Soil conditioner based on rare earth tailings, waste biomass and microorganisms and preparation method thereof

Abstract

The invention relates to a soil conditioner based on rare earth tailings, waste biomass and microorganisms and a preparation method of the soil conditioner. The method comprises the following steps: separating and breeding rare earth mine indigenous bacteria capable of tolerating rare earth elements from rare earth mine soil, and separating and breeding efficient lignin degrading bacteria from a natural environment; then mixing rare earth mine indigenous bacteria and efficient lignin degrading bacteria according to a certain proportion, compounding and culturing to prepare a liquid microbial agent; and mixing the rare earth tailings to be treated, the waste biomass and the liquid microbial agent, composting and fermenting to finally obtain the soil conditioner capable of improving the physical and chemical properties of soil, improving the fertilizer efficiency of the soil and improving the quality of crops. The method simultaneously solves the environmental protection problem caused by massive accumulation of the rare earth tailings and the resource utilization problem of the waste biomass in China, has the advantages of simple process flow, low production cost and the like, and provides a brand new idea for efficient treatment and resource utilization of the rare earth tailings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical fields of rare earth mining and treatment, microorganisms, and the like, and specifically relates to a soil conditioner based on rare earth tailings, waste biomass and microorganisms and a preparation method thereof. BACKGROUND

[0002] Rare earth elements are a general term for yttrium, scandium and 15 lanthanide metal elements, which are widely used in various fields such as electronics, agriculture, precision equipment, national defense industry and green energy. China is recognized as the country with the most abundant reserves of rare earth resources, accounting for about 50% of the world's reserves. Until the last century, China was still using the original pool leaching method and heap leaching method to extract rare earth elements from rare earth mines, and after 2008, these two methods were gradually replaced by in-situ leaching method which does not need to remove the vegetation on the ground. In-situ leaching is considered a relatively environmentally friendly method, but this method also produces a large amount of rare earth tailings containing leachate, and there is currently no effective treatment method, so it can only be discarded on site. In addition, there are nearly 200 million tons of rare earth tailings left over from early heap leaching and pool leaching processes, and how to dispose of these rare earth tailings determines the healthy and sustainable development of the rare earth industry.

[0003] In fact, rare earth tailings are a kind of secondary resources with high utilization value, and if they can be effectively utilized, both environmental pollution and resource waste can be reduced. Previously, physical and chemical methods were usually used to reduce and recycle rare earth tailings, but this method cannot extract and utilize all valuable elements in the tailings, and inevitably causes environmental pollution. In contrast, the application of existing biological methods in rare earth mines is more focused on microbial-plant remediation of rare earth mine sites after leaching, and there is less research on the reuse of rare earth tailings. In recent years, rare earth elements have been increasingly used as trace fertilizers in agriculture to promote plant growth and improve crop yield and quality. For example, the correlation between rare earth elements and fruit quality in Jiangxi Gannan navel orange orchards (10.13718 / j.cnki.xdzk.2021.03.010) showed that trace amounts of rare earth elements not only increased the vitamin C content of navel oranges, but also positively correlated fruit size, peel brightness and redness with rare earth element mass fraction. The positive results of such studies point to a new way for the reuse of rare earth tailings - soil conditioners.

[0004] Previously, we successfully selected high-efficiency phosphorus-dissolving bacteria and high-efficiency potassium-dissolving bacteria from phosphate mine soil and potassium feldspar mine soil, respectively, and then mixed and compounded them with high-efficiency cellulose-degrading bacteria to prepare a microbial agent. Then, the microbial agent was mixed with waste biomass, medium-low grade phosphate ore powder, and potassium feldspar ore powder and repeatedly fermented to prepare a granular soil conditioner, which successfully solved the problem of the development and utilization of medium-low grade phosphate ore and potassium feldspar ore (see Chinese Patent CN115537208B). However, rare earth tailings, medium-low grade phosphate ore, and potassium feldspar ore have great differences in chemical composition, mining methods, and tailings treatment, and the microbial flora in the corresponding mine soil is also completely different, which makes the original strain selection system and method no longer applicable to rare earth tailings. It is urgent to explore and establish a new treatment method suitable for rare earth tailings. SUMMARY

[0005] One of the purposes of the present application is to solve the problems of rare earth tailings treatment and biomass resource recycling and reuse, and to provide a soil conditioner based on rare earth tailings, waste biomass, and microorganisms. The soil conditioner is prepared by mixing a composite microbial agent, rare earth tailings, and waste biomass and then aerobic fermentation. On the one hand, it solves the environmental protection and resource waste problems caused by the large accumulation of rare earth tailings, and on the other hand, it achieves multiple beneficial effects such as improving soil physical and chemical properties, enhancing soil fertility, and improving crop quality, which is also beneficial to the development of rare earth resources and the development of green agriculture.

[0006] As one of the embodiments of the present application, the preparation method of the soil conditioner based on rare earth tailings, waste biomass, and microorganisms comprises: (a) selecting rare earth mine indigenous bacteria from rare earth mine soil and selecting high-efficiency lignin-degrading bacteria from natural environment.

[0007] (b) mixing and compounding the rare earth mine indigenous bacteria and the high-efficiency lignin-degrading bacteria to prepare a composite microbial agent, mixing the composite microbial agent with rare earth tailings and waste biomass, and obtaining a rare earth tailings-based soil conditioner after aerobic composting fermentation.

[0008] In the above process, the selection process of the rare earth mine indigenous bacteria includes steps such as extraction, culture, enrichment, screening, and preservation, and the specific process is as follows: ① Mix the collected rare earth mine soil with water in a certain mass ratio (for example, 1:20-25), shake in a shaker at 28-30°C for 1-2h, and obtain a rare earth mine soil extraction solution.

[0009] ② Mix the mine soil extraction solution with culture medium A (containing rare earth elements) in a certain volume ratio (such as 1:5-10), shake and culture in a shaker at 28-30°C for 2-3 days, and obtain a rare earth mine soil enrichment bacterial solution.

[0010] ③ The enriched bacteria liquid is coated on culture medium B (containing rare earth elements) and incubated at 28-30°C for 2-3 days, and strains that can still form complete single colonies under a certain concentration of rare earth ions are screened out and recorded as rare earth mine indigenous bacteria.

[0011] ④ The rare earth mine indigenous bacteria are streaked on culture medium C and incubated at 28-30°C for 2-3 days, and the purified rare earth mine indigenous bacteria are obtained.

[0012] ⑤ The step ④ is repeated for several times (3-5 times), and the purified rare earth mine indigenous bacteria obtained in the last time are preserved on culture medium F and incubated at 28-30°C for 2-3 days, and then stored in a refrigerator at 4°C for preservation and standby.

[0013] The breeding process of the high-efficiency lignin-degrading bacteria is similar to that of the rare earth mine indigenous bacteria, and also includes steps such as extraction, culture, enrichment, screening, and preservation, and the specific process is as follows: ① Forest soil samples and their surrounding rotten leaf samples are collected.

[0014] ② The rotten leaves are cut into pieces with a particle size similar to that of the surrounding soil samples, and then the leaf pieces, soil particles, and water are mixed in a certain mass ratio (for example, 1:1:20-25), and then incubated at 28-30°C for 1-2 h in a shaker, and then left to stand for 20-30 min to obtain a diluted sample.

[0015] ③ The supernatant of the diluted sample is mixed with culture medium D in a certain mass ratio (for example, 1:10-15), and then incubated at 28-30°C for 24-36 h in a shaker to obtain an enriched sample.

[0016] ④ The enriched sample is coated on culture medium G (containing alkali lignin) in a concentration gradient of 10 -2 , 10 -3 , 10 -4 , 10 -5 , and 10 -6 , and incubated at a constant temperature.

[0017] ⑤ Single colonies growing on the culture medium G are picked and transferred to culture medium C for streaking and purification culture, and the purified strain is obtained after repeating the purification for 3-4 times.

[0018] ⑥ The purified strain is inoculated into culture medium E (aniline blue) and incubated at a constant temperature, and the fading of aniline blue is observed to screen the strain with the highest fading efficiency as the target high-efficiency lignin-degrading bacteria.

[0019] In the above scheme, the rare earth mine indigenous bacteria and the high-efficiency lignin-degrading bacteria need to be reinvigorated before being mixed in a certain proportion to obtain the compound microbial inoculant.

[0020] Further, the volume ratio of the rejuvenated rare earth mine indigenous bacteria liquid and the rejuvenated high-efficiency lignin-degrading bacteria liquid required for preparing the composite microbial agent is 2:1-1.5.

[0021] In the above scheme, the mass percentage content of rare earth oxides in the rare earth tailings is not more than 1%.

[0022] In the above scheme, the waste biomass includes waste biomass carbon material and waste biomass nitrogen material, wherein the waste biomass carbon material is at least one selected from sawdust, rice husk, corn straw powder, wheat straw powder, corn cob, sugarcane residue, coconut dregs, mushroom stick and the like, and the waste biomass nitrogen material is at least one selected from food processing discards such as soybean dregs, rapeseed cake, soybean meal cake, peanut cake, coffee residue, tea residue and beer dregs.

[0023] In the above scheme, the mass ratio of the rare earth tailings and the waste biomass required for preparing the soil conditioner is 0.3-0.5:1.8-2.2, and the mass ratio of the waste biomass carbon material and the waste biomass nitrogen material in the waste biomass is 1:0.8-1.2.

[0024] In the above scheme, the mass of the composite microbial agent required for preparing the soil conditioner is equivalent to 0.1-0.2 times the total mass of the rare earth tailings and the waste biomass.

[0025] In the above scheme, water is also required to be added at regular intervals during the compost fermentation process, and the amount of water added is equivalent to 0.2-0.3 times the total mass of the rare earth tailings and the waste biomass.

[0026] In the above scheme, the compost fermentation temperature is 25-60℃, and the compost fermentation time is 25-30 days.

[0027] The rare earth mine indigenous bacteria and the high-efficiency lignin-degrading bacteria obtained through careful selection are mixed and compounded to prepare a composite microbial agent, which is then mixed and fermented with the rare earth tailings and the waste biomass to obtain a soil conditioner. On the one hand, the disposal and utilization problems of the rare earth tailings and the waste biomass resources are solved, and on the other hand, the soil is regulated and repaired, and the effect of waste treatment is achieved.

[0028] Compared with the existing conventional rare earth tailings treatment technology, the innovation points and advantages of the present application mainly include: (1) In view of the current situation of large accumulation and low utilization rate of rare earth tailings in China, the solution provided by the present application realizes the rational utilization of rare earth tailings and provides a new direction for the resource utilization of rare earth tailings.

[0029] (2) The soil conditioner provided by the application can not only comprehensively utilize rare earth tailings, but also widely use waste biomass as raw material and combine with microbial agents, and has the advantages of improving soil structure, adjusting soil physical and chemical properties, increasing soil beneficial microorganisms and the like. Compared with the use mode of directly applying the untreated waste biomass to the soil, the fertilizer efficiency is more moderate, the nutrient absorption is faster, and the plant growth is more beneficial after the treatment according to the method of the application, and there is no risk of burning roots and the like.

[0030] (3) The application has the advantages of low cost, simple production process, waste treatment with waste, green environmental protection and the like, and the entire production process meets the index requirements of the relevant national standards and conforms to the current resource-saving and environment-friendly concept. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a process flowchart of the application.

[0032] Figure 2 The figure is a comparison chart of the alkali-hydrolyzable nitrogen, available phosphorus and available potassium contents in the soil obtained from the pot experiment in Example 1 and the contents of the "rich" standard in the soil nutrient classification standard of the second national soil survey. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to fully understand the technical solutions and beneficial effects of the application, the following will be further described in detail in combination with specific examples and drawings. It should be emphasized that the following examples are only preferred embodiments of the application and do not constitute any limitation on the application, and on this basis, the application can also have many other embodiments, and any simple modification or replacement based on these examples or embodiments will fall within the protection scope of the application.

[0034] In the process of separating and screening different microorganisms, different formulations of culture media are needed, and the functions of these culture media are different, so the formulations are also different and cannot be equivalent or replaced with each other. Most of these culture media have not been reported, and they are all specially developed by the inventor according to the source of microbial raw materials, the type and habit of microbial flora, the application scene and the like, and play a key and decisive role in the successful implementation of the application.

[0035] The first one is a liquid LB medium containing rare earth, which is referred to as medium A, and the formula is: 1-2 g / L YCl3 or its hydrate, 10-15 g / L protein peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, and the solvent is distilled water.

[0036] The second one is LB agar medium containing rare earth, which is referred to as medium B. The formula of medium B is: 0.5-1 g / L YCl3 or its hydrate, 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water.

[0037] The Y element is added in the above two media in a specific amount. This is because, through element analysis of rare earth tailings, it is found that the content of Y element in the rare earth elements contained in the rare earth tailings is much higher than that of other rare earth elements. Therefore, adding an appropriate amount of Y element in the medium can well simulate the reduction environment of rare earth mines, and at the same time, it can better screen out strains that can grow normally under a certain rare earth concentration environment, avoiding too many miscellaneous bacteria.

[0038] The third one is LB solid medium, which is referred to as medium C. The formula of medium C is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water. After sterilization, medium C can be poured into 75 mm culture dishes and used for purifying strains after solidification.

[0039] The fourth one is LB liquid medium, which is referred to as medium D. The formula of medium D is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, and the solvent is distilled water.

[0040] The fifth one is aniline blue solid medium, which is referred to as medium E. The formula of medium E is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, 0.1-0.2 g / L aniline blue dye, and the solvent is distilled water.

[0041] The sixth one is agar slant medium, which is referred to as medium F. The formula of medium F is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water. After sterilization, medium F can be poured into test tubes and placed at an angle to form a slant, which can be used for short-term storage of strains.

[0042] The seventh one is a preliminary screening medium, which is referred to as medium G. The formula of medium G is: 0.5-1 g / L MgSO4, 1-2 g / L K2HPO4, 0.5-1 g / L NaCl, 2-3 g / L (NH4)2SO4, 5-6 g / L alkali lignin, and the solvent is distilled water.

[0043] The rare earth mine soil and rare earth tailings required for the experiments of this invention were both obtained from an ion-adsorption rare earth leaching site in Longnan County, Ganzhou City, Jiangxi Province. The decayed leaves and surrounding soil samples were obtained from tree stumps in the woods on the campus of this university. Before the experiment, the required rare earth mine native bacteria and highly efficient cellulose-degrading bacteria were isolated, enriched, cultured, and screened from the rare earth mine soil, decayed leaves on campus, and surrounding soil samples according to specific methods.

[0044] (1) Indigenous bacteria of rare earth mines.

[0045] Indigenous bacteria from rare earth mines are isolated and screened from rare earth mine soils. The culture media used include culture medium A, culture medium B, culture medium C, and culture medium F. The specific process is as follows: Rare earth mine soil and water were mixed at a mass ratio of 1:20 (which can be relaxed to 1:20-25) and placed in Erlenmeyer flasks. The flasks were then placed in a 30°C constant-temperature shaker and shaken at 160 rpm for 2 hours. After shaking, the mixture was allowed to stand to obtain diluted soil sample a. The supernatant of diluted soil sample a was mixed with culture medium A at a volume ratio of 1:5-10. The resulting mixture was then placed in a shaker and cultured to obtain enriched bacterial solution a. Enriched bacterial solution a was spread onto culture medium B and then transferred to a 30°C constant-temperature incubator for 3 days. Two single-colony strains that could still grow normally under certain rare earth ion concentrations were screened out and designated as rare earth mine native bacteria a and rare earth mine native bacteria b. Rare earth mine native bacteria a and b were streaked onto culture medium C and cultured at a 30°C constant-temperature incubator for 3 days to obtain the first purified rare earth mine native bacteria a and b. After repeated streak purification culture three times, the two rare earth mining native bacteria a and b were inoculated onto culture medium F and cultured in a constant temperature incubator at 30℃ for 3 days to obtain rare earth mining native bacteria a and b. After being taken out, they were stored in a refrigerator at 4℃ for later use.

[0046] Upon identification, the two rare earth mine native bacteria strains obtained using the above method were both identified as belonging to the genus *Pseudomonas*. A review of relevant literature revealed that this type of bacteria possesses advantages such as improved composting efficiency, shorter composting time, and strong tolerance to heavy metals, making it highly suitable for the reuse and development needs of rare earth tailings.

[0047] (2) Highly efficient cellulose-degrading bacteria.

[0048] The highly efficient cellulose-degrading bacteria were isolated and screened from decaying leaves and surrounding soil samples in the campus woodlands. The culture media used included media C, media D, media E, media F, and media G. The specific process is as follows: The rotten fallen leaf sample and its surrounding soil sample are mixed with water in a mass ratio of 1:1:20 (which can be appropriately relaxed) into a triangular flask, the triangular flask is placed in a 30℃ constant temperature shaker, and the shaking speed is 160r / min for 2 hours to obtain a diluted sample b. The supernatant of the diluted sample b is mixed with the culture medium D in a volume ratio of 1:5 into a triangular flask, the triangular flask is placed in a 30℃ constant temperature shaker, and the shaking speed is 160r / min for 24 hours to obtain an enriched bacteria liquid b. The enriched bacteria liquid b is coated on the culture medium G in a concentration gradient of 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 , and cultured in a 30℃ constant temperature incubator for 3 days. The strains with transparent circles are screened out and recorded as cellulose-degrading bacteria c. The cellulose-degrading bacteria c is streaked on the culture medium C and cultured in a 30℃ constant temperature incubator for 3 days to obtain the first purified cellulose-degrading bacteria c. After repeating the streaking and purification for 3 times, 4 strains of cellulose-degrading bacteria are screened out. The same amount of the 4 strains of cellulose-degrading bacteria is inoculated on the culture medium E, and the degradation of aniline blue dye is observed after 24 hours to determine the cellulose degradation ability of the 4 strains of cellulose-degrading bacteria obtained after the last purification. The strain with the largest degradation circle (corresponding to the strongest cellulose degradation ability) is selected as the target strain (i.e. high-efficiency cellulose-degrading bacteria), which is inoculated on the culture medium F and cultured in a 30℃ constant temperature incubator for 3 days, and then stored in a 4℃ refrigerator for standby.

[0049] After identification, the high-efficiency cellulose-degrading bacteria obtained by the above method is Bacillus, which has excellent lignin degradation ability and can promote the efficient utilization of waste biomass resources.

[0050] The 2 strains of rare earth mine indigenous bacteria and 1 strain of high-efficiency cellulose-degrading bacteria prepared above need to be rejuvenated before use, and the specific process is as follows: the strains to be rejuvenated are inoculated in the culture medium D and cultured in a 30℃ constant temperature shaker for 2 days to complete rejuvenation.

[0051] Example 1 Preparation of microbial inoculant. According to the volume ratio of 1:1:1:50, the 2 strains of rare earth mine indigenous bacteria, 1 strain of high-efficiency cellulose-degrading bacteria and culture medium D separated, purified, cultured and screened out and subjected to rejuvenation culture are put into a triangular flask, the triangular flask is placed in a constant temperature shaker, and the shaking speed is 165r / min at 30℃ for 2 days to obtain a liquid microbial inoculant.

[0052] Preparation of soil conditioner. Sawdust, bean dregs, rapeseed cake and collected rare earth tailings (rare earth oxide content of about 0.8wt%) were mixed uniformly in a mass ratio of 1:0.5:0.5:0.35 to obtain a compost substrate. The compost substrate, water and liquid microbial agent were mixed uniformly in a mass ratio of 1:0.25:0.15 in a compost reactor, and compost fermentation was carried out at room temperature for 30 days to finally obtain the soil conditioner. The analysis and detection results showed that the alkali-hydrolyzable nitrogen content in the soil conditioner was 320 mg / kg, the available phosphorus content was 173 mg / kg, and the available potassium content was 1517 mg / kg.

[0053] The same batch of healthy and normally growing leeks were selected for potting experiments. The soil conditioner was mixed with the ordinary soil collected on campus at an addition ratio of 10wt% to obtain the raw material for the potting experiment (referred to as the experimental group), and was compared with the ordinary soil collected on campus (referred to as the control group). The soil and plants were detected after 20 days of potting, and the results were as follows: The alkali-hydrolyzable nitrogen content in the soil of the experimental group was 140.49 mg / kg, the available phosphorus content was 25.71 mg / kg, the available potassium content was 290.93 mg / kg, the total nitrogen content was 4.54 g / kg, the total phosphorus content was 1.14 g / kg, and the organic matter content was 45.56 g / kg. The alkali-hydrolyzable nitrogen content in the soil of the control group was 87.02 mg / kg, the available phosphorus content was 15.68 mg / kg, the available potassium content was 127.28 mg / kg, the total nitrogen content was 2.26 g / kg, the total phosphorus content was 0.82 g / kg, and the organic matter content was 30.48 g / kg. Analysis showed that compared with the control group without the addition of the soil conditioner, the contents of each element in the experimental group were increased by 61.4%, 64.0%, 128.6%, 100.9%, 39.0% and 49.3%, respectively. In addition, the chlorophyll content in the plants of the experimental group was increased by 25.8% compared with the control group. The above results all showed that even a small amount of the soil conditioner provided by the application could significantly improve and repair the soil and improve the growth of plants.

[0054] We also analyzed the contents of soluble nitrogen, phosphorus and potassium in the soil obtained from the potting experiments of the experimental group and the control group in Example 1, and compared them with the contents of the "rich" standard in the national second soil survey soil nutrient classification standard, as shown in Figure 2 From the figure, it can be seen that the contents of each element in the soil of the experimental group were higher than those in the control group, and the soil of the experimental group had reached the "rich" standard in the national second soil survey soil nutrient classification standard. This shows that the addition of trace rare earth elements can increase the contents of soluble nitrogen, phosphorus and potassium in the soil, i.e. the addition of trace rare earth tailings in the soil conditioner can effectively improve the soil fertility.

[0055] Example 2 Preparation of microbial inoculum. Two strains of rare earth mine indigenous bacteria, one strain of high-efficiency cellulose-degrading bacteria, and culture medium D were mixed in a volume ratio of 1:1:1.5:50 in a triangular flask, and the flask was placed in a constant-temperature shaker at 165 r / min and 28°C for 2 days to obtain a liquid microbial inoculum.

[0056] Preparation of soil conditioner. Rice husks, soybean meal cakes, coffee grounds, and collected rare earth tailings (containing about 0.8 wt% of rare earth oxides) were mixed in a mass ratio of 1:0.6:0.4:0.35 to obtain a compost substrate. The compost substrate, water, and liquid microbial inoculum were mixed in a compost reactor in a mass ratio of 1:0.3:0.15, and compost fermentation was performed at room temperature for 25 days to obtain a soil conditioner. Analysis and detection results showed that the soil conditioner contained 276 mg / kg of alkali-hydrolyzable nitrogen, 148 mg / kg of available phosphorus, and 1269 mg / kg of available potassium.

[0057] A pot experiment was performed using the soil conditioner prepared in Example 2 according to the method in Example 1, and the results were as follows: the alkali-hydrolyzable nitrogen content in the experimental group soil was 66.94 mg / kg, the available phosphorus content was 11.4 mg / kg, the available potassium content was 229.11 mg / kg, the total nitrogen content was 3.63 g / kg, the total phosphorus content was 0.94 g / kg, and the organic matter content was 37.84 g / kg. The alkali-hydrolyzable nitrogen content in the control group soil was 41.18 mg / kg, the available phosphorus content was 6.10 mg / kg, the available potassium content was 127.28 mg / kg, the total nitrogen content was 3.17 g / kg, the total phosphorus content was 0.58 g / kg, and the organic matter content was 30.49 g / kg. Analysis showed that the above-mentioned contents in the experimental group were increased by 61.4%, 86.8%, 80%, 14.6%, 60.6%, and 24.1%, respectively, compared with the control group without the addition of soil conditioner. In addition, the chlorophyll content in the experimental group plants was increased by 14.1% compared with the control group.

[0058] The above results show that even if the soil conditioner is prepared according to the same steps, its fertilizer efficiency will change due to the use of different raw materials, but it can still significantly improve soil fertility and promote plant growth.

Claims

1. A method for the preparation of a soil conditioner based on rare earth tailings, waste biomass and microorganisms, characterized by The method comprises: breeding rare earth mine indigenous bacteria from rare earth mine soil, and breeding high-efficiency lignin-degrading bacteria from natural environment; mixing the rare earth mine indigenous bacteria and the high-efficiency lignin-degrading bacteria to prepare a composite microbial agent; and mixing the composite microbial agent with rare earth tailings and waste biomass to perform composting fermentation, thereby obtaining a soil conditioner.

2. The method of claim 1, wherein The breeding process of the rare earth mine indigenous bacteria comprises: mixing rare earth mine soil with water and fully oscillating to obtain a rare earth mine soil extract; mixing the mine soil extract with culture medium A and fully oscillating to culture, thereby obtaining a rare earth mine soil enrichment bacterial solution; coating the enrichment bacterial solution on culture medium B and incubating at a constant temperature to screen out strains capable of forming complete single colonies, thereby obtaining the rare earth mine indigenous bacteria; inoculating the rare earth mine indigenous bacteria on culture medium C by streaking and oscillating to culture, thereby obtaining purified rare earth mine indigenous bacteria; repeating the previous purification culture for multiple times, and storing the purified rare earth mine indigenous bacteria obtained in the last time on culture medium F and oscillating to culture, thereby obtaining a cold storage for standby use.

3. The method of claim 1, wherein The breeding process of the high-efficiency lignin-degrading bacteria comprises: collecting forest soil samples and rotten leaf samples around the samples; mixing the rotten leaves with soil particles and water after cutting, oscillating at a constant temperature, and then standing to obtain a diluted sample; mixing the supernatant of the diluted sample with culture medium D and oscillating at a constant temperature to culture, thereby obtaining an enrichment sample; coating the enrichment sample on culture medium G by plate dilution coating method and incubating at a constant temperature according to a certain concentration gradient; picking single colonies grown and transferring to culture medium C for streaking and purification culture, repeating the purification culture for multiple times to obtain a purified strain; inoculating the purified strain in culture medium E and incubating at a constant temperature to screen out a strain with the highest discoloration efficiency, thereby obtaining the high-efficiency lignin-degrading bacteria.

4. The method according to claim 2 or 3, characterized in that The formula of the medium A is: 1-2 g / L YCl3 or its hydrate, 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, and the solvent is distilled water; the formula of the medium B is: 0.5-1 g / L YCl3 or its hydrate, 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water; the formula of the medium C is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water; the formula of the medium D is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, and the solvent is distilled water; the formula of the medium E is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, 0.1-0.2 g / L aniline blue dye, and the solvent is distilled water; the formula of the medium F is: 10-15 g / L peptone, 5-8 g / L yeast extract powder, 10-15 g / L NaCl, 15-20 g / L agar, and the solvent is distilled water; the formula of the medium G is: 0.5-1 g / L MgSO4, 1-2 g / L K2HPO4, 0.5-1 g / L NaCl, 2-3 g / L (NH4)2SO4, 5-6 g / L alkali lignin, and the solvent is distilled water.

5. The method of claim 1, wherein: Before preparing the compound microbial agent, the rare earth mine indigenous bacteria and the high-efficiency lignin-degrading bacteria are respectively subjected to rejuvenation culture, and then the rejuvenated rare earth mine indigenous bacteria liquid and the rejuvenated high-efficiency lignin-degrading bacteria liquid are mixed and cultured according to a volume ratio of 2:1-1.5, so as to obtain the compound microbial agent.

6. The method of claim 1, wherein: The waste biomass includes waste biomass carbon material and waste biomass nitrogen material, and the mass ratio of the two is 1:0.8-1.2, wherein the waste biomass carbon material is selected from at least one of sawdust, rice husk, corn straw powder, wheat straw powder, corn cob, sugarcane residue, coconut dregs, and mushroom stick, and the waste biomass nitrogen material is selected from at least one of soybean dregs, rapeseed cake, soybean meal cake, peanut cake, coffee residue, tea residue, and beer lees.

7. The method of claim 1, wherein: The mass ratio of the rare earth tailings and the waste biomass required for preparing the soil conditioner is 0.3-0.5:1.8-2.2, and the mass of the compound microbial agent is equivalent to 0.1-0.2 times the total mass of the rare earth tailings and the waste biomass.

8. The method of claim 1, wherein: The compost fermentation temperature is 25-60℃, the compost fermentation time is 25-30 days, and water needs to be added regularly during the compost fermentation process, and the amount of water added is equivalent to 0.2-0.3 times the total mass of the rare earth tailings and the waste biomass.

9. The method of claim 1, wherein: The mass percentage content of rare earth oxides in the rare earth tailings is not more than 1%.

10. A soil conditioner based on rare earth tailings, waste biomass and microorganisms, characterized by: The soil conditioner is prepared according to any one of the methods in claims 1-9.

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