Functional water and fertilizer retention agent for sandy soil as well as preparation method and application of functional water and fertilizer retention agent

Abstract

The invention belongs to the technical field of soil improvement, and particularly relates to a sandy soil functional water and fertilizer retention agent and a preparation method and application thereof.The preparation method specifically comprises the following steps that 1, modified bentonite, humic acid nano-microspheres and amino acid chelated microelement powder are mixed and stirred; 2, adding sodium alginate-cellulose composite gel and a magnesium ammonium phosphate-urea compound, and stirring to obtain a primary product, and 3, putting the primary product into a granulator, and granulating to obtain the sandy soil functional water and fertilizer retention agent. Through the synergistic effect of multiple components, the performance bottleneck of a single material is broken through, the components have the advantages of being all natural and degradable, the process is simplified, the cost is reduced, and compared with the prior art, the prepared retention agent has remarkable progress in water and fertilizer retention efficiency, environmental compatibility and comprehensive functions.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil improvement, and relates to a functional water and fertilizer retention agent for sandy soil, a preparation method thereof, and an application thereof. Background Art

[0002] Due to the fact that the parent material of sandy soil is mainly composed of coarse silt particles and fine sand particles, and influenced by factors such as long-term wind and sand activities, sandy soil has the characteristics of loose texture, strong dispersibility, fragile structure, poor aggregation, poor water-holding and fertilizer-holding performance, small buffering capacity, low organic matter content, poor nutrient content, and low irrigation and fertilization efficiency. This leads to a large amount of wind erosion, serious soil erosion, and is likely to cause bad environments such as sandstorms. At the same time, it also seriously affects the local grain development. Therefore, improving sandy soil and enhancing the water-holding and fertilizer-holding capacity of sandy soil are of great significance for increasing grain production capacity and maintaining the environment. Among them, using modifiers or retention agents is a commonly used improvement method.

[0003] Common types of sandy soil retention agents include: traditional bentonite-based water retention agents, synthetic polymer material-based retention agents (such as PAM), slow-release fertilizer-based retention agents (such as sulfur-coated urea), and organic-inorganic composite retention agents (humic acid-based). However, the above-mentioned retention agents all have their respective defects. Traditional water retention agents (such as ordinary bentonite, polyacrylamide) are prone to rapid water penetration or evaporation due to loose structure in sandy soil, and have a short water-holding time. Although synthetic polymer materials have strong water retention, their degradation period is long, and the residues may pollute groundwater. The chemical additives contained in them will also affect the activity of soil microorganisms. Traditional fertilizers are easily soluble in water and are prone to leaching in sandy soil. The release rate of slow-release fertilizers is greatly affected by environmental factors and is difficult to match the needs of crops, resulting in low nutrient utilization rate. The process steps of organic-inorganic composite retention agents are cumbersome, the production cost is high, and uneven mixing of multiple components leads to unstable product performance. They cannot simultaneously improve soil structure, retain water and fertilizer, and supplement trace elements, lacking comprehensive improvement ability.

[0004] Therefore, providing a sandy soil retention agent that can effectively improve soil structure, has both water-holding and fertilizer-holding functions, and is harmless to the environment and human body has become an urgent problem to be solved. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a functional water and fertilizer retention agent for sandy soil, a preparation method thereof, and an application thereof, which specifically include the following steps:

[0006] Step 1: Grind bentonite to 100 - 200 meshes, mix it with a sodium carbonate solution in a mass ratio of 1:8, stir and modify it at 80 - 90 °C and 60 - 90 rpm for 4 - 5 h, filter, and calcine and activate the filter residue at 500 - 600 °C for 2 - 3 h to obtain modified bentonite.

[0007] Preferably, the mass concentration of the sodium carbonate solution is 5% - 6%.

[0008] Step 2: Mix carboxymethyl cellulose, sodium alginate and a dispersant in a mass ratio of 3:1:20, freeze at -10 to -15 °C for 1 to 2 h, thaw at 30 to 40 °C for 3 to 4 h, repeat 2 to 3 times, then add a crosslinking agent and stir at 50 to 70 rpm for 30 to 40 min. After supercritical CO2 drying, a sodium alginate-cellulose composite gel is obtained.

[0009] Preferably, the mass ratio of the carboxymethyl cellulose, sodium alginate, dispersant and crosslinking agent is 3:1:20:4. Most preferably, the dispersant includes sodium hydroxide, urea and water in a mass ratio of 3:6:50, and the crosslinking agent is a 0.1 mol / L calcium chloride solution.

[0010] Step 3: Mix humic acid powder and sodium hydroxide solution in a mass ratio of 1:5, stir at 80 to 90 °C and 120 to 150 rpm for 1 to 2 h. Dropwise add hydrochloric acid solution to the solution to adjust the pH to 2.0 - 2.2, centrifuge at 3000 to 4000 rpm for 10 to 15 min to collect the precipitate, wash the precipitate with deionized water until the conductivity of the washing liquid < 50 μS / cm. Mix the precipitate with absolute ethanol, perform ultrasonic treatment at 40 - 50 kHz for 30 to 40 min, and then vacuum dry at 60 - 70 °C to constant weight to obtain humic acid nanospheres.

[0011] Preferably, the concentration of the sodium hydroxide solution is 0.5 mol / L, the concentration of the hydrochloric acid solution is 1 mol / L, and the mass ratio of the precipitate to absolute ethanol is 1:3.

[0012] Step 4: Grind magnesium ammonium phosphate and urea to 70 - 80 mesh respectively, and mix and granulate them in a mass ratio of 3:1 to obtain magnesium ammonium phosphate-urea composite particles with a water content of ≤ 7.5%.

[0013] Step 5: Mix an amino acid and deionized water in a mass ratio of 1:8 to obtain an amino acid solution. Dropwise add a metal salt solution to the amino acid solution, then react at 50 - 60 °C for 15 - 20 min. Concentrate the mixed solution to 1 / 3 of the original volume, cool to 2 - 4 °C to collect the precipitate, and vacuum dry the precipitate at 50 - 60 °C to constant weight to obtain an amino acid chelated trace element powder.

[0014] Preferably, the volume ratio of the amino acid solution to the metal salt solution is 2:1.

[0015] Preferably, the metal salt solution includes ferrous sulfate, zinc sulfate, manganese sulfate, magnesium chloride and water in a mass ratio of 4:3:1:5:100.

[0016] Preferably, the amino acid is one or more of glutamic acid, threonine, proline, isoleucine, lysine and arginine. Most preferably, the amino acid is glutamic acid.

[0017] Step Six: Mix the modified bentonite, humic acid nanospheres and amino acid chelated trace element powder, stir at 30 - 40 °C and 30 - 40 rpm for 10 - 20 min, add water until the water content is 2% - 3%, then add sodium alginate - cellulose composite gel and magnesium ammonium phosphate - urea complex. The magnesium ammonium phosphate - urea complex is added evenly in 3 - 4 times, with an interval of 2 - 3 min each time. Then stir at 35 - 45 °C and 60 - 90 rpm for 15 - 25 min, and then add water until the water content is 3% - 5% to obtain the initial product. Put the initial product into a granulator for granulation, with the particle diameter of 3 - 5 mm and the particle water content of 4% - 5% to obtain the sandy soil functional water and fertilizer retention agent.

[0018] The present invention has the following advantages:

[0019] (1) The modified bentonite prepared by the present invention can significantly improve the adsorption capacity and cation exchange capacity compared with traditional bentonite. The sodium alginate - cellulose composite gel prepared by the present invention has a three - dimensional network structure, can significantly improve the water absorption rate and is biodegradable. The composite gel and the modified bentonite act synergistically to extend the water retention period, which is significantly superior to traditional materials.

[0020] (2) The magnesium ammonium phosphate - urea complex realizes the staged release of nitrogen, phosphorus and magnesium through physical granulation. In the initial stage, urea provides quick - acting nitrogen, and in the later stage, magnesium ammonium phosphate slowly releases phosphorus and magnesium. Amino acid chelated trace elements improve the stability of trace elements, avoid being fixed by the soil, significantly improve the nutrient utilization rate, and the release curve matches the crop fertilizer requirement rule, reducing the risk of water and fertilizer loss.

[0021] (3) All components of the present invention adopt natural or degradable materials, without the risk of chemical residues. A low - concentration calcium chloride is used as the cross - linker to avoid the toxicity problems of traditional cross - linkers (such as glutaraldehyde). The prepared retention agent can be completely degraded in the soil and has no inhibitory effect on the microbial community.

[0022] (4) The humic acid nanospheres of the present invention can improve the soil aggregate structure and enhance the air permeability. Amino acid chelated trace elements directly participate in crop metabolism, enhance the stress resistance, and simultaneously achieve the "four - in - one" effect of water retention, fertilizer retention, structure improvement and trace element supplementation, significantly improving the comprehensive fertility. Detailed implementation mode

[0023] The technical solutions in the invention embodiments are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0024] Example 1

[0025] Step 1: Grind bentonite to 150 mesh, mix it with a sodium carbonate solution with a mass concentration of 5.5% at a mass ratio of 1:8, stir and modify at 90 °C and 90 rpm for 4 h, filter, and calcine and activate the filter residue at 550 °C for 2.5 h to obtain modified bentonite.

[0026] Step 2: Mix carboxymethyl cellulose, sodium alginate, and a dispersant, freeze at -10 °C for 1 h, thaw at 30 °C for 3 h, repeat 3 times, then add a crosslinking agent, stir at 60 rpm for 30 min, and obtain sodium alginate-cellulose composite gel after supercritical CO2 drying. The mass ratio of the carboxymethyl cellulose, sodium alginate, dispersant, and crosslinking agent is 3:1:20:4. The dispersant includes sodium hydroxide, urea, and water, with a mass ratio of 3:6:50. The crosslinking agent is a 0.1 mol / L calcium chloride solution.

[0027] Step 3: Mix humic acid powder with a 0.5 mol / L sodium hydroxide solution at a mass ratio of 1:5, stir at 85 °C and 120 rpm for 1 h, dropwise add a 1 mol / L hydrochloric acid solution to the solution, adjust the pH to 2.0 - 2.2, centrifuge at 3000 rpm for 10 min to collect the precipitate, wash the precipitate with deionized water until the conductivity of the washing liquid < 50 μS / cm, mix the precipitate with absolute ethanol at a mass ratio of 1:3, perform ultrasonic treatment at 50 kHz for 30 min, and then vacuum dry at 65 °C to constant weight to obtain humic acid nanospheres.

[0028] Step 4: Grind magnesium ammonium phosphate and urea to 80 mesh respectively, and mix and granulate them at a mass ratio of 3:1 to obtain magnesium ammonium phosphate-urea composite particles, with the water content of the particles ≤ 7.5%.

[0029] Step 5: Mix glutamic acid with deionized water at a mass ratio of 1:8 to obtain a glutamic acid solution. Dropwise add a metal salt solution to the glutamic acid solution, then react at 55 °C for 20 min, concentrate the mixed solution to 1 / 3 of the original volume, cool to 2 °C to collect the precipitate, and vacuum dry the precipitate at 55 °C to constant weight to obtain glutamic acid chelated trace element powder. The volume ratio of the glutamic acid solution to the metal salt solution is 2:1. The metal salt solution includes ferrous sulfate, zinc sulfate, manganese sulfate, magnesium chloride, and water, with a mass ratio of 4:3:1:5:100.

[0030] Step 6: Mix the modified bentonite, humic acid nanospheres, and glutamic acid chelated trace element powder, stir at 35°C and 40 rpm for 20 min, add water to a water content of 2%, then add sodium alginate-cellulose composite gel and magnesium ammonium phosphate-urea complex. The magnesium ammonium phosphate-urea complex is added in 3 equal portions at intervals of 2 min each, then stir at 40°C and 90 rpm for 20 min, and then add water to a water content of 3% to obtain a preliminary product. Put the preliminary product into a granulator for granulation, with a particle diameter of 3-5 mm and a particle water content of 5%, to obtain a sandy soil functional water and fertilizer retention agent.

[0031] Test Example 1

[0032] Select a local sandy soil area and divide it into several plots on average. Set two treatments. Treatment 1: Apply the PAM soil water retention agent produced by Henan Hongchang Chemical Co., Ltd. Treatment 2: Apply the water and fertilizer retention agent prepared in Example 1. The application rates of both groups of treatments are 300 g / m 2 , and each treatment has 3 replicates. After 72 h, measure the water holding rate and soil aggregate stability. After 7 days, test the nitrogen retention rate, phosphorus and potassium retention rate, increase in organic matter content, and microbial activity. Detect the degradation rate at 1 month, 3 months, 5 months, and 7 months respectively, and calculate the degradation period using analysis software. The results are shown in Table 1.

[0033] Table 1

[0034]

[0035]

[0036] As can be seen from Table 1, the retention agent prepared by the present invention can significantly improve the aggregate stability, nutrient retention rate, and microbial activity of sandy soil compared with the existing PAM soil water retention agent. Its water holding rate is also significantly better than that of the existing PAM soil water retention agent, and the degradation period is significantly shortened.

[0037] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a functional water and fertilizer conservation agent for sandy soil, characterized in that, It includes the following steps: Step 1: Mix and stir modified bentonite, humic acid nanospheres and amino acid chelated trace element powder, and add water until the water content is 2%-3%; Step 2: Add sodium alginate-cellulose composite gel and magnesium ammonium phosphate-urea complex, stir, and add water until the water content is 3%-5% to obtain a preliminary product; Step 3: Put the preliminary product into a granulator for granulation, with the water content of the granules being 4%-5% to obtain a sandy soil functional water and fertilizer retention agent; The mass ratio of the modified bentonite, sodium alginate-cellulose powder composite gel, humic acid nanospheres, magnesium ammonium phosphate-urea complex and amino acid chelated trace element powder is (45-55):(25-35):(10-15):(5-8):(1-2).

2. The preparation method of a functional water and fertilizer conservation agent for sandy soil according to claim 1, characterized in that, The preparation method of the modified bentonite is to mix and stir bentonite and a sodium carbonate solution with a mass fraction of 5%-6% according to a mass ratio of 1:8, filter, and calcine and activate the filter residue at 500-600 °C to obtain modified bentonite.

3. The preparation method of a functional water and fertilizer retention agent for sandy soil according to claim 1, wherein, The preparation method of the sodium alginate-cellulose composite gel is to mix carboxymethyl cellulose, sodium alginate and a dispersant, freeze and thaw and repeat 2-3 times, add a crosslinking agent and mix and stir, and obtain the sodium alginate-cellulose composite gel after supercritical CO2 drying.

4. The preparation method of a functional water and fertilizer retention agent for sandy soil according to claim 3, characterized in that, The mass ratio of the carboxymethyl cellulose, sodium alginate, dispersant and crosslinking agent is 3:1:20:

4. The dispersant includes sodium hydroxide, urea and water, with a mass ratio of 3:6:

50. The crosslinking agent is a 0.1 mol / L calcium chloride solution.

5. The preparation method of a functional water and fertilizer conservation agent for sandy soil according to claim 1, characterized in that, The preparation method of the humic acid nanospheres is to mix and stir humic acid powder and a sodium hydroxide solution according to a mass ratio of 1:5, then add a hydrochloric acid solution, adjust the pH to 2.0-2.2, centrifuge to collect the precipitate, wash the precipitate with deionized water, mix the precipitate with absolute ethanol, perform ultrasonic treatment, and then vacuum dry to constant weight to obtain humic acid nanospheres.

6. The preparation method of a functional water and fertilizer conservation agent for sandy soil according to claim 1, characterized in that The preparation method of the magnesium ammonium phosphate-urea complex is to grind magnesium ammonium phosphate and urea respectively, and granulate them according to a mass ratio of 3:1 to obtain magnesium ammonium phosphate-urea complex particles.

7. The preparation method of a functional water and fertilizer retention agent for sandy soil according to claim 1, characterized in that, The preparation method of the amino acid chelated trace element powder is to mix amino acids and deionized water according to a mass ratio of 1:8 to obtain an amino acid solution, add a metal salt solution to the amino acid solution, react for a period of time and then concentrate the mixed solution, cool at low temperature and collect the precipitate, and vacuum dry the precipitate to constant weight to obtain amino acid chelated trace element powder.

8. The preparation method of a functional water and fertilizer retention agent for sandy soil according to claim 7, characterized in that, The volume ratio of the amino acid solution and the metal salt solution is 2:

1. The metal salt solution includes ferrous sulfate, zinc sulfate, manganese sulfate, magnesium chloride and water, with a mass ratio of 4:3:1:5:

100.

9. A sandy soil functional water and fertilizer retention agent prepared by the method according to any one of claims 1-8.

10. Use of the retention agent according to any one of claims 1-9 in the improvement of sandy soil.

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