Saline-alkali soil composite modifier and preparation method thereof

Abstract

The invention discloses a saline-alkali soil composite modifier and a preparation method thereof, and belongs to the technical field of saline-alkali soil improvement, the composite modifier with high fixing efficiency on microorganisms is prepared by loading the microorganisms with biochar and then embedding the microorganisms with starch-polyvinyl alcohol, and embedding materials such as the biochar provide an appropriate living environment for the microorganisms, so that the survival rate of the microorganisms is improved. The microorganisms are promoted to well proliferate and grow in the saline-alkali soil, so that the saline-alkali soil improvement effect is better exerted; meanwhile, the raw materials such as the biochar have a good soil improvement effect and are combined with microorganisms to comprehensively improve the saline-alkali soil, development and utilization of the saline-alkali soil are promoted, and good application prospects are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of saline-alkali land improvement, and in particular to a saline-alkali land composite improver and a preparation method thereof. Background Art

[0002] my country's saline-alkali land is mainly distributed in the arid and semi-arid areas in the north and coastal areas, accounting for about 10.3% of my country's total land area. Saline-alkali land is mainly caused by natural and human factors. Excessive soil salinity will destroy the soil structure, cause soil compaction, reduce plant water absorption capacity, reduce soil organic matter content, and seriously inhibit the normal growth of plants, causing serious impacts on food safety and ecological security. Scientific and reasonable development of saline-alkali land can effectively improve its social, ecological and economic value.

[0003] At present, the main methods for improving saline-alkali land are physical improvement methods, chemical improvement methods and biological improvement methods. Physical improvement methods include watering to wash salt, deep tillage of soil, etc., which are difficult to operate and costly in actual application, making them difficult to implement on a large scale; chemical improvement methods use the acid-base neutralization principle to adjust soil salinity by applying chemical improvers. In actual application, they need to be applied multiple times according to soil conditions, and long-term application of chemical improvers is likely to cause secondary pollution to the soil, and they are also costly and have poor stability; biological improvement methods currently focus on applying microorganisms to the soil, which have the advantages of high safety, convenient implementation, good improvement effect, and environmental friendliness. They are ideal methods for effectively improving saline-alkali land. However, when microorganisms directly enter saline-alkali soil, they are easily affected by environmental and soil factors, which reduces their activity and inhibits their normal proliferation and growth, thereby reducing the improvement effect of saline-alkali land.

[0004] Therefore, there is a need to find a method for preparing a saline-alkali land improver with microorganisms as active ingredients, reduce the impact of environmental and soil factors on microorganisms, improve the improvement effect of microorganisms on saline-alkali land, and thus promote the development and utilization of saline-alkali land. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a saline-alkali land composite improver and a preparation method thereof, so as to solve the problem that when microorganisms are directly applied to improve saline-alkali land under conventional methods, the microorganisms are easily affected by soil and environmental factors, thereby inhibiting their activity and normal proliferation and growth, resulting in reduced saline-alkali land management effects.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A saline-alkali land composite improver, comprising the following raw materials in parts by weight:

[0008] 20-30 parts of biochar, 1-2 parts of starch, 0.5-1 parts of polyvinyl alcohol, 0.2-0.4 parts of nano-silicon dioxide, 1-1.8 parts of glutamine, 0.01-0.04 parts of p-methylacetophenone, 0.01-0.02 parts of isobutanolamine, and 4-6 parts of composite microbial culture liquid.

[0009] Furthermore, the composite improver comprises the following raw materials in parts by weight:

[0010] 24-26 parts of biochar, 1.4-1.6 parts of starch, 0.6-0.8 parts of polyvinyl alcohol, 0.28-0.32 parts of nano-silicon dioxide, 1.3-1.5 parts of glutamine, 0.02-0.03 parts of p-methylacetophenone, 0.014-0.016 parts of isobutanolamine, and 4.5-5.5 parts of composite microbial culture liquid.

[0011] Furthermore, the composite improver comprises the following raw materials in parts by weight:

[0012] 25 parts of biochar, 1.5 parts of starch, 0.7 parts of polyvinyl alcohol, 0.3 parts of nano-silicon dioxide, 1.4 parts of glutamine, 0.025 parts of p-methylacetophenone, 0.015 parts of isobutanolamine, and 5 parts of composite microbial culture liquid.

[0013] Furthermore, the composite microbial bacterial liquid is obtained by mixing Bacillus subtilis bacterial liquid, Bacillus megaterium bacterial liquid and Bacillus mucilaginosus bacterial liquid in a mass ratio of 2:1:1.

[0014] The present invention also discloses a method for preparing the composite improver, and the specific method for preparing the composite improver is as follows:

[0015] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus are inoculated into LB liquid culture medium respectively, and cultured on a shaker at 30-35° C. and 180-220 rpm for 24-32 h to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; glutamine is dissolved in water and then placed in a reactor together with biochar for heating reaction, and after the reaction is completed, the mixture is allowed to stand overnight, and then the composite microbial culture liquid is added for co-culture and centrifugation to obtain biochar loaded with microorganisms;

[0016] (2) adding nano-silica to water and stirring to disperse, then adding p-methylacetophenone, heating to 70-90° C. to react for 6-10 hours, filtering after the reaction is completed, and drying at 150-200° C. to obtain dried nano-silica; dispersing the dried nano-silica in water, then adding isobutanolamine, heating to 60-80° C. to react for 30-60 minutes, filtering after the reaction is completed, and drying at 45° C. to obtain treated nano-silica;

[0017] (3) Starch is added to water, heated at 80°C for 30 minutes, then cooled to 60°C and polyvinyl alcohol is added to react for 40 minutes to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide is added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; the biochar loaded with microorganisms is added to the mixed glue, stirred at a low speed to mix evenly, and then slowly injected into a 2wt% calcium chloride solution to coagulate into balls, and after standing for 10 to 20 minutes, the gel balls are washed with water and then dried to obtain a composite improver.

[0018] The present invention uses biochar as a carrier to fix microorganisms, thereby providing a suitable living environment for the microorganisms, so as to reduce the impact of saline-alkali soil and environmental factors on the microorganisms. However, the loading and fixing efficiency of single biochar on microorganisms is low. Therefore, before loading the microorganisms, the biochar is first treated with glutamine, and the surface charge properties of the biochar are adjusted to enhance the non-covalent interaction between the biochar and the microorganisms, thereby increasing the adsorption and fixing amount of the biochar on the microorganisms. The biochar loaded with microorganisms is further embedded with starch-polyvinyl alcohol glue and then dried to obtain microbial composite improver particles, which further improves the fixation efficiency of the microorganisms and inhibits the separation and shedding of the microorganisms. At the same time, it better isolates the adverse external environment, provides a suitable growth environment for the microorganisms, and maintains the good proliferation growth and high activity of the microorganisms, so as to ensure the improvement effect of the microorganisms on saline-alkali land.

[0019] However, the mechanical strength of the starch-polyvinyl alcohol glue embedding material is low, the structure is easy to collapse, and the pores are easily blocked, which affects the entry and exit activities of microorganisms and the entry and exit of metabolic products, inhibiting the life activities of microorganisms. Therefore, a high-hardness nano-silicon dioxide material is added to improve the mechanical strength of the starch-polyvinyl alcohol embedding material and maintain structural stability; however, nano-silicon dioxide is easy to adsorb and agglomerate, and has poor dispersibility in the starch-polyvinyl alcohol glue, which is easy to block the channels formed by the starch-polyvinyl alcohol embedding material, reduce the mass transfer of the embedded particles, and may even cause the suffocation and death of the microorganisms. Therefore, in step (2), p-methylacetophenone is used to react with nano-silicon dioxide. After the p-methylacetophenone reacts with the nano-silicon dioxide, the interaction between the nano-silicon dioxide molecules and between the nano-silicon dioxide and the starch-polyvinyl alcohol is weakened, and the aggregation between the nano-silicon dioxide molecules is inhibited, while increasing the interaction between the silicon dioxide and the starch-polyvinyl alcohol. The spacing between the powder and polyvinyl alcohol forms a more developed pore channel inside the embedding material. After the nano-silica is dried at high temperature, isobutanolamine is used to combine with the nano-silica to change the charge properties of silica and increase the adsorption and retention capacity of silica for water molecules, so that these developed pore channels and silica distribution areas can adsorb and accommodate more water. After drying in the later stage, the adsorbed and fixed water molecules evaporate to form good pore channels, thereby enhancing the internal network structure of the composite improver particles, especially the porosity of the network structure of the nano-silica distribution area, so that the comprehensive mechanical strength of the composite improver particles is enhanced while the porosity of the composite improver is improved, so that nutrients and metabolic waste can enter and exit smoothly, maintain the good physiological activity of the internal microorganisms, and ensure the good proliferation and growth of the internal microorganisms, so as to better play its soil improvement effect and improve the efficiency of saline-alkali soil improvement.

[0020] Furthermore, in step (1), the heating reaction temperature is 50 to 80° C., and the reaction time is 4 to 8 hours.

[0021] Furthermore, in step (1), the co-cultivation temperature is 25 to 35° C., and the co-cultivation time is 18 to 24 hours.

[0022] Furthermore, in step (1), the centrifugal speed is 1000-3000 rpm / min, and the centrifugal time is 5-15 min.

[0023] Furthermore, the low-speed stirring operation in step (3) is specifically stirring at a speed of 200 to 300 r / min for 5 to 10 minutes.

[0024] Furthermore, in step (3), the drying temperature of the gel balls is 45°C.

[0025] Beneficial effects:

[0026] 1. The present invention uses glutamine to treat biochar and then loads microorganisms to increase the microbial loading capacity, and then uses starch-polyvinyl alcohol glue to embed the biochar loaded with microorganisms, further improving the fixation efficiency of the microorganisms and inhibiting the separation and shedding of the microorganisms. At the same time, it better isolates the adverse external environment and provides a suitable growth environment for the microorganisms, thereby ensuring the high activity of the microorganisms and better playing the role of improving saline-alkali soil.

[0027] 2. The present invention uses p-methylacetophenone and isobutanolamine to treat nano silicon dioxide and then adds the nano silicon dioxide to the starch-polyvinyl alcohol glue embedding material, thereby enhancing the mechanical strength of the embedding material and improving its internal pore structure, thereby better protecting the internal microorganisms and ensuring the effect of the microorganisms in the composite improver.

[0028] 3. The present invention uses biochar, starch and other raw materials as embedding carriers to embed and fix microorganisms. While ensuring that the microorganisms can better play an improvement effect, the biochar and other materials work together with the microorganisms to reduce the salinity of the soil to a limited extent, while improving the physical and chemical properties of the soil, and comprehensively managing the saline-alkali soil. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to specific embodiments:

[0030] Example 1: Preparation of composite modifier

[0031] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured on a shaker at 32°C and 200 rpm for 28 hours to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly at a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; 1.5 kg of glutamine was dissolved in 30 kg of water and then put into a reactor together with 25 kg of biochar, stirred and reacted at 60°C for 6 hours, and after the reaction was completed, it was allowed to stand overnight, and then 5 kg of the composite microbial culture liquid was added, and co-cultured at 26°C for 20 hours, and then centrifuged at 2000 rpm / min for 8 minutes to obtain biochar loaded with microorganisms;

[0032] (2) adding 0.3 kg of nano-silica to 3 kg of water and stirring to disperse, then adding 0.02 kg of p-methylacetophenone, heating to 80 ° C. to react for 8 hours, filtering after the reaction is completed, and drying at 160 ° C. to obtain dried nano-silica; dispersing the dried nano-silica in 3 kg of water, then adding 0.015 kg of isobutanolamine, heating to 70 ° C. to react for 40 minutes, filtering after the reaction is completed, and drying at 45 ° C. to obtain treated nano-silica;

[0033] (3) 1.5 kg of starch was added to 45 kg of water, heated at 80 ° C for 30 min, then cooled to 60 ° C and added with 0.6 kg of polyvinyl alcohol for 40 min to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide was added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; the biochar loaded with microorganisms was added to the mixed glue, stirred at 250 r / min for 8 min, and after mixing evenly, it was slowly injected into a 2 wt% calcium chloride solution to solidify into balls. After standing for 15 min, the gel balls were washed with water and dried at 45 ° C to obtain a composite improver.

[0034] Example 2: Preparation of composite modifier II

[0035] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured on a shaker at 30°C and 220 rpm for 32 hours to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly at a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; 1 kg of glutamine was dissolved in 20 kg of water and then put into a reactor together with 20 kg of biochar, stirred and reacted at 50°C for 8 hours, and after the reaction was completed, it was allowed to stand overnight, and then 4 kg of the composite microbial culture liquid was added, and co-cultured at 25°C for 24 hours, and then centrifuged at 1000 rpm / min for 15 minutes to obtain biochar loaded with microorganisms;

[0036] (2) adding 0.2 kg of nano-silica to 2 kg of water and stirring to disperse, then adding 0.01 kg of p-methylacetophenone, heating to 70° C. to react for 10 h, filtering after the reaction is completed, and drying at 150° C. to obtain dried nano-silica; dispersing the dried nano-silica in 2 kg of water, then adding 0.01 kg of isobutanolamine, heating to 60° C. to react for 30 min, filtering after the reaction is completed, and drying at 45° C. to obtain treated nano-silica;

[0037] (3) 1 kg of starch was added to 30 kg of water, heated at 80 ° C for 30 min, then cooled to 60 ° C and added with 0.5 kg of polyvinyl alcohol for 40 min to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide was added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; the biochar loaded with microorganisms was added to the mixed glue, stirred at a speed of 200 r / min for 10 min, and after mixing evenly, it was slowly injected into a 2wt% calcium chloride solution to solidify into balls. After standing for 10 min, the gel balls were washed with water and dried at 45 ° C to obtain a composite improver.

[0038] Example 3: Preparation of composite modifier

[0039] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured on a shaker at 35°C and 180 rpm for 24 hours to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; 1.8 kg of glutamine was dissolved in 36 kg of water and then put into a reactor together with 30 kg of biochar, stirred and reacted at 80°C for 4 hours, and after the reaction was completed, it was allowed to stand overnight, and then 6 kg of the composite microbial culture liquid was added, and co-cultured at 26°C for 24 hours, and then centrifuged at 3000 rpm / min for 5 minutes to obtain biochar loaded with microorganisms;

[0040] (2) adding 0.4 kg of nano-silica to 4 kg of water and stirring to disperse, then adding 0.04 kg of p-methylacetophenone, heating to 90 ° C. to react for 6 hours, filtering after the reaction is completed, and drying at 200 ° C. to obtain dried nano-silica; dispersing the dried nano-silica in 4 kg of water, then adding 0.02 kg of isobutanolamine, heating to 80 ° C. to react for 30 minutes, filtering after the reaction is completed, and drying at 45 ° C. to obtain treated nano-silica;

[0041] (3) 2 kg of starch was added to 60 kg of water, heated at 80 ° C for 30 min, then cooled to 60 ° C and added with 1 kg of polyvinyl alcohol for 40 min to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide was added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; the biochar loaded with microorganisms was added to the mixed glue, stirred at 300 r / min for 5 min, and after mixing evenly, it was slowly injected into a 2 wt% calcium chloride solution to solidify into balls. After standing for 20 min, the gel balls were washed with water and dried at 45 ° C to obtain a composite improver.

[0042] Comparative Example 1: Preparation of composite modifier

[0043] In contrast to Example 1, the only difference is that in the preparation of the composite modifier in Comparative Example 1, glutamine is not added in step (1) to treat the biochar, as shown below:

[0044] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured on a shaker at 32°C and 200 rpm for 28 h to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; 25 kg of biochar was added to 30 kg of water and stirred for dispersion, and then 5 kg of the composite microbial culture liquid was added, and the mixture was co-cultured at 26°C for 20 h, and then centrifuged at 2000 rpm / min for 8 min to obtain biochar loaded with microorganisms;

[0045] (2) to (3) are the same as in Example 1.

[0046] Comparative Example 2: Preparation of composite modifier

[0047] In contrast to Example 1, the only difference is that in the preparation of the composite modifier in Comparative Example 2, no p-methylacetophenone is added in step (2) to react with nano-silicon dioxide, as follows:

[0048] (1) Same as Example 1;

[0049] (2) adding 0.3 kg of nano-silicon dioxide to 3 kg of water and stirring to disperse, then adding 0.015 kg of isobutanolamine, heating to 70° C. to react for 40 min, filtering after the reaction is completed, and drying at 45° C. to obtain the treated nano-silicon dioxide;

[0050] (3) Same as Example 1.

[0051] Comparative Example 3: Preparation of composite modifier

[0052] In contrast to Example 1, the only difference is that in the preparation of the composite modifier in Comparative Example 3, no isobutanolamine is added in step (2) to react with nano-silicon dioxide, as follows:

[0053] (1) Same as Example 1;

[0054] (2) adding 0.3 kg of nano-silica to 3 kg of water and stirring to disperse, then adding 0.02 kg of p-methylacetophenone, heating to 80° C. to react for 8 h, filtering after the reaction is completed, and drying at 160° C. to obtain the treated nano-silica;

[0055] (3) Same as Example 1.

[0056] Comparative Example 4: Preparation of composite modifier

[0057] In contrast to Example 1, the only difference is that the original step (2) is missing when preparing the composite modifier in Comparative Example 4, and the nano-silicon dioxide is not processed. Instead, conventional nano-silicon dioxide is directly added in step (3). The remaining steps are the same as in Example 1.

[0058] Comparative Example 5: Preparation of composite modifier

[0059] In contrast to Example 1, the only difference is that in Comparative Example 5, nano-silicon dioxide is not added during the preparation of the composite modifier, and the remaining method steps are the same as those in Example 1.

[0060] Comparative Example 6: Preparation of composite modifier

[0061] In contrast to Example 1, the difference is that in the preparation of the composite modifier in Comparative Example 6, the nano-silicon dioxide is treated once in step (2), as follows:

[0062] (1) Same as Example 1;

[0063] (2) 0.3 kg of nano-silica was added to 3 kg of water and stirred to disperse, and then 0.02 kg of p-methylacetophenone was added, the temperature was raised to 80 ° C and reacted for 8 hours, and then the temperature was lowered to 70 ° C and 0.015 kg of isobutanolamine was added to react for 40 minutes. After the reaction was completed, it was filtered and dried at 45 ° C to obtain the treated nano-silica.

[0064] (3) Same as Example 1.

[0065] Comparative Example 7: Preparation of composite modifier

[0066] In contrast to Example 1, the difference is that the composite improver in Comparative Example 7 lacks steps (2) and (3) when preparing the composite improver, that is, the composite improver is obtained directly by loading the biochar with microorganisms in step (1), as follows:

[0067] Bacillus subtilis, Bacillus megaterium and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured on a shaker at 32°C and 200rpm for 28h to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; 1.5kg of glutamine was dissolved in 30kg of water and put into a reactor together with 25kg of biochar, and stirred for reaction at 60°C for 6h. After the reaction was completed, it was allowed to stand overnight, and then 5kg of the composite microbial culture liquid was added, and co-cultured at 26°C for 20h, and then centrifuged at 2000rpm / min for 8min to obtain biochar loaded with microorganisms, that is, a composite improver.

[0068] Comparative Example 8: Preparation of composite modifier

[0069] In contrast to Example 1, the difference is that in the preparation of the composite improver in Comparative Example 8, biochar is not used to load the microorganisms in step (1), but the microbial bacterial liquid is directly added to the step (3) for embedding to prepare the composite improver, which is specifically as follows:

[0070] (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus were inoculated into LB liquid culture medium respectively, and cultured in a shaking table at 32° C. and 200 rpm for 28 h to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid;

[0071] (2) Same as Example 1;

[0072] (3) 1.5 kg of starch was added to 45 kg of water, heated at 80° C. for 30 min, then cooled to 60° C. and added with 0.6 kg of polyvinyl alcohol for 40 min to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide was added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; 5 kg of composite microbial culture was added to the mixed glue, stirred at 250 r / min for 8 min, and after mixing evenly, slowly injected into a 2 wt% calcium chloride solution to coagulate into balls, and after standing for 15 min, the gel balls were washed with water and dried at 45° C. to obtain a composite improver.

[0073] Experiment: Experiment on the effect of composite improver

[0074] The effect test of the composite modifier was conducted in the experimental site of Zhuanjing Town, Dingbian County, Yulin City, Shaanxi Province. Specifically, an area was selected as the experimental area, and the initial physical and chemical properties of the experimental area were measured (including total salt content, pH, porosity, effective phosphorus content and the number of live Bacillus subtilis). Then the experimental area was divided into 9 small areas, corresponding to Example 1 and Comparative Examples 1 to 8, and the area of ​​each area was 3×3m 2 , respectively, the composite improvers prepared in Example 1 and Comparative Examples 1 to 8 were applied in an amount of 5 kg for Example 1 and Comparative Examples 1 to 7, and the improver in Comparative Example 8 was not added with biochar, so the application amount was only 0.5 kg. After 20 days of application of each group of composite improvers, the number of viable Bacillus subtilis in the soil was measured. After 6 months of application, the total salt content, pH, porosity, and available phosphorus content of the soil in each area were measured again. The experiment was repeated three times, and the average data were shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] According to the data analysis in Table 1:

[0079] (1) According to the method of the present invention, biochar is treated and loaded with microorganisms, and then starch-polyvinyl alcohol is used for embedding and fixing, which can effectively improve the loading efficiency of microorganisms and isolate the adverse external environment to provide a good living environment for microorganisms. After 20 days of application of the improver to the saline-alkali land, the number of viable Bacillus subtilis is high; further, the saline-alkali soil is improved by the combined action of microorganisms and biochar. After 4 months, the total salt content of the soil is reduced from 4.81 g / kg to 2.89 g / kg, the soil pH is reduced from 8.7 to 7.3, and the soil porosity and effective phosphorus content are significantly increased. This shows that the composite improver prepared by the present invention can not only effectively reduce soil salinity, but also effectively improve the physical and chemical properties of the soil, and has good application prospects.

[0080] (2) In comparative example 1, glutamine was not added to treat the biochar during the preparation of the improver, which reduced the interaction between the biochar and the microorganisms, thereby reducing the loading efficiency and the number of viable bacteria, further affecting the improvement effect of the saline-alkali land; in comparative example 2, methylacetophenone was not used to treat the nano-silicon dioxide during the preparation of the improver, and isobutanolamine was not used to treat the nano-silicon dioxide during the preparation of the improver in comparative example 3. Therefore, the underdeveloped internal pore structure of the improvers in comparative examples 2 and 3 affected the metabolic activity of the microorganisms, and thus also affected the treatment effect of the saline-alkali land to a certain extent;

[0081] (3) In Comparative Example 8, the composite improver did not use biochar to load the microorganisms first, which not only reduced the embedding and fixation effect of the microorganisms, but also the biochar as an embedding material played an important role in soil improvement while loading the microorganisms. The composite improver prepared without adding biochar had a significantly reduced improvement effect on saline-alkali soil.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A saline-alkali land composite improver, characterized in that: The composite improver comprises the following raw materials in parts by weight: 20-30 parts of biochar, 1-2 parts of starch, 0.5-1 parts of polyvinyl alcohol, 0.2-0.4 parts of nano-silicon dioxide, 1-1.8 parts of glutamine, 0.01-0.04 parts of p-methylacetophenone, 0.01-0.02 parts of isobutanolamine, and 4-6 parts of composite microbial culture liquid.

2. A saline-alkali land composite improver according to claim 1, characterized in that: The composite improver comprises the following raw materials in parts by weight: 24-26 parts of biochar, 1.4-1.6 parts of starch, 0.6-0.8 parts of polyvinyl alcohol, 0.28-0.32 parts of nano-silicon dioxide, 1.3-1.5 parts of glutamine, 0.02-0.03 parts of p-methylacetophenone, 0.014-0.016 parts of isobutanolamine, and 4.5-5.5 parts of composite microbial culture liquid.

3. A saline-alkali land composite improver according to claim 2, characterized in that: The composite improver comprises the following raw materials in parts by weight: 25 parts of biochar, 1.5 parts of starch, 0.7 parts of polyvinyl alcohol, 0.3 parts of nano-silicon dioxide, 1.4 parts of glutamine, 0.025 parts of p-methylacetophenone, 0.015 parts of isobutanolamine, and 5 parts of composite microbial culture liquid.

4. A saline-alkali land composite improver according to claim 3, characterized in that: The composite microbial bacterial liquid is obtained by mixing Bacillus subtilis bacterial liquid, Bacillus megaterium bacterial liquid and Bacillus mucilaginosus bacterial liquid in a mass ratio of 2:1:

1.

5. A method for preparing a composite saline-alkali land modifier, characterized in that: The preparation method of the composite modifier is as follows: (1) Bacillus subtilis, Bacillus megaterium, and Bacillus mucilaginosus are inoculated into LB liquid culture medium respectively, and cultured on a shaker at 30-35° C. and 180-220 rpm for 24-32 h to obtain Bacillus subtilis culture liquid, Bacillus megaterium culture liquid, and Bacillus mucilaginosus culture liquid respectively, and then mixed evenly in a mass ratio of 2:1:1 to obtain a composite microbial culture liquid; glutamine is dissolved in water and then placed in a reactor together with biochar for heating reaction, and after the reaction is completed, the mixture is allowed to stand overnight, and then the composite microbial culture liquid is added for co-culture and centrifugation to obtain biochar loaded with microorganisms; (2) adding nano-silica to water and stirring to disperse, then adding p-methylacetophenone, heating to 70-90° C. to react for 6-10 hours, filtering after the reaction is completed, and drying at 150-200° C. to obtain dried nano-silica; dispersing the dried nano-silica in water, then adding isobutanolamine, heating to 60-80° C. to react for 30-60 minutes, filtering after the reaction is completed, and drying at 45° C. to obtain treated nano-silica; (3) Starch is added to water, heated at 80°C for 30 minutes, then cooled to 60°C and polyvinyl alcohol is added to react for 40 minutes to obtain starch-polyvinyl alcohol glue; the treated nano-silicon dioxide is added to the starch-polyvinyl alcohol glue and mixed thoroughly to obtain a mixed glue; biochar loaded with microorganisms is added to the mixed glue, stirred at a low speed and then injected into a 2wt% calcium chloride solution to coagulate into balls, and after standing for 10 to 20 minutes, the gel balls are washed with water and then dried to obtain a composite improver.

6. The method for preparing a composite saline-alkali land modifier according to claim 5, characterized in that: In the step (1), the heating reaction temperature is 50 to 80° C. and the reaction time is 4 to 8 hours.

7. The method for preparing a composite saline-alkali land improver according to claim 6, characterized in that: In the step (1), the co-cultivation temperature is 25 to 35° C., and the co-cultivation time is 18 to 24 hours.

8. The method for preparing a composite saline-alkali land modifier according to claim 7, characterized in that: In the step (1), the centrifugal speed is 1000-3000 rpm / min, and the centrifugal time is 5-15 min.

9. The method for preparing a composite saline-alkali land modifier according to claim 8, characterized in that: The low-speed stirring operation in step (3) is specifically stirring at a speed of 200 to 300 r / min for 5 to 10 minutes.

10. The method for preparing a composite saline-alkali land improver according to claim 9, characterized in that: The drying temperature of the gel balls in step (3) is 45°C.

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