CN112854250A

CN112854250A - Method for solidifying road slope soil by combining microorganisms and plants

Info

Publication number: CN112854250A
Application number: CN202011629425.0A
Authority: CN
Inventors: 胡国祥; 肖春桥
Original assignee: Wuhan Institute of Technology
Current assignee: Wuhan Institute of Technology
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2021-05-28
Anticipated expiration: 2040-12-31
Also published as: CN112854250B

Abstract

The invention relates to a method for solidifying road slope soil by combining microorganisms and plants. The method comprises the steps of screening out microorganisms with triple capabilities of high urease yield, plant growth promotion and calcium carbonate precipitation induction from road slope soil and plants with good soil fixation performance, planting the screened plants in the road slope soil, inoculating the screened microorganisms into rhizosphere soil of the soil fixation plants, and performing combined culture for a period of time. The urease-producing microorganisms and the soil-fixing plants selected by the invention are both from the soil of the road side slope, can be well adapted to the ecological environment of the soil of the road side slope, can increase the content of calcium carbonate in the soil through the combined action of the microorganisms and the plants, effectively improves the stability of the soil of the road side slope, and has the advantages of low cost, simple operation, ecological friendliness and the like. Experiments show that the curing efficiency of the method for the road slope soil is close to 70%, and the method has good application prospect and popularization value.

Description

Method for solidifying road slope soil by combining microorganisms and plants

Technical Field

The invention relates to the technical field of road ecological environment, in particular to a method for solidifying road slope soil by combining microorganisms and plants.

Background

With the continuous development and construction of roads and railways, large-area side slope bare soil inevitably appears, and a large amount of raised dust and wind-sand soil pose great threats to the local ecological environment and the health of residents. The aeolian sandy soil belongs to a bad soil body in engineering materials, and loose sandy soil particle structures can aggravate vegetation degradation, water and soil loss and land desertification. Therefore, the need for solidifying the road slope soil is more and more urgent.

The methods currently used for consolidating soil mainly include engineering techniques, chemical techniques and biological techniques. The engineering soil-fixing technology mainly adopts various engineering measures, such as setting wheat straw, rice straw, nylon nets, high-density polyethylene and other materials as barriers on soil, so as to seal, fix, block, dredge and dissipate the soil, and finally achieve the purposes of preventing wind and fixing soil. However, the engineering soil-fixing method has the problems of huge engineering quantity, high cost and the like, and cannot be popularized and applied in a large area. The chemical soil-fixing technology is mainly characterized in that loose soil is combined together by adding chemical cementing substances, so that the stability of the loose soil is enhanced. Although the soil-fixing technology is quick in effect, the cost is generally high, and chemical substances added into soil are likely to cause secondary pollution to the environment. In conclusion, it is very important to research and develop an efficient, green and pollution-free soil stabilization method.

The biological soil fixation technology can be divided into plant soil fixation and microorganism soil fixation, and is a novel biological mineralization method in the field of geotechnical engineering. Many soil-fixing plants have good wind-proof and soil-fixing capabilities, can adapt to a dry soil environment, and play an important role in recovering degraded soil. Because the ecological environment of the soil needing to be fixed is severe, the general survival rate of the plants is short, and the growth period is longer, so that the plant soil fixing technology is not popularized and used in a large area. The Microbial soil fixation is mainly characterized in that calcium carbonate with a cementing effect is rapidly generated through a Microbial induced calcium carbonate precipitation (MICP) process, loose soil is agglomerated together, and the soil strength is improved, so that the MICP technology becomes a hot point of domestic and foreign research at present. The microbes decompose urea in the environment into ammonium ions and carbonate ions through produced urease, and calcium ions added from an external source are gathered near microbial cells with negative electricity to form calcium carbonate precipitates, so that the aim of cementing sandy soil is fulfilled.

At present, the research on the combination of the plant soil fixation technology and the MICP technology for solidifying the soil is relatively lacked at home and abroad, and particularly the combination of microorganisms with MICP capacity and plant growth promoting capacity and plants is aimed at. The experimental results show that the method not only can greatly improve the survival rate of soil-fixing plants and generate calcium carbonate through biological action to enhance the cohesiveness of sandy land, but also can recover the vegetation types of sandy land, and has wide application prospect.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for solidifying road slope soil by combining microorganisms and plants. The method comprises the following steps: (a) collecting a road slope soil sample, and obtaining urease-producing microorganisms through enrichment, purification and screening; (b) screening plants with soil fixing capacity from the soil of the road slope; (c) inoculating the urease-producing microorganisms obtained by screening in the step (a) to the rhizosphere of the soil-fixing plant obtained by screening in the step (b), then planting the rhizosphere in the soil of the road slope to be treated, and carrying out combined culture.

Further, the specific process of step (a) is as follows: mixing the collected soil sample with sterile water to obtain suspension (concentration 10)^-1-10^-3) Filtering, spreading the filtrate supernatant on LB solid culture medium, and performing inverted constant temperature culture at 28-35 deg.C (for 1-2 days) to obtain single colonies of different forms; streaking each single colony respectively, and inoculating the single colony into an LB solid culture medium again to culture under the same condition; performing streak purification culture for 2-3 times until relatively pure strain is obtained; inoculating the purified microorganism strain into urea agar culture medium, culturing at 28-35 deg.C under inverted constant temperature (2-4 days), and selecting the strain with red urea agar culture medium as urease-producing microorganism.

Further, the urease producing microorganisms screened in step (a) were identified as Bacillus megaterium (Bacillus megaterium) and Burkholderia grimmiae (Burkholderia grimmiae).

Furthermore, the LB solid medium comprises the following components in parts by weight: 8-10 parts of peptone, 3-5 parts of yeast extract powder, 8-10 parts of NaCl, 15-25 parts of agar, 1000 parts of distilled water and pH 6-7; the urea agar culture medium comprises the following components in parts by weight:10-20 parts of urea, 5-8 parts of NaCl and KH₂PO₄2-5 parts of peptone, 0.5-1.5 parts of peptone, 0.01-0.02 part of phenol red, 15-25 parts of agar and 1000 parts of distilled water, wherein the pH value is 6-7.

Further, the urease-producing microorganisms obtained in step (a) need to be screened again before being inoculated to the rhizosphere joint culture of soil-fixing plants, and the screening indexes are as follows: whether the plant growth promoting capacity and the calcium carbonate precipitation inducing capacity exist.

Furthermore, the screening process of whether the urease-producing microorganisms have the capability of promoting plant growth is concretely as follows: respectively inoculating the urease-producing microorganisms obtained in the step (a) into a phosphorus-dissolving liquid culture medium, a potassium-dissolving liquid culture medium and a nitrogen-free solid culture medium, culturing at 28-35 ℃, sampling and detecting the phosphorus-dissolving, potassium-dissolving and nitrogen-fixing capacities of microbial strains in a culture period, and screening out target urease-producing microorganisms. The stirring speed of the two liquid culture mediums is 120-170r/min in the culture process, and the constant-temperature shaking culture time is about 7 days; the nitrogen-free solid culture medium is inverted and cultured at constant temperature for 2-4 days. The strain with good capability of dissolving phosphorus, potassium and fixing nitrogen determined in the step is specifically bacillus megaterium.

Further, the phosphorus-dissolving liquid culture medium comprises the following components in parts by weight: 8-10 parts of glucose, 0.3-0.5 part of yeast extract powder, (NH)₄)₂SO₄0.3-0.5 part, KCl0.1-0.3 part, MgSO₄·7H₂0.05 to 0.15 portion of O and CaCl₂0.5-1.5 parts of FeSO₄·7H₂0.02-0.04 part of O and Ca₃(PO₄)₂3-5 parts of distilled water, and the pH value is 6-7; the potassium-dissolving liquid culture medium comprises the following components in parts by weight: 8-10 parts of cane sugar and MgSO (MgSO)₄·7H₂0.3-0.5 part of O, (NH)₄)₂SO₄0.1-0.3 part, NaCl 0.05-0.15 part, CaCO₃0.05-0.15 part of potassium feldspar powder, 3-5 parts of potassium feldspar powder and 1000 parts of distilled water, wherein the pH value is 6-7; the nitrogen-free solid culture medium comprises the following components in parts by weight: glucose 8-10 parts, K₂HPO₄·3H₂0.5 to 0.8 portion of O, 0.1 to 0.3 portion of NaCl and CaCO₃0.5-1.5 parts of MgSO (MgSO)₄·7H₂0.1 to 0.3 portion of O, 15 to 25 portions of agar,1000 parts of distilled water, and the pH value is 6-7.

Further, the screening process of whether the urease-producing microorganisms have the ability of inducing calcium carbonate precipitation is specifically as follows: mixing calcium chloride and urea, adding water to prepare a cementing solution, mixing the screened bacterial solution with the plant growth promoting capability with the cementing solution, standing the obtained mixed solution at the temperature of 28-35 ℃ for constant-temperature culture (1-2 days), sampling and detecting the calcium carbonate precipitation amount in a sample, and determining the target urease-producing microorganism.

Furthermore, the mass ratio of the calcium chloride to the urea is 1-2.5:1, the concentration range of the cementing liquid is 0.125-2mol/L, and the volume ratio of the bacterial liquid to the cementing liquid is 1: 1-4.

Further, the soil-fixing plant screening process in the step (b) is as follows: through literature research and field investigation on road slope soil, collected plant seeds (such as endive, tall fescue, Shadawang, ryegrass, artemisia desertorum and the like) are respectively sown in soil pot plants containing vermiculite, seedlings with good growth vigor are selected and transplanted into the pot plants containing the road slope soil to be treated after 20-30 days of cultivation, sampling is carried out after 60-90 days of growth under natural illumination to detect the generation amount of calcium carbonate in plant rhizosphere soil, and plants which are good in growth and high in calcium carbonate content in the rhizosphere soil are selected as soil-fixing plants.

Furthermore, the soil-fixing plants screened out are specifically Artemisia desertorum (Artemisia desertorum) and Astragalusadsurgen (Astragalusadsurgen), and both plants are very suitable for the soil conditions of the road slope.

Further, the specific process of step (c) is as follows: sowing fresh and full soil-fixing plant seeds into a pot containing road slope soil, inoculating urease-producing microbial strains and cementing liquid into plant rhizosphere soil in proportion after plants grow stably and grow in the same manner, continuously culturing for 60-90 days, finally transplanting the plants into the road slope soil to be treated, regularly watering to keep the water content in the soil to be 60% -80%, observing the growth change of the plants, detecting the calcium carbonate content in the soil, and further evaluating the curing effect.

Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects: (1) the used urease-producing microorganisms and soil-fixing plants are all from the soil of the road side slope and are subjected to multiple directional screening, so that the ecological environment of the soil of the road side slope can be well adapted, the content of calcium carbonate in the soil is rapidly increased through the combined action of the microorganisms and the plants, and the stability of the soil of the road side slope is effectively improved; (2) the method for solidifying the road slope soil by combining the microorganisms and the plants has the advantages of strong pertinence, low cost, environmental friendliness and the like; (3) experimental results show that the method has curing efficiency of approximately 70% on the road slope soil, and has good application prospect and popularization value.

Drawings

FIG. 1 is a comparison graph of soil samples of an experimental group (right) and a control group (left) after the end of the combined culture in example 1;

FIG. 2 is a graph showing soil samples in the experimental group (right) and the control group (left) after the end of the co-cultivation in example 2;

FIG. 3 is a comparison graph of the soil samples of the experimental group (right) and the control group (left) after the end of the combined culture in example 3;

FIG. 4 is a graph showing the comparison of soil samples in the experimental group (right) and the control group (left) after the completion of the combined culture in example 4.

Detailed Description

In order to make those skilled in the art fully understand the technical solutions and advantages of the present invention, the following description is further provided with reference to the specific embodiments and the accompanying drawings.

The formulation of the culture media used in the invention is as follows (in parts by weight):

LB solid medium: 8-10 parts of peptone, 3-5 parts of yeast extract powder, 8-10 parts of NaCl, 15-25 parts of agar, 1000 parts of distilled water and pH 6-7.

Urea agar medium: 10-20 parts of urea, 5-8 parts of NaCl and KH₂PO₄2-5 parts of peptone, 0.5-1.5 parts of peptone, 0.01-0.02 part of phenol red, 15-25 parts of agar and 1000 parts of distilled water, wherein the pH value is 6-7.

Phosphate-dissolving liquid culture medium: 8-10 parts of glucose, 0.3-0.5 part of yeast extract powder, (NH)₄)₂SO₄0.3-0.5 part, KCl0.1-0.3 part, MgSO₄·7H₂0.05 to 0.15 portion of O and CaCl₂0.5-1.5 parts of FeSO₄·7H₂0.02-0.04 part of O and Ca₃(PO₄)₂3-5 parts of distilled water, and the pH value is 6-7.

Potassium-dissolving liquid culture medium: 8-10 parts of cane sugar and MgSO (MgSO)₄·7H₂0.3-0.5 part of O, (NH)₄)₂SO₄0.1-0.3 part, NaCl 0.05-0.15 part, CaCO₃0.05 to 0.15 portion, 3 to 5 portions of potassium feldspar powder (washed by deionized water for 5 times in advance), 1000 portions of distilled water and pH value of 6 to 7.

Nitrogen-free solid medium: glucose 8-10 parts, K₂HPO₄·3H₂0.5 to 0.8 portion of O, 0.1 to 0.3 portion of NaCl and CaCO₃0.5-1.5 parts of MgSO (MgSO)₄·7H₂0.1-0.3 part of O, 15-25 parts of agar and 1000 parts of distilled water, wherein the pH value is 6-7.

(1) Mixing the collected soil sample with sterile water, and making into 10% concentration^-1-10^-3The soil suspension of (1). The supernatant obtained after filtration is evenly coated on an LB solid culture medium, and the culture medium is placed at 28-35 ℃ for inverted constant-temperature culture for 1-2 days. The obtained single colonies with different forms are streaked respectively and inoculated into an LB solid culture medium again, and are inverted again for 1-2 days at the constant temperature of 28-35 ℃. Streaking purification culture was repeated 2-3 times until a purer strain was obtained. Respectively inoculating the purified microbial strains into a urea agar culture medium, carrying out inversion constant-temperature culture at 28-35 ℃ for 2-4 days, and selecting the strain which turns red in the urea agar culture medium to determine the strain as the urease-producing microorganism. Two target urease-producing microorganisms finally screened out in the experiment are identified as bacillus megaterium and burkholderia.

(2) Respectively inoculating the urease-producing microorganisms screened in the last step into a phosphorus-dissolving liquid culture medium, a potassium-dissolving liquid culture medium and a nitrogen-free solid culture medium, placing the two liquid culture media under the conditions of 28-35 ℃ and 120-170r/min for constant-temperature shaking culture for 7 days, and placing the nitrogen-free solid culture medium under the conditions of 28-35 ℃ for inversion and constant-temperature culture for 2-4 days. It should be noted that the strain capable of surviving on the nitrogen-free medium has nitrogen fixing ability; sampling and detecting the soluble phosphorus content and the soluble potassium content of microbial strains in the liquid culture medium during culture so as to determine the urease-producing microorganisms with good phosphorus-dissolving potassium-dissolving nitrogen-fixing capacity. The strain with good capability of dissolving phosphorus, potassium and fixing nitrogen determined by the step is bacillus megaterium.

(3) Uniformly mixing calcium chloride and urea in a mass ratio of 1:1, and adding water to prepare a cementing solution with the concentration of 0.125-2 mol/L. Uniformly mixing the bacterial liquid obtained by screening in the last step and the cementing liquid according to the volume ratio of 1:4, and then standing and culturing for 1-2 days at constant temperature at 28-35 ℃. Sampling and detecting the calcium carbonate precipitation amount generated by the microbial strains, and selecting a bacterial liquid with large precipitation amount to determine the urease-generating microbes with the capacity of inducing calcium carbonate precipitation. The calcium carbonate yield of the bacillus megaterium obtained by screening in the steps is larger, and the bacillus megaterium is an ideal urease-producing microorganism with the capability of inducing calcium carbonate precipitation.

(4) Through literature research and field investigation on road slope soil, the collected seeds of the endive, the tall fescue, the shazhaowang, the ryegrass and the artemisia desertorum are respectively sown in a soil pot plant containing vermiculite, seedlings with good growth vigor and the same growth vigor are selected and transplanted into the pot plant containing the road slope soil after 20-30 days of cultivation, the generation amount of calcium carbonate in plant rhizosphere soil is detected after the plants grow for 60-90 days under natural illumination, and the plants which grow well and have high calcium carbonate content in the rhizosphere soil are selected as soil-fixing plants. The soil-fixing plants finally screened and determined by the experiment are artemisia desertorum and sand shawang, and both the two plants are very suitable for the soil conditions of the road slope soil.

(5) Sowing fresh and plump soil-fixing plant seeds (at least one of artemisia desertorum and Shacaowang) into a pot containing road slope soil, inoculating the screened urease-producing microbial strains and the cementing solution into the plant rhizosphere soil according to a proportion after 5-15 days of stable growth and similar growth vigor of the plants, and continuously culturing for 60-90 days. Regularly watering after planting to keep the water content in the soil to be 60% -80%, observing the growth change of the plants and simultaneously sampling and detecting the calcium carbonate content in the soil.

Example 1

Experimental groups: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, inoculating 10mL of screened bacillus megaterium bacterial liquid and 40mL of cementing liquid (0.125mol/L) into the plant root system soil.

Control group: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, 40mL of cementing solution (0.125mol/L) is inoculated into the soil of the plant root system.

The experimental group and the control group were harvested 60-90 days after the transplantation of the plants (keeping the same days). The plants are taken out and washed, and then are moved into an oven to be dried at 70-80 ℃ until the weight is constant. And taking out the plant rhizosphere soil, drying and weighing, dripping dilute hydrochloric acid until no bubbles are generated, drying again, and weighing the soil. The change of the soil weight before and after adding the dilute hydrochloric acid is the generation amount of the calcium carbonate. The results of the experiment are shown in tables 1-2 and FIG. 1.

TABLE 1 plant Biomass

TABLE 2 plant rhizosphere soil calcium carbonate yield

As can be seen from tables 1-2, the inoculated Bacillus megaterium liquid has a good promoting effect on the growth of soil-fixing plants (Artemisia desertorum and Shacawang), and the dry weight of the plants in the experimental group is 64.59% and 73.14% higher than that in the control group respectively. The yield of calcium carbonate is greatly improved by the synergistic effect of the urease-producing microorganisms and plants, and the content of calcium carbonate in the rhizosphere soil of the experimental group is respectively increased by 43.06% and 40.98% compared with that of the control group. The soil calcium carbonate yield of the sandawang experimental group is high, the soil solidification efficiency is close to 70%, and the remediation effect is good.

Comparative example 1

The same procedures as in example 1 were repeated except for replacing the bacterial solution of example 1 with Burkholderia obtained in step (1) in the same amount. The test was carried out on the samples of the experimental group and the control group in the same manner, and the results are shown in tables 3 to 4.

TABLE 3 plant Biomass

TABLE 4 plant rhizosphere soil calcium carbonate yield

As can be seen from tables 3-4, the inoculated Burkholderia did not have much influence on plant growth; the slight increase in the dry weight of the plants in the experimental group compared to the control group was 27.67% and 24.72%, respectively, which may be due to the weak calcium carbonate-producing ability of the strain; the content of calcium carbonate in the rhizosphere soil of the plants in the experimental group is respectively increased by 3.23 percent and 2.69 percent compared with that in the control group, which shows that the burkholderia is far inferior to the growth promoting capability and the calcium carbonate producing capability of the plants.

Example 2

Experimental groups: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, inoculating 10mL of bacillus megaterium bacterial liquid obtained by screening and 40mL of cementing liquid (0.5mol/L) into the plant root system soil.

Control group: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, 40mL of cementing solution (0.5mol/L) is inoculated into the soil of the plant root system.

The experimental group and the control group were harvested 60-90 days after the transplantation of the plants (keeping the same days). The plants are taken out and washed, and then are moved into an oven to be dried at 70-80 ℃ until the weight is constant. And taking out the plant rhizosphere soil, drying and weighing, dripping dilute hydrochloric acid until no bubbles are generated, drying again, and weighing the soil. The change of the soil weight before and after adding the dilute hydrochloric acid is the generation amount of the calcium carbonate. The results of the experiments are shown in tables 5-6 and FIG. 2.

TABLE 5 plant Biomass

TABLE 6 plant rhizosphere soil calcium carbonate yield

As can be seen from tables 5-6, the Bacillus megaterium solution has a good promoting effect on the growth of soil-fixing plants (sand sagebrush and sandawan), and the dry weight of the plants in the experimental group is 64.04% and 57% higher than that in the control group respectively. Through the synergistic effect of urease-producing microbes and plants, the yield of calcium carbonate is greatly improved, and the content of calcium carbonate in the rhizosphere soil of the experimental group is respectively increased by 50.34% and 59.93% compared with that of the control group.

Example 3

Experimental groups: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, inoculating 10mL of bacillus megaterium bacterial liquid obtained by screening and 40mL of cementing liquid (1.125mol/L) into the plant root system soil.

Control group: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, 40mL of cementing solution (1.125mol/L) is inoculated into the soil of the plant root system.

The experimental group and the control group were harvested 60-90 days after the transplantation of the plants (keeping the same days). The plants are taken out and washed, and then are moved into an oven to be dried at 70-80 ℃ until the weight is constant. And taking out the plant rhizosphere soil, drying and weighing, dripping dilute hydrochloric acid until no bubbles are generated, drying again, and weighing the soil. The change of the soil weight before and after adding the dilute hydrochloric acid is the generation amount of the calcium carbonate. The results of the experiments are shown in tables 7-8 and FIG. 3.

TABLE 7 plant Biomass

TABLE 8 plant rhizosphere soil calcium carbonate yield

From tables 7-8, it can be seen that the bacillus megaterium solution also has a good promoting effect on the growth of soil-fixing plants (sand sagebrush and sandawan), and the dry weight of the plants in the experimental group is respectively 62.9% and 59.91% higher than that in the control group. Through the synergistic effect of urease-producing microbes and plants, the yield of calcium carbonate is greatly improved, and the content of calcium carbonate in the plant rhizosphere soil in the experimental group is respectively increased by 55.46% and 53.29% compared with that in the control group.

Example 4

Experimental groups: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, inoculating 10mL of screened bacillus megaterium bacterial liquid and 40mL of cementing liquid (2mol/L) into the plant root system soil.

Control group: planting sand sagebrush and sandawa seedlings in 500g sterilized soil sample pot of road slope, watering regularly to maintain the water content in the pot soil at 60-80%. After the plant seedlings stably grow for 5-15 days, 40mL of cementing solution (2mol/L) is inoculated into the soil of the plant root system.

The experimental group and the control group were harvested 60-90 days after the transplantation of the plants (keeping the same days). The plants are taken out and washed, and then are moved into an oven to be dried at 70-80 ℃ until the weight is constant. And taking out the plant rhizosphere soil, drying and weighing, dripping dilute hydrochloric acid until no bubbles are generated, drying again, and weighing the soil. The change of the soil weight before and after adding the dilute hydrochloric acid is the generation amount of the calcium carbonate. The results of the experiments are shown in tables 9-10 and FIG. 4.

TABLE 9 plant Biomass

TABLE 10 plant rhizosphere soil calcium carbonate yield

As can be seen from tables 9-10, the Bacillus megaterium solution has a good promoting effect on the growth of soil-fixing plants (sand sagebrush and sandawan), and the dry weight of the plants in the experimental group is 57.35% and 56.64% higher than that in the control group respectively. In addition, the content of calcium carbonate in the rhizosphere soil of the plants in the experimental group is increased by 65.48 percent and 51.83 percent respectively compared with that in the control group.

As can be seen from comparative examples 1 to 3, the plant biomass and the amount of calcium carbonate produced in the rhizosphere soil were significantly reduced at a concentration of 2mol/L, which is probably due to the inhibition of the biological activities of microorganisms and plants by the high concentration of the cementing solution.

Claims

1. A method for solidifying road slope soil by combining microorganisms and plants is characterized by comprising the following steps: (a) collecting a road slope soil sample, and obtaining urease-producing microorganisms through enrichment, purification and screening; (b) screening plants with soil fixing capacity from the soil of the road slope; (c) inoculating the urease-producing microorganisms obtained by screening in the step (a) to the rhizosphere of the soil-fixing plant obtained by screening in the step (b), then planting the soil-fixing plant in the soil of the road slope to be treated, and carrying out combined culture.

2. The method of claim 1, wherein step (a) is performed as follows: mixing the collected soil sample with sterile water to prepare a suspension, filtering, taking the filtrate supernatant, coating the filtrate supernatant on an LB solid culture medium, and performing inversion constant-temperature culture at 28-35 ℃ to obtain single colonies with different forms; streaking each single colony, and inoculating the single colony into an LB solid culture medium again to culture under the same condition; performing streak purification culture for 2-3 times until relatively pure strain is obtained; inoculating the purified microbial strains into a urea agar culture medium, carrying out inversion constant-temperature culture at the temperature of 28-35 ℃, and selecting the strains which enable the urea agar culture medium to turn red to determine the strains as urease-producing microorganisms.

3. The method of claim 2, wherein: the LB solid medium comprises the following components in parts by weight: 8-10 parts of peptone, 3-5 parts of yeast extract powder, 8-10 parts of NaCl, 15-25 parts of agar, 1000 parts of distilled water and pH 6-7; the urea agar culture medium comprises the following components in parts by weight: 10-20 parts of urea, 5-8 parts of NaCl and KH₂PO₄2-5 parts of peptone, 0.5-1.5 parts of peptone, 0.01-0.02 part of phenol red, 15-25 parts of agar and 1000 parts of distilled water, wherein the pH value is 6-7.

4. The method of claim 1, wherein: the urease-producing microorganisms obtained in the step (a) need to be screened again before being inoculated to the rhizosphere joint culture of soil-fixing plants, and the screening indexes are as follows: whether the plant growth promoting capacity and the calcium carbonate precipitation inducing capacity exist.

5. The method according to claim 4, wherein the screening for the capability of urease-producing microorganisms to promote plant growth is carried out by: respectively inoculating the urease-producing microorganisms obtained in the step (a) into a phosphorus-dissolving liquid culture medium, a potassium-dissolving liquid culture medium and a nitrogen-free solid culture medium to culture at 28-35 ℃, sampling and detecting the phosphorus-dissolving, potassium-dissolving and nitrogen-fixing capacities of microbial strains in a culture period, and screening out target urease-producing microorganisms; the stirring speed of the two liquid culture mediums is 120-170r/min in the culture process, the constant temperature shaking culture time is 5-9 days, and the inversion constant temperature culture time of the nitrogen-free solid culture medium is 2-4 days.

6. The method of claim 5, wherein: the phosphorus-dissolving liquid culture medium comprises the following components in parts by weight: 8-10 parts of glucose, 0.3-0.5 part of yeast extract powder, (NH)₄)₂SO₄0.3-0.5 part, KCl0.1-0.3 part, MgSO₄·7H₂0.05 to 0.15 portion of O and CaCl₂0.5-1.5 parts of FeSO₄·7H₂0.02-0.04 part of O and Ca₃(PO₄)₂3-5 parts of distilled water, and the pH value is 6-7; the potassium-dissolving liquid culture medium comprises the following components in parts by weight: 8-10 parts of cane sugar and MgSO (MgSO)₄·7H₂0.3-0.5 part of O, (NH)₄)₂SO₄0.1-0.3 part, NaCl 0.05-0.15 part, CaCO₃0.05-0.15 part of potassium feldspar powder, 3-5 parts of potassium feldspar powder and 1000 parts of distilled water, wherein the pH value is 6-7; the nitrogen-free solid culture medium comprises the following components in parts by weight: glucose 8-10 parts, K₂HPO₄·3H₂0.5 to 0.8 portion of O, 0.1 to 0.3 portion of NaCl and CaCO₃0.5-1.5 parts of MgSO (MgSO)₄·7H₂0.1-0.3 part of O, 15-25 parts of agar and 1000 parts of distilled water, wherein the pH value is 6-7.

7. The method according to claim 4, wherein the screening of whether the urease-producing microorganism has the ability to induce calcium carbonate precipitation is carried out by: mixing calcium chloride and urea, adding water to prepare a cementing solution, mixing the screened bacterial solution with the plant growth promoting capacity with the cementing solution, standing the obtained mixed solution at the temperature of 28-35 ℃, culturing at constant temperature, sampling and detecting the calcium carbonate precipitation amount in a sample, and determining the target urease-producing microorganism.

8. The method of claim 7, wherein: the mass ratio of the calcium chloride to the urea is 1-2.5:1, the concentration range of the cementing liquid is 0.125-2mol/L, and the volume ratio of the bacterial liquid to the cementing liquid is 1: 1-4.

9. The method according to claim 1, wherein the soil-fixing plant of step (b) is selected by the following steps: through literature research and field investigation on road slope soil, respectively sowing collected plant seeds in soil pot plants containing vermiculite, selecting seedlings with good growth vigor after culturing for 20-30 days, transplanting the seedlings into the pot plants containing the road slope soil to be treated, sampling and detecting the generation amount of calcium carbonate in plant rhizosphere soil after the seedlings grow for 60-90 days under natural illumination, and selecting plants with good growth and high calcium carbonate content in the rhizosphere soil as soil-fixing plants.

10. The method of claim 1, wherein step (c) is performed as follows: sowing fresh and full soil-fixing plant seeds into a pot containing road slope soil, inoculating urease-producing microbial strains and a cementing solution into plant rhizosphere soil after plants stably grow, continuously culturing for 60-90 days, finally transplanting the plants into the road slope soil to be treated, regularly watering to keep the water content in the soil to be 60% -80%, observing the growth change of the plants, detecting the calcium carbonate content in the soil, and further evaluating the curing effect.