A mine-source nitro-humic acid complexed phosphorus fertilizer for treating land salinization and a preparation method thereof

Abstract

The application belongs to the technical field of compound fertilizer and specifically relates to a mineral source nitro humic acid complex phosphorus fertilizer for treating land salinization and a preparation method thereof, which comprises the following components by weight: 50-80 parts of mineral source nitro humic acid, 5-20 parts of superphosphate, 1-5 parts of soil conditioner, 1-3 parts of trace elements, 5-15 parts of biochar, 0.5-2 parts of compound microbial agent and 3-8 parts of coating material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of compound fertilizer, and particularly relates to a mineral source nitro humic acid complex phosphorus fertilizer for treating land salinization and a preparation method thereof. BACKGROUND

[0002] Saline-alkali soil is one of the important challenges for global agricultural sustainable development, and the high salt (such as Na + , Cl - , etc.) and high pH (usually more than 8.5) in the soil can inhibit the root development of crops, hinder the nutrient absorption, and cause soil compaction and microbial activity reduction, ultimately leading to crop yield reduction or even absolute loss. According to statistics, the global saline-alkali soil area is more than 950 million hectares, and the saline-alkali soil area in China is also more than 100 million hectares, of which about 30% has improvement potential. However, the traditional saline-alkali soil treatment method has significant defects: on the one hand, it relies on a large amount of fresh water irrigation to leach salt, which aggravates the problem of water resource shortage; on the other hand, the application of chemical modifiers such as lime or gypsum easily leads to secondary salinization of the soil, and the long-term use cost is high.

[0003] In recent years, humic acid substances are widely used for soil improvement due to their characteristics of improving soil structure, adjusting pH, and enhancing nutrient absorption. However, the traditional humic acid fertilizer is mostly made of weathered coal as raw material, which has the problems of limited resources, high cost, and single function. SUMMARY

[0004] Based on the problems mentioned in the background art, the application provides a mineral source nitro humic acid complex phosphorus fertilizer for treating land salinization.

[0005] The technical scheme adopted by the application is as follows: a mineral source nitro humic acid complex phosphorus fertilizer for treating land salinization, comprising the following components by weight: 50-80 parts of mineral source nitro humic acid, 10-20 parts of superphosphate, 1-5 parts of soil conditioner, 1-3 parts of trace element, 5-15 parts of biological carbon, 0.5-2 parts of complex microbial agent, and 3-8 parts of coating material.

[0006] Further, the mineral source nitro humic acid is modified by nitric acid and contains nitrate ions, and the pH is 4-6.

[0007] Further, the trace element is an EDTA chelate of iron or zinc.

[0008] Further, the soil conditioner is diatom shale and bentonite, and the mass ratio is 1:2.

[0009] Further, the complex microbial agent is a mixed microbial flora of nitrogen-fixing bacteria and phosphorus-dissolving bacteria, and the mass ratio is 1:1.

[0010] Further, the coating material is a paraffin-rosin composite film, and the film thickness is 50-100 pm.

[0011] This invention also provides a method for preparing any of the above-mentioned mineral-derived nitrohumic acid complex phosphate fertilizers for treating soil salinization, comprising the following steps: S1, preparing nitrohumic acid: mixing mineral-derived humic acid with 65% nitric acid at a mass ratio of 1:0.3, reacting at 60°C for 2 hours to generate nitrohumic acid, adjusting the pH to 5.5-6.0 with ammonia water to form ammonium salt to enhance water solubility; S2, adding nitrohumic acid and superphosphate to a reaction vessel at a ratio of 2:1, and adding 5% citric acid as... The catalyst was stirred at 80℃ for 1 hour to form a humic acid-phosphoric acid complex. The humic acid-phosphoric acid complex was spray-dried at an outlet temperature of 120℃ to obtain a complex intermediate with a particle size ≤0.5mm. S3: The complex intermediate was mixed with soil conditioner and biochar, and sprayed into a 3% polyvinyl alcohol solution for granulation. The granulated particle size was 2-4mm. The composite microbial agent was sprayed onto the surface of the particles. S4: The particles were coated with a 5% paraffin-rosin composite film with a film thickness of 50-100μm.

[0012] Furthermore, in S3, a twin-helix mixer is used for mixing at a speed of 30-50 rpm for 20 minutes to ensure uniform dispersion of trace elements.

[0013] Furthermore, in S3, the compound microbial agent is sprayed onto the surface of the particles in the form of an aqueous solution with a compound microbial agent:water ratio of 1:5, and the temperature is controlled below 40°C.

[0014] The beneficial effects of this invention are:

[0015] 1. Through the synergistic design of nitrohumic acid complexed phosphate fertilizer, salt-resistant slow-release coating, and biological agents, the soil environment of saline-alkali land is significantly improved in saline-alkali land remediation. The acidic functional groups (-COOH, -NO2, -C6H5) of nitrohumic acid neutralize alkalinity, reducing the soil pH from 8.5-9.5 to 7.0-7.5 (a decrease of 1.5-2.0); nitrohumic acid also improves soil pH through ion exchange (…). Promoting sodium ion leaching, reducing ESP (exchangeable sodium percentage) by 10%–15%; biochar and diatom shale adsorb Cl - SO4 2- Isohalogenated ions decrease soil EC (electrical conductivity) by 30%–50%; humic acid promotes aggregate formation, reducing soil bulk density by 0.2–0.3 g / cm³. 3 Breathability is improved by 40%.

[0016] 2. By complexing superphosphate with nitrohumic acid, it avoids interaction with Ca. 2+ Fe 3+Combining to form insoluble phosphate; paraffin-rosin film controls the release rate of phosphorus, and the effective phosphorus retention time is prolonged to 2-3 times of ordinary phosphorus fertilizer; and the soil phosphorus is decomposed by the phosphorus-dissolving bacteria to release effective phosphorus (PO4 3- ). DETAILED DESCRIPTION

[0017] Example One

[0018] The raw materials are as follows in parts by weight: 65 parts of mineral humic acid, 15 parts of superphosphate, 5 parts of soil conditioner, 10 parts of biochar, 1.5 parts of compound microbial agent, 2 parts of trace elements, and 5 parts of coating material.

[0019] (1) 65 parts of mineral humic acid are reacted with 65% nitric acid at a mass ratio of 1:0.3 at 60°C for 2 hours to generate nitro-humic acid, and then the pH is adjusted to 6.0 with ammonia water.

[0020] (2) The nitro-humic acid is mixed with superphosphate at a ratio of 2:1, 5% citric acid is added, and stirring is performed at 80°C for 1 hour, and then spray drying is performed to obtain a complex intermediate.

[0021] (3) The complex intermediate is mixed with the soil conditioner, biochar, and trace elements, granulated by spraying into a 3% polyvinyl alcohol solution, and the particle size is 3 mm, and then the compound microbial agent is sprayed.

[0022] (4) The granules are coated with the coating material, i.e., paraffin-rosin, by melting, and then cooled and solidified.

[0023] Example Two

[0024] The raw materials are as follows in parts by weight: 65 parts of mineral humic acid, 15 parts of superphosphate, 5 parts of soil conditioner, 10 parts of biochar, 1.5 parts of compound microbial agent, 2 parts of trace elements, and 5 parts of coating material.

[0025] (1) 65 parts of mineral humic acid are reacted with 65% nitric acid at a mass ratio of 1:0.3 at 60°C for 2 hours to generate nitro-humic acid, and then the pH is adjusted to 6.0 with ammonia water.

[0026] (2) The nitro-humic acid is mixed with superphosphate at a ratio of 2:1, 5% citric acid is added, and stirring is performed at 80°C for 1 hour, and then spray drying is performed to obtain a complex intermediate.

[0027] (3) The complex intermediate is mixed with the soil conditioner, biochar, and trace elements, granulated by spraying into a 3% polyvinyl alcohol solution, and the particle size is 3 mm, and then the compound microbial agent is sprayed.

[0028] (4) The granules are coated with the coating material, i.e., paraffin-rosin, by melting, and then cooled and solidified.

[0029] Example Three

[0030] The raw materials are prepared according to parts by weight: 80 parts of mineral source humic acid, 20 parts of calcium superphosphate, 5 parts of soil conditioner, 15 parts of biochar, 2 parts of compound microbial agent, 2 parts of trace elements, and 7 parts of coating material.

[0031] (1) 80 parts of mineral source humic acid is reacted with 65% nitric acid at a mass ratio of 1:0.3 for 2 hours at 60°C to generate nitro humic acid, and then the pH is adjusted to 6.0 with ammonia water.

[0032] (2) The nitro humic acid is mixed with calcium superphosphate at a ratio of 2:1, 5% citric acid is added, and stirred at 80°C for 1 hour, and then spray dried to obtain a complex intermediate.

[0033] (3) The complex intermediate is mixed with the soil conditioner, biochar, and trace elements, sprayed into a 3% polyvinyl alcohol solution to granulate, with a particle size of 3 mm, and sprayed with the compound microbial agent.

[0034] (4) The granules are coated with a coating material, i.e., paraffin-wax-rosin, by melting and solidifying after cooling.

[0035] Comparative Example 1:

[0036] Compared with Example 1, in Comparative Example 1, step (2) of complexing is not performed, the nitro humic acid is mixed with calcium superphosphate at a ratio of 2:1, mixed with the soil conditioner and biochar, sprayed into a 3% polyvinyl alcohol solution to granulate, with a particle size of 3 mm, and sprayed with the compound microbial agent. The rest of the formulation and preparation method are the same as in Example 1.

[0037] Comparative Example 2:

[0038] Compared with Example 1, in Comparative Example 2, step (4) is not performed, and the rest of the formulation and preparation method are the same as in Example 1.

[0039] Comparative Example 3:

[0040] Compared with Example 1, in Comparative Example 3, there is no compound microbial agent, and the rest of the formulation and preparation method are the same as in Example 1.

[0041] The compound fertilizers prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are combined with field test data to verify the effect of the present technology on saline-alkali soil improvement and the effect of phosphorus fertilizer on efficiency.

[0042] Table 1

[0043] Group pH reduction ESP reduction phosphorus utilization yield increase cost (yuan) Example 1 1.4 11％ 48％ 48％ 2200 Example 2 1.2 9％ 38％ 40％ 1800 Example 3 1.5 12％ 42％ 49％ 2300 Comparative Example 1 0.8 4％ 18％ 14％ 1500 Comparative Example 2 1.2 9％ 30％ 31％ 2000 Comparative Example 3 1.3 10％ 35％ 38％ 2100

[0044] Among them, the ESP reduction refers to the reduction of the percentage of exchangeable sodium (Exchangeable Sodium Percentage), which is one of the core indicators for evaluating the effect of saline-alkali soil improvement.

[0045] ESP = Exchangeable sodium content / Soil cation exchange capacity * 100%

[0046] The ESP reduction mechanism of the present application

[0047] (1) -NO2 group: the nitro group (-NO2) introduced by nitration modification of nitro humic acid has strong negative charge, preferentially adsorbs Na + and is replaced by H + or Ca 2+ .

[0048] Reaction example:

[0049] Humic acid-NO2 + Na + → Humic acid-Na + H +

[0050] Release H + neutralize the alkalinity, while reducing the exchangeable sodium content

[0051] (2) Adsorption of biochar and soil conditioner

[0052] Porous structure: biochar and soil conditioner lock free Na by physical adsorption + , reducing the opportunity to participate in soil colloidal exchange.

[0053] (3) Biological desalination of complex microbial agent

[0054] Phosphorus-dissolving bacteria: secrete organic acids to dissolve calcium salts (such as Ca3(PO4)2) in the soil, releasing Ca 2+ replace Na + , promote sodium ion leaching.

[0055] Through Table 1, the data of each item of the compound fertilizer obtained in Example One, Example Two and Example Three are good, and the cost of Example Three is more economical because the number of coating materials is reduced.

[0056] In Comparative Example One, because no complexation is performed, its improvement effect is significantly worse than that of Example One;

[0057] In Comparative Example Two, because no coating is performed, the phosphorus release period is shortened, and it can be seen that the coating component has a prolonging effect on the fertilizer efficiency.

[0058] In Comparative Example Three, because no complex microbial agent is used, the phosphorus utilization rate is reduced, indicating that the complex microbial agent is indispensable for activating soil nutrients.

[0059] In summary, it is shown that the formula of the present application is reasonable, the preparation method is reasonable, and through the synergistic design of nitro humic acid complexing phosphorus fertilizer, salt-resistant slow-release coating and biological microbial agent, the soil environment of saline-alkali land is significantly improved in the treatment of saline-alkali land.

[0060] The present application has been described in detail. The description of specific embodiments is merely intended to help understand the method of the present application and its core idea. It should be pointed out that, for those skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization, comprising the following steps: S1. Preparation of nitrohumic acid: Mix mineral humic acid with 65% nitric acid at a mass ratio of 1:0.3, react at 60℃ for 2 hours to generate nitrohumic acid, adjust the pH to 5.5-6.0 with ammonia water to form ammonium salt to enhance water solubility; S2. Nitrohumic acid and superphosphate were added to the reactor in a ratio of 2:

1. 5% citric acid was added as a catalyst. The mixture was stirred at 80°C for 1 hour to form a humic acid-phosphoric acid complex. The humic acid-phosphoric acid complex was spray-dried at an outlet temperature of 120°C to obtain a complex intermediate with a particle size ≤0.5mm. S3. Mix the complexation intermediate with soil conditioner, biochar and trace elements, spray with 3% polyvinyl alcohol solution to granulate, form by disc granulator, granulation particle size 2-4mm, and spray compound microbial agent on the surface of granules. S4. Coat with a 5% paraffin-rosin composite film, controlling the film thickness to 50-100μm; The prepared complexed phosphate fertilizer comprises the following components by weight: 50-80 parts mineral-derived nitrohumic acid, 10-20 parts superphosphate, 1-5 parts soil conditioner, 1-3 parts trace elements, 5-15 parts biochar, 0.5-2 parts compound microbial agent, and 3-8 parts coating material.

2. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that: The mineral-derived nitrohumic acid is modified with nitric acid and contains nitrate ions, with a pH of 4-6.

3. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that: The trace element is an EDTA chelate of iron or zinc.

4. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that: The soil conditioner is composed of diatomaceous earth shale and bentonite in a mass ratio of 1:

2.

5. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that: The compound bacterial agent is a mixed bacterial group of nitrogen-fixing bacteria and phosphate-solubilizing bacteria in a mass ratio of 1:

1.

6. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that, In S3, a twin-helix mixer is used for mixing at a speed of 30-50 rpm for 20 minutes to ensure uniform dispersion of trace elements.

7. The method for preparing a mineral-derived nitrohumic acid complex phosphate fertilizer for treating soil salinization according to claim 1, characterized in that, In S3, the compound microbial agent is sprayed onto the surface of the particles in the form of an aqueous solution with a compound microbial agent:water ratio of 1:5, and the temperature is controlled below 40℃.