect on improving crop yield and quality. Farmers often need to apply large amounts of fast-acting fertilizers in conjunction with them, thus diminishing the original intention and economic benefits of slow release.

[0005] In summary, neither single microbial agents nor single mineral fertilizers have effectively solved the core problems of phosphorus fixation and supply-demand mismatch in paddy field soils. Current technologies lack a synergistic system capable of efficiently coupling microorganisms with specific mineral substrates in the rhizosphere microenvironment. Therefore, there is an urgent need to develop a novel technology that can achieve in-situ, on-demand activation of phosphorus nutrients, specifically targeting the unique waterlogged, anaerobic, and iron-rich environments of paddy fields. This would fundamentally improve phosphorus bioavailability, thereby achieving the dual goals of high-yield, high-quality rice production and efficient resource utilization. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a microbial-mineral-based composite material.

[0007] The second objective of this invention is to provide a method for preparing this microbial-mineral-based composite material.

[0008] The third objective of this invention is to provide the application of this microbial-mineral-based composite material in improving soil phosphorus bioavailability.

[0009] The fourth objective of this invention is to provide the application of this microbial-mineral-based composite material in improving rice yield and grain quality.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a microbial-mineral-based composite material comprising: iron phosphate powder and iron-reducing microorganisms; wherein the iron-reducing microorganisms include at least one of Shewanella, Geobacterium, Desulfovibrio, Clostridium butyricum, Geoacidophilus, and iron-rich bacteria.

[0011] In some embodiments of the present invention, the dissimilar iron-reducing microorganism is Shewanella. S. oneidensis MR-1.

[0012] In some embodiments of the present invention, the particle size of the iron phosphate powder is 800-1000 nm.

[0013] In some embodiments of the present invention, the iron phosphate powder is prepared by a method comprising the following steps: The iron source solution and the phosphorus source solution were added dropwise and mixed, reacted, and the solid phase was collected by solid-liquid separation, washed and freeze-dried to obtain the iron phosphate powder.

[0014] In some embodiments of the present invention, the iron source solution has a pH of 2.0-3.0 and a concentration of 0.25-0.35 mol / L.

[0015] In some embodiments of the present invention, the iron source solution is selected from at least one of ferric nitrate, ferric chloride, and ferric sulfate.

[0016] In some embodiments of the present invention, the dropping rate of the iron source solution is 1-5 mL / min.

[0017] In some embodiments of the present invention, the phosphorus source solution has a pH of 2.0-3.0 and a concentration of 0.25-0.35 mol / L.

[0018] In some embodiments of the present invention, the phosphorus source solution is selected from at least one of ammonium dihydrogen phosphate, phosphoric acid, sodium phosphate, and diammonium hydrogen phosphate.

[0019] In some embodiments of the present invention, the volume ratio of the iron source solution to the phosphorus source solution is 1:(0.8-1.2).

[0020] In some embodiments of the present invention, the iron source solution and the phosphorus source solution are added and mixed dropwise for 1-2 hours.

[0021] In some embodiments of the present invention, the reaction time is 2-4 h.

[0022] In some embodiments of the present invention, the reaction process is aided by stirring.

[0023] In some embodiments of the present invention, the pH of the reaction system is 2.0-3.0.

[0024] In some embodiments of the present invention, the washing reagent includes ultrapure water, and the washing is performed 2-4 times.

[0025] Specifically, this invention preferably uses self-made ferric phosphate powder. This method offers rapid synthesis and simple operation. During synthesis, controlling the pH to 2.0-3.0 and using a slow dropping rate helps maintain a balance between nucleation and growth, avoiding localized supersaturation that could lead to uneven particle size. After all the solution has been added, continued stirring allows for further growth and maturation of the microcrystals, resulting in a more complete precipitation reaction and the acquisition of fine, uniform ferric phosphate with relatively low crystallinity and high purity. Furthermore, commercially available food-grade and battery-grade ferric phosphate powders, due to their high purity and stable chemical properties, can also be used.

[0026] A second aspect of the present invention provides a method for preparing the microbial-mineral-based composite material described in the first aspect of the present invention, comprising the following steps: Ferric phosphate powder was mixed with a suspension of microorganisms that reduced iron by dissimilar iron to obtain the microbial-mineral-based composite material.

[0027] In some embodiments of the present invention, the OD of the bacterial suspension 600 =0.1-0.15; the solid-liquid ratio of the ferric phosphate powder to the bacterial suspension is (0.37-0.95) g: 10 mL.

[0028] In some preferred embodiments of the present invention, the OD of the bacterial suspension 600 =0.1-0.12; the solid-liquid ratio of the ferric phosphate powder to the bacterial suspension is (0.37-0.95) g : 10 mL.

[0029] In some embodiments of the present invention, the bacterial suspension is prepared by a method comprising the following steps: Using an inoculation loop, the heterotrophic iron-reducing microbial strain preserved in glycerol was inoculated onto LB medium and cultured at 25-23 °C and 160-200 rpm for 12-16 h. After centrifugation at 6000-8000 g for 4-6 min, the supernatant was removed, and the culture was washed with physiological saline at pH 7.0 and centrifuged again. This process was repeated 2-3 times. The washed bacterial culture was then resuspended in physiological saline to obtain the bacterial suspension.

[0030] In some embodiments of the present invention, the LB culture medium comprises the following components: 8-12 g / L tryptone, 8-12 g / L sodium chloride, and 4-6 g / L yeast extract.

[0031] The third aspect of the present invention provides the application of the microbial-mineral-based composite material described in the first aspect of the present invention in improving the bioavailability of phosphorus in soil.

[0032] In some embodiments of the invention, the soil comprises flooded, anaerobic, and iron-rich soil.

[0033] In some embodiments of the present invention, the soil includes paddy field soil.

[0034] In some embodiments of the present invention, the physicochemical properties of the soil include at least one of the following: 1) pH = 5.0-7.0; 2) Organic matter content is 30-45 g / kg; 3) Total iron content is 13-20 g / kg; 4) Total phosphorus content is 0.5-1.0 g / kg.

[0035] In some preferred embodiments of the present invention, the physicochemical properties of the soil include at least one of the following: 1) pH = 5.0-6.0; 2) Organic matter content is 35-42 g / kg; 3) Total iron content is 15-18.5 g / kg; 4) Total phosphorus content is 0.7-0.9 g / kg.

[0036] The fourth aspect of the present invention provides the application of the microbial-mineral-based composite material described in the first aspect of the present invention in improving rice yield and grain quality.

[0037] In some embodiments of the present invention, the microbial-mineral-based composite material is applied to the rice root zone soil by rhizosphere injection before rice transplanting.

[0038] Specifically, using rhizosphere injection can ensure close contact between the microbial-mineral-based composite material and the crop roots, thereby maximizing the synergistic effect.

[0039] In some embodiments of the present invention, the liquid-to-solid ratio of the microbial-mineral-based composite material to the soil is (14-22) mL : 10 g.

[0040] In some preferred embodiments of the present invention, the liquid-to-solid ratio of the microbial-mineral-based composite material to the soil is (16-20) mL : 10g.

[0041] In some embodiments of the present invention, the application rate of the iron phosphate powder component in the soil of the microbial-mineral-based composite material is 0.05-0.2 g / kg, and the bacterial concentration of dissimilar iron-reducing microorganisms in the composite material is 0.8 × 10⁻⁶. 7 cells / mL -1.2×10 7 cells / mL.

[0042] In some preferred embodiments of the present invention, the amount of iron phosphate powder applied to the soil in the microbial-mineral-based composite material is 0.06-0.17 g / kg, and the bacterial concentration of dissimilar iron-reducing microorganisms in the composite material is 0.9 × 10⁻⁶ g / kg. 7 cells / mL -1.1×10 7 cells / mL.

[0043] In some embodiments of the present invention, the rice variety includes Huanghuazhan.

[0044] The basic principles of this invention are explained as follows: The microbial-mineral-based composite material provided by this invention comprises iron phosphate powder and iron-reducing microorganisms. Iron-reducing microorganisms such as Shewanella can use ferric iron as an "electron acceptor" at the end of the respiratory chain to perform anaerobic respiration, thereby obtaining energy. In waterlogged anaerobic soil environments such as paddy fields, oxygen is scarce, and anaerobic respiration becomes extremely important.

[0045] Ferric phosphate itself has extremely low solubility in water, making it difficult for crops to utilize directly. However, dissimilar iron-reducing microorganisms can achieve close contact with ferric phosphate powder particles through special proteins on their cell membranes. They directly transfer electrons generated by intracellular metabolism to Fe(III) in the ferric phosphate. Thus, through the metabolic action of the microorganisms, the originally stable ferric phosphate crystal structure is destroyed, releasing soluble ferrous ions and phosphate ions. This reaction process can be simplified as follows: FePO4 (solid, insoluble) + e - (From microorganisms) → Fe 2+ (Soluble) + PO4 3- (Soluble).

[0046] In flooded soil, crop roots secrete oxygen, forming a unique rhizosphere oxidation zone. The soluble Fe produced during this process... 2+ Upon diffusing to the root surface, it is oxidized into iron oxides and deposited on the root surface, forming a reddish-brown iron film. This iron film has a huge specific surface area and strong adsorption capacity, which can efficiently adsorb and enrich the PO4 that has just been released. 3- This allows phosphorus to accumulate around the roots, preventing it from spreading and being lost in the soil. This enables crops to absorb phosphorus nutrients continuously and efficiently, thereby improving the bioavailability of phosphorus in the soil and promoting crop growth.

[0047] Compared with the prior art, the beneficial effects of the present invention are: The microbial-mineral-based composite material provided by this invention includes the mineral component iron phosphate and dissimilar iron-reducing microorganisms. The dissimilar iron-reducing microorganisms can actively reduce the originally chemically stable and insoluble iron phosphate to Fe(II), which has higher solubility, thereby destroying the crystal structure of iron phosphate and releasing free PO4 that can be absorbed and utilized by plants. 3- This microbial-driven mineral reduction and dissolution process is far more effective than the simple sum of minerals or microorganisms used alone, constituting a highly efficient phosphorus activation mechanism. When the composite material is applied to paddy soil, it increases the bioavailability of fixed phosphorus in the soil, significantly improving the phosphorus absorption efficiency and accumulation per plant in rice. This not only promotes root development, increases tiller number and effective panicle number in rice, but also optimizes nutrient distribution within the plant, directing more photosynthetic products to the grains. Thus, while reducing the application of traditional phosphate fertilizers, it achieves a significant increase in brown rice yield, 100-grain weight, and number of filled grains, while also reducing the risk of non-point source pollution caused by phosphorus loss, thus providing the dual benefits of increased yield, improved quality, and environmental protection. Attached Figure Description

[0048] Figure 1 This is a graph showing the content of different forms of phosphorus components in the soil during different treatment groups at different growth stages of rice in Experiment Example 1. Figure 2 The graph shows the content of extractable phosphorus in the iron film on the root surface of rice in different treatment groups at the maturity stage in Experiment Example 2. Figure 3 This is a graph showing the phosphorus content in various tissues and organs of rice in different treatment groups at the maturity stage in Experiment Example 2. Figure 4 This is a graph showing the dry matter content of various tissues and organs of rice in different treatment groups at the maturity stage in Experiment Example 3. Figure 5 The graph shows the plant trait indicators of different treatment groups at the maturity stage of rice in Experiment Example 3. Detailed Implementation

[0049] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0050] Shewanella used in the following examples S. oneidensis All MR-1 cells were purchased from the ATCC cell bank, with accession number ATCC 700550.

[0051] Example 1 This embodiment prepares a microbial-mineral-based composite material, and the steps are as follows: S1. Slowly add 500 mL of ferric nitrate solution with pH=2.0 and concentration of 0.3 mol / L to 500 mL of ammonium dihydrogen phosphate solution with pH=2.0 and concentration of 0.3 mol / L. During the entire addition process, strictly control the pH of the mixture to 2.0 and maintain a constant dropping rate to ensure that the entire addition process lasts for 1-2 hours. After all the solution has been added, continue stirring for 3 hours. After the reaction is complete, centrifuge and filter to remove the supernatant, wash three times with ultrapure water, freeze-dry and collect the solid powder to obtain ferric phosphate powder (particle size of 800-1000 nm). S2. Using an inoculation loop, collect the MR-1 bacterial culture preserved in glycerol and incubate it in LB medium (composed of 10 g / L tryptone, 10 g / L sodium chloride, and 5 g / L yeast extract) for 15 h at 30 ℃ and 180 rpm. Then, aliquot the bacterial culture into 50 mL centrifuge tubes and centrifuge at 7000 g for 5 min. Discard the supernatant, wash with physiological saline at pH 7.0, and centrifuge again. Repeat the above operation three times. Add an appropriate amount of physiological saline to the washed bacterial culture to adjust its OD. 600 =0.1, to obtain a bacterial suspension; S3. Add ferric phosphate powder to the bacterial suspension at a solid-liquid ratio of 0.67 g : 10 mL, shake well to obtain a microbial-mineral-based composite material.

[0052] Example 2 This embodiment prepares a microbial-mineral-based composite material, and the steps are as follows: S1. Slowly add 500 mL of ferric nitrate solution with pH=2.0 and concentration of 0.3 mol / L to 500 mL of ammonium dihydrogen phosphate solution with pH=2.0 and concentration of 0.3 mol / L. During the entire addition process, strictly control the pH of the mixture to 2.0 and maintain a constant dropping rate to ensure that the entire addition process lasts for 1-2 hours. After all the solution has been added, continue stirring for 3 hours. After the reaction is complete, centrifuge and filter to remove the supernatant, wash three times with ultrapure water, freeze-dry and collect the solid powder to obtain ferric phosphate powder (particle size of 800-1000 nm). S2. Using an inoculation loop, collect the MR-1 bacterial culture preserved in glycerol and incubate it in LB medium (composed of 10 g / L tryptone, 10 g / L sodium chloride, and 5 g / L yeast extract) for 15 h at 30 ℃ and 180 rpm. Then, aliquot the bacterial culture into 50 mL centrifuge tubes and centrifuge at 7000 g for 5 min. Discard the supernatant, wash with physiological saline at pH 7.0, and centrifuge again. Repeat the above operation three times. Add an appropriate amount of physiological saline to the washed bacterial culture to adjust its OD. 600 =0.1, to obtain a bacterial suspension; S3. Add ferric phosphate powder to the bacterial suspension at a solid-liquid ratio of 0.85 g : 10 mL, shake well to obtain a microbial-mineral-based composite material.

[0053] Experimental Example 1 This experiment compared the phosphorus activation performance of different treatment groups through a pot experiment. The steps are as follows: The soil used in the experiment was collected from the topsoil layer (0-20 cm) of typical paddy soil in Zhishan Town, Jiangmen City, Guangdong Province, China. The soil was pretreated by natural air drying, removal of impurities, crushing and passing through a 2 mm sieve. Its basic physicochemical properties are: pH=5.21, sandy loam, organic matter content of 38.74 g / kg, total iron content of 16.91 g / kg, and total phosphorus content of 0.86 g / kg. The rice variety planted in the experiment was the local main variety "Huang Huazhan".

[0054] The pot experiment used white plastic pots (20 cm high, 15 cm base diameter, 25 cm mouth diameter) as cultivation containers. Each pot contained 5 kg of the pretreated soil and 3.6 L of tap water to simulate a flooded environment. The experiment consisted of 6 treatment groups, with 3 replicates per group. Treatment group 1: No exogenous substances were added, representing the natural productivity background of the soil, marked as CK1; Treatment group 2: Only Shewanella MR-1 bacterial suspension was added (bacterial concentration of 1×10⁻⁶). 7 (cells / mL), denoted as CK2; Treatment group 3: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.068 g / kg soil, denoted as FeP1; Treatment group 4: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.17 g / kg soil, denoted as FeP2; Treatment group 5: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.068 g / kg soil, denoted as FeP1+M; Treatment group 6: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.17 g / kg soil, denoted as FeP2+M.

[0055] Before transplanting rice seedlings, the added materials were injected into the potting soil using a syringe. Rice seedlings that had reached the three-leaf stage were then transplanted into the pots, with three seedlings planted in each pot. Conventional water management was used throughout the rice growing season. Samples were taken on days 1, 15, 80, and 122 of rice growth. Soil pore water and rhizosphere soil samples were collected at each time point for phosphorus speciation determination.

[0056] The content of different forms of phosphorus in the soil was determined using the Hedley sequential extraction method, as detailed below: 1) After drying the rhizosphere soil sample, take 0.5 g and place it in a 50 mL centrifuge tube. Add 30 mL of deionized water and shake at 150 rpm for 2 h at 20 ℃. After centrifugation for 10 min, filter with phosphorus-free filter paper. Take the filtrate, add 0.9 mol / L H2SO4 to acidify, freeze at 4 ℃ for 30 min, centrifuge for 10 min, and determine H2O-P. 2) After retaining the residue, add 30 mL of 0.5 mol / L NaHCO3, shake at 20 ℃ and 150 rpm for 2 h, centrifuge for 10 min and filter. Acidify the filtrate with 0.9 mol / L H2SO4, freeze and centrifuge, and then determine NaHCO3-P. 3) Continue to retain the residue, add 30 mL of 0.1 mol / L NaOH, shake, centrifuge for 10 min and filter. Acidify the filtrate with 0.9 mol / L H2SO4, freeze and centrifuge, and then determine NaOH-P. 4) Add 10 mL of 1 mol / L HCl to the residue, heat in an 80 ℃ water bath for 10 min, remove and add 5 mL of HCl, cool, centrifuge for 10 min and transfer the supernatant to a clean container. Then add 10 mL of water to the residue, centrifuge for 10 min and combine the supernatant with the residue in the same container to ensure that the hydrochloric acid is fully extracted. Make up to 25 mL to determine HCl-P. 5) Finally, take 0.2 g of the residue after the HCl extraction and place it in a digestion tube. Add 5 mL of H2SO4 and 2 mL of H2O2, cover with the inner cap, and pre-digest at 150 °C for 15 min. After cooling, digest in a microwave digester at 100 °C for 2 h. After digestion, add 15 mL of deionized water, wait for cooling, filter into a 25 mL volumetric flask, make up to volume, transfer to a centrifuge tube for containing F5, and determine the phosphorus in the solution as Residual-P. 6) The phosphorus content in each extract was determined using an Optima 8000 inductively coupled plasma atomic emission spectrometer.

[0057] Figure 1 This is a graph showing the content of different forms of phosphorus components in the soil during different treatment groups at different growth stages in Experiment 1. Since the results of treatment group 1 and treatment group 2 are quite similar, the results of treatment group 1 are used to represent the two treatment groups and are marked as CK. In the graph, the number of replicate samples in each group is 3, and different capital letters represent different graded treatments within the same treatment group. p <0.05), different lowercase letters indicate different treatments for the same level of classification ( p <0.05). By Figure 1It was found that, compared with other forms of phosphorus, H2O-P and NaHCO3-P have higher mobility and are easily absorbed and utilized by rice plants. On the 15th day of flooding, the H2O-P concentration in the CK treatment group was 5.44 mg / kg, significantly lower than that in other treatment groups. The H2O-P concentrations in the FeP1, FeP2, FeP1+M, and FeP2+M treatment groups were 33.61%, 54.28%, 58.01%, and 93.21% higher than those in the CK treatment group, respectively. Among them, the FeP2+M treatment group had the highest H2O-P concentration, indicating that the high addition of FePO4 and MR-1 synergistically enhanced the reduction of dissimilar iron and promoted the release of dissolved phosphorus. On day 15, the CK treatment group had the lowest NaHCO3-P concentration at 50.89 mg / kg. The NaHCO3-P concentrations in the eP1, FeP2, FeP1+M, and FeP2+M treatment groups were 4.83%, 15.27%, 6.79%, and 10.01% higher than that in the CK treatment, respectively. The higher NaHCO3-P concentration in the FeP2+M treatment group indicates that the phosphorus released by dissimilar iron reduction is not entirely preserved in its available form; some phosphorus is rapidly absorbed and fixed by the iron film on the rice root surface. On day 80 of flooding, the contents of H2O-P and NaHCO3-P in all treatment groups generally decreased, indicating that available phosphorus was gradually absorbed and utilized by the rice plants. In the later stages of flooding, the available phosphorus content further decreased, and on day 122 of flooding, the H2O-P concentration was basically the same as that on day 80 of flooding. In summary, the analysis shows that the synergistic effect of FePO4 and microbial MR-1 in the microbial-mineral matrix composite material during the early stage of flooding promotes phosphorus release, increases the content of available phosphorus in the soil, provides sufficient nutrients for grain filling and brown rice formation in the later stage, and helps to increase rice yield.

[0058] Experimental Example 2 This experiment compared the differences in phosphorus distribution in different parts of rice plants from different treatment groups using a pot experiment. The steps are as follows: The soil used in the experiment was collected from the topsoil layer (0-20 cm) of typical paddy soil in Zhishan Town, Jiangmen City, Guangdong Province, China. The soil was pretreated by natural air drying, removal of impurities, crushing and passing through a 2 mm sieve. Its basic physicochemical properties are: pH=5.21, sandy loam, organic matter content of 38.74 g / kg, total iron content of 16.91 g / kg, and total phosphorus content of 0.86 g / kg. The rice variety planted in the experiment was the local main variety "Huang Huazhan".

[0059] The pot experiment used white plastic pots (20 cm high, 15 cm base diameter, 25 cm mouth diameter) as cultivation containers. Each pot contained 5 kg of the pretreated soil and 3.6 L of tap water to simulate a flooded environment. The experiment consisted of 6 treatment groups, with 3 replicates per group. Treatment group 1: No exogenous substances were added, representing the natural productivity background of the soil, marked as CK1; Treatment group 2: Only Shewanella MR-1 bacterial suspension was added (bacterial concentration of 1×10⁻⁶). 7 (cells / mL), denoted as CK2; Treatment group 3: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.068 g / kg soil, denoted as FeP1; Treatment group 4: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.17 g / kg soil, denoted as FeP2; Treatment group 5: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.068 g / kg soil, denoted as FeP1+M; Treatment group 6: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.17 g / kg soil, denoted as FeP2+M.

[0060] Before transplanting the rice, the added materials were injected into the potting soil using a syringe, and the rice seedlings cultivated to the three-leaf-one-heart stage were transplanted into the pots, with 3 seedlings planted in each pot. The conventional water management mode was used throughout the rice growing season. After harvesting the rice on the 122nd day, the various tissue parts of the rice were separated for the determination of phosphorus content.

[0061] The method for determining the phosphorus content of the iron film on the root surface of rice is as follows: The phosphorus content in the iron film on the root surface was determined by DCB extraction. The specific operation was as follows: 0.5 g of fresh roots were weighed into a 100 mL centrifuge tube, and 40 mL of 0.3 mol / L sodium citrate solution, 5 mL of 1 mol / L sodium bicarbonate solution and 3.0 g of sodium dithionite were added in sequence. The resulting sample was shaken on a shaker at 25 ℃ and 280 r / min for 3 h. The resulting extract was filtered, and the phosphorus content in the filtrate was determined by ICP-OES.

[0062] The method for determining the phosphorus content in various parts and organs of rice is as follows: After rice was harvested on day 122, the various tissues and parts of the rice were separated. Each tissue and part was first blanched in an oven at 105 ℃ for 30 min, and then dried in an oven at 75 ℃ to constant weight. The dried plant samples were then crushed using a high-speed blender. 0.2 g of each rice tissue and part was accurately weighed and placed in a microwave digestion tube. 5 mL of H2SO4 and 2 mL of H2O2 were added, the inner cap was closed, and the mixture was pre-digested at 150 ℃ for 15 min. After cooling, the mixture was digested in a microwave digester at 100 ℃ for 2 h. After digestion, the acid was allowed to evaporate to 1-2 mL at 200 ℃, 15 mL of deionized water was added, and the mixture was allowed to cool. The mixture was then filtered into a 25 mL volumetric flask, diluted to volume, and transferred to a centrifuge tube. The phosphorus content in each extract was determined using an Optima 8000 inductively coupled plasma atomic emission spectrometer.

[0063] Figure 2 This is a graph showing the content of extractable phosphorus in the iron film on the root surface of rice in different treatment groups at the maturity stage in Experiment Example 2. Since the results of treatment group 1 and treatment group 2 are quite similar, the result of treatment group 1 is used to represent the two treatment groups and is labeled CK. In the graph, the number of replicates for each group is 3, and different lowercase letters indicate significant differences between treatments. p <0.05). By Figure 2 It was found that the phosphorus content of the root surface iron film in the FeP1, FeP2, FeP1+M, and FeP2+M treatment groups was 24.50%, 31.21%, 24.73%, and 36.44% higher than that in the CK treatment group, respectively. Among them, the FeP2 and FeP2+M treatment groups had the highest phosphorus content in the root surface iron film, indicating that the high amount of FePO4 alone or in synergy with MR-1 can significantly increase the phosphorus content of the root surface iron film in rice, thereby enhancing the absorption and translocation of phosphorus by the rice roots, so that the rice plants can continuously obtain phosphorus and provide nutrients for the later development of rice grains.

[0064] Figure 3 This is a graph showing the phosphorus content in various tissues and organs of rice at different treatment groups during the maturity stage in Experiment Example 2. Since the results of treatment group 1 and treatment group 2 are quite similar, the result of treatment group 1 is used to represent the two treatment groups and is labeled CK. In the graph, the number of replicates for each group is 3, and different lowercase letters indicate significant differences between treatments. p <0.05), Figure 3 In the figure, (a) represents the phosphorus concentration in the roots of rice in different treatment groups. Figure 3 (b) in the figure represents the phosphorus concentration in the aboveground parts of rice in different treatment groups. Figure 3 (c) in the figure represents the phosphorus distribution ratio in the aboveground parts of rice in different treatment groups. Figure 3 (d) represents the phosphorus use efficiency of rice in different treatment groups. Figure 3 (e) represents the phosphorus accumulation in the roots of rice in different treatment groups. Figure 3 (f) represents the phosphorus accumulation in the aboveground parts of rice in different treatment groups. Figure 3 (g) in the figure represents the phosphorus utilization index of rice in different treatment groups. Figure 3 (h) represents the phosphorus accumulation per rice plant in different treatment groups. Figure 3 It was found that compared with the CK treatment group, the phosphorus concentrations in roots, stems, leaves, and rice husks of the other treatment groups were significantly increased. Specifically, the phosphorus content in the roots of the CK treatment group was approximately 3.73 g / kg, significantly lower than the other treatment groups. The FeP2+M treatment group had the highest root phosphorus content, reaching 5.96 g / kg, an increase of approximately 59% compared to the CK treatment group. This indicates that the synergistic effect of FePO4 and MR-1 significantly promoted the capture and accumulation of phosphorus in rice roots. Regarding the phosphorus accumulation per rice plant, the FeP1+M and FeP2+M treatment groups had higher values, at 108.76 mg / kg and 114.39 mg / kg respectively, while the CK treatment group and the other two treatment groups had lower values, further illustrating that the synergistic effect of FePO4 and MR-1 enhanced the phosphorus accumulation capacity at the individual plant level. In summary, the combined effect of FePO4 and MR-1 improved the bioavailability of phosphorus in the rhizosphere and root uptake, as well as the phosphorus accumulation per plant, providing a stable phosphorus supply during the grain-filling stage. Therefore, the microbial-mineral-based composite material provided by this invention not only improves the absorption and distribution of nutrients in plants, but also provides sufficient nutritional support for nutrient transport and grain formation in subsequent growth stages, thereby optimizing phosphorus utilization efficiency throughout the entire growth cycle of rice.

[0065] Experimental Example 3 This experiment compared the differences in rice growth, yield, and brown rice quality improvement among different treatment groups using a pot experiment. The steps are as follows: The soil used in the experiment was collected from the topsoil layer (0-20 cm) of typical paddy soil in Zhishan Town, Jiangmen City, Guangdong Province, China. The soil was pretreated by natural air drying, removal of impurities, crushing and passing through a 2 mm sieve. Its basic physicochemical properties are: pH=5.21, sandy loam, organic matter content of 38.74 g / kg, total iron content of 16.91 g / kg, and total phosphorus content of 0.86 g / kg. The rice variety planted in the experiment was the local main variety "Huang Huazhan".

[0066] The pot experiment used white plastic pots (20 cm high, 15 cm base diameter, 25 cm mouth diameter) as cultivation containers. Each pot contained 5 kg of the pretreated soil and 3.6 L of tap water to simulate a flooded environment. The experiment consisted of 6 treatment groups, with 3 replicates per group. Treatment group 1: No exogenous substances were added, representing the natural productivity background of the soil, marked as CK1; Treatment group 2: Only Shewanella MR-1 bacterial suspension was added (bacterial concentration of 1×10⁻⁶). 7 (cells / mL), denoted as CK2; Treatment group 3: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.068 g / kg soil, denoted as FeP1; Treatment group 4: Only iron phosphate powder (preparation method is the same as in Examples 1 and 2) was added, and the amount applied was 0.17 g / kg soil, denoted as FeP2; Treatment group 5: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.068 g / kg soil, denoted as FeP1+M; Treatment group 6: The microbial-mineral-based composite material prepared in Example 1 was applied, with a Shewanella MR-1 bacterial concentration of 1×10⁻⁶. 7 The amount of iron phosphate applied to the soil was 0.17 g / kg soil, denoted as FeP2+M.

[0067] Before transplanting rice, the added materials were injected into the potting soil using a syringe, and the rice seedlings cultivated to the three-leaf-one-heart stage were transplanted into the pots, with 3 seedlings planted in each pot. Conventional water management was adopted throughout the rice growing season. After harvesting the rice on day 122, the various tissues and parts of the rice were separated for the determination of the quality of various tissues and organs of the rice plant and the trait indicators of the rice plant.

[0068] The methods for determining the quality of various tissues and organs of rice plants and the trait indicators of rice plants are as follows: After rice has grown for 122 days, mature rice is harvested. The various tissues and parts of rice are separated into roots, stems, leaves, panicles, brown rice, and rice husks. The height of the plant is measured from the ground to the highest point of the plant and recorded. The number of tillers, the number of effective panicles, the number of filled grains, and the weight of 100 grains are counted. At the same time, the collected rice tissues and parts are placed in an oven at 105 ℃ for 30 min to blanch, and then dried in an oven at 75 ℃ to constant weight. The dry weight is measured using an analytical balance and recorded.

[0069] Figure 4 This is a graph showing the dry matter content of various tissues and organs of rice at different treatment groups during the maturity stage in Experiment Example 3. Since the results of treatment group 1 and treatment group 2 are quite similar, the result of treatment group 1 is used to represent the two treatment groups and is labeled CK. In the graph, the number of replicates for each group is 3. Different lowercase letters indicate significant differences between treatments. p <0.05), Figure 4 In the figure, (a) represents the dry matter content of brown rice in different treatment groups. Figure 4 (b) in the figure represents the dry matter content of rice husks in different treatment groups. Figure 4 (c) represents the dry weight of the rachis in different treatment groups. Figure 4 In the figure, (d) represents the leaf dry matter mass of different treatment groups. Figure 4 In the figure, (e) represents the stem dry matter mass of different treatment groups. Figure 4 In the figure, (f) represents the root dry matter mass of different treatment groups, which is derived from... Figure 4 The results showed that the rice plant heights in the CK, FeP2, FeP1, FeP1+M, and FeP2+M treatment groups were 92.66, 102.02, 95.33, 97.33, and 99.10 cm, respectively. This indicates that applying FePO4 alone or in combination with MR-1 can increase the effective supply of soil phosphorus, thereby promoting rice plant growth. The number of tillers and effective panicles in the FeP1+M and FeP2+M treatment groups were significantly higher than those in the other treatment groups, indicating that the synergistic effect of FePO4 and MR-1 increased the number of tillers and effective panicles. The number of filled grains and the weight of 100 grains in the CK treatment group were 85.66 / 100 grains and 1.81 g / 100 grains, respectively, which were lower than those in other treatment groups. The number of filled grains and the weight of 100 grains in the FeP2+M treatment group were 90.20 / 100 grains and 1.85 g / 100 grains, respectively, which were significantly higher than those in other treatment groups. This indicates that applying FePO4 alone or in synergy with MR-1 can effectively increase the number of filled grains and the weight of 100 grains in rice plants.

[0070] Figure 5 The graph shows the plant trait indices of different treatment groups at the rice maturity stage in Experiment Example 3. Since the results of treatment group 1 and treatment group 2 are quite similar, the results of treatment group 1 are used to represent the two treatment groups and are labeled CK. In the graph, the number of replicates for each group is 3, and different lowercase letters indicate significant differences between treatments. p <0.05). By Figure 5It was found that, regarding the stem weight of rice, the FeP1+M and FeP2+M treatment groups had 12.28 g / plant and 12.32 g / plant, respectively, which were higher than the CK treatment group's 10.79 g / plant. The two treatment groups that only added FePO4 had relatively lower stem weights. This indicates that the synergistic effect of FePO4 and MR-1 can effectively promote rice stem growth, providing mechanical support for grain development and enabling the transport of more nutrients. Regarding the husk weight, the FeP1+M and FeP2+M treatment groups had 5.82 g / plant and 5.26 g / plant, respectively, which were higher than the CK and other treatment groups, indicating that the synergistic effect of FePO4 and MR-1 can promote an increase in husk weight to some extent. Regarding panicle weight, the CK treatment group had the lowest weight, approximately 1.07 g / plant, while the FeP1+M and FeP2+M treatment groups had weights of 1.35 g / plant and 1.37 g / plant, respectively, which were 20.74% and 21.90% higher than the CK group, and also higher than the FeP1 and FeP2 treatment groups. This indicates that FePO4 and MR-1 have a certain promoting effect on the development of rice panicles and the stability of the overall structure of rice panicles. Furthermore, the FeP2+M treatment group had the highest brown rice weight, reaching 22.38 g / plant. The brown rice weights of the FeP1, FeP2, and FeP1+M treatment groups were 20.21 g / plant, 21.14 g / plant, and 21.55 g / plant, respectively, significantly higher than the CK treatment group's 18.61 g / plant. This suggests that the synergistic effect of FePO4 and MR-1 can promote increased brown rice yield. Based on the quality of various tissues and organs of rice, the synergistic effect of FePO4 and MR-1 can effectively improve the quality of brown rice, rice husk, panicle and stem, especially the improvement effect on brown rice quality.

Claims

1. A microbial-mineral-based composite material, characterized in that, It comprises the following components: iron phosphate powder and iron-reducing microorganisms; wherein the iron-reducing microorganisms include at least one of Shewanella, Geobacterium, Desulfovibrio, Clostridium butyricum, Geoacidophilus, and iron-rich bacteria.

2. The microbial-mineral-based composite material according to claim 1, characterized in that, The iron-reducing microorganism is Shewanella. S. oneidensis MR-1.

3. The method for preparing the microbial-mineral-based composite material according to claim 1 or 2, characterized in that, Includes the following steps: Ferric phosphate powder was mixed with a suspension of microorganisms that reduced iron by dissimilar iron to obtain the microbial-mineral-based composite material.

4. The preparation method according to claim 3, characterized in that, The OD of the bacterial suspension 600 =0.1-0.15; the solid-liquid ratio of the ferric phosphate powder to the bacterial suspension is (0.37-0.95) g : 10 mL.

5. The application of the microbial-mineral-based composite material according to claim 1 or 2 in improving soil phosphorus bioavailability.

6. The application according to claim 5, characterized in that, The soil includes flooded, anaerobic, and iron-rich soil.

7. The application according to claim 6, characterized in that, The physical and chemical properties of the soil include at least one of the following: 1) pH = 5.0-7.0; 2) Organic matter content is 30-45 g / kg; 3) Total iron content is 13-20 g / kg; 4) Total phosphorus content is 0.5-1.0 g / kg.

8. The application of the microbial-mineral-based composite material according to claim 1 or 2 in improving rice yield and grain quality.

9. The application according to claim 8, characterized in that, The microbial-mineral-based composite material was applied to the rice root zone soil by rhizosphere injection before rice transplanting.

10. The application according to claim 9, characterized in that, The liquid-to-solid ratio of the microbial-mineral-based composite material to the soil is (14-22) mL : 10 g.

Images