Improvement method for improving acid and fertility of red soil cultivated land

Abstract

The invention relates to the technical field of soil treatment, in particular to an improvement method for improving acid and fertility of red soil cultivated land. According to the improvement method, a red soil cultivated land modifier is adopted for improvement, and the red soil cultivated land modifier is obtained by cross-linking sulfonated acetone grafted lignin and epichlorohydrin on the surface of quick lime, dipping in a dipping solution prepared from magnesium chloride, calcium chloride and methanol, drying and grinding. The red soil cultivated land modifier adopted in the improvement method shows an excellent effect on adjusting and maintaining soil acid-base balance, and a feasible and efficient solution is provided for red soil improvement and crop cultivation.

Description

Technical Field

[0001] The invention relates to the technical field of soil treatment, and in particular to a method for improving red soil farmland by converting it into acid and increasing its fertility. Background Art

[0002] Red soil is one of the main soil types in southern my country, accounting for about 11.8% of the country's land area. Due to the uneven seasonal distribution of light, temperature, and water and heat resources in red soil areas, soil organic matter often decomposes rapidly, the structure becomes compacted, air permeability is poor, and acidity is high, resulting in low content of basic nutrients such as potassium, calcium, and magnesium in the soil and poor fertilizer retention. Coupled with intensive planting and over-exploitation in the region, problems such as soil acidification and nutrient depletion are becoming increasingly prominent, and have become the main obstacles to restricting crop growth and increasing grain production.

[0003] In order to give full play to the potential production capacity of red soil areas, corresponding improvement technologies are urgently needed. The main ways to improve the structure of red soil include ecological restoration, planting green manure, balanced fertilization and application of conditioners. Among them, the combined application of balanced fertilization and conditioners is considered to be a key strategy to improve the fertility of red soil and improve 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, phosphogypsum, etc. have achieved remarkable results in improving the production performance of red soil.

[0004] Quicklime is the most commonly used acidified soil conditioner. The application of lime can neutralize soil acidity, slow down the rate of soil acidification, eliminate Al and heavy metal ion toxicity, promote root growth, and increase soil exchangeable Ca 2+ content, which is beneficial for plants to absorb nutrients. However, since lime application provides a large amount of Ca 2+ , while Ca in soil 2+ It has poor mobility and has no obvious effect on the acidity of the underlying soil. Long-term and large-scale application of lime can easily lead to soil calcium enrichment, resulting in an imbalance in soil nutrient ratios, soil compaction and other problems. In addition, the application of quicklime can cause great harm to human skin. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a method for improving red soil farmland from acidification to fertilization, so as to solve the problems that quicklime-based improvers have insufficient pH adjustment ability, which easily causes soil re-acidification, and continuous application of quicklime-based improvers easily leads to soil compaction, which causes great harm to human skin during application.

[0006] Based on the above purpose, the present invention provides a method for improving red soil farmland by converting it into acid and increasing its fertility, which adopts a red soil farmland conditioner for improvement.

[0007] Furthermore, the preparation method of the red soil arable land conditioner is as follows:

[0008] (1) adding alkali lignin and sodium sulfite to deionized water, then adjusting the pH to 8.9-9.5 with sodium hydroxide aqueous solution, adding acetone under nitrogen atmosphere, raising the temperature to 50-60° C., adding a 37 wt % formaldehyde aqueous solution dropwise with stirring, and after the addition is complete, raising the temperature to 90-100° C., carrying out graft copolymerization reaction for 1-3 hours, and drying to obtain sulfonated acetone grafted lignin;

[0009] (2) adding epichlorohydrin, sulfonated acetone grafted lignin and quicklime into anhydrous ethanol, stirring and dispersing, heating to 85-95° C., reflux reaction for 12-18 hours, and purifying to obtain modified quicklime;

[0010] (3) preparing an impregnation solution using magnesium chloride, calcium chloride and methanol, and then impregnating the modified quicklime in the impregnation solution, stirring at a speed of 400-600 rpm for 10-14 hours, filtering, drying, and grinding through a 200-mesh sieve to obtain a red soil arable land 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] Beneficial effects of the present invention:

[0021] The red soil arable land conditioner used in the improvement method of the present invention is significantly superior to the performance of the traditional quicklime conditioner, and its main advantages are reflected in the effect of pH adjustment and long-term stability. By applying it to red soil, the conditioner significantly increases the soil pH and remains stable over a period of 150 days. This ability effectively prevents soil re-acidification, reduces the damage of acidic soil to crop roots and the potential negative impact on the environment, and enables crops to grow healthier in the improved red soil environment.

[0022] Compared with the simple use of sodium lignin sulfonate, sulfonated acetone grafted lignin can better control the release of calcium and magnesium ions, further maintaining the stability of soil pH. In addition, the cross-linking of epichlorohydrin and sulfonated acetone grafted lignin greatly inhibits the sudden release of calcium and magnesium ions.

[0023] The impregnation treatment of 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, helping to avoid magnesium deficiency symptoms in crops.

[0024] The red soil improver used in the improvement method of the present invention shows excellent effects in regulating and maintaining the acid-base balance of the soil, and provides a feasible and efficient solution for red soil improvement and crop cultivation. In addition, since the sulfonated acetone grafted lignin and epichlorohydrin are cross-linked to form a protective layer, damage to human skin during the application of quicklime is avoided. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0026] Embodiment 1:

[0027] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 85 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.2. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 55° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 95° C., and the graft copolymerization reaction was carried out for 2 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

[0028] (2) 35 g of epichlorohydrin and 20 g of sulfonated acetone grafted lignin were added to 200 g of anhydrous ethanol, stirred at 300 rpm for 15 min, then 85 g of quicklime was added, stirring was continued for 30 min, the temperature was raised to 90° C., refluxed for 15 h, filtered, washed, and dried to obtain modified quicklime;

[0029] (3) 9.52 g of magnesium chloride and 5.55 g of calcium chloride were added to 1 L of methanol and stirred to dissolve to obtain an impregnation solution. Then 80 g of modified quicklime was impregnated into the impregnation solution, stirred at 500 rpm for 12 h, filtered, dried, and ground through a 200-mesh sieve to obtain a red soil conditioner.

[0030] Embodiment 2:

[0031] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 67 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 8.9. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 50° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 90° C., and the graft copolymerization reaction was carried out for 3 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

[0032] (2) adding 25 g of epichlorohydrin and 15 g of sulfonated acetone grafted lignin to 200 g of anhydrous ethanol, stirring at 300 rpm for 15 min, then adding 60 g of quicklime, continuing to stir for 30 min, heating to 85° C., reflux reaction for 18 h, filtering, washing, and drying to obtain modified quicklime;

[0033] (3) Add 4.76 g of magnesium chloride and 3.33 g of calcium chloride into 1 L of methanol, stir to dissolve, and obtain an impregnation solution. Then, 50 g of modified quicklime is impregnated into the impregnation solution, stirred at 400 rpm for 14 h, filtered, dried, and ground through a 200-mesh sieve to obtain a red soil conditioner.

[0034] Embodiment 3:

[0035] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 108 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.5. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 60° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 100° C., and the graft copolymerization reaction was carried out for 1 hour, and the mixture was dried at 80° C. for 6 hours to obtain sulfonated acetone grafted lignin;

[0036] (2) 50 g of epichlorohydrin and 25 g of sulfonated acetone grafted lignin were added to 700 g of anhydrous ethanol, stirred at 300 rpm for 15 min, then 100 g of quicklime was added, stirring was continued for 30 min, the temperature was raised to 95° C., refluxed for 12 h, filtered, washed, and dried to obtain modified quicklime;

[0037] (3) 19.04 g of magnesium chloride and 8.88 g of calcium chloride were added to 1 L of methanol and stirred to dissolve to obtain an impregnation solution. Then 100 g of modified quicklime was impregnated into the impregnation solution, stirred at 600 rpm for 10 h, filtered, dried, and ground through a 200-mesh sieve to obtain a red 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 by sodium lignin sulfonate;

[0040] The specific steps are as follows:

[0041] (1) 35 g of epichlorohydrin and 20 g of sodium lignin sulfonate were added to 200 g of anhydrous ethanol, stirred at 300 rpm for 15 min, then 85 g of quicklime was added, the mixture was stirred for 30 min, the temperature was raised to 90° C., refluxed for 15 h, filtered, washed, and dried to obtain modified quicklime;

[0042] (2) 9.52 g of magnesium chloride and 5.55 g of calcium chloride were added to 1 L of methanol, stirred to dissolve, and an impregnation solution was obtained. Then, 80 g of modified quicklime was impregnated into the impregnation solution, stirred at a speed of 500 rpm for 12 h, filtered, dried, and ground through a 200-mesh sieve to obtain an improver.

[0043] Comparative Example 2:

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

[0045] The specific steps are as follows:

[0046] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 85 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.2. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 55° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 95° C., and the graft copolymerization reaction was carried out for 2 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

[0047] (2) adding 55 g of sulfonated acetone grafted lignin to 200 g of anhydrous ethanol, stirring at 300 rpm for 15 min, then adding 85 g of quicklime, continuing to stir for 30 min, heating to 90° C., reflux reaction for 15 h, filtering, washing, and drying to obtain modified quicklime;

[0048] (3) 9.52 g of magnesium chloride and 5.55 g of calcium chloride were added to 1 L of methanol and stirred to dissolve to obtain an impregnation solution, and then 80 g of modified quicklime was impregnated in the impregnation solution, stirred at a speed of 500 rpm for 12 h, filtered, dried, and ground through a 200-mesh sieve to obtain an improver.

[0049] Comparative Example 3:

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

[0051] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 85 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.2. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 55° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 95° C., and the graft copolymerization reaction was carried out for 2 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

[0052] (2) 35 g of epichlorohydrin and 20 g of sulfonated acetone grafted lignin were added to 200 g of anhydrous ethanol, stirred at 300 rpm for 15 min, then 85 g of quicklime was added, stirring was continued for 30 min, the temperature was raised to 90° C., refluxed for 15 h, filtered, washed, and dried to obtain modified quicklime;

[0053] (3) 16.65 g of calcium chloride was added to 1 L of methanol, and the mixture was stirred to dissolve to obtain an impregnation solution. Then 80 g of modified quicklime was impregnated into the impregnation solution, and the mixture was stirred at 500 rpm for 12 h. The mixture was filtered, dried, and ground through a 200-mesh sieve to obtain an improver.

[0054] Comparative Example 4:

[0055] The difference between Comparative Example 4 and Example 1 is that no calcium chloride is added in step (3);

[0056] The specific steps are as follows:

[0057] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 85 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.2. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 55° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 95° C., and the graft copolymerization reaction was carried out for 2 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

[0058] (2) 35 g of epichlorohydrin and 20 g of sulfonated acetone grafted lignin were added to 200 g of anhydrous ethanol, stirred at 300 rpm for 15 min, then 85 g of quicklime was added, stirring was continued for 30 min, the temperature was raised to 90° C., refluxed for 15 h, filtered, washed, and dried to obtain modified quicklime;

[0059] (3) 14.28 g of magnesium chloride was added to 1 L of methanol, and the mixture was stirred to dissolve to obtain an impregnation solution. Then 80 g of modified quicklime was impregnated into the impregnation solution, and the mixture was stirred at 500 rpm for 12 h. The mixture was filtered, dried, and ground through a 200-mesh sieve to obtain an improver.

[0060] Comparative Example 5:

[0061] The difference between Comparative Example 5 and Example 1 is that modified quicklime is directly used as the improver;

[0062] The specific steps are as follows:

[0063] (1) 9.7 g of alkali lignin and 12.6 g of sodium sulfite were added to 85 g of deionized water, and then a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.2. Under a nitrogen atmosphere, 9.7 g of acetone was added, the temperature was raised to 55° C., and the mixture was stirred at 300 rpm. During the stirring process, 28.3 g of a 37 wt % formaldehyde aqueous solution was added dropwise. After the addition was completed, the temperature was raised to 95° C., and the graft copolymerization reaction was carried out for 2 h, and the mixture was dried at 80° C. for 6 h to obtain sulfonated acetone grafted lignin;

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

[0065] Comparative Example 6:

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

[0067] Test site: The test soil is a cultivated red soil developed from the Quaternary red clay and widely distributed in Changsha, Hunan. The basic physical and chemical properties are: 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 4.35.

[0068] Soil culture test: Use red soil from the test site that has been air-dried and passed through a 2 mm sieve, weigh 150 g of red soil, and add 5 g / kg of the red soil amendment prepared in the embodiments and comparative examples, mix well with the red soil and put into plastic bottles, add deionized water at 70% of the field water holding capacity to moisten the soil in each bottle, place the bottle in a constant temperature incubator at 25°C for culture, replenish water by weighing every 3 days, and test soil indicators every 15 days.

[0069] Determination of soil indicators: pH was determined using the water-soil ratio (2.5:1) potentiometric method.

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

[0071]

[0072]

[0073] Data Analysis:

[0074] It can be seen from Examples 1-3 and Comparative Example 6 in Table 1 that the pH of red soil treated with the red soil arable land conditioner prepared by the present invention is significantly higher than the pH of red soil treated with the traditional quicklime conditioner, indicating that the red soil arable land conditioner prepared by the present invention has a better improvement effect. Most importantly, the pH of red soil treated with the red soil arable land conditioner prepared by the present invention has good stability over a period of 150 days, which helps to prevent soil re-acidification and reduce the damage of acidic soil to crop roots and the negative impact of acidic soil on the environment.

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

[0076] From the data of Example 1 and Comparative Example 2 in Table 1, it can be seen that the addition of epichlorohydrin helps to maintain the stability of the red soil pH in the later stage. This is mainly because the cross-linked 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] It can be seen from the data of Example 1 and Comparative Examples 3-5 in Table 1 that the immersion treatment with magnesium chloride and calcium chloride aqueous solutions helps to increase the early pH of red soil and maintain the stability of the later pH, which is mainly due to the regulation of ion concentration.

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

Claims

1. A method for improving red soil farmland by converting it into acid and increasing its fertility, characterized in that: The red soil land conditioner is used for improvement; the preparation method of the red soil land conditioner is as follows: (1) adding alkali lignin and sodium sulfite to deionized water, then adjusting the pH to 8.9-9.5 with sodium hydroxide aqueous solution, adding acetone under nitrogen atmosphere, raising the temperature to 50-60° C., adding a 37 wt % formaldehyde aqueous solution dropwise with stirring, and after the addition is complete, raising the temperature to 90-100° C., carrying out graft copolymerization reaction for 1-3 hours, and drying to obtain sulfonated acetone grafted lignin; (2) adding epichlorohydrin, sulfonated acetone grafted lignin and quicklime into anhydrous ethanol, stirring and dispersing, heating to 85-95° C., reflux reaction for 12-18 hours, and purifying to obtain modified quicklime; (3) preparing an impregnation solution using magnesium chloride, calcium chloride and deionized water, and then impregnating the modified quicklime in the impregnation solution, stirring at a speed of 400-600 rpm for 10-14 hours, filtering, drying, and grinding through a 200-mesh sieve to obtain a red soil arable land conditioner; In the 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 the step (2), the weight ratio of epichlorohydrin, sulfonated acetone grafted lignin and quicklime is 5-10:3-5:12-20; In the step (3), the molar ratio of magnesium chloride to calcium chloride is 1.5-3:

1.

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

3. The method for improving red soil farmland by converting it to acid and improving its fertility according to claim 1, characterized in that: The amount of deionized water added in step (1) is 3-5 times the total weight of alkali lignin and sodium sulfite.

4. The method for improving red soil farmland by converting it to acid and improving its fertility according to claim 1, characterized in that: The amount of anhydrous ethanol added in step (2) is 2-4 times the total weight of epichlorohydrin, sulfonated acetone grafted lignin and quicklime.

5. The method for improving red soil farmland by converting it to acid and improving 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 farmland by converting it to acid and improving its fertility according to claim 1, characterized in that: The concentration of calcium chloride in the immersion solution in step (3) is 0.03-0.08 mol / L.

7. The method for improving red soil farmland by converting it to acidic soil and improving its fertility 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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