Preparation method and application of special biochar-based fertilizer for saline-alkali soil improvement

Abstract

According to the preparation method of the special biochar base fertilizer for saline-alkali soil improvement, the porous characteristic of biomass charcoal and the characteristic that wood vinegar can adjust the pH value of soil are utilized, the special biochar base fertilizer for saline-alkali soil improvement is prepared, and the preparation method is simple, low in cost and environmentally friendly; the obtained charcoal-based fertilizer can be used as a soil conditioner for improvement and recovery of large-area saline-alkali soil. When the biochar base fertilizer is used for saline-alkali soil cotton planting, it is found that the stem diameter, plant height and leaf chlorophyll content of cotton are remarkably increased, the pH, conductivity and volume weight of soil are remarkably reduced, and the porosity and saturated water-holding capacity of the soil are remarkably increased; the biochar-based fertilizer has the potential of adjusting the acid-base imbalance of the saline-alkali soil, improving the soil structure, increasing the organic matter content of the soil, improving the soil fertility and increasing the crop yield, and a sustainable, economical and effective solution can be provided for agricultural production.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural soil improvement, and specifically relates to a preparation method and application of a biochar-based fertilizer specially used for improving saline-alkali soil. Background Art

[0002] At present, the improvement measures for saline-alkali land mainly include physical improvement, chemical improvement and biological improvement. Physical improvement usually adopts methods such as deep plowing, soil turning, irrigation and salt drainage, but these methods are time-consuming and labor-intensive, and require a large amount of water resources. Chemical improvement adjusts the soil pH or neutralizes salt and alkali by applying chemical improvers such as gypsum and ammonium sulfate, but the long-term use of chemical improvers may cause secondary pollution of the soil, affect the balance of the ecosystem, and increase the cost of agricultural production. Biological improvement mainly uses measures such as planting salt-tolerant plants and inoculating salt-tolerant microorganisms to naturally restore the ecosystem of saline-alkali land. In theory, biological methods can achieve ecological sustainability, but the selection and growth cycle of plants are long and it is difficult to see results in the short term. Therefore, a single biological improvement method has limited effect in dealing with severe saline-alkali land. Therefore, it is urgent to develop an environmentally friendly, economical and efficient method for improving saline-alkali land.

[0003] Biochar-based fertilizer is a new type of slow-release fertilizer that uses biochar as a carrier, adds one or more nutrients such as nitrogen, phosphorus, and potassium, and is mixed by chemical or physical methods. It has certain functions of fertilizer retention and efficiency improvement, nitrogen fixation and emission reduction, and increased production and quality improvement. Biochar is a solid substance formed by high-temperature carbonization of organic matter (such as crop straw, wood, rice husk, etc.) under an oxygen-deficient environment through high-temperature pyrolysis. Biochar has the characteristics of high porosity, large specific surface area, and strong adsorption. It can effectively improve soil structure, enhance water and fertilizer retention capacity, promote soil microbial community diversity, and absorb salt in the soil to reduce salt damage to plant roots. Wood vinegar is a liquid obtained by condensing and recovering biomass materials under pyrolysis or dry distillation. It is a by-product in the preparation of biochar and is mainly composed of organic compounds such as methanol, acetone, water, and acetic acid. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil in view of the deficiencies of the above-mentioned prior art. The biochar-based fertilizer is obtained by combining biochar with wood vinegar and applied to saline-alkali soil. The pH value, electrical conductivity (EC) and bulk density of the saline-alkali soil can be effectively reduced, the soil porosity and saturated water holding capacity can be significantly increased, and the growth and development of plants can be promoted.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil, the method comprising the following steps:

[0007] S1. Preparation of biochar

[0008] The cotton straw is dried and crushed, and the crushed cotton straw is carbonized for 2-3 hours at a temperature of 400-600°C using a large-scale industrial continuous agricultural and forestry solid waste pyrolysis polygeneration device to obtain biochar and gas phase products, and the gas phase products are condensed to obtain wood vinegar;

[0009] S2. Preparation of biochar-based fertilizer

[0010] The biochar obtained in S1 and the wood vinegar are evenly mixed in a ratio of 25t: (600-1800)kg to obtain a biochar-based fertilizer.

[0011] Preferably, the biochar particle size is 0.25 mm and the pH value is 10.

[0012] Preferably, the pH value of the wood vinegar is 3.4.

[0013] The present invention also provides an application of the biochar-based fertilizer in improving saline-alkali soil. The biochar-based fertilizer is applied to the saline-alkali soil 0 to 30 cm underground by broadcasting or rotary tillage, and then irrigated to promote the full integration of the biochar-based fertilizer and the soil. The amount of the biochar-based fertilizer is 25 to 27 t / hm 2 .

[0014] The present invention has significant technical effects due to the adoption of the above technical solution:

[0015] 1. The present invention provides a method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil. The method is simple to operate, low in cost, and environmentally friendly. The prepared biochar-based fertilizer can be used as a soil conditioner for the improvement and restoration of large areas of saline-alkali land. It can neutralize the acid-base imbalance of saline-alkali soil, further adjust the soil microenvironment to make it suitable for crop growth, and has the potential to improve soil structure, increase soil organic matter content, improve soil fertility, and increase crop yields, and can provide a sustainable, cost-effective solution for agricultural production.

[0016] 2. The present invention significantly improves the air permeability and water retention of the soil through the porous characteristics of biochar, and effectively reduces the salt content in the soil through its ion exchange capacity, alleviating the impact of salt damage on plant roots. At the same time, the acidic components in wood vinegar can regulate the alkaline environment in the soil and promote the balance of soil pH. Wood vinegar acidified biochar can significantly increase soil biological activity, improve the physical and chemical properties of the soil, effectively promote the increase in the number of soil aggregates, and improve soil structure.

[0017] The present invention is further described in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0018] Example 1

[0019] This embodiment is a method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil, the method comprising the following steps:

[0020] S1. Preparation of biochar

[0021] The cotton straw is dried and crushed, and the crushed cotton straw is carbonized for 2 hours at a temperature of 500°C using a large-scale industrial continuous agricultural and forestry solid waste pyrolysis polygeneration device, and biochar and gas phase products are obtained after separation and purification, and the gas phase products are condensed to obtain wood vinegar;

[0022] S2. Preparation of biochar-based fertilizer

[0023] The biochar obtained in S1 and the wood vinegar were evenly mixed in a ratio of 25t:600kg to obtain a biochar-based fertilizer.

[0024] Example 2

[0025] This embodiment is a method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil, the method comprising the following steps:

[0026] S1. Preparation of biochar

[0027] The cotton straw is dried and crushed, and the crushed cotton straw is carbonized for 3 hours at a temperature of 400°C using a large-scale industrial continuous agricultural and forestry solid waste pyrolysis polygeneration device, and biochar and gas phase products are obtained after separation and purification, and the gas phase products are condensed to obtain wood vinegar;

[0028] S2. Preparation of biochar-based fertilizer

[0029] The biochar obtained in S1 and the wood vinegar were evenly mixed in a ratio of 25t:1200kg to obtain a biochar-based fertilizer.

[0030] Example 3

[0031] This embodiment is a method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil, the method comprising the following steps:

[0032] S1. Preparation of biochar

[0033] The cotton straw is dried and crushed, and the crushed cotton straw is carbonized for 2 hours at a temperature of 600°C using a large-scale industrial continuous agricultural and forestry solid waste pyrolysis polygeneration device, and biochar and gas phase products are obtained after separation and purification, and the gas phase products are condensed to obtain wood vinegar;

[0034] S2. Preparation of biochar-based fertilizer

[0035] The biochar obtained in S1 and the wood vinegar were evenly mixed in a ratio of 25t:1800kg to obtain a biochar-based fertilizer.

[0036] In the biochar-based fertilizer prepared by the present invention, the particle size of the biochar is 0.25 mm, the pH value is 10, and the pH value of the wood vinegar is 3.4.

[0037] Example 4

[0038] This embodiment is the application of biochar-based fertilizer specially used for improving saline-alkali soil, specifically:

[0039] A cotton pot experiment was conducted with the following four treatments, each replicated three times: no biochar-based fertilizer (CK), application of the biochar-based fertilizer of Example 1 (biochar: 25 t / hm 2 , Wood vinegar: 600kg / hm 2 ), applying the biochar-based fertilizer of Example 2 (biochar: 25 t / hm 2 , Wood vinegar: 1200kg / hm 2 ), applying the biochar-based fertilizer of Example 3 (biochar: 25 t / hm 2 , Wood vinegar: 1800kg / hm 2 ) The amount of base fertilizer applied is: urea 600kg / hm 2 , Potassium dihydrogen phosphate 300kg / hm 2 .

[0040] Mix the biomass charcoal-based fertilizer with air-dried saline-alkali soil. Use a flower pot with a height of 15 cm and a diameter of 15 cm for potted plants. Fill each pot with 1 kg of soil. Add water to the pot to make the relative moisture content of the soil reach 60%, and place it outdoors for 5-7 days. When the surface soil (about 5 cm) is loose, start sowing cotton seeds. After sowing, place the potted plants in a well-ventilated and sunny laboratory for cultivation. Replenish water every 1 day, and the amount of watering should be just enough to seep water from the bottom of the pot. Other conventional management measures are consistent with local fields. After 90 days, the cotton plant height, stem diameter and chlorophyll content, soil pH, electrical conductivity (EC), soil bulk density, soil porosity, and soil saturated water holding capacity were measured. The results are shown in Table 1.

[0041] Table 1 Cotton growth and saline-alkali soil improvement effect after applying biochar-based fertilizer for 90 days

[0042]

[0043] As shown in Table 1, different biochar-based fertilizer treatments have different effects on cotton growth. The cotton plant height of Example 3 is the highest, reaching 24.67 cm, which is significantly higher than that of not applying biochar-based fertilizer (9.2 cm), Example 1 (6.77 cm) and Example 2 (8.97 cm); in terms of stem diameter, the stem diameter of Example 3 (2.83 cm) is the thickest, significantly higher than that of not applying biochar-based fertilizer (1.37 cm), and the stem diameters of Example 1 (1.45 cm) and Example 2 (1.43 cm) are slightly higher than that of not applying biochar-based fertilizer (1.37 cm); SPAD value is an indicator of leaf chlorophyll content, and the SPAD values ​​of Examples 1 to 3 are all higher than those of not applying biochar-based fertilizer.

[0044] Different biochar-based fertilizer treatments significantly reduced the pH, EC and bulk density of saline-alkali soil, increased soil porosity, and improved the saturated water holding capacity of the soil. The soil pH was between 7.52 and 8.15, and the soil pH was the lowest after applying the biochar-based fertilizer of Example 3; the soil conductivity was between 725 and 1086 μS / cm, and the soil conductivity was the lowest after applying the biochar-based fertilizer of Example 2; compared with no application of biochar-based fertilizer, the soil bulk density of Examples 1 to 3 was significantly reduced by 9.43% to 14.78%, and the porosity and saturated water holding capacity were significantly increased by 3.19% to 14.07% and 20.41% to 33.65%, respectively. In general, the biochar-based fertilizer of Example 3 has the best effect on improving saline-alkali soil.

[0045] The porous characteristics of biochar of the present invention significantly improve the air permeability and water retention of the soil, and effectively reduce the salt content in the soil through its ion exchange capacity, thereby alleviating the impact of salt damage on plant roots. At the same time, the acidic components in the wood vinegar can adjust the alkaline environment in the soil and promote the balance of soil pH. Experiments have shown that after applying the biochar-based fertilizer of the present invention, the stem diameter, plant height and leaf chlorophyll content of cotton are significantly increased, and the growth rate and health of the plants are significantly better than those of unimproved soil; the soil pH, electrical conductivity, and bulk density are significantly reduced, and the soil porosity and saturated water holding capacity are significantly increased. The method is low-cost, environmentally friendly, suitable for the improvement and restoration of large areas of saline-alkali land, and can provide a sustainable and economical solution for agricultural production.

[0046] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil, characterized in that: The following steps are involved: S1. Preparation of biochar The cotton straw is dried and crushed, and the crushed cotton straw is carbonized for 2-3 hours at a temperature of 400-600°C using an agricultural and forestry solid waste pyrolysis polygeneration device to obtain biochar and gas phase products, and the gas phase products are condensed to obtain wood vinegar; S2. Preparation of biochar-based fertilizer The biochar obtained in S1 and the wood vinegar are evenly mixed in a ratio of 25t: (600-1800)kg to obtain a biochar-based fertilizer.

2. The method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil according to claim 1, characterized in that: The biochar particle size is 0.25 mm and the pH value is 10.

3. The method for preparing a biochar-based fertilizer specifically for improving saline-alkali soil according to claim 1, characterized in that: The pH value of the wood vinegar is 3.

4.

4. Use of the biochar-based fertilizer according to any one of claims 1 to 3 in improving saline-alkali soil, characterized in that: The amount of biochar-based fertilizer used is 25-27 t / hm 2 .

5. The use according to claim 4, characterized in that: The biochar-based fertilizer is applied to the saline-alkali ground 0 to 30 cm by broadcasting or rotary tillage, and then irrigated to promote full integration of the biochar-based fertilizer and the soil.

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