A method for improving acid soil

Abstract

The application provides an acid soil improvement method, comprising the following steps: step one, measuring soil pH, mixing the soil sample to be measured with carbon dioxide-free water, stirring and standing until precipitation, and then measuring the pH of the supernatant by using a pH meter; step two, determining the amount of the improvement agent, pre-setting the soil pH, and determining the application amount of any one of Ca(OH)2, CaO and CaCO3 according to a calculation formula; and step three, an application method, crushing lime, sieving, uniformly spreading on the surface of soil, and then rotary tilling the soil to fully mix the lime with the soil; the application only needs to measure one index of soil basic pH, and then the required application amount of lime can be obtained by substituting the pre-set target pH into the formula; the application is accurate, scientific, efficient, convenient and economical; and the lime should be applied once every 2-3 years to achieve the purpose of long-term improvement of acidification of red soil.

Description

Technical Field

[0001] This invention relates to the field of soil improvement, and more specifically to a method for improving acidic soil. Background Technology

[0002] my country's red soil is mainly distributed south of the Yangtze River, covering an area of ​​approximately 2.18 million square kilometers, accounting for about 22.7% of the country's land area. Red soil regions are the main production areas for crops such as rice and citrus in my country. The suitable soil pH for citrus trees is 5.5-6.5. However, taking Ji'an area as an example, the soil pH in citrus orchards is mostly below 5.0, even below 4.5. The serious acidification of red soil severely restricts the improvement of fruit yield and quality; therefore, soil improvement to enhance crop yield and quality has become a top priority.

[0003] Currently, soil acidification improvement mainly employs methods such as returning organic materials like biochar, crop straw, and livestock manure to the field, or applying alkaline residues and lime-like substances, such as quicklime, hydrated lime, and limestone. However, some soil acidification modifiers are expensive, such as biochar, nitrification inhibitors, and soil acidification conditioners, significantly increasing agricultural production costs and reducing efficiency. Applying organic materials is a relatively ideal method for inhibiting soil acidification, but it is slow to take effect and costly. Lime-like substances are a class of inorganic alkaline materials that can effectively increase soil pH and improve soil acidification problems. They also have advantages such as simple manufacturing and high cost and efficiency, and are widely used in soil acidification improvement in dryland and paddy fields. However, excessive application of lime-like substances can easily lead to soil compaction and loss of nitrogen, phosphorus, potassium, and magnesium nutrients, while insufficient application will fail to achieve the expected acidification target.

[0004] Therefore, the precise application of lime-based substances is crucial for soil improvement. Methods for using lime-based substances to improve acidified soils have been reported, but determining the application rate of the amendment requires measuring multiple indicators such as soil baseline pH, clay content, organic matter content, soil exchangeable acidity, cation exchange capacity, and base saturation. This cumbersome process hinders the widespread adoption of such technologies. Therefore, to improve the industrial scale and market competitiveness of fruit orchards in red soil regions and address orchard soil acidification, proposing a scientific, accurate, and easy-to-operate method for using lime-based substances to improve red soil acidification in orchards has become an urgent problem to be solved. Summary of the Invention

[0005] This invention collected soil samples from the 0-40cm topsoil layer of 23 orchards and used the following methods to determine soil pH, clay content, organic matter content, cation exchange capacity, and total exchangeable bases and base saturation: potentiometry, pipette method, potassium dichromate oxidation method, ammonium acetate method, and ammonium acetate exchange-neutralization titration method.

[0006] To determine the effect of lime on increasing soil pH, this invention weighed three 50g samples of air-dried soil from each orchard, based on a soil bulk density of 1.2g / cm³. 3 Calculate the soil mass of the 0-40cm topsoil layer per hectare, and add the equivalent of 3t / hm². 2 6t / hm 2 and 9t / hm 2 The applied Ca(OH)2 was applied in 3 replicates, and the soil was cultured for 30 days while maintaining a 20% moisture content. The final soil pH was then measured. The rate of increase in soil pH for each orchard was calculated by linear regression of the base pH, the final pH, and different Ca(OH)2 application rate gradients. The slope of the linear equation obtained by using different lime application masses as the x-axis and the soil pH increase as the y-axis is the rate of increase.

[0007] Stepwise regression analysis using SPSS 22.0 software was performed on soil clay content, organic matter content, cation exchange capacity, total exchangeable bases, base saturation, and basal pH with the pH increase rate of the culture soil. The results showed that only the soil basal pH was significantly correlated with the pH increase rate (see Table 1).

[0008] Table 1. Significance of stepwise regression analysis of soil pH increase rate and related soil indicators

[0009]

[0010] Note: ** indicates that the correlation is significant at the 0.01 probability level.

[0011] Therefore, based on the rate of increase and baseline pH, a linear regression analysis yielded the equation y = 0.1873x - 0.7372(R²). 2 =0.7265), such as Figure 1 A method for calculating Ca(OH)2 application rate is disclosed: Ca(OH)2 application rate, Ca(OH)2 (t / hm) 2 The formula is: (pH1 - pH0) / (0.1873 × pH0 - 0.7372). Here, pH0 and pH1 represent the base pH and target pH of the soil, respectively. Furthermore, a method for calculating the application rates of CaO and CaCO3 is derived based on the neutralization values ​​of different limestone substances. This method is applicable to calculating lime application rates for orchard soil acidification improvement in soils with a pH range of 4.3–5.5.

[0012] Based on this, the present invention provides a method for improving acidic soil, comprising the following steps:

[0013] Step 1: Measure the soil pH

[0014] The soil sample to be tested was thoroughly mixed with carbon dioxide-free water, stirred and allowed to stand until precipitation. The pH of the supernatant was then measured with a pH meter to obtain pH 0.

[0015] Preferably, the mass ratio of the soil sample to carbon dioxide-free water is 1:5;

[0016] Preferably, stir for 1-3 minutes;

[0017] Preferably, let it stand for 30-40 minutes;

[0018] Step 2: Determine the amount of lime to be applied.

[0019] Based on planting requirements, the soil pH is pre-set to obtain pH1. Then, the application rates of Ca(OH)2, CaO, and CaCO3 are determined using the calculation formula.

[0020] The formula for calculating the application rate of Ca(OH)2 is as follows:

[0021] Ca(OH)2(t / hm 2 )=(pH1-pH0) / (0.1873×pH0-0.7372)

[0022] The formula for calculating the CaO application rate is as follows:

[0023] CaO(t / hm 2 )=0.76×(pH1-pH0) / (0.1873×pH0-0.7372)

[0024] The formula for calculating the CaCO3 application rate is as follows:

[0025] CaCO3 (t / hm) 2 )=1.36×(pH1-pH0) / (0.1873×pH0-0.7372)

[0026] In the formula, 0.76 is the ratio of the neutralization values ​​of Ca(OH)2 and CaO, and 1.36 is the ratio of the neutralization values ​​of Ca(OH)2 and CaCO3.

[0027] Step 3, Application Method

[0028] Crush the lime, sieve it, and spread it evenly on the soil surface. Then, till the soil to mix the lime thoroughly with the soil. After applying the lime, you can carry out field management and crop planting as usual. Lime should not be applied at the same time as chemical fertilizers and pesticides.

[0029] Preferably, it passes through a 20-30 mesh sieve;

[0030] Preferably, rotary tillage produces a tillage layer of 0-40cm.

[0031] Preferably, since there is a large amount of buffer acid in the soil, the lime will gradually be neutralized after a period of time, leading to soil acidification. Therefore, it is recommended that lime be applied once every 2 to 3 years to achieve the goal of long-term improvement of red soil acidification.

[0032] The present invention has the following effects:

[0033] (1) Compared with existing soil acidification improvement technologies, this invention only requires measuring the basic pH of the soil, and then substituting the predetermined target pH into the formula to obtain the required amount of lime to be applied.

[0034] (2) This invention is not only precise and scientific, efficient and convenient, but also involves economical and affordable materials and is easy to operate. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 A regression model was developed to calculate the application rate of Ca(OH)2.

[0037] Figure 2 Linear fitting of model-calculated values ​​and actual observed values ​​of soil pH under different Ca(OH)2 application rates;

[0038] Figure 3 The effect of Ca(OH)2 application on soil pH. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] A Jinggang pomelo orchard was selected and divided into several plots. The following implementation examples and experimental cases were carried out.

[0041] Take 5g of acidic red soil sample and mix it thoroughly with 25ml of carbon dioxide-free water. Stir for 1 minute and let it stand for 30 minutes. Then use a pH meter to measure the pH of the supernatant and get pH0 = 4.51.

[0042] Example 1

[0043] Based on the formula for calculating the application rate of Ca(OH)2, the application rate of 2.25 t / hm was calculated. 2 4.5t / hm 2 6.75 t / hm 2 9.00t / hm 2 The model-calculated value of pH1 for Ca(OH)2;

[0044] The formula for calculating the application rate of Ca(OH)2 is as follows:

[0045] Ca(OH)2(t / hm 2 )=(pH1-pH0) / (0.1873×pH0-0.7372)

[0046] In the formula, pH0 is the initial pH value of the soil, and pH1 is the final pH value of the soil;

[0047] In October 2021, 2.25 t / hm were applied respectively. 2 4.5t / hm 2 6.75 t / hm 2 9.00t / hm 2 Ca(OH)₂ was crushed, passed through a 20-mesh sieve, and evenly spread on the soil surface. A 40cm tillage layer was then prepared to ensure thorough mixing of the Ca(OH)₂ with the soil. In July 2022, soil pH was randomly sampled and measured. The actual soil pH was compared with the calculated model value (pH₁) using SPSS 22.0 software for regression analysis. Figure 2 .

[0048] According to the calculation method of this invention, the soil pH increase rate after applying Ca(OH)2 is 0.1056 units / ton. Figure 2 It can be seen that the actual observed values ​​of soil pH affected by different amounts of Ca(OH)2 application are basically consistent with the model calculation values.

[0049] Example 2

[0050] A pomelo orchard was selected, and based on the acidic soil improvement method of the present invention, the initial pH of the orchard soil was calculated to be 4.56, and 3 t / hm² of soil was applied. 2 The pH increase rate after applying Ca(OH)2 was found to be 0.1169 units / ton, therefore, an application rate of 3 t / hm² was recommended. 2 The soil pH should be 4.91 after quicklime treatment;

[0051] In October 2020, Ca(OH)2 was applied. Random samples taken in May and December 2021 and May 2022 showed soil pH values ​​of 5.07, 4.94, and 4.80, respectively. Figure 3 .

[0052] according to Figure 3 It can be seen that the results are basically consistent with the model calculation results. However, as time goes on, the effect of lime acidification gradually decreases and the soil pH slowly drops. Therefore, it is necessary to carry out the improvement every 2-3 years.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving acidic soil, characterized in that, Includes the following steps, Step 1: Measure the soil pH The soil sample to be tested was thoroughly mixed with carbon dioxide-free water, stirred and allowed to stand until precipitation. The pH of the supernatant was then measured with a pH meter to obtain pH 0. Step 2: Determine the dosage of the improver. The modifier is any one of Ca(OH)2, CaO, and CaCO3; Pre-set the target pH of the soil to obtain pH1. Then, determine the application rate of any one of Ca(OH)2, CaO, and CaCO3 according to the calculation formula. The formula for calculating the application rate of Ca(OH)2 is as follows: Ca(OH)2(t / hm 2 )=(pH1-pH0) / (0.1873×pH0-0.7372) The formula for calculating the CaO application rate is as follows: CaO(t / hm 2 )=0.76×(pH1-pH0) / (0.1873×pH0-0.7372) The formula for calculating the CaCO3 application rate is as follows: CaCO3(t / hm 2 )=1.36×(pH1-pH0) / (0.1873×pH0-0.7372) In the formula, 0.76 is the ratio of the neutralization values ​​of Ca(OH)2 and CaO, and 1.36 is the ratio of the neutralization values ​​of Ca(OH)2 and CaCO3. Step 3, application After crushing the lime, sieve it and spread it evenly on the soil surface. Then, till the soil to ensure that the lime is fully mixed with the soil.

2. The method for improving acidic soil according to claim 1, characterized in that, In step one, the mass ratio of the soil sample to be tested to carbon dioxide-free water is 1:

5.

3. The method for improving acidic soil according to claim 1, characterized in that, In step one, stir for 1-3 minutes.

4. The method for improving acidic soil according to claim 1, characterized in that, In step one, let it stand for 30-40 minutes.

5. The method for improving acidic soil according to claim 1, characterized in that, In step three, pass the sample through a 20-30 mesh sieve.

6. The method for improving acidic soil according to claim 1, characterized in that, In step three, rotary tillage is performed on a 0-40cm tillage layer.

7. The method for improving acidic soil according to claim 1, characterized in that, The pH of the acidic soil is 4.3-5.

5.

8. The method for improving acidic soil according to claim 1, characterized in that, Acidic soils should be improved using this method every 2-3 years.

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