JP2012026803A - Method for measuring cation exchange capacity in soil and soil analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring cation exchange capacity in the soil capable of easily, and promptly determining cation exchange capacity in the soil and a soil analyzer suitable for measurement of cation exchange capacity in the soil.SOLUTION: The present invention provides the method for measuring the cation exchange capacity in the soil for measuring an index value corresponding to content of humus materials in the soil to convert a measured value of the index value into the cation exchange capacity, and the soil analyzer 1 which includes: data input means 3a-3d for inputting data regarding the soil to be measured; absorbance measurement means 4, 5, 6, 6a for measuring absorbance of an extract 7 containing the humus materials; storage means for showing correlation between the absorbance of a solution containing the humus materials and the content of the humus materials or the cation exchange capacity and storing a relational expression to be selected on the basis of pH of the soil to be measured; selection means for selecting a relational expression to be used on the basis of the pH of the soil to be measured; operation means for calculating the cation exchange capacity based on a measured value of the absorbance and a weighed value of the soil; and display means 2 for displaying the calculated value of the cation exchange capacity.

Description

  The present invention relates to a method for measuring cation exchange capacity (hereinafter also referred to as “CEC”) in soil, and a soil analyzer using the method, and more particularly to a cation exchange capacity in soil. Compared to conventional methods, the ion exchange capacity can be determined easily and quickly, and the cation exchange capacity in the soil can be determined at the soil collection site. The present invention relates to a measurement method and a soil analyzer that can be suitably used for measuring the cation exchange capacity in soil at the site of soil collection using the measurement method.

  The cation exchange capacity in the soil indicates the ability to retain cations in the soil used as minerals, and means the capacity that the cation component added to the soil as a fertilizer component adsorbs to the soil. In recent years, in order to prevent a decrease in agricultural profitability due to excessive fertilization, when determining the amount of fertilizer used, measuring the cation exchange capacity in the soil to which the fertilizer is added has been performed. As a CEC measurement method, For example, as shown in the analysis flowchart of FIG. 3, a method of extracting by the Schöllenberger method and analyzing by the indophenol method is known.

  However, the Schöllenberger method, for example, has a complicated analysis process and requires a lot of time, the type of reagent used, the amount used, etc., so it is more economical, simple and simple cation exchange in soil. Development of a capacity (CEC) measurement method is desired. As such a CEC measurement method, for example, Patent Document 1 proposes a rapid measurement method of soil cation exchange capacity using copper adsorption and a spectrophotometer. There has been a demand for the development of a measurement method that is safer than the use of a substance that contains. In addition, as described above, the Schöllenberger method has a complicated analysis process and many types of reagents to be used, and equipment and specialized techniques are required for that purpose. The measurement of the cation exchange capacity was requested from a specialized organization such as an analysis center, and it took time and money to obtain the results, as well as expenses. Therefore, vegetable producers can calculate the cation exchange capacity in the soil by themselves without requesting a specialized institution, and it is simple and specialized that can be used as a judgment material for determining the amount of fertilizer used. There has been a demand for the development of a method for measuring the cation exchange capacity in soil that can be carried out by using reagents that are easy to handle even if not at home.

Japanese Patent No. 3343240

  The present invention has been made in view of the above circumstances, and establishes an analysis technique capable of measuring CEC, which is an index of the retention ability of cations used as minerals, and further creates a simple analysis apparatus equipped with the analysis technique. Thus, the cation exchange capacity in the soil can be determined easily and quickly. For example, the cation exchange capacity in the soil is obtained at the soil collection site such as the vegetable production site, and the soil is obtained based on the result. Grasping the components, for example, adding a fertilizer to the measured soil, measuring the cation exchange capacity in the soil that can also be used as a judgment material for determining the amount of fertilizer used, etc. An object of the present invention is to provide a soil analyzer that can be suitably used to measure the cation exchange capacity in the soil at the sampling site.

As a result of intensive investigations to achieve the above object, the present inventors focused on the chemical structure of humic substances, which are organic compounds present in soil, and the humic substances have a bias in charge, and the surroundings of the humic substances Depending on the environment such as acid / alkali concentration, it releases protons (H ⁺ ) and has many negatively charged hydroxyl groups, which may interact with cations. If the correlation between the values is obtained, it is found that the CEC value can be estimated by measuring the amount of humus without using the complicated CEC measurement method by the conventional method, and the present invention has been made. It was. That is, humus is an organic compound present in soil, and the model compound is represented by the following chemical formula.

  Humic substances are important substances that affect the chemical and physical properties of the soil due to their chemical structure. For example, they have the ability to retain water, buffer pH, and retain mineral nutrients. It is also possible that humic substances have an impact on soils with aggregate structures suitable for vegetable production, and that this material is a source of nitrogen for the soil. It is important for vegetable producers to know whether it exists to a certain extent, and as a measurement method, for example, the process is not complicated compared to conventional CEC measurement methods, such as the Kumada method, etc. In addition, measurement methods are known in which the types and amounts of reagents required and the number of instruments used for analysis are small. Therefore, as described above, the present inventors do not use a complicated CEC measurement method according to the conventional method, and can quickly and necessaryly obtain a correlation between the content of humic substances in soil and the value of CEC. An indicator of humic mass in soil using a method for measuring humic mass in soil that can be carried out without using reagents that are difficult to handle, reducing the number of reagents, amount used, and analytical equipment It was found that the index value can be converted into a CEC value by measuring the index value, and the present invention has been made.

  That is, the present invention is (1) a method for measuring a cation exchange capacity in soil, wherein an index value corresponding to the content of humic substances in the soil is measured, and the measured value is converted into a cation exchange capacity. A method for measuring the cation exchange capacity in soil, and (2) a soil analyzer used for measuring the cation exchange capacity in soil, wherein the measured soil weight and pH are used as data A data input means for inputting, an absorbance measuring means for measuring the absorbance at the absorption wavelength of the humic substance of the alkaline extract containing the humic substance, and the humic substance used when the pH of the soil to be measured is 7.0 or less. Relational expression showing the correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength and the cation exchange capacity and / or the absorbance at the absorption wavelength of the humic substance and the humic plant In the absorption wavelength of the humic substance used when the soil to be measured is alkaline, and the relational expression showing the correlation between the humic substance content and the cation exchange capacity Relational expression showing correlation between absorbance and cation exchange capacity and / or relational expression showing correlation between absorbance and humic substance content at absorption wavelength of humic substance, humic substance content and cation A storage unit that stores a relational expression indicating a correlation with the exchange capacity, and a relational expression that is used according to the pH of the soil that is input to the data input unit is selected from the relational expressions that are stored in the storage unit. The selection means to select, and the absorbance data measured by the absorbance measurement means, if necessary, absorb the weight per predetermined weight based on the soil weighing value input to the data input means. Calculating means for calculating the cation exchange capacity by converting into degrees and substituting into the relational expression selected by the selecting means, and display means for displaying the value of the cation exchange capacity obtained by the calculating means. A soil analyzer characterized by the above is provided.

  According to the method for measuring cation exchange capacity in soil of the present invention, it becomes possible to determine cation exchange capacity in soil more easily and quickly than conventional measurement methods. When deciding the amount of fertilizer to be used, etc., the vegetable producers themselves do not have to ask the analysis center to measure the cation exchange capacity in the soil at the vegetable production site, such as the vegetable production site. It is also possible to determine the cation exchange capacity in the soil and determine the amount of fertilizer used on the spot. Furthermore, according to the soil analyzer of this invention, it becomes easy to obtain | require the cation exchange capacity in the soil simply and quickly at the sampling site of the soil to measure.

It is a partial cross section schematic plan view of the soil analyzer explaining the soil analyzer of this invention. It is a partial cross section schematic side view of the said soil analyzer. It is an analysis flowchart which shows the Scholeenberger method which is the conventional CEC measuring method in soil. It is an analysis flowchart which shows content of the humic substance in the soil implemented in the Example of this invention, and a CEC measuring method. It is a graph which shows the relationship between humic substance content of the whole soil sample measured in the Example of this invention, and the cation exchange capacity | capacitance extracted by the Scholeenberger method. It is a graph which shows the relationship between the content of the humic substance in the acidic and neutral soil sample measured in the Example of this invention, and the cation exchange capacity extracted by the Scholeenberger method. It is a graph which shows the relationship between the light absorbency of the alkaline extract of the soil sample of pH 7.0 or less measured in the Example of this invention, and humic substance content. It is a graph which shows the relationship between the light absorbency of the alkaline extract of the whole soil sample measured in the Example of this invention, and the cation exchange capacity extracted by the Schollenberger method. It is a graph which shows the relationship between the light absorbency of the alkaline extract of the acidic and neutral soil sample measured in the Example of this invention, and the cation exchange capacity extracted by the Scholeenberger method.

  Hereinafter, the method for measuring the cation exchange capacity in soil of the present invention will be described in more detail. The measurement method of the present invention measures an index value corresponding to the content of humic substances in the soil, and measures the cation exchange capacity in the soil by converting the measured value into a cation exchange capacity. is there. Here, as an index value corresponding to the content of humic substances in the soil, if the extract is obtained by extracting the humic substances in the soil as appropriate using a solution, for example, Absorbance at a predetermined wavelength, simple quantitative value by visual observation using a colorimetric table prepared in advance by coloring the extract, or absorbance at a predetermined wavelength of the colored extract, gas chromatography of the extract, liquid chromatography And the fluorescence spectrum or fluorescence intensity obtained by excitation of the extract at a predetermined wavelength. It is possible to combine a plurality of analysis methods instead of one analysis method. In addition, as mentioned in the examples described later, the humic substance content of the extract is obtained as a measured value by using a soil analyzer used for measuring the humic substance content, and this measured value is obtained. It can also be an index value.

  As a method for measuring the cation exchange capacity in the soil of the present invention, humic substances in the soil are extracted to obtain an extract, and the absorbance at a predetermined wavelength of the extract is used as an index value corresponding to the content of humic substances. A measuring method is more preferable. More specifically, the soil to be a measurement sample (hereinafter, also referred to as “soil to be measured”, “soil to be used for measurement”, “measurement soil”) is weighed, and an alkaline aqueous solution is added thereto, After extracting the extract component containing humic substance in alkaline aqueous solution to obtain an alkaline extract, the absorbance of the alkaline extract at the absorption wavelength of humic substance is measured, and the measured value is converted into cation exchange capacity in soil The method for measuring the cation exchange capacity is preferred. Here, as the extraction method, for example, the soil to be a measurement sample is weighed, put into a container as appropriate, and after adding an alkaline aqueous solution thereto, it is manually stirred with equipment or stirred using a stirrer. An extraction component containing humic substances may be extracted in an alkaline aqueous solution by shaking the container with a lid or manually shaking, but considering the accuracy and reproducibility of the extraction efficiency, a stirrer It is desirable to stir or shake for about 1 to 5 minutes, particularly about 2 to 4 minutes using an apparatus such as a shaker. In addition, it is preferable that the alkaline extract is filtered, and then the filtrate is diluted to an appropriate concentration as necessary and the absorbance is measured. More specifically, the extraction method (see the analysis flowchart of FIG. 4) implemented in the examples described later is more preferable.

  Further, the type of the alkaline aqueous solution is not particularly limited, but examples of the alkaline compound include sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, and the like. It is more preferable that the aqueous solution contains an alkaline compound alone or in combination of two or more. In addition, the density | concentration of the alkaline compound in alkaline aqueous solution is not restrict | limited in particular, It can select suitably so that aqueous solution can be adjusted to desired pH. The pH of the alkaline aqueous solution is more than 7.0 and less than 14.0. However, in consideration of extraction efficiency, reproducibility, etc., preferably more than 8.0 and less than 13.9. Preferably it is more than 8.0 and less than 13.5, more preferably more than 8.5 and less than 13.2, and alcohols such as ethanol may be added. More specifically, the alkaline aqueous solution in the present invention includes a 0.1 M sodium hydroxide / sodium pyrophosphate mixed solution used as an extract of the Kumada method, which is a method for measuring humic substances, sodium hydroxide prepared to an appropriate concentration, etc. An aqueous solution obtained by adjusting the pH of purified water with the above alkaline compound.

  And if the measurement wavelength of an alkaline extract is the absorption wavelength of humic substances, it can select a wavelength suitably and can measure an absorbance, but if measurement accuracy, reproducibility, etc. are considered, especially from 400-650 nm It is preferable to measure at at least one selected wavelength, and more preferably at least one wavelength selected from 500 to 550 nm. In addition, the soil used for the measurement is not particularly limited, but considering reproducibility, measurement accuracy, and the like, neutral to acidic soil is more preferable as the soil used for the measurement. Further, the amount of soil used for the measurement, the amount of the alkaline aqueous solution used in the extraction process, the dilution rate at the time of absorbance measurement, etc. are not particularly limited, and may be appropriately selected according to, for example, the examples described later. it can.

  More specifically, as a method of converting the measured absorbance value into the cation exchange capacity, the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance and the cation exchange capacity in the soil. A method of obtaining a standard curve or a relational expression showing a correlation and converting the measured value of the absorbance to a cation exchange capacity in soil by the standard curve or the relational expression is exemplified. More specifically, a relationship between the absorbance of the alkaline extract from the soil per predetermined weight at a predetermined measurement wavelength and the cation exchange capacity is obtained in advance, and a calibration curve is used as a standard curve indicating these relationships. The measured absorbance value is positively converted by applying a value obtained by converting the measured absorbance value of the measured soil to the absorbance per predetermined weight of the soil, if necessary, to the calibration curve. Convert to ion exchange capacity or obtain a relational expression showing the relationship between absorbance and cation exchange capacity from a calibration curve, and use the measured soil measurement value as the absorbance of the relational expression. A method of converting the measured value of the absorbance to the cation exchange capacity by substituting the value converted into the absorbance per a predetermined weight of the soil as necessary may be mentioned.

Even more specifically, a soil sample with a known pH value of 7.0 or less and at least 1, preferably at least 2 cation exchange capacities at least 3 points, preferably at least 4 points. For an alkaline soil sample with a known value, the absorbance of the alkaline extract from the soil per predetermined weight was measured using one absorption wavelength of the humic substance as the measurement wavelength, and the absorbance in the soil sample having a pH of 7.0 or less From the measured value and the value of the cation exchange capacity corresponding to each measured value, for example, by the appropriate method such as the least square method, at the above measurement wavelength used when the pH of the soil to be measured is 7.0 or less it is a relational expression between the absorbance and cation exchange capacity (cation exchange capacity (me / 100 g soil)) = Contact to _{a 7} × (absorbance) + _{B 7} Together determine the value of A ₇ and B ₇ that, from the value of the cation exchange capacity corresponding to the respective measurement values and the measured values of absorbance at all soil samples, for example by a suitable method such as a least squares method, to measure soil is a relational expression between the absorbance and the cation exchange capacity in the measurement wavelength utilized in the case of alkaline (cation exchange capacity (me / 100 g soil)) = a in a ₈ × (absorbance) + B _{8 8} and methods for determining the value of B ₈ can be mentioned. In addition, although the upper limit of the number of samples of soil samples having a pH of 7.0 or less and alkaline soil samples is not particularly limited, the number of samples of soil samples having a pH of 7.0 or less is considered in consideration of measurement efficiency and the like. The upper limit of about 20 points is preferable, and the upper limit of the number of alkaline soil samples is preferably about 10 points. Further, the ratio of the number of soil samples having a pH of 7.0 or less and the number of samples of the alkaline soil sample is not particularly limited, but the number of samples of the soil sample having a pH of 7.0 or less is less than that of the alkaline soil sample. It is more preferable to set the number of samples to about 1.5 to 3 times. About the suitable upper limit of the sample number of the soil sample whose pH is 7.0 or less and an alkaline soil sample, and the suitable ratio of the sample number, it is the same also about the sample number in the other conversion method demonstrated below. Here, in the present invention, the term “soil sample” refers to the cation exchange capacity, the content of humic substances, and the absorbance, the content of humic substances, the cation exchange capacity of the alkaline extract at a predetermined wavelength. The calibration curve indicating the correlation, the analytical value for obtaining the relational expression, and the meaning of the soil used as the standard sample for the measurement value. “Total soil sample” refers to the soil sample having a pH of 7.0 or less. Combined with alkaline soil sample. And the number of samples of soil samples with a known humic substance content and a pH of 7.0 or less, or alkaline soil samples, in other words, sufficient to derive the relational expression as described above, as will be described later. It is a number that makes a large population. Further, when the substance to be used for the measurement is soil, since the variation in the measured value is large, each of the above formulas is expressed by, for example, (cation exchange capacity (me / 100 g soil)) as in the formulas obtained in Examples described later. = (A ₇ ± a ₇ ) × (absorbance) + (B ₇ ± b ₇ ), (cation exchange capacity (me / 100 g soil)) = (A ₈ ± a ₈ ) × (absorbance) + (B ₇ ± Similarly, it is also possible to obtain the values of A ₇ , A ₈ , B ₇ , B ₈ , a ₇ , a ₈ , b ₇ , b ₈ in the same manner as b ₇ ). More specific examples of these formulas include formulas obtained by examples described later.

  Other conversion methods include a method of calculating the content of humic substances in the soil from the absorbance and converting the calculated value into a cation exchange capacity. More specifically, a relationship between the absorbance of the alkaline extract from the soil per predetermined weight at a predetermined measurement wavelength and the content of humic substances is obtained in advance, and calibration is performed as a standard curve indicating these relationships. Create a line and apply the value obtained by converting the measured value of the absorbance from the measured value of the soil subjected to the measurement to the absorbance per predetermined weight of the soil, if necessary, to the calibration curve. Calculate the content of the substance, or obtain a relational expression indicating the relationship between the absorbance and the content of humic substance from the calibration curve, and use the measured value of the absorbance as the absorbance of the relational expression from the measured weight of the soil. By substituting the value converted into the absorbance per predetermined weight of the soil as necessary, the humic substance content is calculated from the measured absorbance value, and further, the humic substance content and the cation exchange capacity are calculated. By preparing a calibration curve as a standard curve indicating these relationships, and applying the calculated value of the humic substance content obtained from the measured absorbance value to the calibration curve. Convert the calculated value into a cation exchange capacity, or obtain a relational expression showing the relationship between the humic substance content and the cation exchange capacity from the calibration curve, and calculate the absorbance as the humic substance content in the relational expression. By substituting the calculated value of the humic substance content calculated from the measured value, the method of converting the measured value of absorbance to the humic substance content and then converting it to the cation exchange capacity can be mentioned. Thus, when content of humic substance in soil is calculated from light absorbency, the calculated value can be used as soil information important for vegetable producers as mentioned above.

More specifically, a soil sample having a known pH of 7.0 or lower and a humic substance content of at least 2 points, preferably at least 2 points, preferably at least 3 points, preferably at least 4 points. For a known alkaline soil sample, the absorbance of the alkaline extract from the soil per unit weight is measured using one absorption wavelength of the humic substance as a measurement wavelength, and each measured value of absorbance in a soil sample having a pH of 7.0 or less From the humic substance content corresponding to each measured value, the absorbance and humic substance at the measurement wavelength used when the pH of the soil to be measured is 7.0 or less by an appropriate method such as the least square method, for example. is a relational expression between the content of (the content of humic substances (wt%)) = _{a 1} × (absorbance) + _B determines the value of _{a 1} and _{B 1} in ₁ when co In addition, from the measured values of absorbance in all soil samples and the content of humic substances corresponding to the measured values, the above measurement used when the soil to be measured is alkaline by an appropriate method such as the least square method, for example obtains the value of a ₂ and B ₂ in the (content (wt%) of the humic substances) = a ₂ × (absorbance) + B ₂ is a relational expression between the amount of the absorbance and humic substances at a wavelength, further, at least A soil sample with a known cation exchange capacity value of 3 points, preferably at least 4 and a pH of 7.0 or less, and an alkaline soil sample with a known cation exchange capacity value of at least 1 point, preferably at least 2 points For each of the above, the absorbance of the alkaline extract from the soil per predetermined weight at the measurement wavelength is measured, and the pH of the soil sample is 7.0 or less. Each calculated value of the humic substance calculated from the above measured values of absorbance by the above (humic substance content (% by weight)) = A ₁ × (absorbance) + B ₁ and a cation corresponding to each calculated value From the value of the exchange capacity, a relational expression between the humic substance content and the cation exchange capacity to be used when the pH of the soil to be measured is 7.0 or less by an appropriate method such as the least square method (positive ion exchange capacity (me / 100 g soil)) = _{a 3} × (content of humic substances (wt%)) + with determining the value of _{a 3} and _{B 3} in _{B 3,} from each measurement of the absorbance at all soil samples From each calculated value of humic substance content calculated by the above (humic substance content (% by weight)) = A ₂ × (absorbance) + B ₂ and the value of the cation exchange capacity corresponding to each calculated value, Such as least squares The Yichun method, soil to be measured is a relational expression between the content and the cation exchange capacity of the humic substances utilized in the case of alkaline (cation exchange capacity (me / 100 g soil)) = A ₄ × (humic substances content (wt%)) + and a method for determining the values of _{a 4} and _{B 4} in _{B 4.} Further, from the viewpoint of variation in the measured values as described above, the above formulas are expressed as, for example, (humic substance content (% by weight)) = (A ₁ ± a ₁ ) × (absorbance) + (B ₁ ± b ₁ ), (Humic substance content (% by weight)) = (A ₂ ± a ₂ ) × (absorbance) + (B ₂ ± b ₂ ), (cation exchange capacity (me / 100 g soil)) = (A ₃ ± a ₃ ) × humic substance content (% by weight) + (B ₃ ± b ₃ ), (cation exchange capacity (me / 100 g soil)) = (A ₄ ± a ₄ ) × humic substance content (% by weight) ) + (B ₄ ± b ₄ ), and similarly, values of A _{1 to} A ₄ , B _{1 to} B ₄ , a _{1 to} a ₄ , and b _{1 to} b ₄ may be obtained. More specific examples of these formulas include formulas obtained by examples described later.

Or a soil sample with a known pH value of 7.0 or less and at least 1 point, preferably at least 2 points of humic substance, with a humic substance content and cation exchange capacity value of at least 3 points, preferably at least 4 points. About the alkaline soil sample whose content and the value of cation exchange capacity are known, the absorbance of the alkaline extract from the soil per predetermined weight is measured using one absorption wavelength of the humic substance as a measurement wavelength, and the pH is 7. When the pH of the soil to be measured is 7.0 or less by an appropriate method such as the least square method from the measured values of the absorbance in the soil sample of 0 or less and the humic substance contents corresponding to the measured values, respectively. is a relational expression between the amount of the absorbance and humic substances in the measurement wavelength to be used for (the content of humic substances _{(wt%)) = a 1 '×} ( absorbance ) + B 1 together determine the value of and B _{1 ''} A _{1 'in,} and a content of humic substances respectively corresponding to each measurement value and the measurement value of the absorbance at all soil samples, such as for example the least square method It is a relational expression between the absorbance and the humic substance content at the measurement wavelength used when the soil to be measured is alkaline by an appropriate method (humic substance content (% by weight)) = A ₂ ′ × ( 'obtains the value of the (content of humic substances (wt%) absorbance of the from the measured value) = _{a 1'} and _{B 2 'a 2'} in absorbance) + _{B 2} calculated by × (absorbance) + _{B 1} ' From the calculated value of the humic substance content and the value of the cation exchange capacity respectively corresponding to the measured value of the absorbance, the pH of the soil to be measured is 7.0 or less by an appropriate method such as the least square method. Use when Is a relational expression between the content and the cation exchange capacity of the vegetable matter (cation exchange capacity (me / 100 g soil)) = _{A 3} '× (content of humic substances _{(wt%)) + B 3' A} 3 in Humic substances calculated by the above (humic substance content (% by weight)) = A ₂ ′ × (absorbance) + B ₂ ′ from the measured values of the absorbance in all soil samples while obtaining the values of “and B ₃ ” Humic substances to be used when the soil to be measured is alkaline by an appropriate method such as the least squares method, from the calculated value of the content of cation and the value of the cation exchange capacity corresponding to each measured value of the absorbance. a content and relationship between the cation exchange capacity of (cation exchange capacity (me / 100 g soil)) = _{a 4} '× (content of humic substances _{(wt%)) + B 4' a} 4 'in and The value of B ₄ 'can also be obtained . Note that in this case as well, the above-described formulas may be formulas including variations.

  Next, in the case of a soil analyzer that provides the measured value of the humic substance content as an index value, the function in the soil analyzer calculates the humic substance content from the absorbance of the alkaline extract of the soil, It is displayed as a measured value. Therefore, as another conversion method, using a soil analyzer that measures the content of humic substances in the soil, a measured value of the content of humic substances in the soil is obtained, and the measured value is converted to a cation. The method of converting into exchange capacity is also mentioned. More specifically, the relationship between the content of humic substances and the cation exchange capacity is obtained in advance, a calibration curve is prepared as a standard curve showing these relationships, and the sample obtained by the soil analyzer By applying the measured value of the humic substance content of the soil to the calibration curve, the measured value of the humic substance content is converted into the cation exchange capacity, or the humic substance content and the cation exchange capacity are calculated from the calibration curve. By converting the measured value of the humic substance content into the cation exchange capacity by substituting the measured value of the humic substance content as the humic substance content of the relational expression. The method of doing is mentioned.

More specifically, the soil analyzer has a cation exchange capacity value of at least 3 points, preferably at least 4 points, a soil sample having a known pH of 7.0 or less, and at least 1 point, preferably at least 2 points. For an alkaline soil sample with a known cation exchange capacity value, the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance is measured to measure each content of the humic substance in the soil. From the measured value of the humic substance content in a soil sample having a pH of 7.0 or less and the value of the cation exchange capacity corresponding to each measured value, for example, by an appropriate method such as a least square method , Is a relational expression between humic substance content and cation exchange capacity used when the pH of the soil to be measured is 7.0 or less (cation exchange capacity (me / 1 0g soil)) = A ₅ × (content of humic substances (wt%)) + with determining the value of A ₅ and B ₅ in B _5, each measured value and the measurement of the content of the humic substances in all soil samples From the value of the cation exchange capacity corresponding to each value, the relational expression between the humic substance content and the cation exchange capacity used when the soil to be measured is alkaline by an appropriate method such as the least square method. there (cation exchange capacity (me / 100 g soil)) = _{a 6} × (content of humic substances (wt%)) + a method for determining the values of _{a 6} and _{B 6} are mentioned in _{B 6.} In this case as well, each of the above formulas including variations (cation exchange capacity (me / 100 g soil)) = (A ₅ ± a ₅ ) × (humic substance content (% by weight)) + (B ₅ ± b ₅ ), (cation exchange capacity (me / 100 g soil)) = (A ₆ ± a ₆ ) × (humic substance content (% by weight)) + (B ₆ ± b ₆ ). _{5, a 6, B 5,} B 6, a 5, a 6, b 5, be calculated the value of _{b 6} are preferred.

The content of humic substances used in the soil having a pH of 7.0 or less by the least square method from the measured values of the humic substance content and the cation exchange capacity values corresponding to the measured values as described above. (Cation exchange capacity (me / 100 g soil)) = (A ₅ ± a ₅ ) × (humic substance content (% by weight)) + (B ₅ ± b ₅ ) Includes, for example, the following formula (1). If the pH of the measured soil measured in advance is 7.0 or less, that is, if the measured soil is acidic soil or neutral soil, the following formula (1) If the measured value of the content of humic substances in the measured soil is substituted into), the cation exchange capacity in the measured soil can be calculated.

Since the value calculated by the above equation (1) has a width, when the soil to be measured is acidic soil or neutral soil, in order to obtain the value 1 (central value), (cation exchange capacity ( me / 100 g soil)) = A ₅ × (humic substance content (% by weight)) + B ₅ , for example, by substituting the measured value of the humic substance content in the measured soil into the following formula (3) The cation exchange capacity in the soil can be calculated.

  When evaluating and judging the cation exchange capacity in the sample soil based on the measured value of the cation exchange capacity in the soil calculated by the above formula (3), in the sample soil calculated by the above formula (3) The measured value of the cation exchange capacity is preferably evaluated and judged as having a fluctuation range of ± 20%.

On the other hand, it is a relational expression between the content of humic substances and the cation exchange capacity at the measurement wavelength used in alkaline soil (cation exchange capacity (me / 100 g soil)) = (A ₆ ± a ₆ ) × (humic substance The content (weight%)) + (B ₆ ± b ₆ ) includes the following formula (2), and the measured soil pH measured in advance is alkaline soil, that is, measured soil pH> 7. If it is 0, the cation exchange capacity in the measurement soil can be calculated by substituting the measured value of the content of the humic substance in the measurement soil into the following formula (2).

Since the value calculated by the above equation (2) also has a width as in the case of the above equation (1), when the measured soil is an alkaline soil, a value of 1 (center value) is obtained by (positive If the measured value of the humic substance content in the measured soil is substituted into the following formula (4) as ion exchange capacity (me / 100 g soil)) = A ₆ × (humic substance content (% by weight)) + B ₆ The cation exchange capacity in the measured soil can be calculated.

  When the cation exchange capacity in the measured soil is evaluated and judged by the measured value of the cation exchange capacity in the soil calculated by the above formula (4), the cation exchange capacity in the sample soil calculated by the above formula (4) is used. It is desirable to evaluate and judge the measured value of the ion exchange capacity as having a fluctuation width of ± 30%.

  The method for measuring the cation exchange capacity in the soil of the present invention can calculate a numerical value by using, for example, a computer or a calculator, but if the soil analyzer of the present invention is used, for example, sampling of soil The cation exchange capacity in the soil can be determined easily and quickly on site. As described above, the soil analyzer of the present invention is a soil analyzer used for measuring the cation exchange capacity in the soil, and is a data input means for inputting the measured weight value of the soil and pH as data, Absorbance measuring means for measuring the absorbance at the absorption wavelength of the humic substance of the alkaline extract containing the humic substance, and the per unit weight at the absorption wavelength of the humic substance used when the pH of the soil to be measured is 7.0 or less Relational expression showing the correlation between the absorbance of the alkaline extract from the soil and the cation exchange capacity and / or relational expression showing the correlation between the absorbance and the humic substance content at the absorption wavelength of the humic substance and humus The relational expression showing the correlation between the content of the substance and the cation exchange capacity, and the absorption wavelength of the humic substance used when the soil to be measured is alkaline Relational expression showing correlation between luminous intensity and cation exchange capacity and / or relational expression showing correlation between absorbance and humic substance content at absorption wavelength of humic substance, humic substance content and cation exchange A storage means for storing a relational expression indicating a correlation with the capacity, and a relational expression used by the pH of the soil to be measured input to the data input means is selected from the relational expressions stored in the storage means. The selection means, and the absorbance data measured by the absorbance measurement means is selected by the selection means by converting the absorbance data of the soil input to the data input means to the absorbance per predetermined weight as necessary. And calculating means for obtaining the cation exchange capacity by substituting into the relational expression, and display means for displaying the value of the cation exchange capacity obtained by the calculating means. . In addition, each said relational expression in the soil analyzer of this invention can be calculated | required similarly to each said relational expression of the measuring method of this invention.

  Hereinafter, a configuration example of the soil analyzer of the present invention will be described in more detail with reference to FIGS. 1 and 2. FIG. 1 is a front (partial cross-sectional) view of a soil analyzer 1 which is an example of the present invention, and FIG. 2 is a right side (partial cross-sectional) view of the soil analyzer 1. The soil analyzer 1 includes a display unit 2 as display means and input buttons 3a, 3b, 3c, and 3d as data input means on the surface of the analyzer body case 1a. And as a light absorbency measuring means, the light irradiation part 4, the light-receiving part 5, the cell 6, and the cell fixing | fixed part 6a are provided. In the figure, 7 is an alkaline extract for measuring absorbance. The soil analyzer 1 incorporates a CPU (central processing unit) (not shown) in the analyzer body case 1a, and the CPU is provided with storage means, selection means, and calculation means. Further, the analyzer main body case 1a is provided with electric supply means (dry battery, power cord, etc.) (not shown), and can be turned on and off by a power switch (not shown).

  The material of the analyzer main body case 1a is not particularly limited, and can be formed by appropriately selecting a material used as a case material of a known soil analyzer. The display unit 2 is configured to display the humic substance content calculated from the absorbance as described later, together with the value of the cation exchange capacity obtained by the calculation means. Further, before the analysis is performed, the input data by the input buttons 3a, 3b, 3c, 3d is displayed and the data can be confirmed. The input buttons 3a, 3b, 3c, 3d are configured as a condition determination button 3a, an input start button 3b, a condition / numerical value selection button 3c, and a condition / numerical value selection button 3d, respectively. Select either the measured soil measured value or the measured soil pH value by the condition / numerical value selection buttons 3c and 3d, and the input condition is determined by the condition determination button 3a. For example, when the measurement soil weighing value is selected as the condition, the measurement soil weighing value can be selected by the condition / numerical value selection buttons 3c and 3d. Similarly, the measurement soil pH is set as the condition. When selected, the pH of the soil to be measured can be selected by the condition / numerical value selection buttons 3c and 3d. 3a to determine the selected numeric can store conditions and number in storage means of the CPU by pressing.

  The light irradiation unit 4 is composed of an LED and is connected to an electric supply means (not shown) and a CPU. When performing measurement, the light receiving unit 4 is passed through a time cell 6 required for analysis by pressing a condition determination button 3a. 5 can be irradiated with light. The light receiving unit 5 can receive the light irradiated from the light irradiation unit 4 through the cell 6 and convert it into an electrical signal corresponding to the amount of this light. The shape of the cell 6 is not particularly limited, but it is preferable that the cell 6 transmits 80% or more of the light irradiated from the light irradiation unit 4 and does not diffuse or scatter the irradiated light. If the numerical value when the amount of light transmitted from 5 to the light irradiation unit 4 when the cell 6 is not installed is converted to an electrical signal is 255, the amount of light from the light irradiation unit 4 when the cell 6 is installed It is desirable that the numerical value when the signal is converted into an electric signal is 100 or more. The material of the cell 6 is not particularly limited, but it is desirable that the cell 6 does not change its shape within at least one hour after dissolving in alcohol or water, or does not change the absorbance at the measurement wavelength of alcohol or water. Further, it is desirable that the light irradiated from the light irradiation unit 4 transmits 80% or more and does not diffuse or scatter the irradiated light, and the light transmitted through the light receiving unit 5 does not install the cell 6. If the numerical value when the light amount from the light irradiation unit 4 is converted into an electrical signal is 255, the numerical value when the light amount from the light irradiation unit 4 when the cell 6 is installed is converted into an electrical signal is 100 or more. It is desirable that The cell fixing portion 6a is configured to fix and hold the cell 6 and to have an optical path so that light can pass through the light transmitting portion of the cell 6.

In the storage means of the soil analyzer 1, as a relational expression stored by the storage means of the soil analyzer of the present invention described above, (a) the humic substance used when the pH of the soil to be measured is 7.0 or less. Relational expression showing the correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength and the content of humic substances, for example, (humic substance content (% by weight)) = A ₁ × (absorbance) + B ₁ , more specifically, for example, formulas (5) and (b) of the examples described later, and the humic substance content and cation exchange capacity used when the pH of the soil to be measured is 7.0 or less Relational expression showing a correlation, for example, (cation exchange capacity (me / 100 g soil)) = A ₃ × (humic substance content (% by weight)) + B ₃ , more specifically, for example, examples described later (8), (c) the soil to be measured is The relational expression showing the correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance and the humic substance content, for example, the above (the humic substance content (weight %)) = A ₂ × (absorbance) + B ₂ , more specifically, for example, the formula (6) and (d) of the examples described later, and the content of humic substances used when the soil to be measured is alkaline Relational expression showing correlation with cation exchange capacity, for example, (cation exchange capacity (me / 100 g soil)) = A ₄ × (humic substance content (% by weight)) + B ₄ , more specifically For example, Formula (7) of the Example mentioned later is memorize | stored. Such relational expressions (a) to (d) can be obtained, for example, as in Example 2 described later. Moreover, as a relational expression memorize | stored in the memory | storage means of the soil analyzer of this invention, (e) From the soil per predetermined weight in the absorption wavelength of humic substance utilized when pH of the soil to measure is 7.0 or less The relational expression showing the correlation between the absorbance of the alkaline extract and the cation exchange capacity, for example, the above (cation exchange capacity (me / 100 g soil)) = A ₇ × (absorbance) + B ₇ , more specifically, For example, the formula (10) of the example described later or the formula (12) of the example, (f) of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance used when the soil to be measured is alkaline. absorbance and relational expression indicating a correlation between the cation exchange capacity, for example, the (cation exchange capacity (me / 100 g soil)) = a ₈ × (absorbance) + B _8, more specifically, for example, described below The formula (9) of the embodiment or the formula (11) of the embodiment may be used, and the relational expressions (e) and (f) may be stored instead of the relational expressions (a) to (d). Alternatively, the relational expressions (a), (b), (e), and (f) may be stored, or the relational expressions (a) to (f) may be stored. The relational expressions (e) and (f) can be obtained, for example, as in Examples 2 and 3 described later. In addition to these relational expressions, the storage unit of the soil analyzer 1 is also configured to store input data, measured absorbance data (measurement data), and the like, as will be described later.

  Further, the CPU (not shown) has a selection means for selecting a relational expression used by the pH of the soil to be measured input from the data input means from the relational expressions stored in the storage means, and the absorbance measured by the absorbance measurement means. Calculating means for calculating the cation exchange capacity by converting the data of the above into the relational expression selected by the selecting means by converting the absorbance per predetermined weight by the measured soil weight value input to the data input means Is provided. In addition, in the case of this soil analyzer 1, in addition to the above-mentioned calculation, the absorbance of the alkaline extract is calculated from the measured value of the absorbance of pure water (blank) and the measured value of the absorbance of the alkaline extract as described later. Is also computed. The measurement wavelength may be selected on the device side, and only the LED that can irradiate the selected wavelength emits light, or the time for emitting the selected LED and the unselected LED is shifted, and the light is measured at the light receiving unit. By synchronizing the time to be performed with only the light emission time of the LED capable of irradiating the selected wavelength, it can be selected on the device side. Or you may carry out by providing the control means which controls the wavelength of the light irradiation part 4 according to the wavelength input by button 3a, 3b, 3c, 3d for input in CPU.

  According to this soil analyzer 1, if the cell 6 containing the alkaline extract 7 from the measured soil is installed in the soil analyzer 1 and measurement is started by the input buttons 3a, 3b, 3c, 3d, the light irradiation unit The light irradiated from 4 can be measured by the light receiving unit 5. Specifically, pure water is put in the cell 6 in advance, the numerical value (blank value) measured by the light receiving unit 5 is measured for the light emitted from the light source 4, and the blank value is stored in a storage means (not shown). Then, the alkaline extract 7 from the measurement soil is put in the cell 6, the transmitted light intensity of the wavelength of the light irradiated by the alkaline extract 7 is measured, and the blank value and the alkaline extract are calculated by a calculation means (not shown). The absorbance data of the alkaline extract 7 can be obtained from the measured value of the transmitted light intensity 7 and the absorbance data can be stored in a storage means (not shown). For example, the storage means stores the relational expressions (a) to (d) or the relational expressions (a), (b), (e), (f), or (a) to (f). If so, the humic substance content and the cation exchange capacity are calculated based on the absorbance data of the alkaline extract 7 and, if necessary, the above measured value, and the calculated humic substance is calculated on the display unit 2. Display content and cation exchange capacity. That is, the calculating means (not shown) calculates the humic substance content from the absorbance data measured by the absorbance measuring means and, if necessary, the measured weight value, and further calculates the humic substance content value or absorbance data, and The cation exchange capacity is calculated from the measured value as necessary, and the display unit 2 is configured to display the value of the cation exchange capacity obtained by the calculation means and the calculated value of the humic substance content. ing. Prior to the analysis, the measured soil weight and pH can be input using the input buttons 3a, 3b, 3c, and 3d as described above.

  In addition, the soil analyzer of this invention is not limited to the said structure, It can change variously in the range which does not deviate from the summary of this invention.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.

  Table 1 below shows the names of soil (soil samples) used in the examples, soil quality, and cultivation methods in which the soil is used. About 10 g of these soils were weighed, 25 ml of pure water was added thereto, and the mixture was shaken with a shaker (all-agricultural shaker) for 30 minutes. The liquid after shaking was allowed to stand for about 3 minutes, and then the pH was measured with a pH meter (HANNA Instruments; pH 211 Microprocessor pH Meter). The results are also shown in Table 1.

[Example 1]
The humic substance in each soil was measured according to the following procedure according to the Kumada method. FIG. 4 shows a flowchart of the measurement method.
1) 0.50 g of soil was weighed and added as an alkaline extract into 5 ml of a 0.1 M sodium hydroxide / sodium pyrophosphate mixture (pH 13).
2) This mixed liquid was shaken for 3 minutes with a shaker (Zenno-type shaker).
3) The mixture was filtered through a filter paper (No. 2), 0.5 ml of this filtrate was collected, and pure water was added to the filtrate to dilute it 12 times.
4) The diluted solution was analyzed with a soil analyzer (All-Agricultural Soil Analyzer ZA-II) to obtain a measured value of the content of humic substances (% by weight, hereinafter referred to as wt%) in each soil.

  The cation exchange capacity (CEC) of the soil (me / 100 g soil, hereinafter referred to as me / 100 gsoil) was extracted by the Scholeenberger method and analyzed by the indophenol method. That is, about 1 g of soil was weighed. This was added so that it might disperse | distribute to 10 ml of replacement | exchange reagents, and it left still for 15 minutes. After leaving still for 15 minutes, it filtered with the funnel and the filter paper. To the funnel was added 5 ml of washing solution, and the washing solution was filtered. After the washing solution was filtered, 5 ml of washing solution was further added, and this washing solution was filtered. Filtration was continued until the washing liquid was filtered and the soil surface remaining on the filter paper was cracked. When the soil surface remaining on the filter paper did not crack even after 20 minutes had passed, the washing solution was filtered using a pressurizer. The funnel tip was closed to prevent the liquid from leaking, and then 10 ml of an extraction reagent was added to perform extraction for 15 minutes. After extraction for 15 minutes, the funnel tip was opened and the extract was filtered into a 20 ml beaker. This filtrate was used as an extraction filtrate. Two milliliters of the extracted filtrate was collected in a test tube, 23 ml of pure water was added thereto and stirred well, and this was used as a diluted filtrate. 0.2 ml of the diluted filtrate was collected in another test tube, and 2.8 ml of pure water was added thereto to prepare about 3 ml of a measuring reagent. Separately from the measurement reagent, 3 ml of pure water was collected in a test tube and used as a standard reagent. A coloring reagent was added to each of the standard reagent and the measurement reagent and stirred well. After stirring, the mixture was allowed to stand for 20 minutes, and analyzed with a soil analyzer (Zenno Soil Analyzer ZA-II) using a standard reagent to which a coloring solution was added as a standard. About the CEC measurement of soil, the flowchart of a measurement is shown in FIG.

[Example 2]
The diluted solution of Example 1 was put into a cell having an optical path length of 10 mm, pure water was used as a blank, and a deaeration process was not performed by a spectrophotometer (Shimadzu; UV-2400PC), and a room temperature of 22 to 25 ° C. The absorbance (OD) was measured at wavelengths of 524 nm and 632 nm.

[Example 3]
The diluted solution of Example 1 is sucked into a syringe, and a prescribed amount is injected into the soil analyzer MO-01 optical cell (cell length: 8 mm) manufactured by the soil making promotion organization of the limited company. Absorbance (OD) was measured at a wavelength of 524 nm and 632 nm at room temperature of 22-25 ° C.

  Table 2 below shows the results of CEC measurement according to the above-mentioned Example 1, Example 2, Example 3, and the Scholeenberger method.

When the relationship between the content of humic substances in the soil measured in Example 1 and the cation exchange capacity extracted by the Shohlenberger method was plotted on a graph, the result of FIG. 5 was obtained. According to this graph, a first-order correlation was observed between the two, and the correlation coefficient R ² = 0.72, indicating that there was a correlation between the humic substance content and the CEC value. Further, the following relational expression (4) was obtained by the method of least squares. In consideration of variation, the following relational expression (2) was obtained.

Furthermore, when only a soil (acid to neutral soil) having a soil pH of 7.0 or less was selected as a measurement soil (soil sample), a graph was similarly created, and the result of FIG. 6 was obtained, and the correlation coefficient R ² = 0.89, indicating a higher correlation when adding alkaline soil results. Further, the following relational expression (3) was obtained by the method of least squares. In consideration of variation, the following relational expression (1) was obtained.

  From these results, it was shown that the content of humic substances in the measured soil can be measured, and the cation exchange capacity (CEC) of the soil can be easily calculated from the content, especially acidic soil to neutral soil. It was confirmed to be effective in (soil having a pH of 7.0 or less). That is, according to the result of Example 1 above, for example, if the measurement soil collected at a soil collection site such as a vegetable production site is acidic soil to neutral soil (soil having a pH of 7.0 or less), the above (1) The soil when the pH of the soil collected at the vegetable production site or the like is 7.0 or less by substituting the measured value of the humic substance content in the soil measured by the above soil analyzer into the formula or the above formula (3) The cation exchange capacity (CEC) in the medium can be determined. On the other hand, if the measured soil is alkaline soil (pH> 7.0), the above-mentioned formula (2) or (4) By substituting the measured value of the humic substance content in the measured soil, it is recognized that the cation exchange capacity (CEC) in the soil when the soil collected at the vegetable production site etc. is alkaline soil can be obtained. It was.

Next, the absorbance (OD _{524 nm} ) per 0.50 g of the alkaline extract of each soil having a pH of 7.0 or less measured in the above Example 2 at a wavelength of 524 nm and the corresponding pH in the above Example 1 are 7 When the relationship with the measured value of the content of humic substances in each soil of 0.0 or less was plotted on a graph, the result of FIG. 7 was obtained. According to this graph, the correlation between the absorbance (OD _{524 nm} ) per 0.50 g of the alkaline extract of the soil having a pH of 7.0 or less and the measured value of the content of humic substances in the soil is a correlation. The number R ² = 0.89. When the relational expression between the absorbance and the content of humic substance was determined by the least square method, the following expression (5) was obtained. Moreover, the light absorbency ( _OD524nm ) per 0.50g soil of the alkaline extract of the whole soil measured in wavelength of 524nm in the said Example 2, and the content of humic substances of each soil of each corresponding soil in the said Example 1 respectively. When the relationship with the measured value was obtained, the correlation coefficient R ² = 0.99, and when the relational expression between the absorbance and the humic substance content was obtained by the least square method, the following equation (6) was obtained. . Therefore, the absorbance (OD _{524 nm} ) per 0.50 g of soil of the alkaline extract measured at a wavelength of 524 nm in Example 2 above, the following formula (5) for soil of pH 7.0 or less, and the following formula ( Substituting in 6), the humic substance content was calculated. The results are also shown in Table 2 above.
Humic substance content (% by weight) = 14.9 × (OD _{524 nm} ) +0.97 (5)
Humic substance content (% by weight) = 9.8 × (OD _{524 nm} ) +0.96 (6)

Further, when the relationship between the humic substance content obtained from the absorbance measurement value of Example 2 and the cation exchange capacity extracted by the Shohlenberger method was plotted on a graph, a first-order correlation was observed between the two. The correlation coefficient R ^{2 was} 0.67, indicating that there was a correlation between the humic substance content calculated from the absorbance (OD _{524 nm} ) and the CEC value. Further, the following relational expression (7) was obtained by the method of least squares. Further, in neutral to acidic soil, the correlation coefficient R ^{2 was} 0.80, indicating that there was a correlation between the humic substance content calculated from the absorbance (OD _{524 nm} ) and the CEC value. Further, the following relational expression (8) was obtained by the method of least squares. Therefore, if the measurement soil is acidic soil to neutral soil (soil having a pH of 7.0 or less), by substituting the humic substance content calculated from the absorbance (OD ₅₂₄ nm) into the following relational expression (8), The cation exchange capacity (CEC) in the measured soil can be determined. If the measured soil is alkaline soil (pH> 7.0), the humus calculated from the absorbance (OD ₅₂₄ nm) in the following relational expression (7) By substituting the content of the substance, the cation exchange capacity (CEC) in the measurement soil can be obtained.

That is, according to the result of Example 2 above, for example, if the measurement soil collected at a soil collection site such as a vegetable production site is acidic soil to neutral soil (soil having a pH of 7.0 or less), the above (5) By substituting the measured value (OD _{524 nm} ) of the absorbance at a wavelength of 524 nm per 0.50 g of soil of the alkaline extract of the measured soil into the formula, the humic substance content of the measured soil can be calculated. By substituting the calculated value of the humic substance content into the above formula (8), the cation exchange capacity (CEC) in the soil when the pH of the soil collected at the vegetable production site or the like is 7.0 or less. On the other hand, if the measured soil is alkaline soil (pH> 7.0), the alkaline extract of the measured soil at a wavelength of 524 nm per 0.50 g of soil By substituting the value measured by spectrophotometer intensity of (OD _{524 nm)} in the equation (6), it is possible to calculate the content of humic substances measured soil, the calculated value of the content of the humic substances It was recognized that by substituting into the equation (7), the cation exchange capacity (CEC) in the soil when the soil collected at the vegetable production site or the like is alkaline can be obtained.

Furthermore, when the relationship between the absorbance (OD _{524 nm} ) per 0.50 g of soil of the alkaline extract measured in the above Example 2 at a wavelength of 524 nm and the cation exchange capacity extracted by the _{Shoreenberger} method was plotted in a graph, both A first-order correlation was observed between them, and the correlation coefficient R ^{2 was} 0.70. The following relational expression (9) was obtained by the least square method. Furthermore, when only neutral to acidic soil was selected as the measurement soil (soil sample) and the graph was similarly created, the correlation coefficient R ^{2 was} 0.80, and the following relational expression (10) was obtained by the least square method. Obtained. Therefore, if the measurement soil is acidic soil to neutral soil (soil having a pH of 7.0 or less), the cation exchange capacity (CEC) in the measurement soil is substituted by substituting the measured value of absorbance into the following relational expression (10). If the measured soil is alkaline soil (pH> 7.0), the cation exchange capacity (CEC) in the sample soil is substituted by substituting the measured value of absorbance into the following relational expression (9). ). That is, according to the results of Example 2, for example, if the measurement soil collected at a soil collection site such as a vegetable production site is acidic soil to neutral soil (soil having a pH of 7.0 or less), the following (10) By substituting the measured value (OD _{524 nm} ) of the absorbance at a wavelength of 524 nm per 0.50 g of soil of the alkaline extract of the measured soil into the formula, the pH of the soil collected at the vegetable production site or the like is 7.0. The cation exchange capacity (CEC) in the soil in the following cases can be determined. On the other hand, if the measured soil is an alkaline soil (pH> 7.0), 0.50 g of the alkaline extract of the measured soil It was collected at the vegetable production site etc. by substituting the measured value (OD _{524 nm} ) with the spectrophotometer of the absorbance at a wavelength of 524 nm per _unit into the following formula (9) It was found that the cation exchange capacity (CEC) in the soil can be determined when the soil is alkaline.
CEC (me / 100 g soil) = 86 × OD ₅₂₄ nm ₊ 11.9 (9)
CEC (me / 100 g soil) = 88.5 × OD ₅₂₄ nm ₊ 11.0 (10)

Next, a graph plotting the relationship between the absorbance (OD _{524 nm} ) per 0.50 g of soil of the alkaline extract measured at a wavelength of 524 nm in Example 3 above and the cation exchange capacity extracted by the _{Shohlenberger} method is shown in the graph. A result of 8 was obtained. According to this graph, a first-order correlation was observed between the two, and the correlation coefficient R ² = 0.62, and the following relational expression (11) was obtained by the least square method. Furthermore, when only neutral to acidic soil was selected as the sample soil and the graph was similarly prepared, the result of FIG. 9 was obtained, and the correlation coefficient R ² = 0.78 was obtained, and the following relational expression (12 )was gotten. Therefore, if the measured soil is acidic soil to neutral soil (soil having pH 7.0 or lower), the cation exchange capacity (CEC) in the measured soil is substituted by substituting the measured value of absorbance into the following relational expression (12). ), And if the measured soil is alkaline soil (pH> 7.0), the cation exchange capacity (CEC) in the measured soil is substituted by substituting the measured absorbance value into the following relational expression (11). ).
CEC (me / 100 g soil) = 103 × OD ₅₂₄ nm ₊ 12.1 (11)
CEC (me / 100 g soil) = 109 × OD ₅₂₄ nm ₊ 11.0 (12)

That is, according to the result of Example 3, for example, if the measurement soil collected at a soil collection site such as a vegetable production site is acidic soil to neutral soil (soil having a pH of 7.0 or less), the above formula (12) By substituting the measured value (OD _{524 nm} ) by the soil analyzer for the absorbance at a wavelength of 524 nm per 0.50 g of soil of the alkaline extract of the measured soil, the pH of the soil collected at the vegetable production site or the like is 7.0. The cation exchange capacity (CEC) in the soil in the following cases can be determined. On the other hand, if the measured soil is an alkaline soil (pH> 7.0), 0.50 g of the alkaline extract of the measured soil By substituting the measured value (OD _{524 nm} ) of the absorbance at a wavelength of 524 nm by the above soil analyzer into the above formula (11), it is collected at a vegetable production site or the like. It was found that the cation exchange capacity (CEC) in the soil can be determined when the soil taken is alkaline.

  From the above results, it was shown that the cation exchange capacity (CEC) of the soil can be easily calculated from the index value corresponding to the content of humic substances contained in the soil. The method for measuring the cation exchange capacity in the soil of the present invention is, as described above, for example, in determining the amount of fertilizer used in a vegetable production site, the measurement of the cation exchange capacity in the soil is performed at an analysis center or the like. It is also possible for vegetable producers, etc. to determine the cation exchange capacity in the soil at the soil collection site and determine the amount of fertilizer used on the spot, without requesting In order to use it for simple determination, the measured value of the index value corresponding to the humic substance content in the above example and the measured value of the cation exchange capacity have a sufficient correlation. According to the CEC measurement methods of Examples 1 to 3, the CEC measurement time, which took about 2 hours to several days in the conventional method, could be shortened to about 5 minutes. Furthermore, since the number of processes is considerably reduced, it can be said that it can be sufficiently carried out at the vegetable production site.

And as a structural example of the soil analyzer of the present invention, the absorbance measurement wavelength of the soil analyzer 1 described above (see FIGS. 1 and 2) is 524 nm, the cell length is 10 mm, and the pH of the measured soil is 7.0 or less. The following relational expression (5) showing the correlation between the absorbance (OD _{524 nm} ) at a wavelength of 524 nm per 0.50 g of soil of the alkaline extract of the measured soil and the content of humic substance, the calculated humic substance content The following relational expression (8) showing the correlation between the amount and the cation exchange capacity, when the measurement soil is alkaline soil, the absorbance (OD _{524 nm} ) at a wavelength of 524 nm per 0.50 g of the alkaline extract of the measurement soil and humus The following relational expression (6) indicating the correlation with the substance content is stored, and the following relational expression (7) indicating the correlation between the calculated humic substance content and the cation exchange capacity is stored. This simple CEC measurement method is configured so that the content and CEC value of the humic substance obtained by the calculation means are displayed on the display unit 2 (see FIGS. 1 and 2). It was confirmed that it could be implemented. Note that the relational expression mounted on the soil analyzer can be appropriately changed according to the measurement wavelength, the cell length, the specifications of the soil analyzer, and the like.

DESCRIPTION OF SYMBOLS 1 Soil analyzer 1a Analyzer main body case 2 Display part (display means)
3a, 3b, 3c, 3d Input buttons (input means)
4 Light irradiation part (absorbance measurement means)
5 Light receiving part (absorbance measuring means)
6 cells (absorbance measurement means)
6a Cell fixing part (absorbance measuring means)
7 Alkaline extract

Claims (16)

A method for measuring cation exchange capacity in soil, characterized by measuring an index value corresponding to the content of humic substances in soil and converting the measured value to cation exchange capacity. Method for measuring cation exchange capacity. After adding an alkaline aqueous solution to the soil and extracting an extract component containing the humic substance in the alkaline aqueous solution to obtain an alkaline extract, the absorbance of the alkaline extract at the absorption wavelength of the humic substance is measured, The method for measuring a cation exchange capacity in soil according to claim 1, wherein the measured value is converted into a cation exchange capacity. A standard curve or relational expression showing a correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance and the content of the humic substance in the soil is obtained, and the standard curve or the relation is obtained. A standard curve or a relational expression showing the correlation between the measured value of the absorbance according to the formula to the content of the humic substance in the soil and the converted value of the content of the humic substance and the cation exchange capacity in the soil, The method for measuring a cation exchange capacity in soil according to claim 2, wherein the converted value of the humic substance content is converted into a cation exchange capacity in the soil by the standard curve or the relational expression. Measurement wavelength of one absorption wavelength of the above humic substance for a soil sample with a known pH of 7.0 or less and an alkaline soil sample with a known humic substance content of at least one point. And measuring the absorbance of the alkaline extract from the soil sample per predetermined weight, and measuring the absorbance in a soil sample having a pH of 7.0 or less and the content of humic substances corresponding to each measured value. From the relationship between the absorbance and the humic substance content at the measurement wavelength used when the pH of the soil to be measured is 7.0 or less (humic substance content (% by weight)) = A ₁ × (absorbance) + humic substances with determining the value of a ₁ and B ₁ in B _1, corresponding to each measured value of the absorbance and the measured values in all soil samples Is a relational expression between the absorbance and the humic substance content at the measurement wavelength used when the soil to be measured is alkaline (humic substance content (% by weight)) = A ₂ × (absorbance) + calculated values of a ₂ and B ₂ in B _2, the value of the cation exchange capacity of at least three points the value of the cation exchange capacity of known pH is 7.0 or less of soil samples and the at least one point With respect to a known alkaline soil sample, the absorbance of the alkaline extract from the soil per predetermined weight at the measurement wavelength is measured, and the absorbance (humic substance) is measured from the measured values of the absorbance in a soil sample having a pH of 7.0 or less. content (wt%)) = a ₁ × (absorbance) + B ₁ of cation-exchange capacity corresponding to each calculated value and the calculated value of the content of the calculated humic substances by the From, pH of the soil to be measured is a relational expression between the content and the cation exchange capacity of the humic substances utilized in the case of 7.0 or less (cation exchange capacity (me / 100 g soil)) = A ₃ × (content of humic substances (wt%)) + B together determine the value of a ₃ and B ₃ in _3, the from the measurement of the absorbance at all soil samples (the content of humic substances (wt%)) = a _From each calculated value of humic substance content calculated by ₂ × (absorbance) + B ₂ and the value of the cation exchange capacity corresponding to each calculated value, the humic substance used when the soil to be measured is alkaline content and a relational expression between the cation exchange capacity (cation exchange capacity (me / 100 g soil)) = _{a 4} × (content of humic substances (wt%)) + value of _{a 4} and _{B 4} in _{B 4} The claim of claim 3 Method of measuring the cation exchange capacity of 壌中. The content of the humic substance in the soil is calculated from the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance, and the humic substance in the soil is displayed by a soil analyzer that displays the measured value. Obtaining a measurement value of the content, obtaining a standard curve or a relational expression showing a correlation between the measurement value of the content of the humic substance and the cation exchange capacity in the soil, and obtaining the above humic substance from the standard curve or the relational expression The method for measuring the cation exchange capacity in soil according to claim 2, wherein the measured value of the content of cation is converted into a cation exchange capacity. For the soil sample having a known pH value of 7.0 or less and the alkaline soil sample having a known cation exchange capacity value of at least three points by the soil analyzer, The absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength is measured to obtain each measured value of the content of the humic substance in the soil, and the humic substance in the soil sample having a pH of 7.0 or less The humic substance content and the cation exchange capacity used when the pH of the soil to be measured is 7.0 or less, based on the measured value of the content of each cation and the value of the cation exchange capacity corresponding to each measured value. is a relational expression (cation exchange capacity (me / 100 g soil)) = _{a 5} × (content of humic substances (wt%)) + with determining the value of _{a 5} and _{B 5} in _{B 5} From the measured values of the above humic substances in all soil samples and the cation exchange capacity values corresponding to the respective measured values, the humic substance contents and the positive values used when the soil to be measured is alkaline. Claim of determining the values of A ₆ and B ₆ in the relational expression with ion exchange capacity (cation exchange capacity (me / 100 g soil)) = A ₆ × (content of humic substance (% by weight)) + B ₆ 5. A method for measuring a cation exchange capacity in soil according to 5. In the soil of Claim 5 which calculates the cation exchange capacity by substituting the measured value of the content of humic substances in the soil into the following formula (1) when the pH of the soil to be measured is 7.0 or less Method for measuring the cation exchange capacity of

6. The cation exchange capacity in soil according to claim 5, wherein, when the soil to be measured is alkaline, the cation exchange capacity is calculated by substituting the measured value of the humic substance content in the soil into the following formula (2). Measuring method.

A standard curve or a relational expression indicating a correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance and the cation exchange capacity in the soil is obtained, and the standard curve or the relational expression is obtained. The method for measuring a cation exchange capacity in soil according to claim 2, wherein the measured value of absorbance is converted into a cation exchange capacity in soil. The absorption wavelength of one of the above humic substances is determined for at least three soil samples with known cation exchange capacity values of pH 7.0 or less and at least one alkaline soil sample with known cation exchange capacity values. As the measurement wavelength, the absorbance of the alkaline extract from the soil per predetermined weight is measured, and the measured value of the absorbance in a soil sample having a pH of 7.0 or less and the cation exchange capacity corresponding to each measured value. Value is a relational expression between the absorbance and the cation exchange capacity at the measurement wavelength used when the pH of the soil to be measured is 7.0 or less (cation exchange capacity (me / 100 g soil)) = A ₇ × (absorbance) + with determining the value of a ₇ and B ₇ in B _7, respectively corresponding to the measurement values and the measurement value of the absorbance at all soil samples It is a relational expression between the absorbance and the cation exchange capacity at the measurement wavelength used when the soil to be measured is alkaline from the value of the cation exchange capacity to be measured (cation exchange capacity (me / 100 g soil)). = a ₈ × (absorbance) + measuring method of the cation exchange capacity of the soil according to claim 9 for determining the values of a ₈ and B ₈ at B _8. The method for measuring a cation exchange capacity in soil according to claim 4, 6 or 10, wherein the relational expression is obtained by a method of least squares. The cation exchange capacity in soil according to any one of claims 2 to 11, wherein the alkaline aqueous solution is an aqueous solution containing an alkaline compound selected from sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate. Measuring method. The method for measuring a cation exchange capacity in soil according to any one of claims 2 to 12, wherein the pH of the alkaline aqueous solution is more than 8.0 and less than 13.9. The method for measuring a cation exchange capacity in soil according to any one of claims 2 to 13, wherein the absorbance of the alkaline extract is measured at at least one wavelength selected from 400 to 650 nm. A soil analyzer used for measuring the cation exchange capacity in soil, and a data input means for inputting the measured value and pH of the soil to be measured as data, and absorption of humic substances in an alkaline extract containing humic substances Absorbance measuring means for measuring absorbance at a wavelength, and absorbance and cation exchange of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance used when the pH of the soil to be measured is 7.0 or less Relational expression showing correlation with capacity and / or relational expression showing correlation between absorbance and humic substance content at absorption wavelength of humic substance and correlation between humic substance content and cation exchange capacity And the correlation between the absorbance and the cation exchange capacity at the absorption wavelength of the humic substance used when the soil to be measured is alkaline. A relational expression showing the correlation between the absorbance and the humic substance content at the absorption wavelength of the humic substance, and a relational expression showing a correlation between the humic substance content and the cation exchange capacity. The storage means for storing, the selection means for selecting the relational expression used by the pH of the soil to be measured input to the data input means from the relational expression stored in the storage means, and the measurement by the absorbance measurement means Cation exchange capacity by substituting the absorbance data thus converted into absorbance per a predetermined weight based on the measured value of the soil input to the data input means and substituting it into the relational expression selected by the selection means. And a display means for displaying the value of the cation exchange capacity obtained by the computing means. The storage means calculates the correlation between the absorbance of the alkaline extract from the soil per predetermined weight at the absorption wavelength of the humic substance used when the pH of the soil to be measured is 7.0 or less and the content of the humic substance. The relational expression shown, the relational expression showing the correlation between the humic substance content and the cation exchange capacity used when the pH of the soil to be measured is 7.0 or less and / or the pH of the soil to be measured is 7.0 or less The relational expression showing the correlation between the absorbance and the cation exchange capacity at the absorption wavelength of the humic substance used in the case of the above, the absorbance and the humic substance at the absorption wavelength of the humic substance used when the soil to be measured is alkaline Relational expression showing correlation with content, relational expression showing correlation between humic substance content and cation exchange capacity used when soil to be measured is alkaline and / or measurement Storing the relational expression showing the correlation between the absorbance and the cation exchange capacity at the absorption wavelength of the humic substance to be used when the soil to be used is alkaline, the absorbance data measured by the absorbance measuring means by the calculating means And, if necessary, calculating the humic substance content from the measured value, further calculating the cation exchange capacity from the calculated value of the humic substance content or the absorbance at the absorption wavelength of the humic substance, and the display unit The soil analyzer according to claim 15, wherein the soil analyzer is configured to display a value of a cation exchange capacity obtained by the computing means and a calculated value of the content of the humic substance.

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