A method for improving acidification and fertilization of red soil

Abstract

The present application relates to the technical field of soil treatment, in particular to a method for improving red soil farmland to improve acidification and fertilization, wherein the method uses a red soil farmland improver to improve the farmland, and the red soil farmland improver is obtained by impregnating a prepared impregnation liquid into magnesium chloride, calcium chloride and methanol after sulfonated acetone grafted lignin and epoxy chloropropane are crosslinked on the surface of quicklime, and then drying and grinding the crosslinked product. The red soil farmland improver used in the method has excellent effects on adjusting and maintaining the acid-base balance of the soil, and provides a feasible and efficient solution for red soil improvement and crop cultivation.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and in particular to an improved method for converting red soil farmland to acidic soil and improving its fertility. Background Technology

[0002] Red soil is one of the main soil types in southern my country, accounting for approximately 11.8% of the country's land area. Due to the uneven seasonal distribution of sunlight, temperature, and hydrothermal resources in red soil regions, soil organic matter often decomposes rapidly, leading to soil compaction, poor aeration and permeability, and high acidity. This results in low levels of basic nutrients such as potassium, calcium, and magnesium, and poor fertilizer retention. Furthermore, intensive farming and over-exploitation in this region have exacerbated soil acidification, nutrient depletion, and water and fertilizer loss, making these problems increasingly prominent and major obstacles to crop growth and grain production.

[0003] To fully realize the potential productivity of red soil regions, corresponding improvement technologies are urgently needed. The main approaches to improving red soil structure include ecological restoration, planting green manure, balanced fertilization, and the application of soil conditioners. Among these, the combined application of balanced fertilization and soil conditioners is considered a key strategy for improving red soil fertility and soil structure. Soil conditioners are materials that improve the physical, chemical, and biological properties of soil. They effectively reduce soil acidity and improve physical and chemical properties. Commonly used conditioners such as quicklime, humic acid, zeolite, and phosphogypsum have achieved significant results in enhancing the productivity of red soil.

[0004] Quicklime is the most commonly used soil conditioner for acidified soils. Applying lime can neutralize soil acidity, slow down the rate of soil acidification, eliminate the toxicity of Al and heavy metal ions, promote root growth, and increase the exchangeable Ca in the soil. 2+ The content of lime is beneficial for plant nutrient absorption. However, the application of lime provides a large amount of calcium. 2+ And the Ca in the soil 2+ It has poor mobility and does not significantly affect the acidity of the underlying soil. Long-term and excessive application of lime can easily lead to the enrichment of calcium in the soil, resulting in an imbalance of soil nutrients, soil compaction, and other problems. Furthermore, the application of quicklime can cause significant damage to human skin. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose an improved method for acidification and fertilization of red soil cultivated land, in order to solve the problems that quicklime-based soil conditioners have insufficient pH adjustment capabilities, which easily lead to soil re-acidification, and that continuous application of quicklime-based soil conditioners easily leads to soil compaction and causes significant damage to human skin during application.

[0006] To achieve the above objectives, this invention provides a method for improving red soil farmland by converting it to acidic soil and improving its fertility, using a red soil amendment agent.

[0007] Furthermore, the preparation method of the red soil amendment is as follows:

[0008] (1) Add alkali lignin and sodium sulfite to deionized water, then adjust the pH to 8.9-9.5 with sodium hydroxide aqueous solution, add acetone under nitrogen atmosphere, heat to 50-60℃, add 37wt% formaldehyde aqueous solution dropwise with stirring, after the addition is complete, heat to 90-100℃, perform graft copolymerization reaction for 1-3 hours, dry to obtain sulfonated acetone grafted lignin;

[0009] (2) Epichlorohydrin, sulfonated acetone grafted lignin and quicklime were added to anhydrous ethanol, stirred and dispersed, heated to 85-95℃, refluxed for 12-18h, purified, and modified quicklime was obtained.

[0010] (3) Prepare an impregnation solution using magnesium chloride, calcium chloride and methanol, then impregnate the modified quicklime in the impregnation solution, stir at 400-600 rpm for 10-14 hours, filter, dry, grind through a 200-mesh sieve to obtain red soil soil conditioner.

[0011] Furthermore, in step (1), the weight ratio of alkali lignin, sodium sulfite, acetone and formaldehyde aqueous solution is 9.7:12.6:9.7:28.3;

[0012] Furthermore, in step (2), the weight ratio of epichlorohydrin, sulfonated acetone grafted lignin and quicklime is 5-10:3-5:12-20.

[0013] Furthermore, in step (3), the molar ratio of magnesium chloride to calcium chloride is 1.5-3:1.

[0014] Preferably, the concentration of the sodium hydroxide aqueous solution in step (1) is 1 mol / L.

[0015] Preferably, the amount of deionized water added in step (1) is 3-5 times the total weight of alkali lignin and sodium sulfite.

[0016] Preferably, the amount of anhydrous ethanol added in step (2) is 2-4 times the total weight of epichlorohydrin, sulfonated acetone grafted lignin and quicklime.

[0017] Preferably, the concentration of magnesium chloride in the impregnation solution in step (3) is 0.05-0.2 mol / L.

[0018] Preferably, the concentration of calcium chloride in step (3) is 0.03-0.08 mol / L.

[0019] Preferably, the concentration of modified quicklime in the impregnation solution in step (3) is 50-100 g / L.

[0020] The beneficial effects of this invention are:

[0021] The improved red soil conditioner used in this invention significantly outperforms traditional quicklime conditioners, with its main advantages lying in its pH regulation effect and long-term stability. By applying it to red soil, this conditioner significantly increases soil pH and maintains stability over a 150-day period. This effectively prevents soil re-acidification, reduces the damage of acidic soil to crop roots and its potential negative environmental impacts, enabling crops to grow healthier in the improved red soil environment.

[0022] Compared to using sodium lignosulfonate alone, sulfonated acetone-grafted lignin can better control the release of calcium and magnesium ions, further maintaining soil pH stability. Furthermore, the cross-linking of epichlorohydrin with sulfonated acetone-grafted lignin significantly inhibits the sudden release of calcium and magnesium ions.

[0023] Impregnation treatment with magnesium chloride and calcium chloride aqueous solutions demonstrated the efficacy of ion concentration regulation, effectively maintaining and improving the pH and pH stability of red soil, and providing magnesium nutrients to the soil, which helps to prevent magnesium deficiency symptoms in crops.

[0024] The improved method of this invention uses a red soil conditioner that exhibits excellent effects in regulating and maintaining soil pH balance, providing a feasible and efficient solution for red soil improvement and crop cultivation. Furthermore, because sulfonated acetone grafted lignin and epichlorohydrin crosslink to form a protective layer, it avoids the harm to human skin caused by the application of quicklime. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0026] Example 1:

[0027] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 85g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.2. Under nitrogen atmosphere, add 9.7g of acetone, heat to 55℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 95℃ and perform graft copolymerization reaction for 2h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0028] (2) Add 35g epichlorohydrin and 20g sulfonated acetone grafted lignin to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 85g quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, dry, and obtain modified quicklime.

[0029] (3) Add 9.52g magnesium chloride and 5.55g calcium chloride to 1L methanol, stir to dissolve, and obtain impregnation solution. Then impregnate 80g modified quicklime in the impregnation solution, stir at 500rpm for 12h, filter, dry, grind through a 200-mesh sieve to obtain red soil soil conditioner.

[0030] Example 2:

[0031] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 67g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 8.9. Under nitrogen atmosphere, add 9.7g of acetone, heat to 50℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 90℃ and perform graft copolymerization reaction for 3h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0032] (2) Add 25g epichlorohydrin and 15g sulfonated acetone grafted lignin to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 60g quicklime, continue stirring for 30min, heat to 85℃, reflux for 18h, filter, wash, dry, and obtain modified quicklime.

[0033] (3) Add 4.76g magnesium chloride and 3.33g calcium chloride to 1L methanol, stir to dissolve, and obtain impregnation solution. Then impregnate 50g modified quicklime in the impregnation solution, stir at 400rpm for 14h, filter, dry, grind through a 200-mesh sieve to obtain red soil soil conditioner.

[0034] Example 3:

[0035] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 108g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.5. Under nitrogen atmosphere, add 9.7g of acetone, heat to 60℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 100℃ and perform graft copolymerization reaction for 1h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0036] (2) Add 50g epichlorohydrin and 25g sulfonated acetone grafted lignin to 700g anhydrous ethanol, stir at 300rpm for 15min, then add 100g quicklime, continue stirring for 30min, heat to 95℃, reflux for 12h, filter, wash, dry, and obtain modified quicklime.

[0037] (3) Add 19.04g magnesium chloride and 8.88g calcium chloride to 1L methanol, stir to dissolve, and obtain impregnation solution. Then impregnate 100g modified quicklime in the impregnation solution, stir at 600rpm for 10h, filter, dry, grind through a 200-mesh sieve to obtain red soil soil conditioner.

[0038] Comparative Example 1:

[0039] The difference between Comparative Example 1 and Example 1 is that the sulfonated acetone grafted lignin in step (2) is replaced with sodium lignin sulfonate;

[0040] The specific steps are as follows:

[0041] (1) Add 35g epichlorohydrin and 20g sodium lignosulfonate to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 85g quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, dry, and obtain modified quicklime.

[0042] (2) Add 9.52g magnesium chloride and 5.55g calcium chloride to 1L methanol, stir to dissolve, and obtain impregnation solution. Then impregnate 80g modified quicklime in the impregnation solution, stir at 500rpm for 12h, filter, dry, grind through a 200-mesh sieve to obtain the modifier.

[0043] Comparative Example 2:

[0044] The difference between Comparative Example 2 and Example 1 is that epichlorohydrin was not added in step (2);

[0045] The specific steps are as follows:

[0046] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 85g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.2. Under nitrogen atmosphere, add 9.7g of acetone, heat to 55℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 95℃ and perform graft copolymerization reaction for 2h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0047] (2) Add 55g of sulfonated acetone grafted lignin to 200g of anhydrous ethanol, stir at 300rpm for 15min, then add 85g of quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, dry, and obtain modified quicklime.

[0048] (3) Add 9.52g magnesium chloride and 5.55g calcium chloride to 1L methanol, stir to dissolve, and obtain impregnation solution. Then impregnate 80g modified quicklime in the impregnation solution, stir at 500rpm for 12h, filter, dry, grind through a 200-mesh sieve to obtain the modifier.

[0049] Comparative Example 3:

[0050] The difference between Comparative Example 3 and Example 1 is that magnesium chloride was not added in step (3);

[0051] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 85g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.2. Under nitrogen atmosphere, add 9.7g of acetone, heat to 55℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 95℃ and perform graft copolymerization reaction for 2h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0052] (2) Add 35g epichlorohydrin and 20g sulfonated acetone grafted lignin to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 85g quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, dry, and obtain modified quicklime.

[0053] (3) Add 16.65g of calcium chloride to 1L of methanol, stir to dissolve, and obtain an impregnation solution. Then, impregnate 80g of modified quicklime in the impregnation solution, stir at 500rpm for 12h, filter, dry, grind through a 200-mesh sieve to obtain the modifier.

[0054] Comparative Example 4:

[0055] The difference between Comparative Example 4 and Example 1 is that calcium chloride was not added in step (3);

[0056] The specific steps are as follows:

[0057] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 85g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.2. Under nitrogen atmosphere, add 9.7g of acetone, heat to 55℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 95℃ and perform graft copolymerization reaction for 2h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0058] (2) Add 35g epichlorohydrin and 20g sulfonated acetone grafted lignin to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 85g quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, dry, and obtain modified quicklime.

[0059] (3) Add 14.28g of magnesium chloride to 1L of methanol, stir to dissolve, and obtain an impregnation solution. Then, impregnate 80g of modified quicklime in the impregnation solution, stir at 500rpm for 12h, filter, dry, grind through a 200-mesh sieve to obtain the modifier.

[0060] Comparative Example 5:

[0061] The difference between Comparative Example 5 and Example 1 is that modified quicklime was used directly as a modifier.

[0062] The specific steps are as follows:

[0063] (1) Add 9.7g of alkali lignin and 12.6g of sodium sulfite to 85g of deionized water, then add 1mol / L sodium hydroxide aqueous solution to adjust the pH to 9.2. Under nitrogen atmosphere, add 9.7g of acetone, heat to 55℃ and stir at 300rpm. During stirring, add 28.3g of 37wt% formaldehyde aqueous solution dropwise. After the addition is complete, heat to 95℃ and perform graft copolymerization reaction for 2h. Dry at 80℃ for 6h to obtain sulfonated acetone grafted lignin.

[0064] (2) Add 35g epichlorohydrin and 20g sulfonated acetone grafted lignin to 200g anhydrous ethanol, stir at 300rpm for 15min, then add 85g quicklime, continue stirring for 30min, heat to 90℃, reflux for 15h, filter, wash, and dry to obtain modified quicklime, which is the modifier.

[0065] Comparative Example 6:

[0066] The difference between Comparative Example 6 and Example 1 is that quicklime was directly used as a soil conditioner for red soil.

[0067] Test site: The test soil was cultivated red soil, which is widely distributed in Changsha, Hunan Province and developed from Quaternary red clay. Basic physicochemical properties: mineral nitrogen 19.86 mg / kg, available phosphorus 29.63 mg / kg, available potassium 45.55 mg / kg, exchangeable calcium 154.32 mg / kg, exchangeable magnesium 11.25 mg / kg, total exchangeable acid 3.38 cmol / kg, pH value 4.35.

[0068] Soil incubation experiment: 150g of red soil from the test site was weighed after being air-dried and passed through a 2mm sieve. 5g / kg of the red soil soil conditioner prepared in the examples and comparative examples was added and thoroughly mixed with the red soil. The mixture was then placed in plastic bottles. Deionized water was added to each bottle at 70% of the field water holding capacity to moisten the soil. The bottles were placed in a 25℃ constant temperature incubator for incubation. Water was added every 3 days by weighing, and soil indicators were tested every 15 days.

[0069] Soil parameters were determined: pH was measured using the water-to-soil ratio (2.5:1) potentiometric method.

[0070] Table 1. pH test results of soil culture experiment

[0071]

[0072]

[0073] Data Analysis:

[0074] As can be seen from Examples 1-3 and Comparative Example 6 in Table 1, the pH of red soil treated with the red soil conditioner prepared in this invention is significantly higher than that of red soil treated with traditional quicklime conditioner. This indicates that the red soil conditioner prepared in this invention has a better improvement effect. Most importantly, the pH of red soil treated with the red soil conditioner prepared in this invention has good stability over a 150-day period, which helps to prevent soil re-acidification and reduce the damage of acidic soil to crop roots and negative environmental impacts.

[0075] As can be seen from the data in Example 1 and Comparative Example 1 in Table 1, compared with sodium lignosulfonate, sulfonated acetone-grafted lignin helps maintain the pH stability of red soil. This is mainly because the coating layer formed by the cross-linking of sodium lignosulfonate and epichlorohydrin has a denser structure, which prevents the loading of calcium and magnesium ions and the release of quicklime inside, thereby causing the pH of red soil to drop rapidly.

[0076] As can be seen from the data in Table 1 for Example 1 and Comparative Example 2, the addition of epichlorohydrin helps maintain the stability of the pH in the later stage of red soil. This is mainly because the cross-linking structure formed by epichlorohydrin and sulfonated acetone grafted lignin regulates the release of calcium and magnesium ions and prevents the sudden release in the early stage.

[0077] As can be seen from the data in Table 1 of Example 1 and Comparative Examples 3-5, the impregnation treatment with magnesium chloride and calcium chloride aqueous solution helps to increase the early pH of red soil and maintain the stability of the later pH, which is mainly due to the regulating effect of ion concentration.

[0078] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for improving red soil arable land by converting it to acidic soil and increasing its fertility, characterized in that, The soil was improved using a red soil conditioner; the preparation method of the red soil conditioner is as follows: (1) Add alkali lignin and sodium sulfite to deionized water, then adjust the pH to 8.9-9.5 with sodium hydroxide aqueous solution, add acetone under nitrogen atmosphere, heat to 50-60℃, add 37wt% formaldehyde aqueous solution dropwise with stirring, after the addition is complete, heat to 90-100℃, perform graft copolymerization reaction for 1-3 hours, dry to obtain sulfonated acetone grafted lignin; (2) Epichlorohydrin, sulfonated acetone grafted lignin and quicklime were added to anhydrous ethanol, stirred and dispersed, heated to 85-95℃, refluxed for 12-18h, purified, and modified quicklime was obtained. (3) Prepare an impregnation solution using magnesium chloride, calcium chloride and deionized water, then impregnate the modified quicklime in the impregnation solution, stir at 400-600 rpm for 10-14 hours, filter, dry, grind through a 200-mesh sieve to obtain red soil soil conditioner. In step (1), the weight ratio of alkali lignin, sodium sulfite, acetone and formaldehyde aqueous solution is 9.7:12.6:9.7:28.

3. In step (2), the weight ratio of epichlorohydrin, sulfonated acetone grafted lignin and quicklime is 5-10:3-5:12-20. In step (3), the molar ratio of magnesium chloride to calcium chloride is 1.5-3:

1.

2. The method for improving red soil arable land by converting it to acidic soil and increasing its fertility according to claim 1, characterized in that, The concentration of the sodium hydroxide aqueous solution in step (1) is 1 mol / L.

3. The method for improving red soil arable land by acidification and fertilization according to claim 1, characterized in that, In step (1), the amount of deionized water added is 3-5 times the total weight of alkali lignin and sodium sulfite.

4. The method for improving red soil arable land by acidification and fertilization according to claim 1, characterized in that, In step (2), the amount of anhydrous ethanol added is 2-4 times the total weight of epichlorohydrin, sulfonated acetone grafted lignin, and quicklime.

5. The method for improving red soil arable land by converting it to acidic soil and increasing its fertility according to claim 1, characterized in that, The concentration of magnesium chloride in the impregnation solution in step (3) is 0.05-0.2 mol / L.

6. The method for improving red soil arable land by acidification and fertilization according to claim 1, characterized in that, The concentration of calcium chloride in the impregnation solution in step (3) is 0.03-0.08 mol / L.

7. The method for improving red soil arable land by acidification and fertilization according to claim 1, characterized in that, The concentration of modified quicklime in the impregnation solution in step (3) is 50-100 g / L.

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