Rice field soil conditioner and preparation method thereof

Abstract

The invention discloses a rice field soil conditioner which is prepared by mixing a modified zeolite molecular sieve, a biological fertilizer, polymerized bentonite, biochar and nano zero-valent iron according to the mass ratio of (20-25): (30-35): (25-30): (15-20): (5-8), by adding the modified zeolite molecular sieve and the polymerized bentonite, fertilization nutrients in soil can be effectively adsorbed, the nutrient loss speed is greatly reduced, the soil nutrient retention rate is increased, the use of chemical fertilizers is reduced, and sustainable agricultural development is facilitated; the modified zeolite molecular sieve can absorb water at the same time and can release water in high-temperature weather, so that the soil structure is effectively improved, the water-retaining property of rice field soil is improved, and the phenomenon that planted rice is withered due to the fact that water is not supplemented in time in hot weather is avoided; and meanwhile, the combination of the nano zero-valent iron and the biochar can adsorb heavy metal ions in the soil and carry out reduction fixation, so that the heavy metal pollution in the rice field soil is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of farmland soil improvement, and in particular to a paddy field soil improver and a preparation method thereof. Background Art

[0002] The quality of paddy field soil directly affects the growth and yield of rice; traditional soil improvement methods mainly include the application of chemical fertilizers, organic fertilizers, etc., but these methods may have problems such as nutrient loss and environmental pollution. For example, a large amount of phosphate fertilizer lost into river water sources will cause phosphorus pollution in the water body, resulting in the death of large numbers of aquatic organisms such as fish.

[0003] Paddy field soil often leads to imbalance of soil structure and nutrients due to long-term cultivation and use of chemical fertilizers. At present, traditional improvers are still used for paddy field soil conditioning, which have single functionality and cannot improve the nutrient retention rate of paddy field soil. There will still be some nutrient loss. At the same time, a large amount of nitrogen, phosphorus and potassium fertilizers still need to be applied when paddy field soil is cultivated. However, for paddy field soil with low nutrient retention rate, the nutrients of the applied fertilizers cannot be fully utilized. Therefore, the present invention proposes a paddy field soil improver and a preparation method to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a paddy field soil conditioner and a preparation method. The paddy field soil conditioner and the preparation method can effectively absorb fertilizer nutrients in the soil through the addition of modified zeolite molecular sieve and polymerized bentonite, greatly reducing the rate of nutrient loss, improving soil nutrient retention rate, reducing the use of chemical fertilizers, and being conducive to sustainable agricultural development; the modified zeolite molecular sieve can also absorb water and release water in high temperature weather, effectively improving the soil structure, and improving the water retention of paddy field soil, avoiding the phenomenon of planted rice dying due to untimely water replenishment in hot weather; at the same time, nano zero-valent iron combined with biochar can adsorb and reduce and fix heavy metal ions in the soil, reducing heavy metal pollution in paddy field soil.

[0005] To achieve the purpose of the present invention, the present invention is achieved through the following technical solutions: a paddy field soil conditioner and a preparation method, comprising a modified zeolite molecular sieve, a biofertilizer, a polymerized bentonite, a biochar and a nano-zero-valent iron mixed and prepared, wherein the mass ratio of the modified zeolite molecular sieve, the biofertilizer, the polymerized bentonite, the biochar and the nano-zero-valent iron is 20-25:30-35:25-30:15-20:5-8, the modified zeolite molecular sieve is obtained after acid-base treatment, the polymerized bentonite is mixed and modified with potassium salt and phosphate and prepared by mixing with xanthan gum, and the biofertilizer is prepared by co-cultivating nitrogen-fixing bacteria, phosphate-solubilizing bacteria and potassium-solubilizing bacteria and mixed with a fermentation substrate.

[0006] A further improvement is that: the potassium salt is one of potassium chloride and potassium sulfate; the phosphate is one of calcium dihydrogen phosphate, ammonium dihydrogen phosphate and superphosphate lime; the nitrogen-fixing bacteria is one of round brown nitrogen-fixing bacteria and Frankia; the phosphate-solubilizing bacteria is one of Chromobacterium and Micrococcus; the potassium-solubilizing bacteria is one of silicate bacteria and Bacillus KM2.

[0007] A method for preparing a paddy field soil conditioner comprises the following steps:

[0008] Step 1, preparation of modified zeolite molecular sieve: sequentially treating the molecular sieve with acid and alkali solutions, then acid-washing and drying the molecular sieve after acid and alkali treatment to obtain the modified zeolite molecular sieve;

[0009] Step 2, biofertilizer preparation: nitrogen-fixing bacteria, phosphate-dissolving bacteria and potassium-dissolving bacteria are co-cultured, then fully mixed with a fermentation substrate for fermentation treatment, and finally dried and crushed to obtain biofertilizer;

[0010] Step 3, preparation of polymerized bentonite: firstly, the bentonite is nano-grinded and then wetted, and then potassium salt and phosphate are mixed with the bentonite and added into the xanthan gum viscous liquid and stirred to obtain polymerized bentonite;

[0011] Step 4: Preparation and adsorption of nano-zero-valent iron: Nano-zero-valent iron is prepared by electrochemical reduction method, and then mixed with biochar for adsorption to obtain an improved composite;

[0012] Step 5: Preliminary mixing treatment: firstly, the biofertilizer and the modified zeolite molecular sieve are mixed and stirred, and then the mixture is added into the polymerized bentonite for mixing to obtain a premixed improver;

[0013] Step 6: Mixing and granulation: Add the improved compound to the premixed improver and stir and mix to obtain a final mixture, which is placed in a granulator for extrusion granulation to obtain a soil improver.

[0014] The further improvement lies in that the specific treatment method in the step one is to first use an aqueous solution of ethylenediaminetetraacetic acid to perform a heating and acid leaching treatment on the zeolite molecular sieve, then rinse it with hot distilled water and then dry and roast it to obtain an acid-treated molecular sieve; then add the acid-treated molecular sieve to an aqueous solution of sodium hydroxide for heating and alkali treatment, then rinse it with hot distilled water and then dry and roast it to obtain an acid-base treated molecular sieve; finally, use a disodium ethylenediaminetetraacetic acid solution to perform a heating and acid washing treatment on the acid-base treated molecular sieve, rinse it with hot distilled water and then dry it to obtain a modified zeolite molecular sieve.

[0015] The further improvement is that: the concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.18 mol / L; the concentration of the sodium hydroxide aqueous solution is 0.9 mol / L; the concentration of the disodium ethylenediaminetetraacetic acid solution is 0.11 mol / L; the heating treatment adopts a silicone oil bath to heat to 65-100°C, the drying condition is drying at 130°C for 4-5h, and the roasting condition is placing the treated molecular sieve in a muffle furnace and roasting it at 600°C for 5h before cooling it down and taking it out.

[0016] A further improvement is that in step 2, the fermentation substrate is a mixture of straw and livestock manure. Specifically, the straw is first sterilized and cleaned, then dried with livestock manure and crushed, and finally mixed with multiple co-cultured bacterial strains and watered to keep the moisture content of the fermented product at 45%-55% for fermentation.

[0017] The further improvement is that: in step three, the wetting treatment of bentonite is to mix the bentonite after nano-grinding with deionized water, purify and slurry to complete the wetting treatment; when mixing with potassium salt and phosphate, the potassium salt and phosphate are first made into a salt aqueous solution, and then the salt aqueous solution is introduced into the bentonite after the wetting treatment and stirred, and then dried and ground; then the xanthan gum and deionized water are heated and stirred at 60-80°C to obtain a viscous liquid, and finally the ground bentonite is added to the viscous liquid and stirred to obtain polymerized bentonite.

[0018] A further improvement is that in step 4, the preparation of nano zero-valent iron is specifically to dissolve iron salt in water to obtain an iron salt solution, and then electrolyze it through an external current, so that the iron salt is reduced on the cathode to generate nano zero-valent iron deposition, which is then taken out, rinsed and dried to obtain nano zero-valent iron; wherein the iron salt is one of ferric chloride, polyferric chloride and polyferric sulfate.

[0019] The beneficial effects of the present invention are as follows: the present invention can effectively absorb fertilizer nutrients in the soil by adding modified zeolite molecular sieve and polymerized bentonite, greatly reducing the rate of nutrient loss, improving the soil nutrient retention rate, reducing the use of chemical fertilizers, and facilitating sustainable agricultural development;

[0020] Modified zeolite molecular sieve can absorb water and release water in hot weather, which effectively improves soil structure and water retention of paddy soil, thus avoiding the phenomenon of rice dying due to untimely water replenishment in hot weather.

[0021] At the same time, the combination of nano-zero-valent iron and biochar can adsorb and reduce and fix heavy metal ions in the soil, reducing heavy metal pollution in paddy field soil, and has important practical value and environmental significance in agricultural applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is a flow chart of the preparation method of Example 2 of the present invention.

[0023] Figure 2 This is a flow chart of the preparation method of Example 4 of the present invention. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0025] Unless otherwise specified, the raw materials used in the examples of the present invention are obtained through conventional commercial routes.

[0026] Among them, brown nitrogen-fixing bacteria were purchased from China Center for Type Culture Collection with the accession number of CCTCC NO: M2016110; silicate bacteria were purchased from China Center for Type Culture Collection of Wuhan University with the accession number of CCTCC No.M200040; micrococcus was purchased from General Microbiology Center of China Microorganism Culture Collection Administration with the accession number of CGMCC No.7778.

[0027] The composite bacteria co-culture method in the embodiment is: using a culture medium composed of: 0.4% yeast extract, 0.6% peptone, 5% brown sugar, 0.1% Tween-80, 0.05% sodium chloride, 0.05% dipotassium hydrogen phosphate, 0.05% magnesium sulfate, 0.05% calcium carbonate, and the rest is water; culturing at 35°C and 200r / min shaking for 24 hours; the inoculation ratio of the three bacteria is 1:1000.

[0028] Example 1

[0029] The present embodiment provides a paddy field soil conditioner and a preparation method thereof, comprising a mixture of modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano-zero-valent iron, wherein the mass ratio of the modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano-zero-valent iron is 20:30:25:20:5, the modified zeolite molecular sieve is obtained after acid-base treatment, the polymerized bentonite is prepared by mixing and modifying potassium chloride and calcium dihydrogen phosphate and mixing with xanthan gum, and the biofertilizer is prepared by co-culturing round brown nitrogen-fixing bacteria, micrococcus and silicate bacteria and mixing and fermenting with a fermentation substrate.

[0030] according to Figure 1 As shown, this embodiment provides a method for preparing a paddy field soil conditioner, characterized in that it includes the following steps:

[0031] Step 1, preparation of modified zeolite molecular sieve, using acid and alkali solution to acid-base treat the molecular sieve, then acid-washing and drying the acid and alkali treated molecular sieve to obtain the modified zeolite molecular sieve;

[0032] The specific treatment method is to first use an ethylenediaminetetraacetic acid aqueous solution with a concentration of 0.18 mol / L to treat the zeolite molecular sieve by heating it to 70°C in a silicone oil bath, then rinse it with hot distilled water and dry it at 130°C for 4 hours, place the treated molecular sieve in a muffle furnace and roast it at 600°C for 5 hours, then cool it down and take it out to obtain the acid-treated molecular sieve;

[0033] Then, the acid-treated molecular sieve is added to a sodium hydroxide aqueous solution with a concentration of 0.9 mol / L and heated to 65° C. in a silicone oil bath for alkali treatment, and then rinsed with hot distilled water and dried at 130° C. for 4-5 hours. The treated molecular sieve is placed in a muffle furnace and calcined at 600° C. for 5 hours, then cooled and taken out to obtain an acid-base treated molecular sieve;

[0034] Finally, the acid-base treated molecular sieve was acid-washed using a 0.11 mol / L disodium ethylenediaminetetraacetic acid solution heated to 65°C in a silicone oil bath, and then rinsed with hot distilled water and dried at 130°C for 4 hours to obtain a modified zeolite molecular sieve.

[0035] Step 2, biofertilizer fermentation preparation, firstly co-cultivate nitrogen-fixing bacteria, phosphate-dissolving bacteria and potassium-dissolving bacteria, then fully mix them with fermentation substrate (mixing ratio 1:1000) for fermentation treatment for 24 hours, and finally dry and crush to obtain biofertilizer;

[0036] The fermentation substrate is a mixture of straw and livestock manure (mixing ratio 5:1). Specifically, the straw is first sterilized and cleaned, then dried with livestock manure and crushed, and finally mixed with multiple co-cultured bacteria and watered to keep the moisture content of the fermented product at 45%-55% for fermentation.

[0037] Step 3, preparation of polymerized bentonite, firstly subjecting bentonite to nano-grinding and then to wet treatment, then mixing potassium salt and phosphate with bentonite, adding the mixture to the xanthan gum viscous liquid, and stirring and mixing, to obtain polymerized bentonite;

[0038] The specific wet treatment of bentonite is to mix the bentonite after nano-grinding with deionized water, purify and slurry it to complete the wet treatment, and when mixing with potassium salt and phosphate (molar ratio 1:1), first make the potassium salt and phosphate into a salt aqueous solution, and then pour the salt aqueous solution into the bentonite after the wet treatment at an addition amount of 15%, stir it, and dry and grind it, and then heat and stir the xanthan gum and deionized water at 70°C to obtain a viscous liquid, and finally add the ground bentonite into the viscous liquid and stir it to obtain polymerized bentonite.

[0039] Step 4: Preparation and adsorption of nano-zero-valent iron: nano-zero-valent iron is prepared by electrochemical reduction method, and then mixed with biochar for adsorption to obtain an improved composite;

[0040] The preparation of nano zero-valent iron is specifically to dissolve ferric chloride in water to prepare ferric chloride solution, and then electrolyze it through an external current. The ferric chloride is reduced on the cathode to form nano zero-valent iron deposition, which is then taken out, rinsed and dried to obtain nano zero-valent iron.

[0041] Step 5: Preliminary mixing treatment: firstly, the biofertilizer and the modified zeolite molecular sieve are mixed and stirred, and then the mixture is added into the polymerized bentonite for mixing to obtain a premixed improver;

[0042] Step 6: Mixing and granulation treatment: adding the improved composite into the premixed improver and stirring and mixing to obtain a final mixture, and placing the final mixture in a granulator for extrusion granulation to obtain a soil improver.

[0043] Example 2

[0044] The present embodiment provides a paddy field soil conditioner and a preparation method thereof, comprising a mixture of modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano-zero-valent iron, wherein the mass ratio of the modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano-zero-valent iron is 20:35:25:15:5, the modified zeolite molecular sieve is obtained after acid-base treatment, the polymerized bentonite is prepared by mixing and modifying potassium sulfate and superphosphate lime and mixing with xanthan gum, and the biofertilizer is prepared by co-culturing round brown nitrogen-fixing bacteria, micrococcus and silicate bacteria and mixing and fermenting with a fermentation substrate.

[0045] according to Figure 2 As shown, this embodiment provides a method for preparing a paddy field soil conditioner, comprising the following steps:

[0046] Step 1, preparation of modified zeolite molecular sieve, using acid and alkali solution to acid-base treat the molecular sieve, then acid-washing and drying the acid and alkali treated molecular sieve to obtain the modified zeolite molecular sieve;

[0047] The specific treatment method is to first use an ethylenediaminetetraacetic acid aqueous solution with a concentration of 0.18 mol / L to treat the zeolite molecular sieve by heating it to 75°C in a silicone oil bath, then rinse it with hot distilled water and dry it at 130°C for 4 hours, place the treated molecular sieve in a muffle furnace and roast it at 600°C for 5 hours, then cool it down and take it out to obtain the acid-treated molecular sieve;

[0048] Then, the acid-treated molecular sieve was added to a sodium hydroxide aqueous solution with a concentration of 0.9 mol / L and heated to 65°C in a silicone oil bath for alkali treatment, and then rinsed with hot distilled water and dried at 130°C for 4 hours. The treated molecular sieve was placed in a muffle furnace and calcined at 600°C for 5 hours, then cooled and taken out to obtain an acid-base treated molecular sieve;

[0049] Finally, the acid-base treated molecular sieve was acid-washed using a 0.11 mol / L disodium ethylenediaminetetraacetic acid solution heated to 65°C in a silicone oil bath, and then rinsed with hot distilled water and dried at 130°C for 4 hours to obtain a modified zeolite molecular sieve.

[0050] Step 2, biofertilizer fermentation preparation, firstly co-cultivate nitrogen-fixing bacteria, phosphate-dissolving bacteria and potassium-dissolving bacteria, then fully mix them with fermentation substrate (mixing ratio 1:1000) for fermentation treatment for 24 hours, and finally dry and crush to obtain biofertilizer;

[0051] The fermentation substrate is a mixture of straw and livestock manure (mixing ratio 5:1). Specifically, the straw is first sterilized and cleaned, then dried with livestock manure and crushed, and finally mixed with multiple co-cultured bacteria and watered to keep the moisture content of the fermented product at 45%-55% for fermentation.

[0052] Step 3, preparation of polymerized bentonite, firstly subjecting bentonite to nano-grinding and then to wet treatment, then mixing potassium salt and phosphate with bentonite, adding the mixture to the xanthan gum viscous liquid, and stirring and mixing, to obtain polymerized bentonite;

[0053] The specific wet treatment of bentonite is to mix the bentonite after nano-grinding with deionized water, purify and slurry it to complete the wet treatment, and when mixing with potassium salt and phosphate (molar ratio 1:1), first make the potassium salt and phosphate into a salt aqueous solution, and then pour the salt aqueous solution into the bentonite after the wet treatment at an addition amount of 15%, stir it, and dry and grind it, and then heat and stir the xanthan gum and deionized water at 70°C to obtain a viscous liquid, and finally add the ground bentonite into the viscous liquid and stir it to obtain polymerized bentonite.

[0054] Step 4: Preparation and adsorption of nano-zero-valent iron: using a carbothermal reduction method to prepare nano-zero-valent iron, and then mixing it with biochar for adsorption to obtain an improved composite;

[0055] The preparation of nano zero-valent iron is carried out under high temperature conditions, using inorganic carbon such as carbon black and biochar as a reducing agent, and obtaining nano zero-valent iron through an endothermic reaction with nano-scale iron oxides or ferrous salts. Specifically, the iron salt is adsorbed onto activated carbon, washed and dried, and then reduced at a temperature greater than 500°C for 4 hours to obtain nano zero-valent iron; under low temperature conditions, the activated carbon first reduces Fe2O3 to generate Fe3O4, and after the temperature is increased, Fe3O4 continues to be reduced to nano zero-valent iron.

[0056] Step 5: Preliminary mixing treatment: firstly, the biofertilizer and the modified zeolite molecular sieve are mixed and stirred, and then the mixture is added into the polymerized bentonite for mixing to obtain a premixed improver;

[0057] Step 6: Mixing and granulation treatment: adding the improved composite into the premixed improver and stirring and mixing to obtain a final mixture, and placing the final mixture in a granulator for extrusion granulation to obtain a soil improver.

[0058] In order to verify the efficacy of the paddy field soil conditioner prepared by the present invention, the soil conditioners prepared in Example 1 and Example 2 and the traditional soil conditioner on the market named "Tuwobao" were spread on the same paddy field soil for improvement experiments. The experiment lasted for 30 days. On the 5th day, 10th day, 15th day, 20th day, 25th day and 30th day, samples were taken to detect soil nutrients and water retention rate data in the application of different soil conditioners, and the changes in the heavy metal ion content in the soil were determined (mainly cadmium metal), as shown in the following table.

[0059] Paddy field soil improvement experiment table

[0060]

[0061]

[0062] It can be seen from the above table that the soil conditioner prepared in the present application has better effect on improving paddy field soil than the traditional conditioner. In terms of nutrient retention, due to the addition of polymerized bentonite and modified zeolite molecular sieve, the rate of nutrient loss is reduced by utilizing their ability to adsorb and retain nutrients. The traditional conditioner loses nutrients and water quickly, and the nutrient content and water retention rate on the 30th day are much lower than the soil improved by the conditioner prepared in the present application. At the same time, from the perspective of heavy metal ion content, although traditional conditioners can reduce heavy metal pollution, the conditioner prepared in the present application adsorbs and fixes heavy metal ions through biochar and nano zero-valent iron, and the effect of treating heavy metal pollution is better than that of traditional conditioners.

[0063] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A paddy field soil conditioner, characterized in that: The invention comprises a mixture of modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano zero-valent iron, wherein the mass ratio of the modified zeolite molecular sieve, biofertilizer, polymerized bentonite, biochar and nano zero-valent iron is 20-25:30-35:25-30:15-20:5-8, the modified zeolite molecular sieve is obtained after acid-base treatment, the polymerized bentonite is prepared by mixing potassium salt and phosphate and modifying them and mixing them with xanthan gum, and the biofertilizer is prepared by co-culturing nitrogen-fixing bacteria, phosphate-solubilizing bacteria and potassium-solubilizing bacteria and mixing and fermenting them with a fermentation substrate.

2. The paddy field soil conditioner according to claim 1, characterized in that: The potassium salt is one of potassium chloride and potassium sulfate; the phosphate is one of calcium dihydrogen phosphate, ammonium dihydrogen phosphate and superphosphate lime; the nitrogen-fixing bacteria is one of round brown nitrogen-fixing bacteria and Frankia; the phosphate-solubilizing bacteria is one of Chromobacterium and Micrococcus; the potassium-solubilizing bacteria is one of silicate bacteria and Bacillus KM2.

3. A method for preparing a paddy field soil conditioner, characterized in that: The following steps are involved: Step 1, preparation of modified zeolite molecular sieve: sequentially treating the molecular sieve with acid and alkali solutions, then acid-washing and drying the molecular sieve after acid and alkali treatment to obtain the modified zeolite molecular sieve; Step 2, biofertilizer preparation: nitrogen-fixing bacteria, phosphate-dissolving bacteria and potassium-dissolving bacteria are co-cultured, then fully mixed with a fermentation substrate for fermentation treatment, and finally dried and crushed to obtain biofertilizer; Step 3, preparation of polymerized bentonite: firstly, the bentonite is nano-grinded and then wetted, and then potassium salt and phosphate are mixed with the bentonite and added into the xanthan gum viscous liquid and stirred to obtain polymerized bentonite; Step 4: Preparation and adsorption of nano-zero-valent iron: Nano-zero-valent iron is prepared by electrochemical reduction method, and then mixed with biochar for adsorption to obtain an improved composite; Step 5: Preliminary mixing treatment: firstly, the biofertilizer and the modified zeolite molecular sieve are mixed and stirred, and then the mixture is added into the polymerized bentonite for mixing to obtain a premixed improver; Step 6: Mixing and granulation: Add the improved compound to the premixed improver and stir and mix to obtain a final mixture, which is placed in a granulator for extrusion granulation to obtain a soil improver.

4. The method for preparing a paddy field soil conditioner according to claim 3, characterized in that: The specific treatment method in the step 1 is to first use an ethylenediaminetetraacetic acid aqueous solution to perform a heating and acid leaching treatment on the zeolite molecular sieve, then rinse it with hot distilled water and then dry and roast it to obtain an acid-treated molecular sieve; then add the acid-treated molecular sieve to a sodium hydroxide aqueous solution for heating and alkali treatment, then rinse it with hot distilled water and then dry and roast it to obtain an acid-base treated molecular sieve; finally, use a disodium ethylenediaminetetraacetic acid solution to perform a heating and acid washing treatment on the acid-base treated molecular sieve, rinse it with hot distilled water and then dry it to obtain a modified zeolite molecular sieve.

5. The method for preparing a paddy field soil conditioner according to claim 4, characterized in that: The concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.18 mol / L; the concentration of the sodium hydroxide aqueous solution is 0.9 mol / L; the concentration of the disodium ethylenediaminetetraacetic acid solution is 0.11 mol / L; the heating treatment adopts a silicone oil bath to heat to 65-100° C., the drying condition is drying at 130° C. for 4-5 hours, and the roasting condition is placing the treated molecular sieve in a muffle furnace and roasting it at 600° C. for 5 hours, then cooling it down and taking it out.

6. The method for preparing a paddy field soil conditioner according to claim 1, characterized in that: In step 2, the fermentation substrate is a mixture of straw and livestock manure. Specifically, the straw is first sterilized and cleaned, then dried with livestock manure and crushed, and finally mixed with multiple co-cultured bacterial strains and watered to keep the moisture content of the fermented product at 45%-55% for fermentation.

7. The method for preparing a paddy field soil conditioner according to claim 1, characterized in that: In step three, the bentonite is wetted by mixing the nano-grinded bentonite with deionized water, purifying and slurrying the mixture, and then preparing a salt solution of the potassium salt and the phosphate when mixing with the potassium salt and the phosphate. The salt solution is then introduced into the wetted bentonite and stirred, and then dried and ground. The xanthan gum and deionized water are heated and stirred at 60-80°C to obtain a viscous liquid, and finally the ground bentonite is added to the viscous liquid and stirred to obtain polymerized bentonite.

8. The method for preparing a paddy field soil conditioner according to claim 1, characterized in that: The preparation of nano zero-valent iron in step 4 is specifically to dissolve iron salt in water to obtain an iron salt solution, and then electrolyze it through an external current to reduce the iron salt on the cathode to generate nano zero-valent iron deposition, which is then taken out, rinsed and dried to obtain nano zero-valent iron; wherein the iron salt is one of ferric chloride, polyferric chloride and polyferric sulfate.

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