Paddy field lime substance application method based on portable pH meter

Abstract

The invention belongs to the technical field of acid soil improvement, and discloses a rice field lime substance application method based on a portable pH meter, and the method comprises the following steps: constructing a soil pH dynamic response model through gradient test and multi-index synchronous analysis, and significantly improving the lime application accuracy. The potentiometric method and the portable pH meter are combined for cross validation, so that the determination efficiency is ensured, and the data reliability is also improved. The linear regression analysis further reveals the internal correlation between the soil chemical property and the pH change, provides a scientific basis for the optimization of the lime dosage, and effectively balances the soil improvement effect and the cost input. The soil health can be comprehensively evaluated through multi-parameter synchronous measurement, and sustainable development of agriculture is assisted.

Description

Technical Field

[0001] The present invention belongs to the technical field of improving acidic soil and relates to a method for applying lime substances in paddy fields based on a portable pH meter. Background Art

[0002] In agricultural production, the precise regulation of soil pH value is extremely crucial for crop growth. Soil acidification has become the main limiting factor in rice production in the south. Applying lime substances can improve acidified soil and increase rice yield. However, due to the high heterogeneity of the soil, the appropriate lime dosage needs to be determined according to local conditions for each field soil property one by one. Previous studies have shown that the basic soil pH value is the most important index for determining the dosage of lime substances in red soil paddy fields. However, although the high-precision laboratory soil pH meter based on the potentiometric method has accurate testing, it has cumbersome operations and strict requirements for experimental instruments and conditions, and is not suitable for rapid field determination. The portable pH meter is cheap, easy to operate, and can obtain test results immediately. However, the test accuracy of the portable pH meter is lower than that of the high-precision laboratory soil pH meter, and there are also certain differences in the accuracy of the results. Therefore, there is an urgent need for a method to improve the test accuracy of the portable pH meter, and then determine the dosage of lime substances in red soil paddy fields. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem that the test accuracy of the portable pH meter in the prior art is low and the dosage of lime substances in red soil paddy fields cannot be accurately determined, and to provide a method for applying lime substances in paddy fields based on a portable pH meter.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for applying lime substances in paddy fields based on a portable pH meter includes:

[0006] Step 1: Collect several soil samples, collect a fixed weight of soil in each soil sample, set different gradients of Ca(OH)2 application amounts, and measure the soil pH value by the potentiometric method and the portable pH meter respectively;

[0007] Step 2: After obtaining the soil pH value, based on each soil sample, measure the organic matter content, exchangeable acid, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable base amount, and base saturation degree in the soil;

[0008] Step 3: Based on the obtained soil pH value, through the collected soil samples, calculate the soil quality of the 0-40 cm plough layer per hectare according to the soil bulk density, set different gradients of Ca(OH)2 application amounts, and measure the final soil pH.

[0009] Step 4: Based on different application rates of Ca(OH)₂ gradients, construct the linear relationships between the basic pH measured by the potentiometric method and the pH increase rate, and between the basic pH measured by the portable pH meter and the pH increase rate for the soil sample pH value and the final soil pH, respectively;

[0010] Step 5: Conduct a linear regression analysis on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H⁺ ions, soil exchangeable Al³⁺ ions, total exchangeable base amount, and base saturation degree in the soil;

[0011] Step 6: Calibrate the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate based on the linear relationship between the basic pH measured by the potentiometric method and the pH increase rate;

[0012] Step 7: Based on the calibrated equation and the results of the linear regression analysis in Step 5, obtain the application rate of lime-like substances.

[0013] A further improvement of the present invention lies in:

[0014] Furthermore, collect several soil samples, collect a fixed weight of soil in each soil sample, set different gradients of Ca(OH)₂ application rates, and measure the soil pH value by the potentiometric method and the portable pH meter respectively, specifically:

[0015] Set three Ca(OH)₂ application rates, which are 3 t hm -2 (LL), 6 t hm -2 (ML), and 9 t hm -2 (HL); weigh 90 g of each soil sample, repeat 3 times, calculate the weight of the plow layer soil according to the plow layer depth of 40 cm and the soil bulk density of 1.2 g / cm -3 , add an equal amount of lime to the bottle according to the mass ratio; maintain a soil mass water content of 15% - 20%, cultivate at room temperature indoors for 30 d; monitor the change in soil water content, and measure the pH value before and after cultivation respectively, using both the potentiometric method and the portable pH meter.

[0016] Furthermore, the Ca(OH)₂ application rate is

[0017] m (20cm耕层土重) = 10000 * 0.2 * 1.2 = 2.4 * 10 3 t hm -2

[0018] The lime addition amount m (LL) = 3 * 90 / (2.4 * 10 3 ) = 0.1125 g

[0019] m (ML) = m (LL)*2 = 0.225 g

[0020] m (HL) = m (LL) *3 = 0.3375 g.

[0021] Furthermore, based on the obtained soil pH value, through the collected soil samples, calculate the soil mass of the 0 - 40 cm plough layer per hectare according to the soil bulk density, set different gradients of Ca(OH)₂ application rates, and measure the final soil pH. Specifically: Weigh 3 air-dried soil samples from each farmland, each with a mass of 90 g, and calculate the soil mass of the 0 - 20 cm plough layer per hectare according to the soil bulk density of 1.2 g / cm³. Add slaked lime Ca(OH)₂ equivalent to the application rates of 3 t / hm³, 6 t / hm³, and 9 t / hm³ respectively, with 3 replicates. After maintaining a 1 - 2 cm water layer in the artificial climate chamber at 25 °C and culturing in the dark for 30 d, measure the final soil pH. -3 Calculate the soil mass of the 0 - 20 cm plough layer per hectare, and add slaked lime Ca(OH)₂ equivalent to the application rates of 3 t / hm³, -2 6 t / hm³, -2 and 9 t / hm³ -2 respectively. With 3 replicates, after maintaining a 1 - 2 cm water layer in the artificial climate chamber at 25 °C and culturing in the dark for 30 d, measure the final soil pH.

[0022] Furthermore, according to different gradients of Ca(OH)₂ application rates, construct the linear relationships between the basic pH measured by the potentiometric method and the pH increase rate, and between the basic pH measured by the portable pH meter and the pH increase rate for the soil samples and the final soil pH. Specifically: Use Origin 2021 software to perform linear fitting on the soil pH values measured without lime application, 3 t / hm³ (LL), 6 t / hm³ (ML), and 9 t / hm³ (HL) to calculate the pH increase rate and plot the graph. -2 (LL), 6 t / hm³ -2 (ML), and 9 t / hm³ -2 (HL) to calculate the pH increase rate and plot the graph.

[0023] Furthermore, construct the linear relationship between the basic pH measured by the potentiometric method and the pH increase rate. Specifically:

[0024] y1 = -0.3008x1 + 2.1238

[0025] where x1 is the basic soil pH value measured by the potentiometric method;

[0026] The linear relationship between the basic pH measured by the portable pH meter and the pH increase rate is specifically:

[0027] y2 = -0.2708x2 + 1.8935

[0028] where x2 is the basic soil pH value measured by the portable pH meter.

[0029] Further, linear regression analysis was performed on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable bases, and base saturation in the soil. Specifically: Statistical analysis was carried out using SPSS 25.0 software. When the level of P < 0.05, a significance test was conducted; linear stepwise regression analysis was performed on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable bases, and base saturation in the soil.

[0030] Further, based on the linear relationship between the basic pH measured by the potentiometric method and the pH increase rate, the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate was corrected. Specifically:

[0031] The portable linear regression equation was corrected using the linear regression equation of the potentiometric method, and the correction coefficient K = 1.149 was obtained. The corrected equation was y = -0.3112x + 2.1756.

[0032] Further, based on the corrected equation and the results of the linear regression analysis in step 5, the application rate of lime substances was obtained. Specifically:

[0033] Through the fitting of the organic matter content, basic pH value, pH increase rate, exchangeable acidity, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable bases, and base saturation in several groups of soils and the analysis of the fitted linear equation, the actual meaning of y was the increase in soil pH per ton of lime applied per hectare. Thus, the application rate model of slaked lime Ca(OH)2 was established. Specifically:

[0034]

[0035] Among them, y3 was the amount of slaked lime required; x3 was the basic pH value, and x4 was the target pH value;

[0036] According to the acid neutralization capacity of different lime substances, the models for adjusting acidic soils with quicklime and calcium carbonate were obtained:

[0037] The application rate model of quicklime was:

[0038]

[0039] The application rate model of calcium carbonate was:

[0040]

[0041] Among them, The meaning of was the unit conversion from hectares to mu; 136, 100, and 179 were the neutralization values of calcium hydroxide, calcium carbonate, and quicklime, respectively.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] Through gradient experiments and multi-index synchronous analysis, the present invention constructs a dynamic response model of soil pH, significantly improving the accuracy of lime application. Combining potentiometry with cross-validation of a portable pH meter not only ensures the measurement efficiency but also improves the data reliability. Linear regression analysis further reveals the internal relationship between soil chemical properties and pH changes, providing a scientific basis for optimizing lime dosage and effectively balancing the soil improvement effect and cost investment. Synchronous multi-parameter measurement can also comprehensively evaluate soil health, contributing to the sustainable development of agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0045] Figure 1 It is a schematic flow chart of the method for applying lime substances in paddy fields based on a portable pH meter of the present invention;

[0046] Figure 2 It is a schematic structural diagram of the linear relationship between the basic pH and the pH increase rate measured by potentiometry;

[0047] Figure 3 It is a schematic structural diagram of the linear relationship between the basic pH and the pH increase rate measured by a portable pH meter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0050] It should be noted that like reference numerals and letters refer to like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0051] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0052] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0053] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0054] The present invention will be further described in detail below with reference to the accompanying drawings:

[0055] See Figure 1 , the present invention discloses a method for applying lime substances in paddy fields based on a portable pH meter, including:

[0056] S101, collecting several soil samples, collecting a fixed weight of soil in each soil sample, setting different gradients of Ca(OH)2 application rates, and measuring the soil pH values by potentiometry and a portable pH meter respectively;

[0057] Set three Ca(OH)2 application rates, which are 3 t hm -2 (LL), 6 t hm -2 (ML) and 9 t hm -2 (HL); weigh 90 g of each soil sample, repeat 3 times, and through the plough layer depth of 40 cm and the soil bulk density of 1.2 g cm -3Calculate the weight of the plough layer soil, and add an equal amount of lime to the bottle according to the mass ratio. Maintain a soil mass water content of 15%-20%, and cultivate it at room temperature indoors for 30 days. Monitor the change in soil water content, and measure the pH value before and after cultivation using two methods: potentiometry and a portable pH meter.

[0058] The application rate of Ca(OH)2 is

[0059] m (20cm耕层土重) = 10000 * 0.2 * 1.2 = 2.4 * 10 3 thm -2

[0060] The lime addition amount m (LL) = 3 * 90 / (2.4 * 10 3 ) = 0.1125 g

[0061] m (ML) = m (LL) * 2 = 0.225 g

[0062] m (HL) = m (LL) * 3 = 0.3375 g

[0063] S102: After obtaining the soil pH value, based on each soil sample, determine the organic matter content, exchangeable acid, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable bases, and base saturation in the soil; specifically as shown in Table 1:

[0064] Table 1

[0065]

[0066]

[0067]

[0068] Among them, the organic matter content in the soil is determined by the potassium dichromate oxidation method; the content of the cation exchange capacity in the soil is obtained by the ammonium acetate method; the content of the exchangeable acid in the soil is obtained by the potassium chloride exchange-neutralization titration method; the content of the soil exchangeable H ions and soil exchangeable aluminum ions in the soil is determined by the potassium chloride leaching-neutralization titration method; the content of the total exchangeable bases in the soil is obtained by the ammonium acetate exchange-neutralization titration method; the content of the base saturation in the soil is obtained by the HCl rapid determination method.

[0069] S103: Based on the obtained soil pH value, through the collected soil samples, calculate the soil mass of the 0-40 cm plough layer per hectare according to the soil bulk density, set different gradients of Ca(OH)2 application rates, and measure the final soil pH;

[0070] Weigh 3 air-dried soil samples from each farmland, each with a mass of 90 g. According to the soil bulk density of 1.2 g / cm -3 Calculate the soil mass of the 0-20 cm plough layer per hectare, and add calcium hydroxide Ca(OH)2 equivalent to 3 t / hm -2 , 6 t / hm -2 and 9 t / hm -2 application rates. Repeat 3 times. After maintaining a 1-2 cm water layer and culturing in the dark at 25°C in an artificial climate chamber for 30 days, measure the final soil pH.

[0071] S104: According to different gradients of Ca(OH)2 application rates, construct the linear relationships between the basic pH measured by the potentiometric method and the pH increase rate, and between the basic pH measured by the portable pH meter and the pH increase rate for the soil sample pH value and the final soil pH;

[0072] Use Origin 2021 software to perform linear fitting on the soil pH values measured without lime application, 3 t / hm -2 (LL), 6 t / hm -2 (ML) and 9 t / hm -2 (HL) to calculate the pH increase rate and plot the graph.

[0073] See Figure 2 , construct the linear relationship between the basic pH measured by the potentiometric method and the pH increase rate, specifically:

[0074] y1 = -0.3008x1 + 2.1238

[0075] where x1 is the basic soil pH value measured by the potentiometric method;

[0076] See Figure 3 , the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate, specifically:

[0077] y2 = -0.2708x2 + 1.8935

[0078] where x2 is the basic soil pH value measured by the portable pH meter.

[0079] S105: Conduct a linear regression analysis on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable base amount, and base saturation degree in the soil;

[0080] Statistical analysis was performed using SPSS 25.0 software. When the level of P < 0.05, a significance test was conducted; linear stepwise regression analysis was performed on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable bases, and base saturation in the soil.

[0081] S106: Calibrate the linear relationship between the basic pH measured by potentiometry and the pH increase rate to the linear relationship between the basic pH measured by a portable pH meter and the pH increase rate;

[0082] Calibrate the portable linear regression equation using the linear regression equation of potentiometry, and the calibration coefficient K = 1.149 was obtained. The calibrated equation is y = -0.3112x + 2.1756.

[0083] The process of obtaining the calibration coefficient is as follows:

[0084] When x is 5, the value of y1 is 0.61964, and the value of y2 is 0.53928.

[0085] The calibration coefficient is:

[0086]

[0087] The calibration equation is:

[0088] y = y2 * k

[0089] Therefore, the calibrated equation is y = -0.3112x + 2.1756.

[0090] S107: Based on the calibrated equation and the linear regression analysis results in S105, obtain the application rate of lime-like substances.

[0091] Through the fitting of the organic matter content, basic pH value, pH increase rate, exchangeable acidity, cation exchange capacity, total exchangeable bases, and base saturation in the soil of 97 groups in Table 1 and the analysis of the fitting linear equation, it is obtained that the actual meaning of y is the increase in soil pH per ton of lime applied per hectare. Thus, a model for the application rate of slaked lime Ca(OH)2 is established, specifically:

[0092]

[0093] Among them, y3 is the amount of slaked lime required; x3 is the basic pH value, and x4 is the target pH value;

[0094] According to the acid neutralization capacity of different lime-like substances, models for the adjustment of acidic soil by quicklime and calcium carbonate are obtained:

[0095] The model for the application rate of quicklime is:

[0096]

[0097] The calcium carbonate application rate model is as follows:

[0098]

[0099] Among them, represents the unit conversion from hectares to mu; 136, 100, and 179 are the neutralization values of calcium hydroxide, calcium carbonate, and quicklime, respectively.

[0100] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application method of lime-like substances in paddy fields based on a portable pH meter, characterized in that, Including: Step 1: Collect several soil samples. Collect a fixed weight of soil in each soil sample, set different gradients of Ca(OH)₂ application rates, and measure the soil pH values by potentiometry and a portable pH meter respectively; Step 2: After obtaining the soil pH values, based on each soil sample, measure the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H⁺ ions, soil exchangeable Al³⁺ ions, total exchangeable base amount, and base saturation degree in the soil; Step 3: Based on the obtained soil pH values, through the collected soil samples, calculate the soil mass of the 0 - 40 cm plow layer per hectare according to the soil bulk density, set different gradients of Ca(OH)₂ application rates, and measure the final soil pH; Step 4: According to different gradients of Ca(OH)₂ application rates, for the soil sample pH values and the final soil pH, construct the linear relationships between the basic pH measured by potentiometry and the pH increase rate, and the linear relationships between the basic pH measured by the portable pH meter and the pH increase rate respectively; Step 5: Conduct a linear regression analysis on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H⁺ ions, soil exchangeable Al³⁺ ions, total exchangeable base amount, and base saturation degree in the soil; Step 6: Correct the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate based on the linear relationship between the basic pH measured by potentiometry and the pH increase rate; Step 7: Based on the corrected equation and the results of the linear regression analysis in Step 5, obtain the application rate of lime substances.

2. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 1, wherein The specific method for collecting several soil samples, collecting a fixed weight of soil in each soil sample, setting different gradients of Ca(OH)₂ application rates, and measuring the soil pH values by potentiometry and a portable pH meter respectively is as follows: Three Ca(OH)2 application rates were set, namely 3 t hm -2 (LL), 6 t hm -2 (ML) and 9 t hm -2 (HL); 90 g of each soil sample was weighed and replicated 3 times. The weight of the plough layer soil was calculated through the plough layer depth of 40 cm and the soil bulk density of 1.2 g cm -3 . According to the mass ratio, an equal amount of lime was added to the bottle; the soil moisture content was maintained at 15%-20%, and it was cultured indoors at room temperature for 30 d; the change in soil moisture content was monitored, and the pH value was measured before and after cultivation, respectively, by two methods: the potentiometric method and a portable pH meter.

3. The application method of lime substances in paddy fields based on a portable pH meter according to claim 2, wherein, The Ca(OH)₂ application rate is m (20cm耕层土重) = 10000 * 0.2 * 1.2 = 2.4 * 10 3 t hm -2 Lime addition amount m (LL) = 3 * 90 / (2.4 * 10 3 ) = 0.1125 g m (ML) = m (LL) * 2 = 0.225 g m (HL) = m (LL) * 3 = 0.3375 g.

4. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 3, wherein Based on the obtained soil pH value, through the collected soil samples, calculate the soil quality of the 0-40 cm plough layer per hectare according to the soil bulk density, set different gradients of Ca(OH)2 application rates, and measure the final soil pH. Specifically: Weigh 3 air-dried soil samples from each farmland, each with a mass of 90 g, and calculate the soil quality of the 0-20 cm plough layer per hectare according to the soil bulk density of 1.2 g / cm -3 Add slaked lime Ca(OH)2 equivalent to 3 t hm -2 , 6 t hm -2 and 9 t hm -2 application rates, with 3 replicates. After culturing in the dark with a 1-2 cm water layer in an artificial climate chamber at 25°C for 30 days, measure the final soil pH.

5. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 4, characterized in that, Based on different application rates of Ca(OH)2 gradients, linear relationships between the basic pH measured by the potentiometric method and the pH increase rate, and between the basic pH measured by the portable pH meter and the pH increase rate are constructed for the soil sample pH value and the final soil pH, specifically as follows: Using Origin 2021 software, linear fitting is performed on the soil pH values measured without lime application, 3 t hm -2 (LL), 6 t hm -2 (ML), and 9 t hm -2 (HL) to calculate the pH increase rate and plot the graph.

6. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 5, wherein, The specific method for constructing the linear relationship between the basic pH measured by potentiometry and the pH increase rate is as follows: y1 = -0.3008x1 + 2.1238 Where, x1 is the basic soil pH value measured by potentiometry; The specific method for the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate is as follows: y2 = -0.2708x2 + 1.8935 Where, x2 is the basic soil pH value measured by the portable pH meter.

7. The application method of lime substances in paddy fields based on a portable pH meter according to claim 6, characterized in that, The specific method for conducting a linear regression analysis on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H⁺ ions, soil exchangeable Al³⁺ ions, total exchangeable base amount, and base saturation degree in the soil is as follows: Use SPSS 25.0 software for statistical analysis. When at the level of P < 0.05, conduct a significance test; conduct a linear stepwise regression analysis on the organic matter content, exchangeable acidity, cation exchange capacity, soil exchangeable H⁺ ions, soil exchangeable Al³⁺ ions, total exchangeable base amount, and base saturation degree in the soil.

8. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 7, characterized in that, The specific method for correcting the linear relationship between the basic pH measured by the portable pH meter and the pH increase rate based on the linear relationship between the basic pH measured by potentiometry and the pH increase rate is as follows: The portable linear regression equation was calibrated using the potentiometric linear regression equation, and the calibration coefficient K = 1.149 was obtained. The calibrated equation is y = -0.3112x + 2.1756.

9. The method for applying lime-like substances in paddy fields based on a portable pH meter according to claim 8, characterized in that, Based on the calibrated equation and the linear regression analysis results in step 5, the application rate of lime substances was obtained, specifically: Through the fitting of the organic matter content, basic pH value, pH increase rate, exchangeable acid, cation exchange capacity, soil exchangeable H ions, soil exchangeable aluminum ions, total exchangeable base amount, and base saturation degree in several groups of soils and the analysis of the fitted linear equation, the actual meaning of y is the pH increase amplitude of the soil per hectare when applying one ton of lime. Thus, the model for the application rate of slaked lime Ca(OH)2 was established, specifically: Among them, y3 is the amount of slaked lime required; x3 is the basic pH value, and x4 is the target pH value; According to the acid neutralization capacity of different lime substances, the models for the adjustment of acidic soils by quicklime and calcium carbonate were obtained: The model for the application rate of quicklime is: The model for the application rate of calcium carbonate is: Among them, means the unit conversion of hectares to mu; 136, 100, and 179 are the neutralization values of calcium hydroxide, calcium carbonate, and quicklime, respectively.

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