A soil acidification reducer and its preparation method for upland red soil in the south

Abstract

The present invention provides an acid-reducing soil conditioner for upland red soil in the south and a preparation method thereof, belonging to the technical field of soil conditioners. Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloliquefaciens are encapsulated to prepare bacterial microspheres, which are added to a gel formed by carboxymethyl chitosan and silk fibroin peptide to prepare a slow-release bacterial microsphere gel. The slow-release bacterial microsphere gel is uniformly mixed with porous silica loaded with basalt and biochar, and then dried to obtain the acid-reducing soil conditioner for upland red soil in the south. In addition to increasing the soil pH value, the acid-reducing soil conditioner for upland red soil in the south of the present invention can also loosen the soil to a certain extent, improve the soil aeration, and promote the absorption of water and nutrient elements by crops by improving the physical and chemical properties of the soil, so as to ensure the normal growth of crops, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioners, and particularly relates to a soil acidification reducing soil conditioner for upland red soil in the south and a preparation method thereof. Background Art

[0002] Soil acidification changes the soil microecological environment. Harmful microorganisms multiply in large numbers under acidic conditions, while the root systems of plants have weak stress resistance and are easily eroded by pathogens in such acidified soil. At the same time, it also leads to changes in the beneficial microorganism population in the soil. The individual growth of bacteria becomes smaller, and the growth and reproduction speed decreases. For example, the numbers of the main microbial groups such as Bacillus, Actinomycetes, Methanomonas and related fungi that decompose organic matter and its proteins decrease, affecting the benign cycle of nutrient elements and causing agricultural production reduction. In particular, the numbers of ammonifying bacteria and nitrogen-fixing bacteria in the soil are reduced, resulting in a decline in the ammonification and nitrification abilities of soil microorganisms, which is very unfavorable to crops.

[0003] In the upland red soil area of southern China, affected by environmental conditions such as high temperature and heavy rainfall and various factors of the soil parent material, nutrients such as phosphorus and potassium in the soil are easily lost through various ways such as migration and leaching, resulting in soil nutrient deficiency, strong acidity and poor structure. This has become one of the important reasons for low crop yields, poor quality and difficult soil tillage in this area, and this phenomenon is particularly prominent in upland red soil. According to statistics, the area of upland in the upland red soil area of southern China is about 200 million mu, but the yield per unit area is very low and the production efficiency is poor. Improving the yield and quality of upland crops and improving the physical and chemical properties of upland have become important guarantees for the sustainable development of agriculture and the increase of farmers' income in the southern region. To ensure the continuous high and stable yield and high quality of upland crops, from the current production reality and existing research results, it is first necessary to supplement or activate nutrient elements such as phosphorus, potassium and calcium in the soil and improve the physical and chemical properties of upland soil. Therefore, developing special conditioners with corresponding functions is of great significance for the high-quality and high-yield of upland red soil crops, the improvement and fertilization of upland red soil, etc.

[0004] Chinese Patent Application CN101445730A discloses a soil structure conditioner for red and yellow soil, Chinese Patent Application CN1304973A discloses a no-tillage soil conditioner, and Chinese Patent Application CN102911671A discloses a preparation method of a soil conditioner based on rice husk waste. These technologies are all effective for improving the structure of red soil, but have limited effects on nutrient expansion and soil acidification reduction of red soil. Summary of the Invention

[0005] The object of the present invention is to provide a soil acidification reducing soil conditioner for dry land in red soil in the south and its preparation method. Besides increasing the soil pH value, it can also loosen the soil to a certain extent, improve the soil aeration, and promote the absorption of water and nutrient elements by crops by improving the physical and chemical properties of the soil, thereby ensuring the normal growth of crops and having broad application prospects.

[0006] The technical solution of the present invention is realized as follows:

[0007] The present invention provides a preparation method of a soil acidification reducing soil conditioner for dry land in red soil in the south. Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloliquefaciens are embedded to prepare microbial microspheres, which are added to a gel formed by carboxymethyl chitosan and silk fibroin peptide to prepare a slow-release microbial microsphere gel, and then mixed evenly with porous silica loaded with basalt and biochar, and dried to obtain the soil acidification reducing soil conditioner for dry land in red soil in the south.

[0008] As a further improvement of the present invention, it includes the following steps:

[0009] S1. Preparation of microbial microspheres: Sodium alginate and an emulsifier are dissolved in water, the bacterial solutions of Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloliquefaciens are added, and the mixture is dropped into diesel for emulsification, then a calcium chloride solution is dropped, solidified at room temperature, centrifuged, washed, and dried to obtain microbial microspheres;

[0010] S2. Preparation of biochar: Straw is dried, crushed, and pyrolyzed and carbonized to obtain biochar;

[0011] S3. Preparation of modified porous silica: An alkyl orthosilicate is added to ethanol, hydrochloric acid, a pore-forming agent, and water are added, and the mixture is heated and stirred evenly, aged, dried, and calcined to obtain porous silica. The porous silica is added to water, dopamine hydrochloride and a catalyst are added, and the mixture is heated and stirred for reaction, filtered, washed, and dried to obtain modified porous silica;

[0012] S4. Preparation of porous silica loaded with basalt / biochar: Basalt is crushed and ball-milled to obtain basalt powder, which is mixed evenly with biochar, added to water, and modified porous silica is added, and the mixture is ultrasonically mixed evenly and dried to obtain porous silica loaded with basalt / biochar;

[0013] S5. Preparation of slow-release microbial microsphere gel: Carboxymethyl chitosan is dissolved in water, EDC is added, and the mixture is stirred evenly, then silk fibroin peptide and microbial microspheres are added, and the mixture is stirred for reaction to obtain a slow-release microbial microsphere gel;

[0014] S6. Preparation of the soil acidification reducing soil conditioner for dry land in red soil in the south: The slow-release microbial microsphere gel and the porous silica loaded with basalt / biochar are mixed evenly and dried to obtain the soil acidification reducing soil conditioner for dry land in red soil in the south.

[0015] As a further improvement of the present invention, in step S1, the mass ratio of sodium alginate, emulsifier, Bacillus subtilis bacterial solution, Bacillus licheniformis bacterial solution, Bacillus amyloliquefaciens bacterial solution, and calcium chloride is 15-20:1-2:4-6:5-7:2-4:0.5-1. The emulsifier is selected from at least one of Tween-20, Tween-40, Tween-60, Tween-80, and Tween-85. The bacterial content of the Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloliquefaciens bacterial solutions is 10 11 -10 12 cfu / mL.

[0016] As a further improvement of the present invention, the conditions for pyrolytic carbonization in step S2 are as follows: under the protection of an inert gas, maintain at 300-400 °C for 1-2 h, and then heat up to 600-800 °C and maintain for 2-4 h.

[0017] As a further improvement of the present invention, in step S3, the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate. The mass ratio of the alkyl orthosilicate, ethanol, hydrochloric acid, pore-forming agent, and water is 12-15:70-100:3-5:1-2:10-15. The temperature for heating and stirring to mix evenly is 40-50 °C, and the time is 5-7 h. The aging time is 20-24 h. The calcination temperature is 400-500 °C, and the time is 1-2 h. The mass ratio of the porous silica, dopamine hydrochloride, and catalyst is 10-12:8-10:1-2. The catalyst is a Tris-HCl solution with a pH of 8.5-9.5. The temperature for heating and stirring the reaction is 45-55 °C, and the time is 2-4 h. The pore-forming agent is cetyltrimethylammonium chloride or cetyltrimethylammonium bromide.

[0018] As a further improvement of the present invention, in step S4, the mass ratio of basalt, biochar, and modified porous silica is 3-4:2-3:10. The power for ultrasonic mixing to be uniform is 1000-2000 W, and the time is 10-20 min.

[0019] As a further improvement of the present invention, in step S5, the mass ratio of carboxymethyl chitosan, EDC, silk fibroin peptide, and bacterial microspheres is 8-10:1-2:4-6:5-7. The time for stirring and mixing is 10-20 min, and the time for the stirring reaction is 7-10 h.

[0020] As a further improvement of the present invention, in step S6, the mass ratio of the sustained-release bacterial microsphere gel and the porous silica loaded with basalt / biochar is 15-20:4-7.

[0021] The present invention further protects a soil acidification reducer for upland red soil in the south prepared by the above preparation method.

[0022] The present invention further protects the application of the above-mentioned acid-reducing soil conditioner for upland red soil in the south in reducing soil acidity, improving soil fertility, and reducing soil heavy metal content.

[0023] The present invention has the following beneficial effects:

[0024] Soil acidification mainly refers to the increase in the amounts of H + and Al 3+ in the soil, resulting in the depletion of the soil cation pool. This not only causes soil nutrient loss and deterioration of soil physical and chemical properties, but also increases the activity of aluminum ions and heavy metals and reduces the activity of soil microorganisms, thereby leading to a reduction in crop yields and even causing toxic effects on crops.

[0025] The biochar of the present invention is a solid material produced by straw pyrolysis, containing a large specific surface area, rich alkaline substances and functional groups. It has a strong adsorption and fixation ability for Al 3+ and helps with soil improvement, ecological restoration and gas emission reduction. It affects soil physical and chemical properties, heavy metal content, crop growth and development, and soil microbial communities through its own physical and chemical properties. The decarboxylation of the attached organic anions consumes protons and can also associate with H + to increase the soil pH, effectively alleviating soil acidification and promoting crop growth. Silicate rocks such as basalt produce alkaline substances during weathering, reducing soil acidification caused by overuse of ammonium fertilizers, elemental sulfur fertilizers, urea and repeated harvesting of crops, and improving soil organic carbon sequestration by increasing the organic carbon input of roots and mycorrhizal fungi, which helps to restore soil health. After the porous silica material prepared by sol-gel reaction is surface-modified with polydopamine, it has a good adsorption effect on biochar and basalt powder. After entering the pores, it fills the pores and adsorbs on the silica surface, promoting soil remediation. In addition, the polyhydroxy and amino structures of polydopamine can help to fix soil heavy metal pollution ions, prevent plants from adsorbing and fixing them in the plants, and reduce the heavy metal load of plants, which is more environmentally friendly.

[0026] Bacillus amyloliquefaciens can effectively control pathogenic bacteria and reduce the crop disease infection rate. In addition, by inoculating Bacillus licheniformis, acidic soil can be repaired. When they absorb nitrate nitrogen, they release OH -To maintain charge balance, alleviate soil acidification, and improve soil productivity and crop yields. The Bacillus subtilis bacterium agent can secrete colloidal substances to bond soil particles, enhancing its air permeability and water retention. There is also a synergistic effect among the three strains of bacteria. The Bacillus bacterium fertilizer can increase the soil pH and organic matter content, significantly improving the soil microenvironment. Through sodium alginate embedding and adding to the hydrogel of carboxylated chitosan and silk fibroin peptide, on the one hand, chitosan and sodium alginate can amplify the functional groups of biochar, improving the acid buffering capacity. On the other hand, the carboxylated hydrogel will shrink acidically in acidic soil, inhibiting the release of the bacterium microspheres. When the soil pH value increases, the carboxylated chitosan slowly swells and slowly releases the bacterium microspheres. After degrading the shell layer, the content of Bacillus bacteria is released into the soil, further playing a role in regulating the physical and chemical properties of the soil. Moreover, the oxygen-containing functional groups (such as carboxyl groups) of chitosan can form more stable aluminum complexes, significantly enhancing the stability of the soil microstructure and reducing aluminum toxicity.

[0027] In addition to increasing the soil pH value, the acid-reducing soil conditioner for upland red soil in the south of this invention can also loosen the soil to a certain extent, improve the soil aeration, and promote the absorption of water and nutrient elements by crops by improving the physical and chemical properties of the soil, thus ensuring the normal growth of crops and having broad application prospects. Specific embodiments

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Bacillus subtilis, 20 billion cfu / g; Bacillus licheniformis, 20 billion cfu / g; Bacillus amyloliquefaciens, 20 billion cfu / g. The bacteria content in the bacterial liquid is 10^11 - 10^12 cfu / mL.

[0030] EDC, 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

[0031] Example 1

[0032] This example provides a preparation method for an acid-reducing soil conditioner for upland red soil in the south, including the following steps:

[0033] S1. Preparation of Bacterial Microspheres: Dissolve 15 g of sodium alginate and 1 g of Tween-20 in 200 mL of water, add 4 g of Bacillus subtilis bacterial solution, 5 g of Bacillus licheniformis bacterial solution, and 2 g of Bacillus amyloliquefaciens bacterial solution, dropwise add them into 500 mL of diesel oil, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of calcium chloride solution containing 0.5 g, solidify at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres;

[0034] S2. Preparation of Biochar: Dry and crush the straw, under nitrogen protection, maintain at 300 °C for 1 h, heat up to 600 °C and maintain for 4 h to obtain biochar;

[0035] S3. Preparation of Modified Porous Silica: Add 12 g of methyl orthosilicate to 70 g of ethanol, add 3 g of hydrochloric acid, 1 g of cetyltrimethylammonium chloride, and 10 g of water, heat to 40 °C, stir and mix for 5 h, age for 20 h, dry, calcine at 400 °C for 1 h to obtain porous silica. Add 10 g of porous silica to 200 mL of water, add 8 g of dopamine hydrochloride and 1 g of catalyst, heat to 45 °C, stir and react for 4 h, filter, wash, and dry to obtain modified porous silica;

[0036] The catalyst is a Tris-HCl solution with a pH of 8.5;

[0037] S4. Preparation of Porous Silica Loaded with Basalt / Biochar: Crush 3 g of basalt, ball mill for 1 h to obtain basalt powder, mix it evenly with 2 g of biochar, add it to 100 mL of water, add 10 g of modified porous silica, ultrasonically mix at 1000 W for 10 min, and dry to obtain porous silica loaded with basalt / biochar;

[0038] S5. Preparation of Sustained-Release Bacterial Microsphere Gel: Dissolve 8 g of carboxymethyl chitosan in 150 mL of water, add 1 g of EDC, stir and mix for 10 min, add 4 g of silk fibroin peptide and 5 g of bacterial microspheres, stir and react for 7 h to obtain sustained-release bacterial microsphere gel;

[0039] S6. Preparation of Acid-Reducing Soil Amendment for Southern Red Soil Dryland: Stir and mix 15 g of sustained-release bacterial microsphere gel and 4 g of porous silica loaded with basalt / biochar for 15 min, and dry to obtain the acid-reducing soil amendment for southern red soil dryland.

[0040] Example 2

[0041] This example provides a preparation method of an acid-reducing soil amendment for southern red soil dryland, including the following steps:

[0042] S1. Preparation of Bacterial Microspheres: Dissolve 20 g of sodium alginate and 2 g of Tween-40 in 200 mL of water, add 6 g of Bacillus subtilis bacterial solution, 7 g of Bacillus licheniformis bacterial solution, and 4 g of Bacillus amyloliquefaciens bacterial solution, dropwise add it into 500 mL of diesel oil, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 1 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres;

[0043] S2. Preparation of Biochar: Dry and crush the straw, and under nitrogen protection, maintain it at 400 °C for 2 h, then raise the temperature to 800 °C and maintain it for 2 h to obtain biochar;

[0044] S3. Preparation of Modified Porous Silica: Add 15 g of tetraethyl orthosilicate to 100 g of ethanol, add 5 g of hydrochloric acid, 2 g of cetyltrimethylammonium bromide, and 15 g of water, heat to 50 °C, stir and mix for 7 h, age for 24 h, dry, and calcine at 500 °C for 2 h to obtain porous silica. Add 12 g of porous silica to 200 mL of water, add 10 g of dopamine hydrochloride and 2 g of catalyst, heat to 55 °C, stir and react for 2 h, filter, wash, and dry to obtain modified porous silica;

[0045] The catalyst is a Tris-HCl solution with a pH of 9.5;

[0046] S4. Preparation of Porous Silica Loaded with Basalt / Biochar: Crush 4 g of basalt, ball mill for 1 h to obtain basalt powder, mix it evenly with 3 g of biochar, add it to 100 mL of water, add 10 g of modified porous silica, ultrasonically mix at 2000 W for 20 min, and dry to obtain porous silica loaded with basalt / biochar;

[0047] S5. Preparation of Sustained-Release Bacterial Microsphere Gel: Dissolve 10 g of carboxymethyl chitosan in 150 mL of water, add 2 g of EDC, stir and mix for 20 min, add 6 g of silk fibroin peptide and 7 g of bacterial microspheres, stir and react for 10 h to obtain sustained-release bacterial microsphere gel;

[0048] S6. Preparation of Acid-Reducing Soil Conditioner for Southern Red Soil Dryland: Stir and mix 20 g of sustained-release bacterial microsphere gel and 7 g of porous silica loaded with basalt / biochar for 15 min, and dry to obtain an acid-reducing soil conditioner for southern red soil dryland.

[0049] Example 3

[0050] This example provides a preparation method of an acid-reducing soil conditioner for southern red soil dryland, including the following steps:

[0051] S1. Preparation of bacterial microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 5 g of Bacillus subtilis bacterial solution, 6 g of Bacillus licheniformis bacterial solution, and 3 g of Bacillus amyloliquefaciens bacterial solution, and dropwise add them into 500 mL of diesel. Emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres;

[0052] S2. Preparation of biochar: Dry and crush the straw, and under nitrogen protection, maintain it at 350 °C for 1.5 h, then raise the temperature to 700 °C and maintain it for 3 h to obtain biochar;

[0053] S3. Preparation of modified porous silica: Add 13 g of tetraethyl orthosilicate to 85 g of ethanol, add 4 g of hydrochloric acid, 1.5 g of cetyltrimethylammonium bromide, and 12 g of water, heat to 45 °C, stir and mix for 6 h, age for 22 h, dry, and calcine at 450 °C for 1.5 h to obtain porous silica. Add 11 g of porous silica to 200 mL of water, add 9 g of dopamine hydrochloride and 1.5 g of catalyst, heat to 50 °C, stir and react for 3 h, filter, wash, and dry to obtain modified porous silica;

[0054] The catalyst is a Tris-HCl solution with a pH of 9;

[0055] S4. Preparation of porous silica loaded with basalt / biochar: Crush 3.5 g of basalt and ball-mill it to obtain basalt powder, mix it evenly with 2.5 g of biochar, add it to 100 mL of water, add 10 g of modified porous silica, and ultrasonically mix at 1500 W for 15 min, then dry to obtain porous silica loaded with basalt / biochar;

[0056] S5. Preparation of sustained-release bacterial microsphere gel: Dissolve 9 g of carboxymethyl chitosan in 150 mL of water, add 1.5 g of EDC, stir and mix for 15 min, add 5 g of silk fibroin peptide and 6 g of bacterial microspheres, and stir and react for 8 h to obtain sustained-release bacterial microsphere gel;

[0057] S6. Preparation of acid-reducing soil conditioner for red soil dryland in the south: Stir and mix 17 g of sustained-release bacterial microsphere gel and 5 g of porous silica loaded with basalt / biochar for 15 min, then dry to obtain the acid-reducing soil conditioner for red soil dryland in the south.

[0058] Comparative Example 1

[0059] Compared with Example 3, the difference is that the Bacillus subtilis bacterial solution was not added in step S1.

[0060] Specifically as follows:

[0061] S1. Preparation of bacterial microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 6 g of Bacillus licheniformis bacterial solution and 3 g of Bacillus amyloliquefaciens bacterial solution, dropwise add them into 500 mL of diesel, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres.

[0062] Comparative Example 2

[0063] Compared with Example 3, the difference lies in that the Bacillus licheniformis bacterial solution was not added in step S1.

[0064] Specifically as follows:

[0065] S1. Preparation of bacterial microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 5 g of Bacillus subtilis bacterial solution and 3 g of Bacillus amyloliquefaciens bacterial solution, dropwise add them into 500 mL of diesel, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres.

[0066] Comparative Example 3

[0067] Compared with Example 3, the difference lies in that the Bacillus amyloliquefaciens bacterial solution was not added in step S1.

[0068] Specifically as follows:

[0069] S1. Preparation of bacterial microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 5 g of Bacillus subtilis bacterial solution and 6 g of Bacillus licheniformis bacterial solution, dropwise add them into 500 mL of diesel, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres.

[0070] Comparative Example 4

[0071] Compared with Example 3, the difference lies in that polydopamine modification was not carried out in step S3.

[0072] Specifically as follows:

[0073] S3. Preparation of modified porous silica: Add 13 g of tetraethyl orthosilicate to 85 g of ethanol, add 4 g of hydrochloric acid, 1.5 g of cetyltrimethylammonium bromide and 12 g of water, heat to 45 °C, stir and mix for 6 h, age for 22 h, dry, and calcine at 450 °C for 1.5 h to obtain porous silica.

[0074] Comparative Example 5

[0075] Compared with Example 3, the difference is that biochar is not added in step S4.

[0076] Specifically as follows:

[0077] S4. Preparation of basalt-loaded porous silica: Crush 6 g of basalt, ball-mill to obtain basalt powder, add it to 100 mL of water, add 10 g of modified porous silica, mix ultrasonically at 1500 W for 15 min, and dry to obtain basalt-loaded porous silica.

[0078] Comparative Example 6

[0079] Compared with Example 3, the difference is that basalt is not added in step S4.

[0080] Specifically as follows:

[0081] S4. Preparation of biochar-loaded porous silica: Add 6 g of biochar to 100 mL of water, add 10 g of modified porous silica, mix ultrasonically at 1500 W for 15 min, and dry to obtain biochar-loaded porous silica.

[0082] Comparative Example 7

[0083] Compared with Example 3, the difference is that step S4 is not carried out.

[0084] Specifically as follows:

[0085] S1. Preparation of bacterial microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 5 g of Bacillus subtilis bacterial solution, 6 g of Bacillus licheniformis bacterial solution, and 3 g of Bacillus amyloliquefaciens bacterial solution, dropwise add it to 500 mL of diesel, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacterial microspheres;

[0086] S2. Preparation of biochar: Dry and crush the straw, and under nitrogen protection, maintain it at 350 °C for 1.5 h, then heat it to 700 °C and maintain it for 3 h to obtain biochar;

[0087] S3. Preparation of modified porous silica: Add 13 g of tetraethyl orthosilicate to 85 g of ethanol, add 4 g of hydrochloric acid, 1.5 g of cetyltrimethylammonium bromide, and 12 g of water, heat to 45 °C, stir and mix for 6 h, age for 22 h, dry, and calcine at 450 °C for 1.5 h to obtain porous silica. Add 11 g of porous silica to 200 mL of water, add 9 g of dopamine hydrochloride and 1.5 g of catalyst, heat to 50 °C, stir and react for 3 h, filter, wash, and dry to obtain modified porous silica;

[0088] The Tris-HCl solution with a pH of 9 of the catalyst;

[0089] S4. Preparation of the slow-release bacteria microsphere gel: Dissolve 9 g of carboxymethyl chitosan in 150 mL of water, add 1.5 g of EDC, stir and mix for 15 min, add 5 g of silk fibroin peptide and 6 g of bacteria microspheres, and stir and react for 8 h to obtain the slow-release bacteria microsphere gel;

[0090] S5. Preparation of the acid-reducing soil conditioner for upland red soil in the south: Stir and mix 17 g of the slow-release bacteria microsphere gel and 5 g of modified porous silica for 15 min, and dry to obtain the acid-reducing soil conditioner for upland red soil in the south.

[0091] Comparative Example 8

[0092] Compared with Example 3, the difference is that no bacteria microspheres are added in step S5.

[0093] Specifically as follows:

[0094] S1. Preparation of biochar: Dry and crush the straw, and under nitrogen protection, maintain it at 350 °C for 1.5 h, then raise the temperature to 700 °C and maintain it for 3 h to obtain biochar;

[0095] S2. Preparation of modified porous silica: Add 13 g of tetraethyl orthosilicate to 85 g of ethanol, add 4 g of hydrochloric acid, 1.5 g of cetyltrimethylammonium bromide and 12 g of water, heat to 45 °C, stir and mix for 6 h, age for 22 h, dry, and calcine at 450 °C for 1.5 h to obtain porous silica. Add 11 g of porous silica to 200 mL of water, add 9 g of dopamine hydrochloride and 1.5 g of the catalyst, heat to 50 °C, stir and react for 3 h, filter, wash, and dry to obtain modified porous silica;

[0096] The Tris-HCl solution with a pH of 9 of the catalyst;

[0097] S3. Preparation of porous silica loaded with basalt / biochar: Crush 3.5 g of basalt and ball-mill it to obtain basalt powder, mix it evenly with 2.5 g of biochar, add it to 100 mL of water, add 10 g of modified porous silica, and ultrasonically mix at 1500 W for 15 min, and dry to obtain porous silica loaded with basalt / biochar;

[0098] S4. Preparation of the gel: Dissolve 9 g of carboxymethyl chitosan in 150 mL of water, add 1.5 g of EDC, stir and mix for 15 min, add 5 g of silk fibroin peptide, and stir and react for 8 h to obtain the gel;

[0099] S5. Preparation of acid-reducing soil conditioner for upland red soil in southern China: Mix 17 g of gel and 5 g of porous silica loaded with basalt / biochar and stir for 15 min, then dry to obtain the acid-reducing soil conditioner for upland red soil in southern China.

[0100] Comparative Example 9

[0101] Compared with Example 3, the difference lies in that no slow-release bacteria microsphere gel was added in step S6.

[0102] Specifically as follows:

[0103] S1. Preparation of biochar: Dry and crush the straw, and under nitrogen protection, maintain at 350 °C for 1.5 h, then raise the temperature to 700 °C and maintain for 3 h to obtain biochar;

[0104] S2. Preparation of modified porous silica: Add 13 g of tetraethyl orthosilicate to 85 g of ethanol, add 4 g of hydrochloric acid, 1.5 g of cetyltrimethylammonium bromide and 12 g of water, heat to 45 °C, stir and mix for 6 h, age for 22 h, dry, and calcine at 450 °C for 1.5 h to obtain porous silica. Add 11 g of porous silica to 200 mL of water, add 9 g of dopamine hydrochloride and 1.5 g of catalyst, heat to 50 °C, stir and react for 3 h, filter, wash, and dry to obtain modified porous silica;

[0105] The catalyst is a Tris-HCl solution with a pH of 9;

[0106] S3. Preparation of porous silica loaded with basalt / biochar: Crush 3.5 g of basalt, ball-mill to obtain basalt powder, mix evenly with 2.5 g of biochar, add to 100 mL of water, add 10 g of modified porous silica, ultrasonically mix at 1500 W for 15 min, and dry to obtain porous silica loaded with basalt / biochar, which is the acid-reducing soil conditioner for upland red soil in southern China.

[0107] Comparative Example 10

[0108] Compared with Example 3, the difference lies in that no porous silica loaded with basalt / biochar was added in step S6.

[0109] Specifically as follows:

[0110] S1. Preparation of bacteria microspheres: Dissolve 17 g of sodium alginate and 1.2 g of Tween-85 in 200 mL of water, add 5 g of Bacillus subtilis bacterial solution, 6 g of Bacillus licheniformis bacterial solution, and 3 g of Bacillus amyloliquefaciens bacterial solution, dropwise add to 500 mL of diesel oil, emulsify at 8000 r / min for 15 min, dropwise add 20 mL of a calcium chloride solution containing 0.7 g, cure at room temperature for 30 min, centrifuge, wash, and dry to obtain bacteria microspheres;

[0111] S2. Preparation of slow-release bacterial microsphere gel: Dissolve 9 g of carboxymethyl chitosan in 150 mL of water, add 1.5 g of EDC, stir and mix for 15 min, add 5 g of silk fibroin peptide and 6 g of bacterial microspheres, stir and react for 8 h to obtain the slow-release bacterial microsphere gel, which is the acid-reducing soil conditioner for upland red soil in the south.

[0112] Test Example 1

[0113] The test soil is the upland soil in the typical red soil hilly areas of Dongxiang County and Yujiang County, Jiangxi Province. Collect the surface soil (0-20 cm) of paddy fields in this area. Pass through a 2 mm sieve and remove sundries such as plant roots and small stones.

[0114] Rice variety: Gan Zaoxian 49.

[0115] Test object: The acid-reducing soil conditioner for upland red soil in the south of Examples 1-3 and Comparative Examples 1-10.

[0116] Test method: Each pot of upland soil weighs 1500 g. Mix 10 g of the acid-reducing soil conditioner for upland red soil in the south into each pot, and mix an equal amount of the same kind of upland soil in the blank group. Mix evenly. Plant 5 rice plants in each pot and sample (soil, plant) for determination after 50 days.

[0117] The results are shown in Table 1 and Table 2.

[0118] Table 1 Physical and chemical properties of soil

[0119]

[0120] As can be seen from the above table, the acid-reducing soil conditioner for upland red soil in the south prepared by the present invention can significantly improve soil fertility, reduce the heavy metal content in the soil, and improve the soil structure.

[0121] Table 2 Nutrient content in rice plants

[0122]

[0123] As can be seen from the above table, the acid-reducing soil conditioner for upland red soil in the south prepared in Examples 1-3 of the present invention can significantly promote the absorption of nitrogen, phosphorus and potassium by plants.

[0124] In Comparative Examples 1-3 compared with Example 3, the Bacillus subtilis bacterial liquid, Bacillus licheniformis bacterial liquid or Bacillus amyloliquefaciens bacterial liquid was not added respectively. In Comparative Example 8 compared with Example 3, the bacterial microspheres were not added in step S5. The pH value decreased, the organic matter, total nitrogen, available phosphorus and available potassium decreased significantly, the heavy metal ion content increased, and the N, P, and K contents in the plants decreased. Bacillus amyloliquefaciens can effectively prevent pathogenic bacteria and reduce the crop disease infection rate. In addition, the acidic soil can be repaired by inoculating Bacillus licheniformis, and OH will be released when they absorb nitrate nitrogen. -To maintain charge balance, alleviate soil acidification, and improve soil productivity and crop yields. The Bacillus subtilis bacterial agent can secrete colloidal substances to bond soil particles, enhancing their air permeability and water retention. There is also a synergistic effect among the three strains. The Bacillus bacterial fertilizer can increase the soil pH and organic matter content, significantly improving the soil microenvironment.

[0125] Compared with Example 3, in Comparative Example 4, polydopamine modification was not carried out in step S3. The pH value decreased and the heavy metal ion content increased. After the porous silica material prepared by sol-gel reaction was surface-modified with polydopamine, it had a good adsorption effect on biochar and basalt powder. After entering the pores, it filled the pores and adsorbed on the silica surface, promoting soil remediation. In addition, the polyhydroxy and amino structures of polydopamine can help fix heavy metal pollution ions in the soil, prevent plants from adsorbing and fixing them in the plant body, reduce the heavy metal load of plants, and are more environmentally friendly.

[0126] Compared with Example 3, in Comparative Example 5, biochar was not added in step S4. Compared with Example 3, in Comparative Example 6, basalt was not added in step S4. Compared with Example 3, in Comparative Example 7, step S4 was not carried out. Compared with Example 3, in Comparative Example 10, porous silica loaded with basalt / biochar was not added in step S6. The pH value decreased, the soil porosity decreased, and the heavy metal content increased. The biochar of the present invention is a solid material produced by straw pyrolysis, containing a large specific surface area, abundant alkaline substances and functional groups, and has a strong adsorption and fixation ability for Al 3+ and helps with soil improvement, ecological restoration and gas emission reduction. It affects soil physical and chemical properties, heavy metal content, crop growth and development, and soil microbial communities through its own physical and chemical properties. The attached organic anions decarboxylate to consume protons and can also associate with H + to increase the soil pH through an association reaction, effectively alleviating soil acidification and promoting crop growth. Silicate rocks such as basalt produce alkaline substances during weathering, reduce soil acidification caused by overuse of ammonium fertilizers, elemental sulfur fertilizers, urea and repeated harvesting of crops, and improve soil organic carbon sequestration by increasing the organic carbon input of roots and mycorrhizal fungi, helping to restore soil health.

[0127] Comparative Example 9 is compared with Example 3. In step S6, the slow-release bacterial microsphere gel is not added. The pH value decreases, the soil porosity decreases, and the contents of N, P, and K in the plants decrease. Through sodium alginate embedding and adding into the hydrogel of carboxylated chitosan and silk fibroin peptide, on the one hand, chitosan and sodium alginate can amplify the functional groups of biochar and improve the acid buffering capacity. On the other hand, the carboxylated hydrogel will shrink acidically in acidic soil, inhibiting the release of bacterial microspheres. When the soil pH value increases, the carboxylated chitosan slowly swells and slowly releases the bacterial microspheres. After the shell layer is degraded, the content Bacillus is released into the soil, further playing a role in regulating the physical and chemical properties of the soil. Moreover, the oxygen-containing functional groups (such as carboxyl groups) of chitosan can form more stable aluminum complexes, significantly enhancing the stability of the soil microstructure and reducing aluminum toxicity.

[0128] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a soil conditioner for reducing acidity in red soil dryland in the south, characterized in that: The following steps are involved: S1. Preparation of bacterial microspheres: Sodium alginate and an emulsifier were dissolved in water, Bacillus subtilis, Bacillus licheniformis and Bacillus amyloliquefaciens were added dropwise to diesel, emulsified, calcium chloride solution was added dropwise, solidified at room temperature, centrifuged, washed and dried to obtain bacterial microspheres; S2. Preparation of biochar: drying, crushing, pyrolyzing and carbonizing the straw to obtain biochar; S3. Preparation of modified porous silica: adding alkyl orthosilicate to ethanol, adding hydrochloric acid, a porogen and water, heating and stirring to mix evenly, aging, drying, calcining to obtain porous silica, adding porous silica to water, adding dopamine hydrochloride and a catalyst, heating and stirring to react, filtering, washing, and drying to obtain modified porous silica; S4. Preparation of porous silica loaded with basalt / biochar: crushing basalt, ball milling to obtain basalt powder, mixing it with biochar, adding it to water, adding modified porous silica, ultrasonically mixing it, and drying it to obtain porous silica loaded with basalt / biochar; S5. Preparation of sustained-release bacterial microsphere gel: dissolving carboxymethyl chitosan in water, adding EDC, stirring and mixing, adding silk fibroin peptide and bacterial microspheres, stirring and reacting, and preparing sustained-release bacterial microsphere gel; S6. Preparation of acid-reducing soil conditioner for dry red soil in southern China: The slow-release bacterial microsphere gel and porous silica loaded with basalt / biochar were uniformly mixed and dried to prepare the acid-reducing soil conditioner for dry red soil in southern China.

2. The preparation method according to claim 1, characterized in that: The mass ratio of sodium alginate, emulsifier, Bacillus subtilis solution, Bacillus licheniformis solution, Bacillus amyloliquefaciens solution and calcium chloride in step S1 is 15-20:1-2:4-6:5-7:2-4:0.5-1, the emulsifier is selected from at least one of Tween-20, Tween-40, Tween-60, Tween-80 and Tween-85, the bacterial content of Bacillus subtilis, Bacillus licheniformis and Bacillus amyloliquefaciens solution is 10 11 -10 12 cfu / mL.

3. The preparation method according to claim 1, characterized in that: The pyrolysis carbonization conditions in step S2 are: maintaining at 300-400° C. for 1-2 hours under inert gas protection, and then heating to 600-800° C. for 2-4 hours.

4. The preparation method according to claim 1, characterized in that: The alkyl orthosilicate in step S3 is methyl orthosilicate or ethyl orthosilicate, the mass ratio of the alkyl orthosilicate, ethanol, hydrochloric acid, porogen and water is 12-15:70-100:3-5:1-2:10-15, the temperature of the heating and stirring mixing is 40-50°C, the time is 5-7h, the aging time is 20-24h, the calcination temperature is 400-500°C, the time is 1-2h, the mass ratio of the porous silica, dopamine hydrochloride and the catalyst is 10-12:8-10:1-2, the catalyst is a Tris-HCl solution with a pH of 8.5-9.5, the temperature of the heating and stirring reaction is 45-55°C, the time is 2-4h, and the porogen is hexadecyltrimethylammonium chloride or hexadecyltrimethylammonium bromide.

5. The preparation method according to claim 1, characterized in that: In step S4, the mass ratio of basalt, biochar and modified porous silica is 3-4:2-3:10, and the power of ultrasonic mixing is 1000-2000W, and the time is 10-20min.

6. The preparation method according to claim 1, characterized in that: In step S5, the mass ratio of carboxymethyl chitosan, EDC, silk fibroin peptide and bacterial microspheres is 8-10:1-2:4-6:5-7, the stirring and mixing time is 10-20 minutes, and the stirring reaction time is 7-10 hours.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the sustained-release bacteria microsphere gel to the porous silica loaded with basalt / biochar in step S6 is 15-20:4-7.

8. A southern red soil dryland acid-reducing soil conditioner prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the southern red soil dryland acid-reducing soil conditioner as claimed in claim 8 in reducing soil acidity, improving soil fertility and reducing soil heavy metal content.

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