Compound microbial fertilizer capable of efficiently reducing chromium pollution of rice and preparation process of compound microbial fertilizer

Abstract

The invention discloses a compound microbial fertilizer capable of efficiently reducing chromium pollution of rice and a preparation process of the compound microbial fertilizer, and belongs to the technical field of microbial fertilizer preparation. The preparation method comprises the following steps: stirring and mixing the compound fertilizer and the modified biochar, drying and crushing. The biochar is modified, so that hexavalent chromium ions in soil can be better reduced into trivalent chromium precipitates and adsorbed in a porous structure of the biochar, and the possibility that trivalent chromium is oxidized into hexavalent chromium again is reduced. By adding sodium silicate nonahydrate, the stress resistance of plants is enhanced, and the chromium ion absorption of rice is reduced. The complex microbial inoculants are added, and the fertilizer is wrapped by the biochar, so that too fast degradation of nutrients is avoided. The compound microbial fertilizer has the functions of efficiently reducing chromium pollution of rice and slowly releasing nutrition.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial fertilizer preparation, and particularly relates to a composite microbial fertilizer for efficiently reducing chromium pollution in rice and a preparation process thereof. Background Art

[0002] China is a major agricultural production country, and rice is the main food crop in China. Soil is the core component of the ecological environment, the main source of plant growth and nutrient acquisition, and also the basis for human survival and development, playing an important role in the ecosystem. High concentrations of chromium in the soil have a certain impact on rice growth, inhibiting rice seed germination, seedling growth, and root development. At the same time, as the chromium content increases, the root length of rice significantly shortens, the number of roots significantly decreases, the plant membrane structure is severely damaged, resulting in cell metabolic disorders, a decrease in the content of leaf pigments, soluble sugars, and soluble proteins, a decrease in the total number of main stem leaves of rice, dwarfing and wilting of plants, a delay in the heading stage, inhibiting the normal growth and development of plants, and a significant decrease in yield. After heavy metal chromium enters the soil, it will damage the farmland soil environment, reduce the yield and quality of crops, and even affect China's food security. Through the food chain, it accumulates in animals and plants, endangering human health.

[0003] Patent CN111436342B discloses a method for coupling biochar and water management to synergistically reduce chromium absorption during rice cultivation, including: 1) biochar preparation; 2) applying the biochar to chromium-contaminated soil, mixing evenly, and then planting rice; 3) adopting the method of flooding at key growth stages for water management during rice growth. The method of coupling biochar and water management to reduce chromium absorption in rice of the present invention can play a synergistic effect, effectively solve the problem of rice production in chromium-contaminated farmland, effectively reduce the chromium content in the rice produced in chromium-contaminated farmland. After measurement, the chromium content in the rice planted by the method of the present invention meets the national food safety standard (rice chromium < 1.0 mg / kg), providing an effective way for the safe utilization of chromium-contaminated farmland.

[0004] Patent CN114031461B discloses an organosilicon fertilizer for reducing the chromium and arsenic content in rice, and its preparation method and application. The organosilicon fertilizer includes: 10-20 parts of wine lees, 35-50 parts of conditioners, 8-12 parts of humic acid, 4-6 parts of enzyme bacteria, 10-15 parts of diatomaceous earth, 5-15 parts of nanosilicon, and 2-3 parts of potassium chloride. The raw material components are widely available, low cost, simple preparation method, good repair effect on heavy metal contaminated soil, can effectively reduce the biological effectiveness of chromium and arsenic in contaminated soil, and can also improve soil structure, have fertilization and yield-increasing effects, and achieve the effect of repair and fertilization in one; the method for reducing the chromium and arsenic content in rice provided by the present invention, by applying organosilicon fertilizer, combined with water management measures, simple technology, strong operability, low energy consumption, green environmental protection advantages, can be extended to other farmland planting with slightly excessive chromium and arsenic.

[0005] Although the above two patents have a certain effect on reducing the chromium content in rice, the principle is to convert hexavalent chromium with high bioavailability in the soil into trivalent chromium with low bioavailability. In soil with heavy chromium pollution, trivalent chromium and hexavalent chromium will convert into each other, and both methods require water management, which is relatively cumbersome.

[0006] Therefore, it is of great significance to develop a fertilizer that can be applied once without topdressing or with less topdressing and can treat heavily chromium-contaminated soil. Summary of the invention

[0007] In view of the deficiencies of the prior art, the present invention modifies biochar so that it can better reduce hexavalent chromium ions in the soil into trivalent chromium precipitates and adsorb them in its porous structure, reducing the possibility of trivalent chromium being oxidized to hexavalent chromium again. By adding sodium silicate nonahydrate, the plant's ability to resist stress is enhanced and the absorption of chromium ions by rice is reduced. By adding a composite bacterial agent and using biochar to wrap fertilizers to avoid excessive nutrient degradation, the technical problems raised in the background technology are solved. Specifically, the technical solution of the present invention includes the following contents:

[0008] A composite microbial fertilizer for efficiently reducing chromium pollution in rice, the composite microbial fertilizer being composed of modified biochar and composite fertilizer in a mass ratio of 3:10.

[0009] Furthermore, the method for preparing the modified biochar comprises the following steps:

[0010] Dilute sulfuric acid, activated ferric sulfate and silicon-containing biochar are mixed in a weight ratio of 3:1:2-3, and stirred at 40°C and 200 r / min for 1 hour to obtain a biochar base;

[0011] Completely immerse the biochar in the Shewanella oneidensis culture solution, shake and culture it at 30 °C and 180 r / min for 24 h, and then dry and crush it to obtain the modified biochar.

[0012] Furthermore, the activated ferric sulfate is obtained by filtering and drying after shaking ferrous sulfate heptahydrate and hydrogen peroxide at a weight ratio of 2:1 at a rotation speed of 200 r / min for 24 h.

[0013] Furthermore, the silicon-containing biochar is obtained by crushing and mixing wheat straw and sodium silicate at a weight ratio of 5:1 and then carbonizing it in an anaerobic environment at 500-550 °C for 5 h.

[0014] Furthermore, the dilute sulfuric acid is a dilute sulfuric acid solution with a pH of 4.

[0015] Furthermore, the liquid medium of the Shewanella oneidensis culture solution is obtained by mixing glucose, urea, soy peptone, sodium chloride, and distilled water at a weight ratio of 2:1:1:1:40.

[0016] Furthermore, the preparation method of the compound fertilizer includes the following steps:

[0017] Mix urea, sodium silicate nonahydrate, potassium chloride, water, and compound bacterial agent at a weight ratio of 300:120:80:500:80.

[0018] Furthermore, the compound bacterial agent is obtained by mixing Bacillus subtilis agent, Paenibacillus mucilaginosus agent, and Rhizobium agent at a weight ratio of 1:1:1.

[0019] Furthermore, the bacterial solution concentrations of the Bacillus subtilis agent, the Paenibacillus mucilaginosus agent, and the Rhizobium agent are all 5.0×10 8 CFU / mL to 7.0×10 8 CFU / mL.

[0020] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, the preparation method includes the following steps:

[0021] Mix the compound fertilizer and the modified biochar at a weight ratio of 3:10, stir at a rotation speed of 50 r / min for 30 min to 60 min, and then dry and crush it to obtain the compound microbial fertilizer.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The present invention first modifies biochar. By utilizing the porous adsorption structure of the modified biochar and the characteristic that Shewanella oneidensis loaded therein can convert hexavalent chromium into trivalent chromium under the catalysis of ferric sulfate, the hexavalent chromium ions in paddy soil and water are converted into trivalent chromium precipitates and adsorbed and encapsulated, thereby reducing the total amount of chromium ions that rice can absorb. Then, by utilizing the characteristic that rice has strong abilities of absorbing, transporting, and accumulating silicon, the stress resistance of rice to chromium ions is enhanced by adding sodium silicate nonahydrate that can be directly absorbed by rice, thereby reducing the absorption of the remaining chromium ions in water by rice. Finally, by adding a compound microbial agent and combining with the porous adsorption structure of biochar, the purpose of slow release of nutrients is achieved, the utilization rate of fertilizers is improved, and the dosage and fertilization frequency of chemical fertilizers are reduced. Detailed implementation manners

[0024] The technical solutions of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products or can be prepared by known methods.

[0026] Strain numbers: Shewanella oneidensis with strain number CICC 25104, Bacillus subtilis with strain number CICC 10455, Paenibacillus mucilaginosus with strain number CICC 21698, and Rhizobium with strain number CICC 20026, purchased from the China Center for Industrial Culture Collection;

[0027] The mother liquor and the bacterial liquid concentration of each microbial agent are both 5.0×10 8 CFU / mL to 7.0×10 8 CFU / mL. For the specific culture method, please refer to the official website of the China Center for Marine Culture Collection;

[0028] Ferrous sulfate heptahydrate and sodium silicate nonahydrate were purchased from the Sinopharm Chemical Reagent Co., Ltd.

[0029] Preparation Example 1:

[0030] The preparation method of activated ferric sulfate specifically includes the following process:

[0031] Dissolve 2 parts by weight of ferrous sulfate heptahydrate in an appropriate amount of deionized water to obtain a ferric sulfate solution. Continuously add 1 part by weight of hydrogen peroxide with a mass concentration of 30% to the ferrous sulfate heptahydrate solution at a constant speed for six hours, while oscillating at a speed of 200 r / min for 24 h. Then filter the oscillated solution through filter paper to remove excess water, and finally spread it flat on a glass plate and dry it at 30 °C to obtain activated ferric sulfate.

[0032] Preparation Example 2:

[0033] A method for preparing silicon-containing biochar specifically includes the following process:

[0034] Mix 5 parts by weight of wheat straw with 1 part by weight of sodium silicate, crush them, and put them into a sealed dry baking oven. Carbonize them at 500 °C for 5 h in an anaerobic environment.

[0035] Preparation Example 3:

[0036] A method for preparing silicon-containing biochar specifically includes the following process:

[0037] Mix 5 parts by weight of wheat straw with 1 part by weight of sodium silicate, crush them, and put them into a sealed dry baking oven. Carbonize them at 550 °C for 5 h in an anaerobic environment.

[0038] Preparation Example 4:

[0039] A method for preparing a liquid culture medium specifically includes the following process:

[0040] Add 2 parts by weight of glucose, 1 part by weight of urea, 1 part by weight of soybean peptone, 1 part by weight of sodium chloride, and 40 parts by weight of distilled water to a beaker, stir until completely dissolved, then pour it into a conical flask and perform moist heat sterilization at 121 °C for 30 min, and finally cool it naturally to obtain a liquid culture medium.

[0041] Preparation Example 5:

[0042] A method for preparing a compound fertilizer specifically includes the following process:

[0043] Pour 1 part by weight of Bacillus subtilis agent, 1 part by weight of Paenibacillus mucilaginosus agent, and 1 part by weight of Rhizobium agent into a beaker and mix to obtain a compound bacterial agent. Then pour 300 parts by weight of urea, 100 parts by weight of sodium silicate nonahydrate, 80 parts by weight of potassium chloride, 500 parts by weight of water, and 80 parts by weight of the compound bacterial agent into a beaker and stir until completely dissolved to obtain a compound fertilizer.

[0044] Preparation Example 6:

[0045] A method for preparing a compound fertilizer specifically includes the following process:

[0046] Pour 1 part by weight of Bacillus subtilis agent, 1 part by weight of Paenibacillus mucilaginosus agent and 1 part by weight of Rhizobium agent into a beaker and mix to obtain a compound bacterial agent. Then pour 300 parts by weight of urea, 120 parts by weight of sodium silicate nonahydrate, 80 parts by weight of potassium chloride, 500 parts by weight of water and 80 parts by weight of the compound bacterial agent into the beaker and stir until completely dissolved to obtain a compound fertilizer.

[0047] Preparation Example 7:

[0048] A preparation method of a compound fertilizer, specifically including the following process:

[0049] Pour 300 parts by weight of urea, 120 parts by weight of sodium silicate nonahydrate, 80 parts by weight of potassium chloride and 500 parts by weight of water into a beaker and stir until completely dissolved to obtain a compound fertilizer.

[0050] Preparation Example 8:

[0051] A preparation method of a compound fertilizer, specifically including the following process:

[0052] Pour 1 part by weight of Bacillus subtilis agent, 1 part by weight of Paenibacillus mucilaginosus agent and 1 part by weight of Rhizobium agent into a beaker and mix to obtain a compound bacterial agent. Then pour 300 parts by weight of urea, 80 parts by weight of potassium chloride, 500 parts by weight of water and 80 parts by weight of the compound bacterial agent into the beaker and stir until completely dissolved to obtain a compound fertilizer.

[0053] Example 1:

[0054] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0055] Pour 3 parts by weight of a dilute sulfuric acid solution with pH = 4, 1 part by weight of activated ferric sulfate obtained in Preparation Example 1 and 2 parts by weight of silicon-containing biochar obtained in Preparation Example 2 into a beaker, and stir at 40 °C and 200 r / min for one hour to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and oscillate and culture at 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain modified biochar. Pour 3 parts by weight of the compound fertilizer obtained in Preparation Example 5 and 10 parts by weight of the modified biochar into a beaker and mix, stir with a stirrer at 50 r / min for 30 min, then place it at room temperature of 25 °C for drying, and finally crush it into particles that can pass through a 10-mesh sieve with a powder mill to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0056] Example 2:

[0057] A preparation method of a composite microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0058] Put 3 parts by weight of dilute sulfuric acid solution with pH = 4, 1 part by weight of activated ferric sulfate obtained in Preparation Example 1, and 2 parts by weight of silicon-containing biochar obtained in Preparation Example 2 into a beaker, and stir for one hour at 40°C and 200 r / min to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the mother liquor of Shewanella oneidensis into the beaker and mix them. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and oscillate and culture at 30°C and 180 r / min for 24 h, then place it at room temperature of 25°C for drying. After drying, crush it to obtain modified biochar. Put 3 parts by weight of the composite fertilizer obtained in Preparation Example 6 and 10 parts by weight of the modified biochar into a beaker and mix them. Stir with a stirrer at 50 r / min for 30 min, then place it at room temperature of 25°C for drying, and finally crush it with a powder grinder into particles that can pass through a 10-mesh sieve to obtain a composite microbial fertilizer for efficiently reducing chromium pollution in rice.

[0059] Example 3:

[0060] A preparation method of a composite microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0061] Put 3 parts by weight of dilute sulfuric acid solution with pH = 4, 1 part by weight of activated ferric sulfate obtained in Preparation Example 1, and 2 parts by weight of silicon-containing biochar obtained in Preparation Example 3 into a beaker, and stir for one hour at 40°C and 200 r / min to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the mother liquor of Shewanella oneidensis into the beaker and mix them. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and oscillate and culture at 30°C and 180 r / min for 24 h, then place it at room temperature of 25°C for drying. After drying, crush it to obtain modified biochar. Put 3 parts by weight of the composite fertilizer obtained in Preparation Example 5 and 10 parts by weight of the modified biochar into a beaker and mix them. Stir with a stirrer at 50 r / min for 40 min, then place it at room temperature of 25°C for drying, and finally crush it with a powder grinder into particles that can pass through a 10-mesh sieve to obtain a composite microbial fertilizer for efficiently reducing chromium pollution in rice.

[0062] Example 4:

[0063] A preparation method of a composite microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0064] Put 3 parts by weight of a dilute sulfuric acid solution with pH = 4, 1 part by weight of the activated ferric sulfate obtained in Preparation Example 1, and 2 parts by weight of the silicon-containing biochar obtained in Preparation Example 3 into a beaker, and stir for one hour at 40 °C and 200 r / min to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Put it into a shaker and culture it by oscillation at 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain the modified biochar. Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 6 and 10 parts by weight of the modified biochar into a beaker and mix, stir with a stirrer at 50 r / min for 40 min, then place it at room temperature of 25 °C for drying, and finally crush it with a pulverizer into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0065] Example 5:

[0066] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0067] Put 3 parts by weight of a dilute sulfuric acid solution with pH = 4, 1 part by weight of the activated ferric sulfate obtained in Preparation Example 1, and 3 parts by weight of the silicon-containing biochar obtained in Preparation Example 2 into a beaker, and stir for one hour at 40 °C and 200 r / min to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Put it into a shaker and culture it by oscillation at 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain the modified biochar. Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 5 and 10 parts by weight of the modified biochar into a beaker and mix, stir with a stirrer at 50 r / min for 50 min, then place it at room temperature of 25 °C for drying, and finally crush it with a pulverizer into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0068] Example 6:

[0069] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0070] Put 3 parts by weight of a dilute sulfuric acid solution with a pH of 4, 1 part by weight of the activated ferric sulfate obtained in Preparation Example 1, and 3 parts by weight of the silicon-containing biochar obtained in Preparation Example 2 into a beaker, and stir at 40 °C and 200 r / min for one hour to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and culture it under the conditions of 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain the modified biochar. Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 6 and 10 parts by weight of the modified biochar into a beaker and mix. Stir with a stirrer at 50 r / min for 50 min, then place it at room temperature of 25 °C for drying, and finally crush it with a pulverizer into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0071] Example 7:

[0072] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0073] Put 3 parts by weight of a dilute sulfuric acid solution with a pH of 4, 1 part by weight of the activated ferric sulfate obtained in Preparation Example 1, and 3 parts by weight of the silicon-containing biochar obtained in Preparation Example 3 into a beaker, and stir at 40 °C and 200 r / min for one hour to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and culture it under the conditions of 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain the modified biochar. Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 5 and 10 parts by weight of the modified biochar into a beaker and mix. Stir with a stirrer at 50 r / min for 60 min, then place it at room temperature of 25 °C for drying, and finally crush it with a pulverizer into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0074] Example 8:

[0075] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice, specifically including the following process:

[0076] Put 3 parts by weight of a dilute sulfuric acid solution with pH = 4, 1 part by weight of the activated ferric sulfate obtained in Preparation Example 1, and 3 parts by weight of the silicon-containing biochar obtained in Preparation Example 3 into a beaker, and stir for one hour at 40 °C and 200 r / min to obtain a biochar base. Pour 9 parts by weight of the liquid medium obtained in Preparation Example 4 and 1 part by weight of the Shewanella oneidensis mother liquor into the beaker and mix. Pour the mixed solution into the modified biochar until the modified biochar is just completely immersed in the mixed solution and seal it. Place it in a shaker and shake and culture at 30 °C and 180 r / min for 24 h, then place it at room temperature of 25 °C for drying. After drying, crush it to obtain the modified biochar. Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 6 and 10 parts by weight of the modified biochar into a beaker and mix, stir with a stirrer at 50 r / min for 60 min, then place it at room temperature of 25 °C for drying, and finally crush it with a powder mill into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0077] Comparative Example 1:

[0078] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice specifically includes the following process:

[0079] Put 3 parts by weight of the compound fertilizer obtained in Preparation Example 6 and 10 parts by weight of the silicon-containing biochar obtained in Preparation Example 3 into a beaker and mix, stir with a stirrer at 50 r / min for 60 min, then place it at room temperature of 25 °C for drying, and finally crush it with a powder mill into particles that can pass through a 10-mesh sieve to obtain a compound microbial fertilizer for efficiently reducing chromium pollution in rice.

[0080] Comparative Example 2:

[0081] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice specifically includes the following process:

[0082] Replace the compound fertilizer in Example 4 with the compound fertilizer obtained in Preparation Example 7, and keep the other conditions the same as those in Example 6.

[0083] Comparative Example 3:

[0084] A preparation method of a compound microbial fertilizer for efficiently reducing chromium pollution in rice specifically includes the following process:

[0085] Replace the compound fertilizer in Example 4 with the compound fertilizer obtained in Preparation Example 8, and keep the other conditions the same as those in Example 6.

[0086] A total of 11 groups were set up in the pot experiment, with 10 parallel samples in each group. The pot containers were transparent rectangular containers made of plexiglass, and the bottom of the pot was covered with pebbles to obtain the culture containers. A mixed solution of soil and muddy water from the same paddy field was taken and an appropriate amount of chromium nitrate nonahydrate was added to adjust the chromium content in the mixed solution to be between 1200 and 1400 mg / kg (determined by potassium permanganate oxidation and diphenylcarbazide photometry) to obtain a heavily chromium-polluted mixed solution. The heavily chromium-polluted mixed solution was evenly filled into the culture containers and the compound microbial fertilizers of Examples 1-8 and Comparative Examples 1-3 were added in a proportion of one percent. Then, a well-grown and uniform rice seedling was inoculated respectively and cultured under uniform light. The light time in the culture room was 16 h, the temperature was 25 ± 0.1 °C, the illuminance was 2000 lx, and water was replenished regularly; the dark time was 8 h, the temperature was 20 ± 0.1 °C; the relative humidity was maintained at 70%-75%. The rice cultivation period was 35 days in total. During the 35-day experiment process, the growth and development of the rice seedlings were monitored and recorded. After 35 days of cultivation, samples were taken and various physiological indexes of the rice seedlings and the heavy metal chromium content in the soil were measured. The results are shown in the following table:

[0087]

[0088]

[0089] It can be seen from the data in the above table that:

[0090] (1) The antistatic compound microbial fertilizers of Examples 1-8 can effectively reduce the total amount of chromium ions in paddy fields, reduce the absorption of ions by rice, and improve the utilization rate of nutrients.

[0091] (2) It can be seen from Comparative Example 1 that although the silicon-containing biochar with a porous adsorption structure can adsorb a part of the chromium precipitate in paddy fields, due to the instability of the chromium precipitate in a high-concentration environment, part of the chromium precipitate will still be converted into free chromium ions and absorbed by rice.

[0092] (3) It can be seen from Comparative Example 2 that although it has a good function of reducing the total amount of chromium ions in paddy fields, due to the lack of the functions of potassium-solubilizing, phosphorus-solubilizing and nitrogen-fixing of the compound microbial agent to improve the utilization rate of nutrients, the rice develops slowly due to insufficient nutrients in the later stage of cultivation.

[0093] (4) It can be seen from Comparative Example 3 that although it can effectively reduce the total amount of chromium ions in paddy fields, due to the initial paddy field being a heavily chromium-polluted paddy field, in the initial stage of cultivation, the rice absorbed a part of chromium, resulting in an impact on the overall development of the rice.

[0094] The above-described embodiments have elaborated in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A compound microbial fertilizer for efficiently reducing chromium pollution in rice, characterized in that, The compound microbial fertilizer is composed of modified biochar and compound fertilizer in a mass ratio of 3:

10.

2. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as claimed in claim 1, characterized in that The preparation method of the modified biochar includes the following steps: Mix dilute sulfuric acid, activated ferric sulfate and silicon-containing biochar in a weight ratio of 3:1:2-3, and stir at 40°C and 200 r / min for 1 h to obtain a biochar base; Completely immerse the biochar base in Shewanella oneidensis MR-1 bacterial liquid, oscillate and culture at 30°C and 180 r / min for 24 h, and then dry and pulverize to obtain the modified biochar.

3. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as described in claim 2, characterized in that, The activated ferric sulfate is obtained by mixing ferrous sulfate heptahydrate and hydrogen peroxide in a weight ratio of 2:1, oscillating at 200 r / min for 24 h, and then filtering and drying.

4. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as described in claim 2, characterized in that, The silicon-containing biochar is obtained by pulverizing and mixing wheat straw and sodium silicate in a weight ratio of 5:1, and carbonizing in an anaerobic environment at 500-550°C for 5 h.

5. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as claimed in claim 2, characterized in that, The liquid medium of the Shewanella oneidensis MR-1 bacterial liquid is obtained by mixing glucose, urea, soy peptone, sodium chloride and distilled water in a weight ratio of 2:1:1:1:

40.

6. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as described in claim 1, characterized in that, The preparation method of the compound fertilizer includes the following steps: Mix urea, sodium silicate nonahydrate, potassium chloride, water and compound bacterial agent in a weight ratio of 300:80-120:80:500:

2.

7. The composite microbial fertilizer for efficiently reducing chromium pollution in rice as claimed in claim 6, wherein The compound bacterial agent is obtained by mixing Bacillus subtilis agent, Paenibacillus mucilaginosus agent and Rhizobium agent in a weight ratio of 1:1:

1.

8. A preparation method of a composite microbial fertilizer for efficiently reducing chromium pollution in rice as described in any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: Mix the compound fertilizer and the modified biochar in a weight ratio of 3:10, stir at 50 r / min for 30 min-60 min, and then dry and pulverize to obtain the compound microbial fertilizer.

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