An acidified soil amendment conditioner, its preparation method and application

Abstract

The application belongs to the technical field of soil improvement, and particularly relates to an acidified soil improvement conditioner, a preparation method and application thereof. The preparation method of the soil improvement conditioner comprises the following steps: (1) grinding and treating mixed fermentation substrate obtained by mixing chopped fresh guayule and oyster shell powder; (2) inoculating bacillus in the mixed fermentation substrate of step (1) to perform fermentation culture, and obtaining activated fermentation product; and (3) uniformly mixing the activated fermentation product of step (2) with a silicon-calcium-potassium-magnesium soil conditioner to obtain the acidified soil improvement conditioner. The preparation method of the application adopts the mixed fermentation substrate of guayule and oyster shell powder, and performs fermentation treatment through bacillus, so that the calcium source of the oyster shell powder can be activated, and the effect of reducing cadmium on soil and planted crops can be improved through biological EPS adsorption.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to an acidified soil conditioner, its preparation method, and its application. Background Technology

[0002] Soil acidification is a serious global problem that significantly impacts the sustainable development of agricultural production. Soil acidification promotes the conversion of fixed aluminum to active aluminum, leading to a significant increase in the concentration of exchangeable aluminum in the soil and a decrease in the silicon-aluminum ratio. This inhibits crop growth and root development, ultimately reducing crop yield. Furthermore, soil acidification is often accompanied by cadmium (Cd) pollution; acidic soils are more susceptible to Cd contamination. 2+ It is easily migrated and absorbed by plants, affecting crop growth and indirectly impacting human health.

[0003] Improving acidic soils using soil conditioners is a widely used and effective method. Oyster shells, with their excellent porous structure and good adsorption properties, can absorb nutrients, providing a slow-release effect and long-term calcium supplementation for crops. They also regulate soil pH and bulk density, making them widely used in acidic soil conditioners. For example, patent document CN 113666786A discloses a method for activating oyster shells, a mixed solution, an oyster shell composition, and a method for preparing a soil conditioner. Through the action of exogenous microorganisms and the endogenous enzymes of by-products, fermentation occurs, creating an acidic environment. Under these acidic conditions, the calcium in the oyster shells can be activated. This not only improves the soil but also provides good fertilization effects because the calcium is easily absorbed. Patent document CN115637151B discloses an acidic soil conditioner comprising the following raw materials in parts by weight: 50-88 parts of alkaline salt modified silicate-based composite material, 10-50 parts of oyster shell powder, and 5-25 parts of sophorolipid-modified silicon-rich calcium biochar. This soil conditioner can efficiently and stably mitigate the aluminum toxicity of acidic soils and significantly reduce the harm of aluminum toxicity to plant growth.

[0004] However, the aforementioned soil conditioners generally only achieve the effects of improving soil pH, modifying soil structure, and appropriately improving fertilizer efficiency. Their effects on reducing the available Cd content in the soil and reducing crop absorption of Cd are very limited.

[0005] Bio-EPS (extracellular polymeric substances) adsorption is a process in which natural organic complexes secreted by microorganisms through metabolic activities can undergo ion exchange, complexation, and precipitation reactions with heavy metal ions, thereby enhancing the adsorption and retention of heavy metal ions. However, the practical application of bio-EPS adsorption in soil conditioners for acidification is currently limited. The main technical challenge lies in preventing the decomposition and re-release of EPS adsorbates in natural soil planting environments. Summary of the Invention

[0006] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for preparing an acidified soil conditioner.

[0007] Another object of the present invention is to provide an acidified soil conditioner prepared by the above method.

[0008] Another object of the present invention is to provide the application of the above-mentioned acidified soil conditioner in the improvement of acidic farmland soil.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing an acidified soil conditioner includes the following preparation steps:

[0011] (1) After mixing chopped fresh stevia with oyster shell powder, the mixture is ground to obtain a mixed fermentation substrate;

[0012] (2) Bacillus was inoculated into the mixed fermentation substrate in step (1) for fermentation culture to obtain activated fermentation products;

[0013] (3) Mix the activated fermentation product from step (2) with the silicon-calcium-potassium-magnesium soil conditioner to obtain an acidified soil conditioner.

[0014] Further, the mass ratio of the fresh stevia to the oyster shell powder in step (1) is 1:0.5-2.

[0015] This invention uses fresh stevia and oyster shell powder as a mixed fermentation substrate. The substrate contains relatively few competing microorganisms, and stevia provides the carbon, nitrogen, and trace elements such as phosphorus and potassium required for Bacillus fermentation. Furthermore, the porous structure of oyster shell powder provides a carrier for rapid fermentation. These conditions collectively promote the growth, reproduction, and metabolism of Bacillus. Simultaneously, Bacillus fermentation activates the calcium source in the oyster shell powder, improving soil pH, soil structure, and fertilizer efficiency. The resulting bio-EPS synergistically adsorbs heavy metal Cd ions, reducing the available Cd content in the soil and decreasing Cd absorption by crops. The porous carrier structure of the oyster shell powder effectively reduces the decomposition and re-release of EPS adsorbates in natural soil planting environments. Through these synergistic effects, a cadmium reduction effect is achieved in both the soil and the crops. Additionally, the fermented mixture increases soil organic matter content, thereby improving soil fertility.

[0016] Furthermore, the Bacillus mentioned in step (2) is Bacillus subtilis (Bacillus subtilis). Bacillus subtilis ) and Bacillus megaterium ( Bacillus megaterium A mixed bacterial solution of Bacillus subtilis and Bacillus megaterium. Preferably, the concentration ratio of Bacillus subtilis to Bacillus megaterium in the mixed bacterial solution is 1:0.5-2. Bacillus subtilis ( Bacillus subtilis ) and Bacillus megaterium ( Bacillus megaterium All of these are commercially available strains commonly used in this field.

[0017] The purpose of this invention, which uses Bacillus subtilis and Bacillus megaterium for mixed fermentation, is twofold: firstly, to improve the soil fertility; and secondly, to ensure that their mixed metabolites have a better adsorption and retention effect on heavy metal Cd ions, thereby improving the cadmium reduction effect of soil improvement.

[0018] Furthermore, the fermentation culture in step (2) is carried out at a temperature of 30-37°C for 24-48 hours.

[0019] Furthermore, the activated fermentation product described in step (2) is further dried to a moisture content of <20%.

[0020] Furthermore, the silicon-calcium-potassium-magnesium soil conditioner described in step (3) has a silicon (SiO2) content ≥25%, a calcium (CaO) content ≥15%, a potassium (K2O) content ≥5%, and a magnesium (MgO) content ≥1%. It is a commercially available raw material commonly used in this field.

[0021] Furthermore, the mass ratio of the activated fermentation product to the silicon-calcium-potassium-magnesium soil conditioner in step (3) is 1-3:1.

[0022] An acidified soil conditioner is prepared by the above method.

[0023] Furthermore, the acidified soil conditioner has a calcium (CaO) content ≥20%, a silicon (SiO2) content ≥10%, an organic matter content ≥12%, and a pH value of 10-12.

[0024] Application of the above-mentioned soil conditioner for acidification in the improvement of acidic farmland soil.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The soil conditioner of the present invention uses oyster shell powder and silicon-calcium-potassium-magnesium soil conditioner as the main pH value regulator and structure regulator. Under the condition of resource utilization of natural oyster shell powder, it reduces soil acidity and increases soil CEC value and silicon-aluminum ratio.

[0027] (2) Through a specific fermentation process, the present invention can activate the calcium source in oyster shell powder, improve the absorption of calcium by crops, and have a better effect on soil structure improvement.

[0028] (3) In this invention, Bacillus is inoculated into a mixed fermentation substrate of stevia and oyster shell powder for fermentation culture. The bio-EPS produced after fermentation can synergistically adsorb heavy metal Cd ions by porous oyster shell powder. At the same time, the porous carrier structure of oyster shell powder can effectively reduce the decomposition and re-release of EPS adsorbates in natural soil planting environment. Through the above synergistic effect, the effective Cd content in the soil and the absorption of Cd by crops are reduced. Moreover, the mixed product after fermentation can also increase the soil organic matter content, thereby improving soil fertility. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Example

[0030] A method for preparing an acidified soil conditioner includes the following preparation steps:

[0031] (1) The chopped fresh stevia and oyster shell powder were mixed in a mass ratio of 1:1 and then ground to obtain a mixed fermentation substrate.

[0032] (2) Inoculate the mixed fermentation substrate in step (1) with Bacillus subtilis at a concentration ratio of 1:1 (w / w). Bacillus subtilis ) and Bacillus megaterium ( Bacillus megaterium The mixed bacterial culture was fermented at an inoculum size of 3 wt% at a temperature of 35°C for 36 hours to obtain activated fermentation products.

[0033] (3) After drying the activated fermentation product of step (2) to a moisture content of <20%, mix it with silicon-calcium-potassium-magnesium soil conditioner (commercially purchased, with silicon (SiO2) content ≥25%, calcium (CaO) content ≥15%, potassium (K2O) content ≥5%, and magnesium (MgO) content ≥1%) at a mass ratio of 2:1 to obtain an acidified soil conditioner.

[0034] The resulting soil conditioner for acidified soil contained 42.8% calcium (CaO), 12.5% ​​silicon (SiO2), 13.0% organic matter, and had a pH of 11.4. Example

[0035] A method for preparing an acidified soil conditioner includes the following preparation steps:

[0036] (1) The chopped fresh stevia and oyster shell powder were mixed at a mass ratio of 1:0.5 and then ground to obtain a mixed fermentation substrate.

[0037] (2) Inoculate the mixed fermentation substrate in step (1) with Bacillus subtilis at a concentration ratio of 1:0.5. Bacillus subtilis ) and Bacillus megaterium ( Bacillus megaterium The mixed bacterial culture was fermented at an inoculum size of 3 wt% at a temperature of 35°C for 36 hours to obtain activated fermentation products.

[0038] (3) After drying the activated fermentation product of step (2) to a moisture content of <20%, mix it with silicon-calcium-potassium-magnesium soil conditioner (commercially purchased, with silicon (SiO2) content ≥25%, calcium (CaO) content ≥15%, potassium (K2O) content ≥5%, and magnesium (MgO) content ≥1%) at a mass ratio of 1:1 to obtain an acidified soil conditioner.

[0039] The resulting soil conditioner for acidified soil contained 37.6% calcium (CaO), 17.1% silicon (SiO2), 12.2% organic matter, and had a pH of 11.5. Example

[0040] A method for preparing an acidified soil conditioner includes the following preparation steps:

[0041] (1) The chopped fresh stevia and oyster shell powder were mixed in a mass ratio of 1:2 and then ground to obtain a mixed fermentation substrate.

[0042] (2) Inoculate the mixed fermentation substrate in step (1) with Bacillus subtilis at a concentration ratio of 1:2. Bacillus subtilis ) and Bacillus megaterium ( Bacillus megaterium The mixed bacterial culture was fermented at an inoculum size of 3 wt% at a temperature of 35°C for 36 hours to obtain activated fermentation products.

[0043] (3) After drying the activated fermentation product of step (2) to a moisture content of <20%, mix it with silicon-calcium-potassium-magnesium soil conditioner (commercially purchased, with silicon (SiO2) content ≥25%, calcium (CaO) content ≥15%, potassium (K2O) content ≥5%, and magnesium (MgO) content ≥1%) at a mass ratio of 3:1 to obtain an acidified soil conditioner.

[0044] The resulting soil conditioner for acidified soil contained 45.6% calcium (CaO), 10.3% silicon (SiO2), 14.7% organic matter, and had a pH of 10.8. Example

[0045] A method for preparing an acidified soil conditioner, compared with Example 1, uses Bacillus subtilis alone (… Bacillus subtilis (Use the mixed bacterial solution as a substitute for fermentation culture, otherwise the same.) Example

[0046] A method for preparing an acidified soil conditioner, compared with Example 1, uses Bacillus megaterium (Beta vulgaris) alone. Bacillus megaterium (Use the mixed bacterial solution as a substitute for fermentation culture, otherwise the same.)

[0047] Comparative Example 1

[0048] A method for preparing an acidified soil conditioner includes the following preparation steps:

[0049] (1) Mix chopped fresh stevia with oyster shell powder at a mass ratio of 1:1, grind and then dry until the moisture content is <20% to obtain the mixture.

[0050] (2) Mix the mixture from step (1) with a silicon-calcium-potassium-magnesium soil conditioner (commercially purchased, with silicon (SiO2) content ≥25%, calcium (CaO) content ≥15%, potassium (K2O) content ≥5%, and magnesium (MgO) content ≥1%) at a mass ratio of 2:1 to obtain an acidified soil conditioner.

[0051] The resulting soil conditioner for acidified soil contained 42.5% calcium (CaO), 12.6% silicon (SiO2), 12.4% organic matter, and had a pH of 11.7.

[0052] The application performance of the soil conditioners for acidified soil obtained in the above embodiments and comparative examples was tested:

[0053] 1. The test soil was red-yellow clay developed from Quaternary red clay. Before the experiment, a mixed sample of the topsoil was taken from the test site to determine the soil fertility as moderate, pH value as 5.0, total cadmium content as 0.72 mg / kg, and available cadmium as 0.48 mg / kg, as shown in Table 1 below:

[0054] Table 1 Soil test results before the experiment

[0055]

[0056] 2. The tested crop and variety was the hybrid rice variety "Chuanxiangyou 2".

[0057] 3. Experimental Methods: A total of 7 treatments were set up, with 3 replicates, for a total of 21 plots, arranged in a randomized block design. Each plot had an area of ​​30 m². 2 The small areas were separated by earthen ridges covered with agricultural film, and protective rows 1.5m wide were set up around the perimeter. Treatment 1: Control (CK), conventional fertilization (30kg of 40% compound fertilizer + 7.5kg of urea + 5kg of potassium chloride per mu), no soil conditioner was applied; Treatments 2-6: conventional fertilization + 100kg / mu of soil conditioner from Examples 1-5 and Comparative Example 1.

[0058] 4. Experimental field management

[0059] Field management followed the principles of "optimal" and "consistent." Except for fertilization, all other management measures were kept consistent across treatments and met production requirements, all completed by designated personnel on the same day. Sowing took place on June 15th, land preparation on July 20th, followed by application of a soil conditioner (except for treatment 1). Transplanting occurred on July 21st. All other management measures remained consistent across treatments. Soil and rice samples were collected from the topsoil of each plot on October 15th, and harvesting took place on October 16th. Yield measurements were conducted on each plot to assess multiple economic traits and determine actual yields for each treatment.

[0060] 5. Sample collection and analysis methods

[0061] Before early rice cultivation, basic soil samples were collected using a 9-point "S"-shaped sampling method at a depth of 20 cm. The Cd content and other physicochemical properties of the soil were analyzed. One day before harvest, rice plant and soil samples were collected from different plots. Five uniformly growing rice plants were sampled using a 5-point sampling method. Grains, stems, and leaves were dried and their Cd content was determined. At each of the rice plant sampling points, a 20 cm sample of the top 20 cm soil was taken from 10 cm away. After mixing and air-drying, stones, visible roots, and other impurities were removed, and the soil was pulverized and passed through 20-mesh and 100-mesh sieves. The Cd content and physicochemical properties of the soil were then determined. Total cadmium in the soil was determined using aqua regia-perchloric acid digestion-atomic absorption spectrometry; available cadmium was determined using atomic absorption spectrometry (GB / T23739-2009). Soil pH was determined using the water extraction glass electrode method; conventional analytical methods were used to determine the soil physicochemical properties. The total Cd content in rice stems, leaves, and grains was determined by microwave digestion with HNO3-H2O2 and ICP-MS.

[0062] 6. Experimental Results and Analysis

[0063] 6.1 The effects of applying soil conditioner on soil properties are shown in Table 2 below.

[0064] Table 2 Soil test results for each treatment

[0065]

[0066] As shown in Table 2, the application of the soil conditioner of this invention had no significant effect on the total cadmium content of the soil, but it had a significant effect on improving the available cadmium content. The maximum reduction in available cadmium was 0.18 mg / kg, with a reduction rate of 37.5%. The soil pH increased by 0.3-0.7 units; the CEC value increased by 0.4-0.6; the silica-alumina ratio increased by 0.23-0.27; the soil organic matter increased slightly, reaching a maximum of 2.5 g / kg; and the available nitrogen, phosphorus, and potassium in the soil were all improved to some extent. The soil treated with the soil conditioner of this invention was significantly better than the control and the soil before the experiment.

[0067] Meanwhile, the comparison results between treatment group 7 (Comparative Example 1) and treatment group 2 show that the fermentation treatment of this invention can significantly improve the soil conditioner's effect on reducing effective cadmium. This is because the bio-EPS produced after fermentation can synergistically enhance the adsorption and retention of heavy metal Cd ions by porous oyster shell powder. Furthermore, the comparison results between treatment groups 5-6 and treatment group 2 show that the mixed fermentation of Bacillus subtilis and Bacillus megaterium can further improve the cadmium reduction effect of the soil compared to single-strain fermentation. This is because the metabolites of mixed fermentation have a better adsorption and retention effect on heavy metal Cd ions.

[0068] 6.2 The effects of applying soil conditioner on the cadmium content of rice are shown in Table 3 below.

[0069] Table 3 Comparative analysis of cadmium (Cd) content in rice from different treatments

[0070]

[0071] The results in Table 3 show that the application of the soil conditioner of this invention can significantly reduce the absorption of cadmium by crops, thereby significantly reducing the cadmium content in crops. Consistent with the results in Table 2, fermentation treatment and the use of mixed fermentation with Bacillus subtilis and Bacillus megaterium play a crucial role in the cadmium reduction effect.

[0072] 6.3 The effects of soil conditioner application on rice yield are shown in Table 4 below.

[0073] Table 4. Statistical data on rice yield for each treatment

[0074]

[0075] As shown in Table 4, the application of the soil conditioner of this invention significantly increased rice yield compared to the control group. Furthermore, the fermentation treatment also showed a significant difference in yield increase compared to the unfermented treatment. This is because the fermentation process activates the calcium source in oyster shell powder, improving crop calcium absorption while simultaneously enhancing soil structure, thus promoting higher quality and yield.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an acidified soil conditioner, characterized in that, The preparation steps include the following: (1) After mixing chopped fresh stevia with oyster shell powder, the mixture is ground to obtain a mixed fermentation substrate; (2) Bacillus was inoculated into the mixed fermentation substrate in step (1) for fermentation culture to obtain activated fermentation products; (3) Mix the activated fermentation product from step (2) with the silicon-calcium-potassium-magnesium soil conditioner to obtain an acidified soil conditioner; The mass ratio of fresh stevia to oyster shell powder in step (1) is 1:0.5-2; The Bacillus mentioned in step (2) is a mixed bacterial culture of Bacillus subtilis and Bacillus megaterium; the concentration ratio of Bacillus subtilis to Bacillus megaterium in the mixed bacterial culture is 1:0.5-2; the fermentation culture temperature is 30-37℃ and the time is 24-48h; The mass ratio of the activated fermentation product to the silicon-calcium-potassium-magnesium soil conditioner in step (3) is 1-3:

1.

2. The method for preparing an acidified soil conditioner according to claim 1, characterized in that, The activated fermentation product described in step (2) is further dried to a moisture content of <20%.

3. The method for preparing an acidified soil conditioner according to claim 1, characterized in that, The silicon-calcium-potassium-magnesium soil conditioner described in step (3) has a silicon content of ≥25%, a calcium content of ≥15%, a potassium content of ≥5%, and a magnesium content of ≥1%.

4. A soil conditioner for acidified soil, characterized in that, It is prepared by the method described in any one of claims 1-3.

5. The soil conditioner for acidification according to claim 4, characterized in that, The acidified soil conditioner has a calcium content ≥20%, a silicon content ≥10%, an organic matter content ≥12%, and a pH value of 10-12.

6. The application of the soil conditioner according to claim 4 or 5 in the improvement of acidic farmland soil.

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