Coastal saline-alkali soil carbon-based modifier as well as preparation method and application thereof

Abstract

The invention relates to a coast saline-alkali soil carbon-based modifier and a preparation method and application thereof. The coast saline-alkali soil carbon-based modifier is prepared from, by mass, 50-60 parts of straw biochar, 20-30 parts of vinegar residues, 15-20 parts of humic acid and 5 parts of calcium sulfate. According to the invention, the problems of high salinity content, low nutrient storage capacity, weak fertilizer retention capability and the like of the coastal saline-alkali soil are effectively solved: straw charcoal, vinegar residues, humic acid and calcium sulfate are combined, so that the salinity and pH of the soil can be reduced, and salt return of the soil is effectively inhibited; meanwhile, the content of organic carbon, nitrogen and phosphorus nutrients in the soil can be increased, and the fertilizer retention capacity of the soil is effectively enhanced; in addition, formation of soil aggregates can be effectively promoted, the soil physical structure of the coastal saline-alkali soil is improved, and then the conversion process of the coastal saline-alkali soil to agricultural soil is accelerated.

Description

Technical Field

[0001] This invention relates to carbon-based soil conditioners for coastal saline-alkali land, their preparation and application methods, and particularly to a carbon-based soil conditioner suitable for coastal saline-alkali land in my country, which has the functions of reducing salinity and increasing carbon content and fertility, as well as its preparation method and application. Background Technology

[0003] Coastal saline-alkali soils are characterized by high salinity, significant annual variations in water and salt transport, and a climate characterized by simultaneous rainfall and heat. The salinity of the topsoil varies considerably with rainfall. Key problems include recurring salinization, low nutrient capacity, and weak fertilizer retention. Therefore, key measures for improving coastal saline-alkali soils are: first, reducing salinity and pH; and second, increasing organic matter to accelerate nutrient capacity expansion. Soil organic colloids carry a large number of negative charges, and their cation exchange capacity and water absorption rate are several times, even tens of times, greater than those of soil clay particles, which can greatly improve the fertilizer retention capacity of saline-alkali soils. Increasing soil organic carbon can effectively regulate the pH of saline-alkali soils, mainly because the acidic substances released during the decomposition and transformation of organic matter have a certain regulatory and buffering effect on soil pH. Furthermore, increasing soil organic carbon can promote the formation of soil aggregates in saline-alkali soils, thereby improving soil physical structure and further promoting soil desalination and inhibiting salt return. Therefore, the research and application of key soil amendments focusing on increasing soil organic carbon are effective ways to reduce salinity, increase carbon, improve fertility, and promote the transformation of coastal saline-alkali soils into agricultural soils. Summary of the Invention

[0004] This invention addresses the prominent problems of high salinity, low nutrient capacity, and weak fertilizer retention in coastal saline-alkali soils. One objective of this invention is to provide a carbon-based soil conditioner for coastal saline-alkali soils. Another objective is to provide a method for preparing this carbon-based soil conditioner for coastal saline-alkali soils. A further objective is to provide a method for improving saline-alkali soils using this carbon-based soil conditioner.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A biochar-based amendment for coastal saline-alkali land contains, by weight: 50-60 parts straw biochar, 20-30 parts vinegar residue, 15-20 parts humic acid, and 5 parts calcium sulfate.

[0007] The straw biochar is made from wheat straw. The wheat straw is crushed to 3-5 cm and placed in a tube furnace. N2 is introduced into the tube furnace to remove air. The temperature is raised to 500℃ at a rate of 5℃ / min. After pyrolysis for 2 hours, the heating program is turned off and the temperature is lowered to room temperature to obtain straw biochar. The biochar has a pH of 9.0-10.0, an ash content of ≥25%, a carbon content of ≥60%, and a nitrogen content of ≥10%.

[0008] The vinegar residue is the residue left after brewing vinegar from rice, wheat, sorghum, etc., with an organic matter content (dry basis) ≥85wt.%, moisture content ≤70wt.%, and pH 4.5-5.5.

[0009] The humic acid has a pH of 5.0-6.0, a carbon content of ≥25%, a fulvic acid content of ≥15%, and a total calcium, magnesium, and sulfur content of ≥10%.

[0010] The calcium sulfate mentioned is gypsum (CaSO4), a white crystalline powder with a CaSO4 content of ≥90%.

[0011] On the other hand, the present invention also provides a method for preparing a carbon-based amendment for coastal saline-alkali land, wherein straw biochar, vinegar residue and humic acid are uniformly mixed using a mixer, and calcium sulfate is added, wherein the amount of calcium sulfate added is 5% of the total mass of straw biochar, vinegar residue and humic acid, and the mixture is stirred evenly.

[0012] On the other hand, this invention provides a method for applying a carbon-based amendment to coastal saline-alkali land, namely, a method for improving saline-alkali land with a carbon-based amendment. In slightly saline-alkali land with a salt content <3g / kg, the dosage is 1-2 tons / mu, applied directly as a base fertilizer; in moderately saline-alkali land with a salt content of 3-6g / kg, the dosage is 3 tons / mu, applied directly as a base fertilizer; and in severely saline-alkali land with a salt content >6g / kg, the dosage is 4-5 tons / mu, applied directly as a base fertilizer.

[0013] After the soil conditioner is evenly spread into the soil, use a rotary tiller to mix the conditioner evenly with the 0-20cm soil. It will be naturally stable in the field for ≥30 days.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0015] (1) Straw biochar has a high specific surface area and pore structure, which reduces soil moisture evaporation in saline-alkali land and increases the effective water content of the soil; it is rich in elements such as carbon, nitrogen, calcium, and magnesium, and at the same time adsorbs nitrogen and phosphorus nutrients in saline-alkali land soil, enhancing the soil's ability to retain and supply fertilizer.

[0016] (2) Vinegar residue can adjust pH, promote the formation of aggregates in saline-alkali soil, improve the soil structure of saline-alkali land, break the capillaries that conduct salt, and reduce the salt content of the surface soil of saline-alkali land; increase the content of soil organic matter and nutrients such as N and P, and provide nutrients for plant growth.

[0017] (3) Humic acid improves soil structure and increases soil water holding capacity; regulates soil pH and enhances soil buffering capacity; rich in organic matter and minerals necessary for plant growth, promotes plant growth, and can improve and promote the absorption of nutrients and water by plants; stimulates the growth and reproduction of beneficial microorganisms in saline-alkali soil.

[0018] (4) Calcium sulfate and sodium-calcium exchange accelerate soil desalination and inhibit soil salinization; Ca 2+ Once it enters the soil, it can further promote the formation of soil aggregates. Attached Figure Description

[0019] Figure 1 Comparative graph of surface soil salinity in coastal saline-alkali land after applying different formulations of carbon-based amendments. Each data point represents the average value of three experimental plots; the surface soil salinity of the BV1, BV2, and BV3 treatments was significantly lower than that of the other treatments.

[0020] Figure 2 Comparison of pH values ​​of surface soil in coastal saline-alkali land after applying different formulations of carbon-based amendments. Each data point represents the average value of three experimental plots; the pH values ​​of surface soil in the BV1 and BV2 treatments were significantly lower than those in the other treatments.

[0021] Figure 3 Comparison of the content of >0.25mm water-stable aggregates in the surface soil of coastal saline-alkali land after applying different formulations of carbon-based amendments. Each data point represents the average value of three experimental plots; the content of >0.25mm water-stable aggregates in the surface soil of saline-alkali land treated with BV2 was significantly higher than that of other treatments.

[0022] Figure 4 Comparative graph of organic carbon content in surface soil of coastal saline-alkali land after applying different formulations of carbon-based amendments. Each data point represents the average value of three experimental plots; the organic carbon content in the surface soil of saline-alkali land in treatments BC, BV2, and BV3 was significantly higher than that in other treatments.

[0023] Figure 5 Comparison of total nitrogen content in surface soil of coastal saline-alkali land after applying different formulations of carbon-based amendments. Each data point represents the average value of three experimental plots; the total nitrogen content in the surface soil of saline-alkali land in treatments BC, BV2, and BV4 was higher than that in other treatments.

[0024] Figure 6 Comparison of maize yields in light, moderate, and severe saline-alkali lands with different dosages of carbon-based soil conditioner. Each data point represents the average of three experimental plots. The optimal dosage of soil conditioner for lightly saline-alkali land is 1-2 tons / mu, for moderately saline-alkali land it is 3 tons / mu, and for severely saline-alkali land it is 4-5 tons / mu. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] A carbon-based soil conditioner for coastal saline-alkali land contains, by weight: 50-60 parts straw biochar, 20-30 parts vinegar residue, 15-20 parts humic acid, and 5 parts calcium sulfate. The straw biochar is made from wheat straw, which is crushed to 3-5 cm and placed in a tube furnace. N2 is introduced into the tube furnace to purge air, and the temperature is raised to 500℃ at a rate of 5℃ / min. After pyrolysis for 2 hours, the heating program is turned off, and the mixture is cooled to room temperature to obtain the straw biochar. The biochar has a pH of 9.0-10.0, an ash content ≥25%, a carbon content ≥60%, and a nitrogen content ≥10%. The vinegar residue is the residue from vinegar brewing from rice, wheat, sorghum, etc., with an organic matter content (dry basis) ≥85 wt.%, a moisture content ≤70 wt.%, and a pH of 4.5-5.5. The vinegar residue used in this embodiment was purchased from Zhenjiang Hengrun Biotechnology Co., Ltd. Humic acid pH 5.0-6.0, carbon content ≥25%, fulvic acid content ≥15%, total calcium, magnesium, and sulfur content...

[0027] ≥10%. Calcium sulfate is gypsum (CaSO4), a white crystalline powder with a CaSO4 content ≥90%.

[0028] The straw biochar, vinegar residue, and humic acid were mixed evenly using a mixer, and calcium sulfate was added. The amount of calcium sulfate added was 5% of the total mass of the straw biochar, vinegar residue, and humic acid. The mixture was then stirred evenly.

[0029] Example 1

[0030] The coastal saline-alkali land had a soil salinity of 4.34 g / kg in the 0-20 cm layer and a soil pH of 8.90. Experimental location: Tiaozini Reclamation Area, Dongtai City, Jiangsu Province; Experimental period: June 2021 - May 2022. The experimental plot was reclaimed in 2015, and no human cultivation measures were implemented afterward.

[0031] A randomized block design was conducted in the field, with each plot measuring 4.0 m × 5.0 m. Six treatments were established using different soil amendment formulations: CK, BC, BV1, BV2, BV3, and BV4, with each treatment replicated three times. The amendments were applied to each plot in April 2021 and mixed thoroughly with the topsoil layer (0–20 cm) using a rotary tiller. Soil samples were collected in May 2022 for testing and analysis.

[0032] CK: blank, without any modifiers, and all other measures are exactly the same.

[0033] BC: 100 portions of straw biochar.

[0034] BV1: 40 parts straw biochar; 30 parts vinegar residue; 25 parts humic acid; 5 parts calcium sulfate.

[0035] BV2: 50 parts straw biochar; 25 parts vinegar residue; 20 parts humic acid; 5 parts calcium sulfate.

[0036] BV3: 60 parts straw biochar; 20 parts vinegar residue; 15 parts humic acid; 5 parts calcium sulfate.

[0037] BV4: 70 parts straw biochar; 15 parts vinegar residue; 10 parts humic acid; 5 parts calcium sulfate.

[0038] The results of the salinity measurements in the 0-20cm topsoil layer for each treatment are shown in the table below. Figure 1 Each carbon-based soil amendment formulation significantly reduced the salinity content of coastal saline-alkali soil. Specifically, the salinity content in the top 0-20 cm soil layer of treatments BV1, BV2, and BV3 was significantly lower than that of other treatments. The pH results of the top 0-20 cm soil layer for each treatment are shown in [link to data]. Figure 2 Each carbon-based soil amendment formulation significantly reduced the pH of the 0-20 cm topsoil layer. Specifically, the pH of the 0-20 cm topsoil layer in the BV1 and BV2 treatments was significantly lower than that in the other treatments. The results of the determination of >0.25 mm water-stable aggregates in the 0-20 cm topsoil layer for each treatment are shown in [the table below]. Figure 3 Among them, the content of >0.25mm water-stable aggregates in the topsoil of saline-alkali land in treatment BV2 was significantly higher than that in other treatments. The results of the determination of organic carbon and total nitrogen in the 0-20cm topsoil of each treatment are shown in [the table below]. Figure 4 and Figure 5 Among them, the organic carbon and total nitrogen content of the surface soil in treatments BC and BV2 were significantly higher than those in other treatments. Considering the data on soil salinity, pH, water-stable macroaggregates, organic carbon, and total nitrogen in saline-alkali land, the optimal formulation for a soil conditioner suitable for coastal saline-alkali land is BV2. However, considering the application cost and actual effectiveness of the conditioner in practical applications, both formulations BV2 and BV3 are applicable.

[0039] Taking the BV2 formula as an example, the main components include straw biochar, vinegar residue, humic acid, and calcium sulfate. The main preparation steps include:

[0040] (1) Add 25 parts of vinegar residue and 20 parts of humic acid to straw biochar and mix thoroughly.

[0041] (2) Add 5 parts of calcium sulfate powder to the (1) system and stir thoroughly to obtain a carbon-based improver for coastal saline-alkali land.

[0042] (3) Application methods: For light, moderate, and severe saline-alkali land in coastal areas, the soil conditioner should be applied in a single application. For lightly saline-alkali land with a salt content <3g / kg, the optimal application rate is 1-2 tons / mu, applied directly as a base fertilizer. For moderately saline-alkali land with a salt content of 3-6g / kg, the optimal application rate is 3 tons / mu, applied directly as a base fertilizer. For severely saline-alkali land with a salt content >6g / kg, the optimal application rate is 4-5 tons / mu, applied directly as a base fertilizer. After the soil conditioner is evenly spread into the soil, use a rotary tiller to mix the conditioner evenly with the 0-20cm soil. After application and natural stabilization for 30 days, salt-tolerant crops can be planted.

[0043] Example 2

[0044] The coastal lightly, moderately, and severely saline-alkali land had soil salinity of 2.45 g / kg, 4.50 g / kg, and 6.85 g / kg in the 0-20 cm topsoil layer, respectively, with soil pH values ​​of 9.04, 8.98, and 8.90. Experimental location: May 2022 – October 2022. The experimental plots were reclaimed in 2015, and no further human cultivation measures were implemented afterward.

[0045] A randomized block design was conducted in the field, with each plot measuring 4.0m × 5.0m. Six treatments were established using different dosages of the carbon-based soil conditioner BV2: 0, 1, 2, 3, 4, and 5 tons / acre, with each treatment replicated three times. The conditioner was applied to each plot in May 2022 and mixed thoroughly with the topsoil layer (0–20cm) using a rotary tiller. Maize was planted in each plot from June to October 2022. Maize yield was measured in October 2022.

[0046] The effects of different application rates of carbon-based soil conditioners on maize yield in lightly, moderately, and severely saline-alkali soils are shown in [reference needed]. Figure 6 Under slightly saline-alkali soil conditions (salt content 2.45 g / kg), applying 1-2 tons of soil conditioner can achieve a higher corn yield; under moderately saline-alkali soil conditions (salt content 4.50 g / kg), applying 3 tons of soil conditioner can achieve a higher corn yield; under severely saline-alkali soil conditions (salt content 6.85 g / kg), applying 4-5 tons of soil conditioner is required to achieve a higher corn yield.

[0047] This invention effectively solves the problems of high salinity, low nutrient capacity, and weak fertilizer retention capacity in coastal saline-alkali soils: by combining biochar, vinegar residue, humic acid, and calcium sulfate, it can effectively reduce soil salinity and pH, increase soil organic carbon and nitrogen and phosphorus nutrient content, effectively enhance soil fertilizer retention capacity, promote the formation of soil aggregates, improve the physical structure of coastal saline-alkali soils, and thus accelerate the transformation of coastal saline-alkali soils into agricultural soils.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A carbon-based amendment for coastal saline-alkali land, characterized in that: It contains, by weight: 50-60 parts straw biochar, 20-30 parts vinegar residue, 15-20 parts humic acid, and 5 parts calcium sulfate.

2. The coastal saline-alkali land carbon-based amendment as described in claim 1, characterized in that: The straw biochar is made from wheat straw. The wheat straw is crushed to 3-5 cm and then placed in a tube furnace. N2 is introduced into the tube furnace to remove air. After heating and pyrolysis, the heating program is turned off and the straw biochar is obtained after cooling to room temperature. The straw biochar has a pH of 9.0-10.0, an ash content of ≥25%, a carbon content of ≥60%, and a nitrogen content of ≥10%.

3. The coastal saline-alkali land carbon-based amendment as described in claim 1, characterized in that: The vinegar residue is the residue after brewing vinegar from rice, wheat or sorghum, with an organic matter content (dry basis) ≥85wt.%, moisture content ≤70wt.%, and pH 4.5-5.

5.

4. The coastal saline-alkali land carbon-based amendment as described in claim 1, characterized in that: The humic acid has a pH of 5.0-6.0, a carbon content of ≥25%, a fulvic acid content of ≥15%, and a total calcium, magnesium, and sulfur content of ≥10%.

5. The coastal saline-alkali land carbon-based amendment as described in claim 1, characterized in that: The calcium sulfate mentioned is gypsum (CaSO4), a white crystalline powder with a CaSO4 content ≥90%.

6. A method for preparing a carbon-based amendment for coastal saline-alkali land as described in any one of claims 1-5, characterized in that: Straw biochar, vinegar residue, and humic acid are mixed evenly, and calcium sulfate is added. The amount of calcium sulfate added is 5% of the total mass of straw biochar, vinegar residue, and humic acid. The mixture is stirred evenly to obtain a carbon-based amendment for coastal saline-alkali land.

7. A method for improving saline-alkali land using any one of the carbon-based amendments for coastal saline-alkali land according to claims 1-5, characterized in that: For slightly saline-alkali land with a salt content of <3g / kg, apply 1-2 tons / mu as base fertilizer by direct application; for moderately saline-alkali land with a salt content of 3-6g / kg, apply 3 tons / mu as base fertilizer by direct application; for severely saline-alkali land with a salt content of >6g / kg, apply 4-5 tons / mu as base fertilizer by direct application.

8. The method for improving saline-alkali land with the carbon-based amendment as described in claim 7, characterized in that: After the carbon-based soil conditioner is evenly spread into the soil in coastal saline-alkali land, use a rotary tiller to mix the carbon-based soil conditioner evenly with the 0-20cm soil. It will be naturally stable in the field for ≥30 days.

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