Preparation method and application of biomass charcoal-based soil conditioner

Abstract

The invention provides a preparation method and application of a biomass charcoal-based soil conditioner. The method comprises the following steps: carrying out ball milling on biochar and titanium gypsum to prepare titanium gypsum-biochar (TBC), and immobilizing sphingomonas by using TBC to obtain the TBC immobilized sphingomonas. The biomass charcoal-based soil conditioner prepared by the invention has the advantages of large specific surface area, high porosity, high calcium ion content and the like, and when the biomass charcoal-based soil conditioner is applied to the problems caused by continuous cropping of cowpeas, the phenolic acid content in soil can be reduced, the stress resistance of the cowpeas can be effectively improved, the physicochemical properties of the soil are improved, and the quality of the cowpeas is improved. Therefore, the adverse effect of continuous cropping obstacles on the growth of cowpeas is relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil improvement, and in particular relates to a preparation method and application of a biomass charcoal-based soil conditioner. Background Art

[0002] Cowpea, also known as long beans, is an annual vegetable belonging to the Leguminosae family. Cowpea is drought-resistant and heat-resistant, has strong adaptability, high nutritional value, and many ways to eat it. As a vegetable, it is deeply loved by the public and has a large market demand. In order to pursue economic benefits, people have rapidly developed facility cultivation and continuous cropping and overlapping planting of cowpea. However, due to the continuous planting of cowpea, the soil has been in a special environment of human interference for a long time (no natural environment leaching, high temperature, and high evaporation). The salt in the deep soil rises to the surface. In addition, the long-term application of fertilizers further increases the accumulation of salt in the surface soil, aggravating the secondary salinization of the soil. At the same time, the acid radical ions in the fertilizer will cause the soil pH to decrease. In addition, in the case of continuous cropping, the rhizosphere of cowpea will secrete a large amount of phenolic acid allelopathic substances, which will also reduce the pH of the soil. These problems jointly lead to the continuous cropping obstacle of cowpea, so it is very necessary to provide a soil conditioner to alleviate the continuous cropping obstacle of cowpea.

[0003] Among the methods currently used to deal with the secondary salinization and soil acidification problems caused by continuous cropping, biochar is the most commonly used carbon material. It has a large specific surface area, porous structure and rich functional groups (such as carboxyl, phenolic hydroxyl, alcoholic hydroxyl and carbonyl), which can improve soil quality by regulating soil physical and chemical properties and biological characteristics. However, biochar cannot fundamentally alleviate the problem of soil salt pressure. For this, gypsum materials containing calcium are added to reduce soil salinity through ion replacement and salt conversion reactions. In addition, when improving continuous cropping, the microbial environment in the soil is also a concern. Improving the microbial structure in the rhizosphere of cowpea will also have a positive effect on its growth. Sphingomonas is an aerobic Gram-negative bacterium with excellent biodegradation, biomass synthesis and phenolic acid degradation capabilities. However, in the complex environment of high soil salinity and acidification, the survival of Sphingomonas is restricted and its biological activity is greatly reduced.

[0004] In view of the above problems, the present invention provides a method for preparing a biomass charcoal-based soil conditioner, which has the functions of degrading phenolic acid, promoting cowpea growth, and alleviating cowpea continuous cropping obstacles. Summary of the invention

[0005] In view of the problems in the prior art, the present invention provides a preparation method and application of a biomass charcoal-based soil conditioner, with the aim of developing a biomass charcoal-based soil conditioner with properties such as large specific surface area, high porosity, and high calcium ion content. The biomass charcoal-based soil conditioner can be applied to cowpea continuous cropping soil with coexistence of secondary salinization and acidification to reduce the phenolic acid content in the soil, increase the stress resistance of cowpea, and improve the physical and chemical properties of the soil, thereby alleviating the adverse effects of continuous cropping obstacles on cowpea growth.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method and application of a biomass charcoal-based soil conditioner, characterized in that the preparation of the biomass charcoal-based soil conditioner comprises the following steps:

[0008] (1) Preparation of biochar (BC): The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis was carried out at 600-900°C for 1.5-4 h, with a heating rate of 5-8°C / min. After pyrolysis, the biochar cooled to 22-28°C was ground and sieved with 30-45 mesh to obtain biochar (BC);

[0009] (2) Pretreatment of titanium gypsum (T): The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for 3 to 5 times, and then dried in an oven at a constant temperature of 100 to 120°C for 1.5 to 3 hours. The dried sample was ground into fine powder particles and sieved with 10 to 25 mesh to obtain titanium gypsum (T);

[0010] (3) Preparation of titanium gypsum-biochar (TBC): The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill, the ball mill is sealed and fixed on a ball mill for ball milling for 1.5 to 3 hours, and sieved with 30 to 45 mesh to obtain titanium gypsum-biochar (TBC);

[0011] (4) Preparation of bacterial suspension: Sphingomonas was inoculated into NB liquid culture medium and cultured at 30°C and 150 rpm for 5 days, then centrifuged at 3800-4500 rpm for 3-5 times, and the centrifuged Sphingomonas was placed in sterile physiological saline to obtain a bacterial suspension with an OD value of 1.6-1.8;

[0012] (5) Preparation of TBC-immobilized Sphingomonas (TBCS): The TBC prepared in step (3) is sterilized and mixed with the bacterial suspension prepared in step (4), and the mixture is shaken at 28-30° C. and 100-150 rpm for 42-50 h to obtain TBC-immobilized Sphingomonas (TBCS).

[0013] In one implementation method, the mass ratio of biochar, titanium gypsum and zirconia balls in step (3) is 1: (0.4-1): (40-60).

[0014] In one implementation method, the ingredients of the NB liquid culture medium in step (4) include: 3g beef extract, 10g peptone, 5g NaCl, and 1L distilled water. The prepared liquid culture medium is sterilized by high pressure sterilization at 121°C for 15min for use.

[0015] In one implementation method, the ratio of Sphingomonas to NB liquid culture medium in step (4) is 1:10.

[0016] In one implementation method, the sterilization conditions of TBC in step (5) are high pressure sterilization at 121° C. for 15 min, and the ratio of the mass (g) of TBC to the volume (mL) of the bacterial suspension is 1:5.

[0017] In one implementation method, a biomass charcoal-based conditioner is applied to the cowpea continuous cropping soil at a mass fraction of 5-10%, mixed and pre-cultivated for one week before planting, during which the soil moisture is maintained at 60%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The biomass charcoal-based conditioner of the present invention has higher porosity, larger specific surface area, and more reaction sites after being prepared by high temperature and ball milling, so that the overall performance of the conditioner is improved. The conditioner increases the pH value, water retention capacity and organic matter content of the soil. At the same time, the conditioner can effectively reduce the salt content of the soil, ultimately improving the soil environment and promoting the growth of cowpea.

[0020] 2. The biomass charcoal base of the present invention provides nutrition and habitat for Sphingomonas, and improves the biological activity of Sphingomonas in soil with high salinity and acidification problems. While degrading phenolic acids in continuously cropped soil, Sphingomonas can improve the stress resistance of cowpea and enhance the colonization ability of beneficial colonies in the rhizosphere of cowpea, thereby reducing the adverse effects of continuous cropping obstacles on cowpea growth.

[0021] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the content of proline in cowpea leaves after different treatments.

[0023] Figure 2 This is the effect of different treatments on the antioxidant enzyme activities in cowpea leaves. DETAILED DESCRIPTION

[0024] The present invention is specifically described below by way of examples, which are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. It should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0025] The embodiment and comparative example used soil from which cowpea had been planted for 5 years. The embodiment and comparative example were applied to the soil from which cowpea had been planted for 5 years at a soil mass fraction of 8%, respectively, and mixed and pre-cultured for one week, during which the soil moisture was maintained at 60%. Soil without the addition of a conditioner was set as a blank control group. The soil after pre-culture was used to plant cowpea, and the area of ​​the cowpea planting area was 22.2 m 2 .

[0026] Example 1

[0027] The preparation method of the biomass carbon-based soil conditioner is as follows:

[0028] (1) Preparation of biochar (BC): The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis time was 2 h at 700 °C and the heating rate was 5 °C / min. After pyrolysis, the biochar cooled to 22 °C was ground and sieved with 40 mesh to obtain biochar (BC).

[0029] (2) Pretreatment of titanium gypsum (T): The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for three times, and then dried in an oven at a constant temperature of 105°C for 2 hours. The dried sample was ground into fine powder particles and sieved through a 20-mesh sieve to obtain titanium gypsum (T).

[0030] (3) Preparation of titanium gypsum-biochar (TBC): The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill at a ratio of 5:10:480. The ball mill is sealed and fixed on a ball mill for ball milling for 2 h. The mixture is sieved through a 40-mesh sieve to obtain titanium gypsum-biochar (TBC).

[0031] (4) Preparation of bacterial suspension: Weigh 3 g beef extract, 10 g peptone, and 5 g NaCl, add them to a conical flask containing 1 L distilled water, stir evenly, and obtain NB liquid culture medium. The conical flask containing the liquid culture medium is sterilized by high pressure at 121°C for 15 min for later use. 1 mg of Sphingomonas was inoculated into 10 mL of NB liquid culture medium, and cultured at 30°C and 150 rpm for 5 days. The culture was centrifuged at 4000 rpm for 3 times, and the Sphingomonas was placed in sterile physiological saline to obtain a bacterial suspension. The OD value of the bacterial suspension was adjusted to 1.6.

[0032] (5) Preparation of TBC-immobilized Sphingomonas (TBCS): 1 g of the TBC prepared in step (3) was sterilized and mixed with 5 mL of the bacterial suspension prepared in step (4), and the mixture was shaken at 30° C. and 120 rpm for 48 h to obtain TBC-immobilized Sphingomonas (TBCS).

[0033] Example 2

[0034] The preparation method of the biomass carbon-based soil conditioner is as follows:

[0035] (1) Preparation of biochar (BC): The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis time was 1.5 h at 600 °C and the heating rate was 6 °C / min. After pyrolysis, the biochar cooled to 25 °C was ground and sieved with 40 mesh to obtain biochar (BC).

[0036] (2) Pretreatment of titanium gypsum (T): The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for 4 times, and then dried in an oven at a constant temperature of 100° C. for 1.5 h. The dried sample was ground into fine powder particles and sieved through a 20-mesh sieve to obtain titanium gypsum (T).

[0037] (3) Preparation of titanium gypsum-biochar (TBC): The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill at a ratio of 6:10:400. The ball mill is sealed and fixed on a ball mill for ball milling for 1.5 h. The mixture is sieved through 45 mesh to obtain titanium gypsum-biochar (TBC).

[0038] (4) Preparation of bacterial suspension: Weigh 3 g beef extract, 10 g peptone, and 5 g NaCl, add them to a conical flask containing 1 L distilled water, stir evenly, and obtain NB liquid culture medium. The conical flask containing the liquid culture medium is sterilized by high pressure at 121°C for 15 min for later use. 3 mg of Sphingomonas was inoculated into 30 mL of NB liquid culture medium, and cultured at 30°C and 150 rpm for 5 days. The culture medium was centrifuged at 3800 rpm for 4 times, and the Sphingomonas was placed in sterile physiological saline to obtain a bacterial suspension. The OD value of the bacterial suspension was adjusted to 1.7.

[0039] (5) Preparation of TBC-immobilized Sphingomonas (TBCS): 5 g of the TBC prepared in step (3) was sterilized and mixed with 25 mL of the bacterial suspension prepared in step (4), and the mixture was shaken at 30° C. and 100 rpm for 42 h to obtain TBC-immobilized Sphingomonas (TBCS).

[0040] Example 3

[0041] The preparation method of the biomass carbon-based soil conditioner is as follows:

[0042] (1) Preparation of biochar (BC): The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis time was 4 h at 900 °C and the heating rate was 8 °C / min. After pyrolysis, the biochar cooled to 28 °C was ground and sieved with 45 mesh to obtain biochar (BC).

[0043] (2) Pretreatment of titanium gypsum (T): The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for 5 times, and then dried in an oven at a constant temperature of 120°C for 3 hours. The dried sample was ground into fine powder particles and sieved through 25 mesh to obtain titanium gypsum (T).

[0044] (3) Preparation of titanium gypsum-biochar (TBC): The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill at a ratio of 10:10:600. The ball mill is sealed and fixed on a ball mill for ball milling for 3 h. The mixture is sieved through a 30-mesh sieve to obtain titanium gypsum-biochar (TBC).

[0045] (4) Preparation of bacterial suspension: Weigh 3 g beef extract, 10 g peptone, and 5 g NaCl, add them to a conical flask containing 1 L distilled water, stir evenly, and obtain NB liquid culture medium. The conical flask containing the liquid culture medium is sterilized by high pressure at 121°C for 15 min for later use. 3 mg of Sphingomonas was inoculated into 30 mL of NB liquid culture medium, and cultured at 30°C and 150 rpm for 5 days. The culture medium was centrifuged at 4500 rpm for 5 times, and the Sphingomonas was placed in sterile physiological saline to obtain a bacterial suspension. The OD value of the bacterial suspension was adjusted to 1.8.

[0046] (5) Preparation of TBC-immobilized Sphingomonas (TBCS): 3 g of the TBC prepared in step (3) was sterilized and mixed with 15 mL of the bacterial suspension prepared in step (4), and the mixture was shaken at 28° C. and 150 rpm for 50 h to obtain TBC-immobilized Sphingomonas (TBCS).

[0047] Comparative Example 1

[0048] The preparation method of the pine needle biochar is as follows:

[0049] (1) Preparation of biochar: The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis time was 2 h at 700 °C and the heating rate was 5 °C / min. After pyrolysis, the biochar cooled to 22 °C was ground and sieved with 40 mesh to obtain biochar (BC).

[0050] Comparative Example 2

[0051] The preparation method of the titanium gypsum is as follows:

[0052] (1) Pretreatment of titanium gypsum: The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for three times, and then dried in an oven at a constant temperature of 105°C for 2 h. The dried sample was ground into fine powder particles and sieved through a 20-mesh sieve to obtain titanium gypsum (T).

[0053] Comparative Example 3

[0054] The preparation method of the titanium gypsum-biochar is as follows:

[0055] (1) Preparation of biochar: The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis time was 2 h at 700 °C and the heating rate was 5 °C / min. After pyrolysis, the biochar cooled to 25 °C was ground and sieved with 40 mesh to obtain biochar (BC).

[0056] (2) Pretreatment of titanium gypsum: The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for three times, and then dried in an oven at a constant temperature of 105°C for 2 hours. The dried sample was ground into fine powder particles and sieved through a 20-mesh sieve to obtain titanium gypsum (T).

[0057] (3) Preparation of titanium gypsum-biochar: The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill at a ratio of 4:10:480. The ball mill is sealed and fixed on a ball mill for ball milling for 2 h. The ball mill is sieved with 40 mesh to obtain titanium gypsum-biochar (TBC).

[0058] Experimental methods

[0059] The blank group, Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to relevant tests, wherein the BET, soil physical and chemical properties, soil organic matter and phenolic acid content, cowpea growth and yield, leaf chlorophyll and proline content and enzyme activity, soil enzyme activity, cowpea rhizosphere soil microbial count, Sphingomonas activity test methods and results are as follows:

[0060] 1. BET test: The titanium gypsum-biochar (TBC) samples of comparative example 3 and the biochar samples of comparative example 1 were measured using a fully automatic specific surface area and porosity analyzer (BET). The samples were first degassed (with nitrogen) before being measured, and the degassing temperature was set at 200°C and the degassing time was 4h.

[0061] 2. Soil physical and chemical properties test:

[0062] (1) Sample collection: Soil samples from the 0-20 cm soil layer were collected after the cowpea harvest period using the 5-point method. After collection, the soil samples were quickly brought back to the laboratory for air drying and passed through a 2 mm nylon sieve. The sieved samples were used for the determination of soil physical and chemical properties.

[0063] (2) Sample testing:

[0064] ① Conductivity and pH value: Mix the soil sample with deionized water (water-soil ratio 5:1), ultrasonicate for 1.5 hours, centrifuge with a centrifuge, and measure and record with a conductivity meter and a pH meter.

[0065] ② Bulk density: Use a ring cutter with an inner diameter of 5 cm, a height of 4 cm, and a wall thickness of 1.5 mm to take a sample, dry it at 90°C for 24 hours, weigh it, and divide the volume of soil inside the ring cutter by the volume of soil inside the ring cutter to get the soil density, g / cm 3 .

[0066] ③ Field water holding capacity: Immerse the ring cutter filled with original soil into water with the bottom cover with holes facing downward for no less than 24 hours until the soil is saturated with moisture. Dry and weigh to constant mass.

[0067] ④Organic matter, available phosphorus, available potassium, and alkaline-hydrolyzable nitrogen: The soil organic matter was determined by the potassium dichromate volumetric method-external heating method; the available phosphorus was determined by the 0.5 moL / LNaHCO3 method; the available potassium was determined by the NH4OAc extraction flame photometry; and the alkaline-hydrolyzable nitrogen content in the soil samples was determined by the alkaline diffusion method.

[0068] 3. Cowpea growth and yield test: Use a ruler to measure the plant height; conduct actual harvest and yield measurement when the cowpea is mature.

[0069] 4. Determination of chlorophyll: Take the chopped leaves, add 80% by volume acetone to grind, filter and make up the volume in a volumetric flask, use 80% by volume acetone as blank, measure the absorbance at 645nm and 633nm, and calculate the chlorophyll content.

[0070] 5. Cowpea stress resistance test:

[0071] ① Proline: acid ninhydrin colorimetric method.

[0072] ② Malondialdehyde (MDA): thiobarbituric acid (TBA) colorimetric method.

[0073] ③Superoxide dismutase (SOD) activity: determined by xanthine oxidase kit.

[0074] ④Peroxidase (POD) activity: determined by spectrophotometric kit.

[0075] ⑤ Catalase (CAT) activity: determined by UV spectrophotometry kit.

[0076] 6. Determination of soil phenolic acid content: Weigh 25g of fresh soil into a centrifuge tube, add 25mL of 1moL / mL NaOH and place overnight, shake for 30min the next day, centrifuge and acidify the filtered centrifuge liquid to pH=2.5 with 12moL / L hydrochloric acid, centrifuge to remove humic acid (brown to dark brown humic acid in the soil that is only soluble in dilute alkali but not in dilute acid), and then directly measure the supernatant with high performance liquid chromatography, repeat 3 times, and the results are converted according to the dried soil, and the average value is taken. Standard sample preparation: Accurately weigh 10mg of phenylacetic acid, cinnamic acid, p-hydroxybenzoic acid, and phthalic acid respectively and place them in the same 100mL volumetric flask, dissolve them with methanol and make up to 100mL, the concentration of each phenolic acid in the standard mixed solution is 100μg / mL, and the American Waters ultra-high performance liquid chromatograph is used for determination. Chromatographic conditions: the mobile phase was acetonitrile (A) and deionized water (B) (the pH was adjusted to 2.8 with glacial acetic acid), the detection wavelength was 270 nm, and the column temperature was 30°C; the gradient elution was set at 0-1.5 min, A:B was 15%:85%, and after 1.5 min, it was 35%:65%; the injection volume was 3 μL, and the flow rate was 0.25 μL / min.

[0077] 7. The rhizosphere soil of cowpea was collected by the peeling separation method. One part of the fresh soil was stored at 4°C for the isolation and counting of bacteria, actinomycetes and fungi, and the other part was air-dried for the determination of enzyme activity in the rhizosphere soil.

[0078] (1) The dilution plate method was used to count the microorganisms in the soil: beef extract peptone medium was used for bacteria; Gould's medium No. 1 was used for actinomycetes; and Martin's medium was used for fungi.

[0079] (2) Determination of soil enzyme activity: Urease was determined by the indophenol colorimetric method. The results were expressed as NH4 + -N; the activity of polyphenol oxidase was determined by the pyrogallol colorimetric method and expressed as the milligrams of purple gallin produced in 1g of soil after 2h; the activity of sucrase was determined by the 3,5-dinitrosalicylic acid colorimetric method and expressed as the milligrams of glucose in 1g of soil after 24h.

[0080] 8. Activity test of Sphingomonas: After sampling according to the 5-point sampling method, mix the samples collected at the 5 points into one sample to represent the soil sample of the area. Take 5g of soil sample, add 50mL of sterile water, shake at 4℃ for 30min, dilute the sample by ten-fold dilution method, spread on streptomycin-piperacillin selective growth medium (glucose solid medium) plates, and culture at 28℃ for 2d for counting.

[0081] Two groups of test soil (sterile continuous cropping soil) were set up, the first group was added with Example 1 (the addition amount was 8% of the soil), and the second group (control group) was added with Sphingomonas. The amount of Sphingomonas added was the same as the number of bacteria required in the example. After applying to 125g of soil and pre-culturing for one week, the colony count was measured with the pre-cultured soil of Example 1.

[0082] The test results are shown in the attached manual. Figures 1-2 , Tables 1 to 9.

[0083] Table 1 shows the BET test results of biochar (BC) and titanium gypsum-biochar (TBC) prepared in Comparative Examples 1 and 3. As can be seen from Table 1. The specific surface area and total pore volume of the titanium gypsum-biochar in Comparative Example 3 are higher than those of the biochar in Comparative Example 1, and are increased by 12.60% and 21.24% respectively. The reason for this phenomenon may be that after ball milling of biochar (BC) and titanium gypsum (T), the specific surface area and total pore volume of the titanium gypsum-biochar prepared in Comparative Example 3 are increased. Therefore, the titanium gypsum-biochar of the present invention has a larger specific surface area and a higher total pore volume, which is beneficial to improving the ion exchange of titanium gypsum-biochar in secondary salinized soil.

[0084] Table 1 BET test results of samples of Comparative Example 1 and Comparative Example 3

[0085] Material <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> Comparative Example 3 81.89 0.1924 Comparative Example 1 73.08 0.1587

[0086] Table 2 shows the test results of the physical and chemical properties of the soil of continuous cowpea cropping after different treatments. As can be seen from Table 2, both the embodiment and the comparative example can increase the pH value of the soil, and the embodiment has a better effect than the comparative example 3 because the sphingomonas degrades the phenolic acid substances produced by continuous cowpea cropping. The volume density of embodiments 1 to 3 and comparative examples 1 to 3 is lower than that of the blank group. The reason why the reduction of comparative examples 1 to 2 is not as large as that of embodiments 1 to 3 and comparative example 3 may be that the conditioners of embodiments 1 to 3 and comparative example 3 have a large specific surface area and high porosity; the reason why the soil volume density of comparative example 2 is larger than that of comparative example 1 may be that the titanium gypsum in comparative example 2 will be gradually dissolved by the water in the soil, and the solubility of gypsum is limited. Finally, the gypsum particles will fill the pores in the soil, reducing the volume density of the soil. The volume density of soil is negatively correlated with the porosity of soil, while the porosity of soil is positively correlated with the water holding capacity. When the bulk density of the soil decreases, the porosity of the soil will increase, and the field water holding capacity of the soil will also increase accordingly, resulting in the field water holding capacity of Examples 1 to 3 and Comparative Example 3 being 1.67 to 1.87 times higher than that of the blank group. Therefore, the biomass carbon-based conditioner of the present invention can effectively improve the pH and water retention capacity of the continuously cropped soil.

[0087] Soil conductivity is an important indicator for measuring the content of dissolved salts in the soil. Within a certain concentration range, the salt content in the soil solution is proportional to the conductivity, that is, the more salts are dissolved, the greater the conductivity of the solution. In Table 2, the conductivity of Examples 1 to 3 and Comparative Example 3 is reduced by 0.5 to 0.76 ms / cm compared with the blank group, while Comparative Examples 1 to 2 are only reduced by 0.12 ms / cm and 0.23 ms / cm, respectively, which is less than that of Examples 1 to 3 and Comparative Example 3. The reason is that biochar can increase the pH, porosity and water holding capacity of the soil, indirectly affecting the conductivity of the soil, but cannot effectively reduce the salt content. The calcium ions in titanium gypsum can exchange ions with salt ions in the continuous cropping soil. After applying it to the modification of biochar, the effect of the biochar-based conditioner is improved, which can effectively reduce the conductivity of the soil. Therefore, the conditioner of the present invention can effectively reduce the salt in secondary salinized soil.

[0088] Table 2 Test results of physical and chemical properties of soil in cowpea continuous cropping after different treatments

[0089]

[0090] Table 3 shows the organic matter test results of the cowpea continuous cropping soil after different treatments. It can be seen from Table 3 that the comparative example 2 also increased compared with the blank group, but the effect of titanium gypsum on increasing soil organic matter was poor, while the soil organic matter of Examples 1 to 3 and Comparative Examples 1 and 3 increased by 0.72 to 0.78 times compared with the blank group. This is because the examples and comparative examples 1 and 3 all contain biochar, which contains a certain amount of organic matter. In addition, Examples 1 to 3 have the addition of Sphingomonas, which improves the microbial structure in the soil, and the beneficial microorganisms can activate the rhizosphere soil nutrients, so that the organic matter content of the examples is generally higher than that of the comparative examples.

[0091] Compared with the blank group, the contents of available phosphorus, available potassium and fully alkaline nitrogen in the embodiments and comparative examples 1 to 3 were all increased, while the effect of comparative example 2 was not as good as that of the other groups, which may be because the biochar in the other groups has the effect of increasing the contents of available phosphorus, available potassium and fully alkaline nitrogen in the soil, while there is no biochar in comparative example 2. In addition, the improvement effect of the embodiments on soil nitrogen, phosphorus and potassium is better than that of comparative example 3 because the addition of bacteria enhances the microbial activity in the soil. Therefore, the biochar, titanium gypsum and bacteria in the biomass charcoal-based conditioner of the present invention can play a synergistic role and effectively increase the content of organic matter in the soil, thereby reducing the effect of secondary salinization soil on the growth of cowpea.

[0092] Table 3 Test results of soil nutrients in continuous cowpea cropping after different treatments

[0093]

[0094] Table 4 shows the growth of cowpea after different treatments. It can be seen from Table 4 that the average plant height of cowpea in the embodiments and comparative examples is increased compared with the blank group, and the plant height of embodiments 1 to 3 is all above 169 cm, which is significantly higher than the comparative example. Similarly, in terms of the yield of cowpea, compared with the blank group, the yield of comparative examples 1 to 3 only increased by 6.72% to 13.39%, while the yield of cowpea in embodiments 1 to 3 increased by 32.7% to 40.56%. The reason for the increase in cowpea plant height and yield is that the conditioner of the present invention improves the physical and chemical properties of the soil and increases the nutrients in the soil, and the reason why the embodiment is better than the comparative example is that Sphingomonas has the effect of promoting the growth of cowpea.

[0095] Table 4 Growth of cowpea after different treatments

[0096]

[0097] Table 5 shows the chlorophyll content in cowpea leaves after different treatments. It can be concluded from Table 5 that the chlorophyll content of cowpea in the embodiments and comparative examples is higher than that in the blank group, and the effects of embodiments 1 to 3 on the chlorophyll of cowpea leaves in continuous cropping are greater than those of comparative examples 1 to 3. The chlorophyll a, chlorophyll b and chlorophyll a+b contents of cowpea leaves treated with embodiments 1 to 3 are increased by 50.6 to 58.9%, 15.69 to 41.18% and 42.11 to 54.55% respectively compared with the blank group. This indicates that the sphingomonas contained in embodiments 1 to 3 has the effect of promoting the growth of cowpea, so the biochar conditioner of the present invention can increase the chlorophyll content of cowpea leaves in continuous cropping and further improve the growth of cowpea.

[0098] Table 5 Chlorophyll content in cowpea leaves after different treatments

[0099]

[0100]

[0101] Figure 1 is the content of proline in cowpea leaves after different treatments. Compared with the blank group, the proline content of Examples 1 to 3 has been significantly improved, and Comparative Examples 1 to 3 have also been improved, but not as much as that of Examples 1 to 3. The reason is that Sphingomonas will secrete a large amount of Welan gum when subjected to continuous cropping stress, and Welan gum can promote cowpea to accumulate more proline, and proline can maintain cell osmotic pressure. Therefore, the conditioner of the present invention can promote cowpea to accumulate proline, so as to maintain cell stability and reduce the degree of damage.

[0102] Figure 2The effect of different treatments on the antioxidant enzyme activity in cowpea leaves. SOD, POD, and CAT are important antioxidant enzymes in plants. As can be seen from the figure, compared with the blank group, the three enzyme activities of the embodiments and comparative examples are all improved, and the increase in embodiments 1 to 3 is higher than that of comparative examples 1 to 3. The reason is that the sphingomonas in the embodiments promotes the accumulation of proline in cowpea, and proline can maintain the stability of the intracellular membrane and the activity of the enzyme, and improve the enzyme activity in the cell. In addition, the MDA content of the blank group is higher than that of embodiments 1 to 3 and comparative examples 1 to 3. MDA is a product of membrane lipid peroxidation, and the presence of SOD can eliminate excessive active oxygen and reduce the content of MDA. Therefore, under the treatment of embodiments 1 to 3, the SOD activity in cowpea leaves is relatively high, which makes the content of MDA significantly decreased, with a maximum decrease of 42.38%. Therefore, the biomass carbon-based conditioner of the present invention can improve the stress resistance of cowpea under continuous cropping obstacles and alleviate the impact of continuous cropping obstacles on cowpea growth.

[0103] Table 6 shows the contents of four phenolic acids in the rhizosphere soil of cowpea after different treatments. It can be seen from Table 6 that, compared with the blank group, Examples 1 to 3 and Comparative Examples 1 to 3 all have a reducing effect on the four phenolic acids in the rhizosphere soil of cowpea, and Examples 1 to 3 have the best effect on reducing phenolic acids, among which cinnamic acid can be reduced to 10.84 to 12.09, phenylacetic acid can be reduced to 1.28 to 1.71, p-hydroxybenzoic acid can be reduced to 26.93 to 28.42, and phthalic acid can be reduced to 10.98 to 12.85, while the reducing effect of Comparative Examples 1 to 3 is poor, because the mechanism of action of Comparative Examples 1 to 3 on phenolic acids in the soil is only adsorption, while the mechanism of action of Examples 1 to 3, in addition to adsorption, also has the degradation effect of Sphingomonas. Therefore, the biomass carbon-based conditioner of the present invention can better reduce the content of phenolic acids in the rhizosphere soil of cowpea.

[0104] Table 6 Contents of four phenolic acids in rhizosphere soil of cowpea after different treatments (mg / kg)

[0105] Group Cinnamic acid Phenylacetic acid Parabens Phthalic acid blank 21.07 2.57 37.39 18.07 Example 1 10.84 1.54 28.42 12.85 Example 2 12.09 1.71 27.14 11.77 Example 3 11.86 1.28 26.93 10.98 Comparative Example 1 18.45 2.09 32.45 14.07 Comparative Example 2 19.04 2.21 33.06 14.49 Comparative Example 3 16.55 2.01 30.48 13.57

[0106] Table 7 shows the changes in the number of various microorganisms in the cowpea soil after different treatments. As shown in the table below, the total number of microorganisms after treatment in Examples 1 to 3 and Comparative Examples 1 to 3 was higher than that in the blank group. Specifically, the number of bacteria and actinomycetes increased, and the number of fungi decreased. Moreover, the effect of Examples 1 to 3 in improving the soil microbial structure is better than that in the comparative example, because the conditioner in the example is loaded with sphingomonas, which can promote the colonization of beneficial colonies in the rhizosphere of cowpea, which is beneficial to improving the soil microbial structure. In addition, the effect of Comparative Example 3 in improving the soil microbial structure is better than that of Comparative Examples 1 to 2. The reason for this phenomenon may be that the biochar and titanium gypsum in the treatment of Comparative Example 3 play a synergistic role. Therefore, the biomass charcoal-based conditioner prepared by the present invention can improve the microbial structure in the soil.

[0107] Table 7 Changes in the number of various microorganisms in cowpea soil after different treatments

[0108]

[0109] Table 8 shows the changes in enzyme activity of cowpea soil after different treatments. It can be seen from Table 8 that the soil enzyme activities of Examples 1 to 3 and Comparative Examples 1 to 3 are all improved compared with the blank group. The polyphenol oxidase of the soil of Examples 1 to 3 is increased from 0.15 to 0.31 to 0.48, urease is increased from 2.95 to 3.98 to 4.33, and sucrase is increased from 2.45 to 4.09 to 4.74, while the soil enzyme activity of Comparative Examples 1 to 3 is not as much as that of Examples 1 to 3. The reason for this phenomenon is that the soil biomass charcoal-based conditioners of Examples 1 to 3 have a strong effect on improving the physical and chemical properties of soils coexisting with secondary salinization and acidification, and Examples 1 to 3 contain sphingomonas, which can improve the microbial structure of the soil and enhance the microbial activity of the soil. Therefore, the biomass charcoal-based conditioner of the present invention can effectively improve the soil enzyme activity.

[0110] Table 8 Changes in enzyme activity in cowpea soil after different treatments

[0111]

[0112]

[0113] Table 9 shows the test results of the number of Sphingomonas colonies in Example 1 and the control group. As can be seen from Table 9, the number of colonies in Example 1 is higher than that in the control group. The reason for this phenomenon is that the Sphingomonas in Example 1 is loaded on titanium gypsum-biochar, which provides a relatively stable living environment for Sphingomonas. Therefore, the conditioning agent of the present invention provides a habitat for Sphingomonas, which is conducive to the survival and reproduction of Sphingomonas.

[0114] Table 9 Sphingomonas colony counts (cfu / g) of Example 1 and the control group

[0115] Group Example 1 Control group Sphingomonas colony count <![CDATA[2.41×10 7 ]]> <![CDATA[0.83×10 6 ]]>

[0116] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A preparation method and application of a biomass carbon-based soil conditioner, characterized in that: The preparation of the biomass charcoal-based soil conditioner comprises the following steps: (1) Preparation of biochar (BC): The pine needle sample was crushed and placed in a tube furnace. In an inert nitrogen atmosphere, the pyrolysis was carried out at 600-900°C for 1.5-4 h, with a heating rate of 5-8°C / min. After pyrolysis, the biochar cooled to 22-28°C was ground and sieved with 30-45 mesh to obtain biochar (BC); (2) Pretreatment of titanium gypsum (T): The original titanium gypsum was placed in an ultrasonic cleaning machine and washed with deionized water for 3 to 5 times, and then dried in an oven at a constant temperature of 100 to 120°C for 1.5 to 3 hours. The dried sample was ground into fine powder particles and sieved with 10 to 25 mesh to obtain titanium gypsum (T); (3) Preparation of titanium gypsum-biochar (TBC): The titanium gypsum obtained in step (2), the biochar obtained in step (1) and zirconia balls with a diameter of 20 mm are placed in a zirconia ball mill, the ball mill is sealed and fixed on a ball mill for ball milling for 1.5 to 3 hours, and sieved with 30 to 45 mesh to obtain titanium gypsum-biochar (TBC); (4) Preparation of bacterial suspension: Sphingomonas was inoculated into NB liquid culture medium and cultured at 30°C and 150 rpm for 5 days, then centrifuged at 3800-4500 rpm for 3-5 times, and the Sphingomonas obtained by centrifugation was placed in sterile physiological saline to obtain a bacterial suspension with an OD value of 1.6-1.8; (5) Preparation of TBC-immobilized Sphingomonas (TBCS): The TBC prepared in step (3) is sterilized and mixed with the bacterial suspension prepared in step (4), and the mixture is shaken at 28-30° C. and 100-150 rpm for 42-50 h to obtain TBC-immobilized Sphingomonas (TBCS).

2. The preparation method according to claim 1, characterized in that: The mass ratio of the biochar, titanium gypsum and zirconium oxide balls described in step (3) is 1: (0.4-1): (40-60).

3. The preparation method according to claim 1, characterized in that: The ingredients of the NB liquid culture medium described in step (4) include: 3g beef extract, 10g peptone, 5g NaCl, and 1L distilled water. The prepared liquid culture medium is sterilized by high pressure sterilization at 121°C for 15min for later use.

4. The preparation method according to claim 1, characterized in that: The ratio of Sphingomonas (mg) to NB liquid culture medium (mL) in step (4) is 1:

10.

5. The method according to claim 1, characterized in that: The sterilization conditions of TBC in step (5) are high pressure sterilization at 121° C. for 15 min, and the ratio of the mass (g) of TBC to the volume (mL) of the bacterial suspension is 1:

5.

6. Use of the biomass carbon-based conditioning agent prepared by the method according to claims 1 to 5, characterized in that: The biomass carbon-based conditioner is applied to the cowpea continuous cropping soil at a mass fraction of 5-10%, mixed and pre-cultivated for one week before planting, during which the soil moisture is maintained at 60%.

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