A modified biochar composite improver for improving soil acidification and low organic matter content and its preparation method

Abstract

The present invention relates to the technical field of soil conditioners, and more particularly to a modified biochar composite conditioner for improving soil acidification and low organic matter content, and a preparation method thereof. The modified biochar composite conditioner for improving soil acidification and low organic matter content is prepared by modifying corn stalk particles with 3-(triethoxysilyl)propyl succinic anhydride, loading them with magnesium chloride and sodium silicate, and calcining and sieving them. The conditioner can effectively increase the pH value, cation exchange capacity, and organic matter content of the soil, while significantly increasing the clay content in the soil, improving soil structure, enhancing the soil's water and fertilizer retention capacity, and improving nutrient supply efficiency, thereby promoting crop growth.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioners, and in particular to a modified biochar composite conditioner for improving soil acidification and low organic matter content, and a preparation method thereof. Background Art

[0002] Soil acidification and low organic matter content are two major problems that are prevalent in current agricultural production, seriously restricting soil fertility and crop yields. Soil acidification is mainly caused by factors such as long-term application of chemical fertilizers, unreasonable farming methods, and acidic precipitation. It manifests as a decrease in soil pH, a decrease in cation exchange capacity (CEC), increased aluminum ion toxicity, and reduced nutrient availability. Acidified soil not only affects the normal growth of crop roots, but also leads to deterioration of soil structure, further exacerbating soil erosion and nutrient loss. In addition, the insufficient application of organic fertilizers in modern agriculture has led to a year-on-year decline in soil organic matter content, a weakening of the soil's ability to retain water and fertilizer, and a reduction in nutrient supply efficiency, ultimately affecting crop growth and quality.

[0003] Biochar, as a new soil conditioner, has attracted widespread attention in recent years due to its porous structure, high specific surface area, and good adsorption properties. Traditional biochar preparation methods usually use crop straw as raw material and produce it through high-temperature calcination. However, traditional biochar has limited effect in improving acidified soils and increasing organic matter content. The main reasons are that it has insufficient surface active sites, lacks the ability to adsorb cations, and has a weak effect on improving soil structure. Therefore, how to improve the performance of biochar through modification methods so that it can play a more significant role in improving acidified soils and increasing organic matter content has become a hot topic of current research. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to propose a modified biochar composite improver and preparation method for improving soil acidification and low organic matter, and to improve the performance of biochar through modification means, so that it can play a more significant role in improving acidified soil and increasing organic matter content.

[0005] Based on the above objectives, the present invention provides a method for preparing a modified biochar composite amendment for improving soil acidification and low organic matter, comprising the following steps:

[0006] (1) Add corn straw particles to dimethyl sulfoxide and allow to swell for 4-6 hours, then add 3-(triethoxysilyl)propyl succinic anhydride, heat to 155-165°C, add N-methylimidazole, stir and react for 5-7 hours, wash, filter and dry after the reaction to obtain modified corn straw;

[0007] (2) adding the modified corn straw to deionized water, ultrasonically stirring, then adding magnesium chloride and sodium silicate, heating to 55-65°C, stirring and reacting for 10-14 hours, and then standing for 10-14 hours. After standing, washing, filtering, and drying to obtain silicon-magnesium composite corn straw;

[0008] (3) The silicon-magnesium composite corn straw is calcined in a nitrogen atmosphere, cooled to room temperature after calcination, and sieved to obtain a modified biochar composite improver for improving soil acidification and organic matter.

[0009] Preferably, the preparation method of the corn straw pellets is as follows: air-dry the corn straw in a natural state, clean it, cut it short, dry it in a drying oven at 100-120° C. to constant weight, grind it and pass it through an 80-120 mesh sieve to obtain corn straw pellets.

[0010] Preferably, in step (1), the weight ratio of corn straw particles, dimethyl sulfoxide, 3-(triethoxysilyl)propyl succinic anhydride and N-methylimidazole is 10:40-60:0.5-2:1-5.

[0011] Preferably, in step (2), the weight ratio of modified corn straw, deionized water, magnesium chloride and sodium silicate is 10:80-120:0.2-1:1.2-5.

[0012] Preferably, the calcination temperature in step (3) is 500-600° C., and the holding time is 2.5-3.5 hours.

[0013] Preferably, the flow rate of nitrogen in step (3) is 150-300 mL min -1 .

[0014] Preferably, the sieving in step (3) is to sieve through 0.25 and 0.15 mm to obtain the powder with a particle size of 0.15-0.25 mm in the middle interception portion.

[0015] Furthermore, the present invention also provides a modified biochar composite improver for improving soil acidification and low organic matter, which is obtained by the preparation method of the modified biochar composite improver for improving soil acidification and low organic matter.

[0016] Beneficial effects of the present invention:

[0017] The modified biochar composite amendment prepared by the present invention demonstrates significant advantages in improving acidified soils. It can effectively increase soil pH, cation exchange capacity, and organic matter content, while significantly increasing the clay content, improving soil structure, and enhancing the soil's ability to retain water and fertilizer, increasing nutrient supply efficiency, and thus promoting crop growth.

[0018] The present invention adopts 3-(triethoxysilyl)propyl succinic anhydride to modify corn straw, which significantly enhances the soil's adsorption capacity for cations (such as calcium, magnesium, potassium, etc.) by changing the pore structure of corn straw and providing more magnesium-silicon attachment sites, promotes the slow release and effectiveness of nutrients, and improves the acid-base balance and fertility level of the soil. The addition of magnesium chloride forms alkaline adsorption sites through calcination, effectively neutralizes soil acidity, enhances cation exchange capacity (CEC), and further improves the nutrient supply capacity of the soil. The addition of sodium silicate cross-links the silanol groups on the modified straw through hydrolysis, and forms stable silicon oxides and silicate minerals after calcination, which promotes the generation of new clay minerals, thereby increasing the clay content, improving soil structure, and enhancing water and fertilizer conservation effects. DETAILED DESCRIPTION

[0019] 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 with reference to specific embodiments.

[0020] Example 1:

[0021] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 100° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0022] (2) 10 g corn straw particles were added to 40 g dimethyl sulfoxide and swelled for 4 h. 0.5 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 155 °C. 1 g N-methylimidazole was then added and stirred for 5 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0023] (3) 10 g of modified corn straw was added to 80 g of deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 0.2 g of magnesium chloride and 1.2 g of sodium silicate were added. The temperature was raised to 55 ° C, stirred for 10 h, and then allowed to stand for 10 h. After standing, it was washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain silicon-magnesium composite corn straw;

[0024] (4) The silicon-magnesium composite corn straw was placed in a quartz ark, which was then placed in a tube furnace and heated in a nitrogen atmosphere (flow rate of 150 mL min -1 ) The temperature was raised to 500°C under the protection of a carbon dioxide atmosphere, kept warm for 2.5 hours, cooled to room temperature, and the powder with a particle size of 0.15-0.25 mm in the middle was sieved through 0.25 and 0.15 mm sieves, which was the modified biochar composite improver for improving soil acidification and organic matter.

[0025] Example 2:

[0026] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0027] (2) 10 g corn straw particles were added to 50 g dimethyl sulfoxide and swelled for 5 h. 1 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 160 °C. 2 g N-methylimidazole was then added and stirred for 6 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0028] (3) 10 g of modified corn straw was added to 100 g of deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 0.5 g of magnesium chloride and 2.4 g of sodium silicate were added. The temperature was raised to 60 ° C, stirred for 12 h, and then allowed to stand for 12 h. After standing, the mixture was washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain silicon-magnesium composite corn straw;

[0029] (4) The silicon-magnesium composite corn straw was placed in a quartz ark and then placed in a tube furnace. -1 ) The temperature was raised to 550°C under atmosphere protection, kept warm for 3 hours, cooled to room temperature, and the powder with a particle size of 0.15-0.25 mm in the middle was sieved through 0.25 and 0.15 mm, which was the modified biochar composite improver for improving soil acidification and organic matter.

[0030] Example 3:

[0031] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 120° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0032] (2) 10 g corn straw particles were added to 60 g dimethyl sulfoxide and swelled for 6 h. 2 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 165 °C. 5 g N-methylimidazole was then added and stirred for 7 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0033] (3) 10 g of modified corn straw was added to 120 g of deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 1 g of magnesium chloride and 5 g of sodium silicate were added. The temperature was raised to 65 ° C, stirred for 14 h, and then allowed to stand for 14 h. After standing, it was washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain silicon-magnesium composite corn straw;

[0034] (4) The silicon-magnesium composite corn straw was placed in a quartz ark and then placed in a tube furnace. -1 ) The temperature was raised to 600 ° C under the protection of the atmosphere, kept warm for 3.5 hours, cooled to room temperature, and the powder with a particle size of 0.15-0.25 mm in the middle was sieved through 0.25 and 0.15 mm, which was the modified biochar composite improver for improving soil acidification and organic matter.

[0035] Comparative Example 1:

[0036] The difference between Comparative Example 1 and Example 2 is that the modified corn straw in step (3) is replaced with corn straw particles;

[0037] The specific steps are as follows:

[0038] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0039] (2) 10 g corn straw particles were added to 100 g deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 0.5 g magnesium chloride and 2.4 g sodium silicate were added. The temperature was raised to 60 ° C, stirred for 12 h, and then allowed to stand for 12 h. After standing, the particles were washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain silicon-magnesium composite corn straw.

[0040] (3) The silicon-magnesium composite corn straw was placed in a quartz ark and then placed in a tube furnace. -1 ) Heat to 550℃ under atmosphere protection, keep warm for 3 hours, cool to room temperature, and sieve through 0.25 and 0.15mm to obtain the powder with a particle size of 0.15-0.25mm in the middle, which is the improver.

[0041] Comparative Example 2:

[0042] The difference between Comparative Example 2 and Example 2 is that: magnesium chloride is not added in step (3);

[0043] The specific steps are as follows:

[0044] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0045] (2) 10 g corn straw particles were added to 50 g dimethyl sulfoxide and swelled for 5 h. 1 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 160 °C. 2 g N-methylimidazole was then added and stirred for 6 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0046] (3) 10 g of modified corn straw was added to 100 g of deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 2.4 g of sodium silicate was added. The temperature was raised to 60 ° C, stirred for 12 h, and then allowed to stand for 12 h. After standing, it was washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain silicon composite corn straw;

[0047] (4) The silicon-magnesium composite corn straw was placed in a quartz ark and then placed in a tube furnace. -1 ) Heat to 550℃ under atmosphere protection, keep warm for 3 hours, cool to room temperature, and sieve through 0.25 and 0.15mm to obtain the powder with a particle size of 0.15-0.25mm in the middle, which is the improver.

[0048] Comparative Example 3:

[0049] The difference between Comparative Example 3 and Example 2 is that: sodium silicate is not added in step (3);

[0050] The specific steps are as follows:

[0051] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0052] (2) 10 g corn straw particles were added to 50 g dimethyl sulfoxide and swelled for 5 h. 1 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 160 °C. 2 g N-methylimidazole was then added and stirred for 6 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0053] (3) 10 g of modified corn straw was added to 100 g of deionized water, ultrasonicated for 20 min, stirred for 30 min, and then 0.5 g of magnesium chloride was added. The temperature was raised to 60 ° C, stirred for 12 h, and then allowed to stand for 12 h. After standing, it was washed with deionized water three times, filtered, and dried at 80 ° C for 24 h to obtain magnesium composite corn straw;

[0054] (4) The silicon-magnesium composite corn straw was placed in a quartz ark and then placed in a tube furnace. -1) Heat to 550℃ under atmosphere protection, keep warm for 3 hours, cool to room temperature, and sieve through 0.25 and 0.15mm to obtain the powder with a particle size of 0.15-0.25mm in the middle, which is the improver.

[0055] Comparative Example 4:

[0056] The difference between Comparative Example 4 and Example 2 is that the silicon-magnesium composite corn straw in step (4) is replaced with modified corn straw;

[0057] The specific steps are as follows:

[0058] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0059] (2) 10 g corn straw particles were added to 50 g dimethyl sulfoxide and swelled for 5 h. 1 g 3-(triethoxysilyl)propyl succinic anhydride was then added. The temperature was raised to 160 °C. 2 g N-methylimidazole was then added and stirred for 6 h. After the reaction, the particles were washed three times with anhydrous ethanol, filtered, and dried at 80 °C for 12 h to obtain modified corn straw.

[0060] (3) The modified corn straw was placed in a quartz ark and then placed in a tube furnace under nitrogen (flow rate of 200 mL min -1 ) Heat to 550℃ under atmosphere protection, keep warm for 3 hours, cool to room temperature, and sieve through 0.25 and 0.15mm to obtain the powder with a particle size of 0.15-0.25mm in the middle, which is the improver.

[0061] Comparative Example 5:

[0062] The difference between Comparative Example 5 and Example 2 is that the silicon-magnesium composite corn straw in step (4) is replaced by corn straw particles.

[0063] The specific steps are as follows:

[0064] (1) The corn stalks were air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 110° C. to a constant weight, crushed with a multifunctional crusher, and passed through a 100-mesh sieve to obtain corn stalk pellets;

[0065] (2) The corn stalk particles were placed in a quartz ark, which was then placed in a tube furnace and heated under nitrogen (flow rate of 200 mL min -1 ) Heat to 550℃ under atmosphere protection, keep warm for 3 hours, cool to room temperature, and sieve through 0.25 and 0.15mm to obtain the powder with a particle size of 0.15-0.25mm in the middle, which is the improver.

[0066] Performance testing:

[0067] Soil sample analysis method: Soil pH was stirred at a soil-water ratio of 1:2.5 and determined using the composite electrode method; soil cation exchange capacity (CEC) was determined using the 1 mol / L ammonium acetate exchange method; soil organic matter was determined using the externally heated potassium dichromate volumetric method, and clay content was determined using the centrifugation method.

[0068] The test soil was collected from an acidified soil in Hainan Province at a depth of 0 to 20 cm. The soil samples were air-dried, ground, and passed through 2 mm, 1 mm, and 0.149 mm sieves, mixed thoroughly, and used for further analysis. The basic properties of the test soil are shown in Table 1.

[0069] Table 1 Basic properties of the tested soil

[0070]

[0071] Test method: Using a simulated fertilization method, 200g of air-dried soil (passed through a 2mm sieve) and 15g / kg of biomass material (passed through a 2mm sieve) were weighed into a 500mL plastic beaker. After mixing, the water content of the mixed system was adjusted to 75% of the field water holding capacity (soil field saturated water holding capacity was determined using the ring knife method) with deionized water to ensure that the soil was moist and aerated. Except for the control (CK), each soil was set with 8 improvement treatments, including Examples 1-3 and Comparative Examples 1-5. Each treatment was repeated 3 times. A constant temperature aerobic incubation method was used. A polyethylene plastic film was covered on the mouth of the beaker and tightened with a rubber band. A small hole was opened in the middle of the plastic film to ensure that the air in the cup could be freely exchanged with the outside world and to prevent excessive loss of soil moisture. The above treatments were placed in a 25°C constant temperature incubator in a random arrangement and weighed and replenished with water every 2 days. The incubation test lasted for 45 days. After the incubation, the soil samples were taken out, air-dried, ground and passed through 2 mm, 1 mm and 0.149 mm sieves, and the properties of the soil samples were tested. The results are shown in Table 2.

[0072] Table 2 Properties of soil samples after simulated fertilization

[0073]

[0074] Data Analysis:

[0075] From the data of Examples 1-3 and the control group in Table 2, it can be seen that the modified biochar composite amendment prepared by the present invention can effectively increase the pH value, cation exchange capacity and organic matter content of acidified soil, and can significantly increase the clay content in the soil, which helps to improve soil structure, enhance the soil's water and fertilizer retention capacity, improve nutrient supply efficiency and promote crop growth.

[0076] From the data of Example 2 and Comparative Example 1 in Table 2, it can be seen that the amendment prepared by modifying corn straw with 3-(triethoxysilyl)propyl succinic anhydride can significantly increase the pH value, cation exchange capacity, and organic matter content of the soil. This is mainly because 3-(triethoxysilyl)propyl succinic anhydride changes the pore structure of the corn straw and provides more magnesium and silicon attachment sites, thereby enhancing the soil's adsorption capacity for cations (such as calcium, magnesium, potassium, etc.), promoting the slow release and effectiveness of nutrients, and improving the acid-base balance and fertility level of the soil.

[0077] From the data of Example 2 and Comparative Example 2 in Table 2, it can be seen that the addition of magnesium chloride helps to increase the pH value and cation exchange capacity of the soil. This is because after the corn straw is calcined to form biochar, the internal magnesium will form alkaline adsorption sites, thereby neutralizing the soil acidity, enhancing the cation exchange capacity (CEC) and improving the nutrient supply capacity of the soil.

[0078] From the data of Example 2 and Comparative Example 3 in Table 2, it can be seen that the addition of sodium silicate helps to increase the pH value and organic matter content of the soil. Most importantly, it improves the soil structure, increases the clay content, and improves the water and fertilizer retention capacity of the soil. This is mainly because sodium silicate can be hydrolyzed and cross-linked on the silanol groups on the modified straw, and after calcination, it will form stable silicon oxides (such as silicon dioxide, SiO2) and silicate minerals. These silicon oxides combine with cations such as aluminum and iron in the soil, promoting the formation of new clay minerals, thereby increasing the clay content in the soil.

[0079] From the data of Example 2 and Comparative Example 4 in Table 2, it can be seen that sodium silicate and magnesium chloride can synergistically increase the pH value, cation exchange capacity and organic matter content of the soil, improve the soil structure, and enhance the water and fertilizer retention effect of the soil.

[0080] As shown in Table 2, the data from Example 2 and Comparative Example 5 demonstrate that the modified biochar composite amendment prepared in this invention demonstrates significant advantages in improving acidified soils compared to biochar prepared from conventional corn straw pellets. It effectively increases soil pH, cation exchange capacity, and organic matter content, while significantly improving soil structure and enhancing its water and fertilizer retention capacity, providing a superior soil environment for crop growth.

[0081] 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. Within the scope 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 preparing a modified biochar composite improver for improving soil acidification and low organic matter, characterized in that: The following steps are involved: (1) Add corn straw particles to dimethyl sulfoxide and allow to swell for 4-6 hours, then add 3-(triethoxysilyl)propyl succinic anhydride, heat to 155-165°C, add N-methylimidazole, stir and react for 5-7 hours, wash, filter and dry after the reaction to obtain modified corn straw; (2) adding the modified corn straw to deionized water, ultrasonically stirring, then adding magnesium chloride and sodium silicate, heating to 55-65°C, stirring and reacting for 10-14 hours, and then standing for 10-14 hours. After standing, washing, filtering, and drying to obtain silicon-magnesium composite corn straw; (3) The silicon-magnesium composite corn straw is calcined in a nitrogen atmosphere, cooled to room temperature after calcination, and sieved to obtain a modified biochar composite improver for improving soil acidification and organic matter.

2. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: The preparation method of the corn straw pellets is as follows: the corn straw is air-dried, cleaned, and cut short in a natural state, dried in a drying oven at 100-120° C. to a constant weight, crushed, and passed through an 80-120 mesh sieve to obtain corn straw pellets.

3. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: In the step (1), the weight ratio of corn straw particles, dimethyl sulfoxide, 3-(triethoxysilyl)propyl succinic anhydride and N-methylimidazole is 10:40-60:0.5-2:1-5.

4. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: In the step (2), the weight ratio of the modified corn straw, deionized water, magnesium chloride and sodium silicate is 10:80-120:0.2-1:1.2-5.

5. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: The calcination temperature in step (3) is 500-600° C., and the holding time is 2.5-3.5 hours.

6. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: The flow rate of nitrogen in step (3) is 150-300 mL min -1 .

7. The method for preparing the modified biochar composite improver for improving soil acidification and low organic matter according to claim 1, characterized in that: In the step (3), the sieving is performed through 0.25 and 0.15 mm sieves, and the powder with a particle size of 0.15-0.25 mm is retained in the middle.

8. A modified biochar composite improver for improving soil acidification and low organic matter, characterized in that: The modified biochar composite improver for improving soil acidification and low organic matter content is obtained by the preparation method of any one of claims 1 to 7.

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