Soil conditioner and preparation method thereof

Abstract

The invention discloses a soil conditioner and a preparation method thereof, and belongs to the technical field of soil remediation. The preparation method of the soil conditioner comprises the following steps: preparing polyglutamic acid by using bacillus subtilis and bacillus natto as fermentation strains, continuously adding sterilized straw powder after fermentation is completed, carrying out secondary fermentation, drying the obtained fermentation product, and mixing the dried fermentation product with decomposed straw and ardealite to obtain the soil conditioner. The soil conditioner provided by the invention has the advantages of simple preparation steps and cheap and easily available raw materials. The prepared soil conditioner has a good improvement effect on saline-alkali soil. The saline-alkali soil improved by the soil conditioner provided by the invention cannot stress the growth of crops due to salt and alkali, the improved soil has high organic matter content and lasting fertility, and the yield of the crops can be obviously increased. After the soil conditioner provided by the invention is applied, the required irrigation and drainage amount is small, and the removal rate of harmful anions and cations in the saline-alkali soil is high. The soil conditioner and the preparation method thereof provided by the invention are high in economic value and have wide popularization and application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of soil remediation, and in particular relates to a soil conditioner and a preparation method thereof. Background Art

[0002] Soil is the material basis for human survival and development. It is the most important renewable natural resource and eternal means of production. Soil pollution directly threatens human health and survival and development. Land salinization is an important issue of concern to the world today. Saline-alkali soil, as a very common soil type, is distributed all over the world. It is a general term for various salinization and saline-alkali soil types affected by salinity. Soil salinization poses a serious threat to agricultural production around the world. As a land resource, saline-alkali soil has huge development potential. Salinization control can not only improve the ecological environment in saline-alkali areas, enrich the local green landscape pattern, and provide new habitats for biodiversity, but also better solve the problems encountered in regional environmental development and forestry economic development, and provide broad space for achieving ecological benign cycles and sustainable development.

[0003] Soil conditioners are preparations that can improve soil structure and physical and chemical indicators. After being applied to the soil, they can improve soil structure, increase soil nutrients and maintain soil moisture. They are increasingly widely used in curbing soil degradation, improving medium and low-yield fields, increasing capacity and storage, etc. At the same time, soil conditioners have been widely used in crop production, forest protection planting, grassland production, urban greening, highway greening and flower production.

[0004] However, the ion content in the soil improved by the current saline-alkali soil conditioners is relatively high, which affects the growth of crops. It is necessary to combine irrigation and drainage to reduce the ion content in the soil, but excessive irrigation and drainage will lead to the loss of organic matter. Finding a saline-alkali soil conditioner that can effectively reduce the ion content in the soil with only a small amount of irrigation and drainage after improvement is a direction worthy of research at present. Summary of the invention

[0005] The object of the present invention is to provide a soil conditioner and a preparation method thereof. The present invention obtains a soil conditioner capable of improving saline-alkali soil by combining polyglutamic acid and small molecule micro-carbon produced by fermentation with decomposed straw and phosphogypsum. The obtained soil conditioner can effectively chelate nutrients such as calcium, magnesium, iron, manganese, zinc, etc. in the soil, precipitate heavy metal elements, and can remove a large amount of anions and sodium in the saline-alkali soil through a small amount of irrigation and drainage, thereby reducing the salinity of the soil.

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

[0007] One of the technical solutions of the present invention is to provide a method for preparing a soil conditioner, comprising the following steps: preparing polyglutamic acid using Bacillus subtilis and Bacillus natto as fermentation strains, adding sterilized straw powder after fermentation, performing secondary fermentation, drying the obtained fermentation product, mixing it with decomposed straw and phosphogypsum, and obtaining the soil conditioner.

[0008] The invention prepares polyglutamic acid by co-fermentation of Bacillus subtilis and Bacillus natto. The obtained polyglutamic acid is used as a soil improvement material. The abundant anions on the surface of the polyglutamic acid can chelate the nutrients such as calcium, magnesium, iron, manganese, zinc and the like in the soil, and can form flocculent precipitation with heavy metal ions, and will not chelate sodium ions. After being improved by the soil improver containing polyglutamic acid, the high concentration of nitrate ions (NO3) in saline-alkali soil that inhibits the normal growth of crops can be reduced. 3- ), sulfate ion (SO4 2- ), chloride ion (Cl - ) and sodium ions (Na + ) and other anions and cations are free, and high concentrations of harmful ions in saline-alkali soil can be easily removed by further irrigation and drainage; the nutrients such as calcium, magnesium, iron, manganese, zinc, etc. chelated by polyglutamic acid provide long-acting trace elements for crop growth through slow release, and polyglutamic acid can also be absorbed by crops as amino acids after degradation. Adding the sterilized straw powder after crushing can not only increase the content of polyglutamic acid through co-fermentation, but also produce a large amount of small molecule micro-carbon fertilizer through fermentation. The produced small molecule micro-carbon fertilizer can activate and promote the reproduction of beneficial microorganisms such as halophilic bacteria and alkaliphilic bacteria, and realize the in-situ repair of saline-alkali soil. The decomposed straw in the soil conditioner can provide rich organic matter for the soil and improve soil fertility; the purpose of adding phosphogypsum is to adjust the pH value of the soil and improve the soil structure. Natto Bacillus and Bacillus subtilis in the fermentation product obtained by the present invention can also adjust the pH value of the soil by producing acidic metabolites, and promote the formation of soil aggregate structure, thereby enhancing the permeability of the soil and providing a better growth environment for crops.

[0009] Preferably, the ratio of the inoculated live bacteria of the Bacillus subtilis to the Bacillus natto is 1-2:1.

[0010] Under this live bacteria inoculation ratio, more polyglutamic acid can be produced.

[0011] Preferably, the fermentation culture medium used in the preparation of the polyglutamic acid contains 40-55 g / L glucose, 10-12 g / L yeast extract, 1.5-2.5 g / L potassium monohydrogen phosphate, 0.2-0.3 g / L magnesium sulfate and 35-45 g / L sodium glutamate, and the pH value is 7-8.

[0012] Preferably, the fermentation temperature is 35-45°C and the fermentation time is 3-4 days.

[0013] Preferably, the temperature of the secondary fermentation is 35-45°C and the time is 3-5 days.

[0014] Preferably, the particle size of the sterilized straw powder does not exceed 2 mm.

[0015] Preferably, the usage ratio of the sterilized straw powder to the fermentation medium is 150-200 g:1L.

[0016] Preferably, the mass ratio of the dried fermentation product to the decomposed straw and the phosphogypsum is 0.5-1:20-30:8-10.

[0017] The second technical solution of the present invention is to provide a soil improver prepared according to the preparation method of the above-mentioned soil improver.

[0018] The third technical solution of the present invention is to provide an application of the above-mentioned soil conditioner in improving saline-alkali soil.

[0019] The fourth technical solution of the present invention is to provide a method for applying the above-mentioned soil conditioner, comprising the following steps: spreading the soil conditioner on the surface of saline-alkali soil, rotary tilling to mix the soil conditioner with the saline-alkali soil, and irrigating and draining the soil after 20 to 30 days to remove free harmful ions to reduce salinity.

[0020] Preferably, for saline-alkali soil with a salinity of 5-20%, the application amount of the soil conditioner is 300-400 kg / mu, for saline-alkali soil with a salinity of 20-45%, the application amount of the soil conditioner is 400-1200 kg / mu, and for saline-alkali soil with a salinity of 20-45%, the application amount of the soil conditioner is 1200-1600 kg / mu.

[0021] Preferably, the rotary tillage depth is 15 to 25 cm.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] The soil conditioner provided by the invention has simple preparation steps and the raw materials are cheap and easily available. The prepared soil conditioner has a good improvement effect on saline-alkali soil.

[0024] The saline-alkali soil improved by the soil conditioner provided by the present invention will not stress the growth of crops due to the salt and alkali, and the improved soil has high organic matter content and lasting fertility, and can significantly increase the yield of crops.

[0025] After the soil improver provided by the invention is applied, the amount of irrigation and drainage required is small, and the removal rate of harmful anions and cations in saline-alkali soil is high.

[0026] The soil conditioner and the preparation method thereof provided by the invention have high economic value and broad prospects for promotion and application. DETAILED DESCRIPTION

[0027] Phosphogypsum plays multiple roles in soil improvement, including improving soil structure, regulating soil pH, promoting crop growth and increasing soil fertility. Phosphogypsum is a by-product produced during the wet process of phosphoric acid production. Its main component is calcium sulfate dihydrate, and it also contains a small amount of free acid, phosphate, fluoride, organic matter and trace elements.

[0028] First, phosphogypsum can improve the soil structure, making it loose and more breathable, which is conducive to the extension of the root system and the growth of crops. At the same time, phosphogypsum can reduce soil crusting and prevent crops from being frustrated by poor drainage. Secondly, as a neutral substance, phosphogypsum can neutralize the pH of acidic and alkaline soils, making the pH of the soil tend to be neutral, which is the most ideal growth environment for many crops. In addition, phosphogypsum can increase the fertility of the soil and release minerals such as calcium, sulfur, magnesium, and potassium, which are very important for the growth of crops, thereby increasing the yield and quality of crops. Finally, phosphogypsum can also improve soil quality, improve its water and fertilizer retention capacity, enhance crop drought resistance and disease and pest resistance, and reduce the content of heavy metals in the soil to reduce harm to crops.

[0029] Bacillus subtilis belongs to the genus Bacillus, has no capsule, has flagella around, is a Gram-positive bacterium, and can form endogenous spores. Bacillus subtilis can ferment to produce γ-polyglutamic acid, and is a glutamate-dependent γ-polyglutamic acid production strain. Bacillus natto is a subspecies of Bacillus subtilis, and the cells of Bacillus natto are long rod-shaped, Gram-positive bacteria, and can form spores under unfavorable environments. The spores are columnar or elliptical, the spore capsules are swollen, have flagella, and are acid-resistant and heat-resistant. The present invention obtains a soil conditioner that is more suitable for improving saline-alkali soil by compounding the two and optimizing the culture matrix.

[0030] In the present invention, when Bacillus subtilis and Bacillus natto are used as fermentation strains to prepare polyglutamic acid, Bacillus subtilis and Bacillus natto are inoculated into a fermentation medium with a seed culture solution, and the spore content in the seed culture solution is 10 6 ~10 9 Pieces / mL is appropriate.

[0031] When the saline-alkali soil improver prepared by the invention is used to improve saline-alkali soil for rice planting, the irrigation and drainage standard is to start transplanting rice when the electrical conductivity of field surface water does not exceed 1.8 mS / cm.

[0032] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0033] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] The straw powder used in the embodiment of the present invention is rice straw powder that is dried and crushed to a particle size of no more than 2 mm.

[0037] The decomposed straw used in the embodiment of the present invention is decomposed rice straw that is dried and crushed to a length not exceeding 1 cm.

[0038] The particle size of the phosphogypsum used in the embodiments of the present invention is 0.2-2 mm.

[0039] The Bacillus natto and Bacillus subtilis used in the embodiments of the present invention are both commercially available products, and their sources do not affect the technical effects of the present invention.

[0040] Example 1

[0041] Preparation of soil conditioner:

[0042] (1) Bacillus natto seed solution (spore content 2×10 8 / mL) and Bacillus subtilis seed solution (spore content 1×10 8 / mL) was inoculated into the fermentation medium (containing 50g / L glucose, 10g / L yeast extract, 2g / L potassium dihydrogen phosphate, 0.25g / L magnesium sulfate and 50g / L sodium glutamate, pH 7.0), and the inoculation amount was 8% (V / V);

[0043] (2) 50 L of the inoculated fermentation medium was transferred to a 100 L fermentation tank, and the culture was carried out at 37° C. for 72 h. Then, 10 kg of straw powder was added (it was sterilized with wet heat before addition to kill bacteria and avoid affecting fermentation), and the culture was carried out at 37° C. for 72 h to obtain a fermentation product;

[0044] (3) The fermentation product was released from the fermentation tank, spread out and air-dried at 40-50° C. to obtain 13.5 kg of dry fermentation product, which was then mixed evenly with 340 kg of decomposed straw and 115 kg of phosphogypsum to obtain a soil conditioner.

[0045] Comparative Example 1

[0046] Preparation of soil conditioner:

[0047] (1) Bacillus natto seed solution (spore content 2×10 8 / mL) and Bacillus subtilis seed solution (spore content 1×10 8 / mL) was inoculated into the fermentation medium (containing 50g / L glucose, 10g / L yeast extract, 2g / L potassium dihydrogen phosphate, 0.25g / L magnesium sulfate and 50g / L sodium glutamate, pH 7.0), and the inoculation amount was 8% (V / V);

[0048] (2) transferring 50 L of the inoculated fermentation medium into a 100 L fermentation tank, and fermenting and culturing at 37° C. for 72 h to obtain a fermentation product;

[0049] (3) The fermentation product was released from the fermentation tank, spread out and air-dried at 40-50° C. to obtain 4.2 kg of dry fermentation product, which was then mixed evenly with 350 kg of decomposed straw (compared with Example 1, the 10 kg of straw powder omitted in step 2 was added to 10 kg of decomposed straw in step 3 to keep the organic matter content of the two materials equivalent) and 115 kg of phosphogypsum to obtain a soil conditioner.

[0050] The content of polyglutamic acid in the dried fermentation products of Example 1 and Comparative Example 1 was measured:

[0051] Method: the dried fermentation product is dispersed in water, hydrochloric acid is added to adjust the pH value to 3.0 to reduce the viscosity, diatomaceous earth of 10% by mass of the dried fermentation product is added to adsorb impurities, and then filtered with 800 mesh filter cloth to remove bacteria, straw powder and organic carbon; sodium hydroxide solution is added to the filtrate to adjust the pH value to 7.0 and the temperature is raised to 90° C. to denature the protein, and then ultrafiltration is performed with a 0.45 μm hollow fiber membrane to remove the protein; the filtrate is statically adsorbed with a cationic resin to remove most of the metal ions and positively charged impurities; then activated carbon of 2% by mass of the filtrate is added for adsorption and decolorization; finally, 0.2 μm filter membrane is used to filter to obtain a sample to be tested; polyglutamic acid is used as a standard, and the content of polyglutamic acid in the sample to be tested is detected by high performance liquid chromatography, and the content of polyglutamic acid in the dried fermentation product is further converted, and the calculation results of the content and total amount of polyglutamic acid in the dried fermentation product in Example 1 and Comparative Example 1 are shown in Table 1.

[0052] Table 1 Polyglutamic acid content in the dried fermentation products of Example 1 and Comparative Example 1

[0053]

[0054]

[0055] It can be seen from the data in Table 1 that the addition of straw powder during the polyglutamic acid fermentation preparation process of the present invention can further increase the total amount of polyglutamic acid in the fermentation product.

[0056] The improvement effects of the soil conditioners prepared in Example 1 and Comparative Example 1 on saline-alkali soil were investigated:

[0057] The test site selected was a saline-alkali rice field in Heilongjiang with a salinity of 25%.

[0058] The soil conditioner prepared in Example 1 and Comparative Example 1 was respectively applied on the surface of the saline-alkali rice field at a rate of 550 kg / mu, and the soil on the surface of the saline-alkali rice field was mixed with the soil conditioner by rotary tillage of 15 cm. The saline-alkali rice field was left for 25 days, and then water was irrigated to a depth of about 10 cm on the surface of the field. The field was left for another 2 days to allow anions and cations in the soil to leach out, and the conductivity of the field surface water was measured. The field surface water was then drained, and water was continued to be irrigated to a depth of about 10 cm on the surface of the field. The conductivity of the field surface water was measured after being left for 2 days. This process was repeated until the conductivity of the field surface water was lower than 1.8 mS / cm, and then the water was drained to a depth of about 2 cm on the surface of the field. The rice was beaten, and rice seedlings (variety: Longjing 31 rice) were transplanted. The rice was managed according to conventional procedures until it matured.

[0059] The control group was treated with a soil conditioner mixed with an equal amount of 350 kg of decomposed straw and 120 kg of phosphogypsum, and the irrigation and drainage times were the same as those of the Example 1 group. The Comparative Example 2 group was treated with an equal amount of the soil conditioner of the Comparative Example 1 group and the irrigation and drainage times were the same as those of the Example 1 group.

[0060] The abundance of halophiles and alkaliphiles in each group was measured 25 days after the application of soil conditioners, the conductivity of field water from irrigation to transplanting, and the yield of each group were statistically analyzed. The results are shown in Tables 2 and 3.

[0061] Table 2 Abundance of soil microorganisms in the process of improving saline-alkali paddy fields in each experimental group

[0062]

[0063]

[0064] It can be seen from Table 2 that the abundance of halophilic bacteria in Example 1 is significantly higher than that in Comparative Examples 1 and 2, indicating that the soil conditioner prepared by co-fermentation of straw with Bacillus natto and Bacillus subtilis is more conducive to activating halophilic bacteria. The reason may be that more small molecule micro-carbon fertilizers are produced during the fermentation process.

[0065] Table 3 Field water conductivity and rice yield during the process of improving saline-alkali rice fields in each experimental group

[0066]

[0067] As can be seen from Table 3, the conductivity of Example 1 group, which is relatively high in polyglutamic acid content, is higher than that of Comparative Example 1 group after the first irrigation, indicating that the addition of polyglutamic acid helps the dissolution of harmful ions. Further irrigation and drainage, Example 1 group can make the field surface water conductivity lower than 1.8mS / cm after only two irrigations and drainages, reaching the planting standard. In terms of yield, after the soil improvement of Example 1 group, the per-acre yield of rice is equivalent to the yield of Longjing 31 planted in non-saline-alkali soil, indicating that the soil conditioner of the present invention has excellent improvement effect. Although the conductivity of Comparative Example 1 group dropped to below 1.8mS / cm after multiple irrigations and drainages, the rice yield was reduced due to the consumption of other beneficial nutrients by multiple irrigations and drainages, while the yield of Comparative Example 2 group and the control group, which exceeded the standard for salinity and alkali, was greatly reduced.

[0068] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a soil conditioner, characterized in that: The following steps are involved: Bacillus subtilis and Bacillus natto are used as fermentation strains to prepare polyglutamic acid, and after the fermentation is completed, sterilized straw powder is added for secondary fermentation, and the obtained fermentation product is dried and mixed with decomposed straw and phosphogypsum to prepare the soil conditioner.

2. The method for preparing a soil conditioner according to claim 1, characterized in that: The ratio of the inoculated live bacteria of the Bacillus subtilis and the Bacillus natto is 1-2:

1.

3. The method for preparing the soil conditioner according to claim 1, characterized in that: The fermentation culture medium used in the preparation of the polyglutamic acid contains 40-55 g / L of glucose, 10-12 g / L of yeast extract, 1.5-2.5 g / L of potassium monohydrogen phosphate, 0.2-0.3 g / L of magnesium sulfate and 35-45 g / L of sodium glutamate, and the pH value is 7-8.

4. The method for preparing a soil conditioner according to claim 1, characterized in that: The fermentation temperature is 35-45° C. and the fermentation time is 3-4 days; and / or the secondary fermentation temperature is 35-45° C. and the fermentation time is 3-5 days.

5. The method for preparing the soil conditioner according to claim 1, characterized in that: The particle size of the sterilized straw powder does not exceed 2 mm; and / or the dosage ratio of the sterilized straw powder to the fermentation medium is 150-200 g:1L.

6. The method for preparing a soil conditioner according to claim 1, characterized in that: The mass ratio of the dried fermentation product to the decomposed straw and the phosphogypsum is 0.5-1:20-30:8-10.

7. A soil conditioner prepared according to the method for preparing the soil conditioner according to any one of claims 1 to 6.

8. Use of the soil conditioner according to claim 7 in improving saline-alkali soil.

9. A method for applying the soil conditioner according to claim 7, characterized in that: The following steps are involved: The soil conditioner is spread on the surface of saline-alkali soil, rotary tillage is performed to mix the soil conditioner with the saline-alkali soil, and irrigation and drainage are performed after 20 to 30 days to remove free harmful ions to reduce salinity.

10. The method for applying the soil conditioner according to claim 9, characterized in that: For saline-alkali soil with a salinity of 5-20%, the application amount of the soil conditioner is 300-400 kg / mu, for saline-alkali soil with a salinity of 20-45%, the application amount of the soil conditioner is 400-1200 kg / mu, for saline-alkali soil with a salinity of 20-45%, the application amount of the soil conditioner is 1200-1600 kg / mu; and / or, the depth of the rotary tillage is 15-25 cm.

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