Method for rapidly testing hydrolytic nitrogen in soil and application
By combining pure water shaking extraction with Nessler's reagent spectrophotometry and ion chromatography, the cumbersome procedures and errors in soil hydrolyzable nitrogen testing have been solved, enabling rapid and accurate testing of soil hydrolyzable nitrogen, which is suitable for evaluating soil nitrogen supply capacity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 吉林省吉林生态环境监测中心
- Filing Date
- 2026-01-29
- Publication Date
- 2026-05-08
AI Technical Summary
Existing methods for testing hydrolyzable nitrogen in soil are cumbersome, prone to human error, and inaccurate, making it difficult to achieve rapid and accurate testing.
A pure water shaking extraction method was adopted, and soil samples were classified and tested by Nessler's reagent spectrophotometry and ion chromatography. This simplified the operation process, avoided errors in the titration process, and improved the precision and accuracy of the test.
It shortens the testing steps, improves the precision and accuracy of sample testing, and achieves a low-carbon and environmentally friendly testing process, which is suitable for evaluating soil nitrogen supply capacity.
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Figure CN121994731A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of soil testing, and in particular to a rapid testing method and application for hydrolyzable nitrogen in soil. Background Technology
[0002] Soil hydrolyzable nitrogen characterizes the amount of nitrogen in the soil that can actually be absorbed and utilized by crops; it is also called available nitrogen or readily available nitrogen. Its content can determine the soil's nitrogen supply capacity and further guide rational fertilization, which is of great significance. Hydrolyzable nitrogen in soil exists in the forms of inorganic nitrogen, consisting of ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen, as well as some easily decomposable and relatively simple organic nitrogen from organic matter. Among these, ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen are the core nitrogen forms in soil that affect plant growth and environmental risk; their content directly reflects the soil's nitrogen supply intensity and status. Therefore, accurately measuring these three nitrogen forms is crucial for assessing soil nitrogen supply capacity, guiding scientific fertilization, and preventing environmental pollution.
[0003] Currently, the main testing method for hydrolyzable nitrogen in soil is the "Determination of Nitrogen in Forest Soils" (4. Determination of Hydrolyzable Nitrogen, LY / T1228-2015). This method uses 1.8 mol / L sodium hydroxide to hydrolyze the soil, then places the diffusion dish in a constant temperature chamber at 40℃ (24±0.5) for an hour, removes it, and titrates the boric acid solution that has absorbed ammonia with standard hydrochloric acid solution to calculate the hydrolyzable nitrogen in the soil. The local standard "Determination of Available Nitrogen in Soil" (DB13 / T843-2007) emphasizes that hydrolyzable nitrogen in soil includes ammonium nitrogen and nitrate nitrogen. The soil undergoes hydrolysis and reduction under strongly alkaline conditions and in the presence of ferrous sulfate, converting easily hydrolyzable nitrogen and nitrate nitrogen into ammonia gas which is absorbed by boric acid solution. The ammonia in the absorption solution is then titrated with standard acid.
[0004] The above methods all employ alkaline diffusion, which is generally quite cumbersome. For example, the diffusion dish needs to be alkaline-digested in a constant temperature incubator for a long time before the experiment can be conducted. It also requires multiple operations such as boric acid absorption and hydrochloric acid titration. Not only is the process lengthy, but the titration process is also very prone to introducing human error, resulting in poor parallelism and accuracy of the experiment. Summary of the Invention
[0005] The purpose of this application is to provide a rapid testing method and application for hydrolyzable nitrogen in soil. The method uses pure water shaking extraction, and after classifying and testing the existing forms of hydrolyzable nitrogen, the samples are summed to achieve rapid and accurate testing of hydrolyzable nitrogen in soil.
[0006] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a rapid test method for hydrolyzable nitrogen in soil, comprising: Soil samples were obtained and processed to obtain dried soil samples; The dried soil sample was mixed with ultrapure water and shaken to extract the soil mixture. The soil mixture was then filtered to obtain a soil extract solution. The soil extract solution was divided into a first test sample and a second test sample. The first test sample was tested for water-soluble ammonia nitrogen by Nessler's reagent spectrophotometry to obtain the water-soluble ammonia nitrogen content. The second test sample was tested for water-soluble nitrate nitrogen and water-soluble nitrite nitrogen by ion chromatography to obtain the water-soluble nitrate nitrogen content and water-soluble nitrite nitrogen content. Obtain blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values for blank control; Based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value, the ammonia nitrogen hydrolyzable nitrogen content, nitrate hydrolyzable nitrogen content, and nitrite hydrolyzable nitrogen content were obtained. The soil hydrolyzable nitrogen content is obtained by summing the contents of the ammonia nitrogen hydrolyzable nitrogen, the nitrate hydrolyzable nitrogen, and the nitrite hydrolyzable nitrogen.
[0007] In one embodiment, the step of obtaining the hydrolyzable nitrogen content of ammonia nitrogen, hydrolyzable nitrogen content of nitrate, and hydrolyzable nitrogen content of nitrite based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value specifically includes: The difference between the water-soluble ammonia nitrogen content and the blank water-soluble ammonia nitrogen content value is calculated as the first difference. The first difference is multiplied by the fixed volume of the soil sample to obtain the first product. Then, the ratio of the first product to the mass of the dry soil sample is calculated to obtain the ammonia nitrogen hydrolyzable nitrogen content. The difference between the water-soluble nitrate nitrogen content and the blank water-soluble nitrate nitrogen content is calculated as a second difference. The second difference is multiplied by the fixed volume of the soil sample to obtain a second product. The ratio of the second product to the mass of the dry soil sample is then calculated to obtain the nitrate hydrolysable nitrogen content. The difference between the water-soluble nitrite nitrogen content and the blank water-soluble nitrite nitrogen content is calculated as the third difference. The third difference is multiplied by the fixed volume of the soil sample to obtain the third product. The ratio of the third product to the mass of the dry soil sample is then calculated to obtain the nitrite hydrolyzable nitrogen content.
[0008] In one embodiment, the step of processing the soil sample to obtain a dried soil sample specifically includes: After drying, the soil samples were ground and crushed, and then filtered through a 100-mesh sieve to obtain dried soil samples with a particle size of no more than 0.15 mm.
[0009] In one embodiment, the step of mixing the dried soil sample with experimental ultrapure water and performing a shaking extraction to obtain a soil mixture, and then subjecting the soil mixture to vacuum filtration and filtration to obtain a soil extract solution, specifically includes: Place 2.0g of the prepared dry soil sample into a graduated 100mL stoppered colorimetric tube, add 70-100mL of experimental ultrapure water, and extract the soil mixture by horizontal shaking. The soil mixture is transferred into a vacuum filtration device for filtration, and then filtered through a filter membrane. The filtered soil mixture is then transferred into a 100 mL volumetric flask and diluted to volume to obtain a soil extract solution.
[0010] In one embodiment, the conditions for the oscillation extraction are: an oscillation frequency of 300-500 rpm and an extraction time of 30-45 min.
[0011] In one embodiment, the filter membrane is a 0.45-micron pore size filter membrane.
[0012] In one embodiment, the step of obtaining the blank water-soluble ammonia nitrogen content value, blank water-soluble nitrate nitrogen content value, and blank water-soluble nitrite nitrogen content value for the blank control specifically includes: Take 2g of quartz sand as a blank control sample of soil. Perform the same shaking extraction, vacuum filtration, filtration treatment, water-soluble ammonia nitrogen test, water-soluble nitrate nitrogen and water-soluble nitrite nitrogen test on the quartz sand as on the dry soil sample to obtain blank water-soluble ammonia nitrogen content value, blank water-soluble nitrate nitrogen content value and blank water-soluble nitrite nitrogen content value.
[0013] In one embodiment, the step after obtaining the soil hydrolyzable nitrogen content further includes: Based on the detection results of the hydrolyzable nitrogen content in the soil, the mass or volume of the dried soil sample is adjusted accordingly, so that the concentration of the water-soluble ammonia nitrogen content is within the test range of the Nessler's reagent spectrophotometric method, and the water-soluble nitrate nitrogen content and the water-soluble nitrite nitrogen content are within the test range of the ion chromatography method.
[0014] In one embodiment, the method further includes: Multiple standard soils with different hydrolyzable nitrogen contents were collected as quality control samples. The entire process of hydrolyzable nitrogen testing was carried out simultaneously with the soil samples to be tested to obtain the corresponding quality control test results.
[0015] This application also provides the application of the rapid testing method for hydrolyzable nitrogen in the soil in soil nitrogen supply capacity evaluation technology.
[0016] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a rapid testing method for hydrolyzable nitrogen in soil. Soil samples are obtained and processed to obtain dried soil samples. These dried soil samples are then mixed with ultrapure water and subjected to shaking extraction to obtain a soil mixture. The soil mixture is then filtered to obtain a soil extract solution, which can be used for subsequent instrumental testing. Compared to traditional alkaline hydrolysis and diffusion methods, this method shortens the sample pretreatment time. Furthermore, a simple spectrophotometric method is used to detect ammonia nitrogen in the hydrolyzed soil sample, and water-soluble nitrate nitrogen and nitrite nitrogen are tested using ion chromatography, avoiding the human error that is easily introduced during titration. The present invention addresses the problem by employing simplified technical methods and mechanized testing, which can further improve the precision and accuracy of sample testing and ensure test quality. Furthermore, it obtains blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values for blank control, thus avoiding the introduction of unnecessary background errors. In addition, compared to traditional methods that require a large amount of chemical reagents and environmental consumption such as sodium hydroxide reagent alkaline hydrolysis, boric acid absorption, and hydrochloric acid titration, the extraction technique adopted in this application is pure water shaking extraction, which is more conducive to establishing a low-carbon and environmentally friendly testing environment.
[0017] In summary, this application employs pure water shaking extraction, and by classifying and testing the existing forms of hydrolyzable nitrogen before summing, it achieves a relatively rapid and accurate test for hydrolyzable nitrogen in soil. Compared with traditional methods, it shortens the testing steps, saves time and costs, improves the precision and accuracy of sample testing, and realizes the concept of low-carbon and environmentally friendly testing. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a flowchart illustrating a rapid testing method for hydrolyzable nitrogen in soil according to an embodiment of this application. Detailed Implementation
[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0022] See Figure 1 This application provides a rapid test method for hydrolyzable nitrogen in soil, comprising the following steps: S100: Obtain soil samples and process them to obtain dry soil samples; S200: The dried soil sample is mixed with ultrapure water and shaken to extract the soil mixture. The soil mixture is then filtered to obtain a soil extract solution. S300: The soil extract solution is divided into a first test sample and a second test sample. The first test sample is tested for water-soluble ammonia nitrogen by Nessler's reagent spectrophotometry to obtain the water-soluble ammonia nitrogen content. The second test sample is tested for water-soluble nitrate nitrogen and water-soluble nitrite nitrogen by ion chromatography to obtain the water-soluble nitrate nitrogen content and water-soluble nitrite nitrogen content. S400: Obtain blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values for blank control; S500: Based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value, the ammonia nitrogen hydrolyzable nitrogen content, nitrate hydrolyzable nitrogen content, and nitrite hydrolyzable nitrogen content are obtained; S600: Calculate the sum of the hydrolyzable nitrogen content of ammonia nitrogen, hydrolyzable nitrogen content of nitrate, and hydrolyzable nitrogen content of nitrite to obtain the hydrolyzable nitrogen content of the soil.
[0023] In S100, specifically, the step of processing the soil sample to obtain a dried soil sample includes: drying the soil sample, grinding and crushing it, and then filtering it through a 100-mesh sieve to obtain a dried soil sample with a particle size of no more than 0.15 mm.
[0024] For example, soil samples can be collected from a vegetable garden in region A in accordance with the "Technical Specification for Soil Environmental Monitoring" (HJ / T 166-2004). The "Technical Specification for Soil Environmental Monitoring" is a national environmental protection industry standard. Collecting soil samples in accordance with this standard ensures that the subsequent testing process is based on standardization and normalization.
[0025] In S200, the steps of mixing dried soil samples with ultrapure water and extracting by shaking to obtain a soil mixture, followed by filtration to obtain a soil extract solution, include: placing 2.0 g of the prepared dried soil sample into a graduated 100 mL stoppered colorimetric tube, adding 70–100 mL of experimental ultrapure water, and extracting by horizontal shaking at a frequency of 300–500 rpm for 30–45 min to obtain a soil mixture; transferring the soil mixture into a vacuum filtration device for filtration, simultaneously rinsing the stoppered colorimetric tube, and filtering the filtered soil mixture through a 0.45 μm pore membrane; transferring the filtered soil mixture into a 100 mL volumetric flask, making up to volume to obtain the soil extract solution for analysis.
[0026] This application also includes the entire process of collecting multiple standard soils with different hydrolyzable nitrogen contents as quality control samples, and simultaneously conducting soil hydrolyzable nitrogen testing with the soil samples to be tested, so as to obtain the corresponding quality control test results. By introducing standard soils covering different hydrolyzable nitrogen contents as quality control samples and conducting full-process testing simultaneously with the samples to be tested, the accuracy of the testing process and the reliability of the overall method can be effectively monitored.
[0027] For example, black soil ASA-7 from region B with high hydrolyzable nitrogen content and yellow cotton soil ASA-9 from region C with moderate hydrolyzable nitrogen content were selected as quality control samples. These were pretreated together with the soil samples to be tested, i.e., the treatment process in S200. Since ASA-7 has a relatively high nitrogen content, 1.0 g of dried ASA-7 quality control sample was weighed and placed in a graduated 100 mL stoppered colorimetric tube. 2.0 g of ASA-9 quality control sample and the vegetable garden soil sample to be tested were weighed and placed in graduated 100 mL stoppered colorimetric tubes. Approximately 70 mL of ultrapure water was added to each. After extraction with horizontal shaking at 300 rpm for 45 min, the three soil mixtures were transferred to their respective vacuum filtration devices for filtration. The stoppered colorimetric tubes were rinsed simultaneously, and each mixture was filtered through a 0.45 μm pore membrane. All solutions of different types were then transferred to 100 mL volumetric flasks and diluted to volume. Each sample was treated three times in parallel, and the results were recorded and prepared for testing.
[0028] In S300, for example, 50 mL of the vegetable garden soil extract solution is transferred from the volumetric flask, and the water-soluble ammonia nitrogen is tested according to the Nessler's reagent spectrophotometric method for the determination of ammonia nitrogen in water (HJ535-2009). The test results are expressed as the water-soluble ammonia nitrogen content. The remaining liquid is in accordance with the "Water Quality Inorganic Anion (F) Standard". - Cl - NO 2- ,Br - NO 3- PO4 3- SO3 2- SO4 2- The determination of water-soluble nitrate nitrogen and water-soluble nitrite nitrogen was performed using ion chromatography (HJ 84-2016). The results were expressed as the content of water-soluble nitrate nitrogen. Water-soluble nitrite nitrogen content It should be noted that the soil extract solutions of the ASA-7 and ASA-9 quality control samples were tested using the same methods described above, specifically Nessler's reagent spectrophotometry and ion chromatography, respectively, to obtain the corresponding quality control test results. The results are detailed in Table 1 below.
[0029] Table 1. Summary of Water-Soluble Nitrogen Content Tests (Unit: mg / L)
[0030] In this application embodiment, the method described in "Determination of Ammonia Nitrogen in Water by Nessler's Reagent Spectrophotometry" (HJ535-2009) typically utilizes the principle that ammonia nitrogen reacts with Nessler's reagent (an alkaline solution of mercuric iodide and potassium iodide) to form a pale reddish-brown complex. The absorbance is measured at a specific wavelength (420 nm) using a spectrophotometer to quantify the ammonia nitrogen concentration in the water sample. Alternatively, automated instruments can be used for measurement. In this application, it is used to determine the water-soluble ammonia nitrogen content in soil leachate. The method also relates to "Inorganic Anions in Water (F...)". - Cl - NO 2- ,Br - NO 3- PO4 3- SO3 2- SO4 2- The determination of ions by ion chromatography (HJ84-2016) is based on the method of ion chromatography, which uses an anion exchange column to determine the concentration of various inorganic anions (such as fluoride) in water samples. - Cl - NO 2- NO 3- The nitrogen (etc.) is separated and measured using a conductivity detector. In this application, it is used to simultaneously determine the water-soluble nitrate nitrogen content and the water-soluble nitrite nitrogen content in soil leachate.
[0031] Specifically, in S400, the steps for obtaining blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values for blank control include: taking 2g of quartz sand as a soil blank control sample, and performing the same shaking extraction, vacuum filtration, filtration treatment, water-soluble ammonia nitrogen test, water-soluble nitrate nitrogen and water-soluble nitrite nitrogen test on the quartz sand as on the dry soil sample, that is, performing S200 and S300 to obtain blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values.
[0032] This application incorporates a blank control sample to avoid introducing unnecessary background errors, ensuring that the final soil hydrolyzable nitrogen determination results accurately reflect the sample's actual content. The test results are used... The values are shown in Table 2 below, with units of mg / L.
[0033] Table 2. Summary of Blank Tests (Unit: mg / L)
[0034] It should be noted that if the blank water-soluble ammonia nitrogen content value of the quartz sand extraction solution is... Blank water-soluble nitrate nitrogen content value Blank water-soluble nitrite nitrogen content value If not detected, calculate as 0.
[0035] In S500, the steps for obtaining the hydrolyzable nitrogen content of ammonia nitrogen, hydrolyzable nitrogen content of nitrate, and hydrolyzable nitrogen content of nitrite based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value specifically include: The difference between the water-soluble ammonia nitrogen content and the blank water-soluble ammonia nitrogen content is calculated as the first difference. The first difference is multiplied by the fixed volume of the soil sample to obtain the first product. Then, the ratio of the first product to the mass of the dry soil sample is calculated to obtain the ammonia nitrogen hydrolyzable nitrogen content.
[0036] The calculation formula for the above steps is as follows: In the formula, This refers to the content of hydrolyzable nitrogen in the form of ammonia nitrogen. This refers to the water-soluble ammonia nitrogen content. This represents the blank water-soluble ammonia nitrogen content value. The volumetric volume of the soil sample is, for example, 100 mL. The mass of the dried soil sample taken can be, for example, 2g.
[0037] The difference between the water-soluble nitrate nitrogen content and the blank water-soluble nitrate nitrogen content is calculated as the second difference. The second difference is multiplied by the fixed volume of the soil sample to obtain the second product. The ratio of the second product to the mass of the dry soil sample is then calculated to obtain the nitrate hydrolysable nitrogen content.
[0038] The calculation formula for the above steps is as follows: In the formula, The content of hydrolyzable nitrate nitrogen. This refers to the content of water-soluble nitrate nitrogen. This represents the blank water-soluble nitrate nitrogen content value. The volumetric volume of the soil sample is, for example, 100 mL. The mass of the dried soil sample taken can be, for example, 2g.
[0039] The difference between the water-soluble nitrite nitrogen content and the blank water-soluble nitrite nitrogen content is calculated as the third difference. The third difference is multiplied by the fixed volume of the soil sample to obtain the third product. The ratio of the third product to the mass of the dry soil sample is then calculated to obtain the nitrite hydrolyzable nitrogen content.
[0040] The calculation formula for the above steps is as follows: In the formula, The content of hydrolyzable nitrite nitrogen, This refers to the content of water-soluble nitrite nitrogen. This represents the blank water-soluble nitrite nitrogen content value. The volumetric volume of the soil sample is, for example, 100 mL. The mass of the dried soil sample taken can be, for example, 2g.
[0041] In S600, the hydrolyzable nitrogen content in soil includes the sum of hydrolyzable nitrogen in ammonia nitrogen, hydrolyzable nitrogen in nitrate, and hydrolyzable nitrogen in nitrite. The calculation expression is as follows: The table below shows the test results and statistical results for actual samples and quality control samples: Table 3. Summary of test results for actual samples and quality control samples, unit: mg / kg
[0042] Table 4. Summary of Mathematical Statistical Results (Unit: mg / kg)
[0043] In summary, statistical analysis of the calculation results in Table 3 is detailed in Table 4. The reference value for ASA-7 quality control samples is 157±11 mg / kg, and the average value of the ASA-7 quality control samples tested in this application is 149.3 mg / kg, which meets the range requirements of the reference value. The reference value for ASA-9 quality control samples is 45±4 mg / kg, and the average value of the ASA-9 quality control samples tested in this application is 43.1 mg / kg, which also meets the range of the reference value. According to Table 4, the relative standard deviation (RSD) of the test method used in this application for standard samples ranges from 0.48% to 2.90%, and the RSD for actual samples is 4.05%, indicating good repeatability and high accuracy.
[0044] In this embodiment of the application, the step after obtaining the hydrolyzable nitrogen content in the soil further includes: adjusting the mass or volume of the dried soil sample according to the detection results of the hydrolyzable nitrogen content in the soil, so that the concentration of the water-soluble ammonia nitrogen content is within the curve test range of Nessler's reagent spectrophotometry, and the water-soluble nitrate nitrogen content and water-soluble nitrite nitrogen content are within the curve test range of ion chromatography.
[0045] Specifically, if the hydrolyzable nitrogen content in the soil sample Higher levels can be achieved by reducing the mass of the dried soil sample. Or increase the constant volume Further extraction and testing were conducted to ensure the water-soluble ammonia nitrogen content was maintained. The concentration range is within the curve test range of "Determination of Ammonia Nitrogen in Water Quality - Nessler's Reagent Spectrophotometric Method" (HJ535-2009), and the water-soluble nitrate nitrogen content... and water-soluble nitrite nitrogen content Concentration range within the range of inorganic anions (F) in water quality - Cl - NO 2- ,Br - NO 3- PO4 3- SO3 2- SO4 2- The determination of ions by ion chromatography (HJ 84-2016) is within the curve test range.
[0046] If the soil sample contains hydrolyzable nitrogen content The content is low, which can be addressed by increasing the mass of the dried soil sample. Or reduce the fixed volume Further extraction and testing were conducted to ensure the water-soluble ammonia nitrogen content was maintained. The test concentration was higher than the minimum detection limit of Nessler's reagent spectrophotometric method for the determination of ammonia nitrogen in water (HJ535-2009), indicating a low water-soluble nitrate nitrogen content. and water-soluble nitrite nitrogen content The tested concentration was higher than that specified in the "Water Quality Inorganic Anions (F)" standard. - Cl - NO 2- ,Br - NO 3- PO4 3- SO3 2- SO4 2- The lowest detection limit of ion chromatography (HJ 84-2016) for the determination of ion chromatography.
[0047] In this application, if the concentration of the test solution is too high during the testing process, it can be diluted before testing. However, when detecting the water-soluble ammonia nitrogen content... Water-soluble nitrate nitrogen content and water-soluble nitrite nitrogen content Subsequently, when the diluted content value needs to be substituted into the subsequent calculation formula, it must be multiplied by the dilution factor to convert it back to the original concentration before dilution in order to ensure the accuracy of the final calculation result.
[0048] The beneficial effects of this application are as follows: Firstly, compared with existing technologies, this application eliminates the cumbersome step of placing the traditional diffusion dish in a 40℃ constant temperature chamber (24±0.5) for an hour before titration. Instead, it uses ultrapure water to extract the sample by horizontal shaking at a frequency of 300-500 rpm for 30-45 minutes before testing. Existing technologies take more than 24 hours to test a single sample, while the technology of this application can control the testing time for a single sample to less than 1 hour, greatly saving testing time costs.
[0049] Secondly, existing technical methods, whether the traditional testing methods in LY / T1228-2015 or DB13 / T843-2007, require titration of the nitrogen-absorbed boric acid solution with standard hydrochloric acid solution. The determination of the titration endpoint and the reading of the titration volume are very prone to human error, leading to deviations in the results. This application uses a simple spectrophotometric method to test ammonia nitrogen in hydrolyzed soil samples and performs ion chromatography testing on water-soluble nitrate nitrogen and nitrite nitrogen. The simplified technical methods and mechanized testing can further improve the precision and accuracy of sample testing and ensure test quality.
[0050] Third, existing technologies require a large amount of chemical reagents and environmental consumption, such as sodium hydroxide alkaline hydrolysis, boric acid absorption, and hydrochloric acid titration; the extraction technology adopted in this application is pure water shaking extraction, which is more conducive to establishing a low-carbon and environmentally friendly testing environment.
[0051] This application also provides a rapid testing method for hydrolyzable nitrogen in soil and its application in soil nitrogen supply capacity evaluation technology. By measuring the hydrolyzable nitrogen content, the potential of soil to provide nitrogen to crops in the short term can be intuitively judged, which is an important scientific basis for guiding precision fertilization and optimizing nitrogen fertilizer management.
[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0053] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A rapid test method for hydrolyzable nitrogen in soil, characterized in that, include: Soil samples were obtained and processed to obtain dried soil samples; The dried soil sample was mixed with ultrapure water and shaken to extract the soil mixture. The soil mixture was then filtered to obtain a soil extract solution. The soil extract solution was divided into a first test sample and a second test sample. The first test sample was tested for water-soluble ammonia nitrogen by Nessler's reagent spectrophotometry to obtain the water-soluble ammonia nitrogen content. The second test sample was tested for water-soluble nitrate nitrogen and water-soluble nitrite nitrogen by ion chromatography to obtain the water-soluble nitrate nitrogen content and water-soluble nitrite nitrogen content. Obtain blank water-soluble ammonia nitrogen content values, blank water-soluble nitrate nitrogen content values, and blank water-soluble nitrite nitrogen content values for blank control; Based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value, the ammonia nitrogen hydrolyzable nitrogen content, nitrate hydrolyzable nitrogen content, and nitrite hydrolyzable nitrogen content were obtained. The soil hydrolyzable nitrogen content is obtained by summing the contents of the ammonia nitrogen hydrolyzable nitrogen, the nitrate hydrolyzable nitrogen, and the nitrite hydrolyzable nitrogen.
2. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The steps for obtaining the hydrolyzable nitrogen content of ammonia nitrogen, hydrolyzable nitrogen content of nitrate, and hydrolyzable nitrogen content of nitrite based on the fixed volume of the soil sample, the mass of the dried soil sample, the water-soluble ammonia nitrogen content, the blank water-soluble ammonia nitrogen content value, the water-soluble nitrate nitrogen content, the blank water-soluble nitrate nitrogen content value, the water-soluble nitrite nitrogen content, and the blank water-soluble nitrite nitrogen content value specifically include: The difference between the water-soluble ammonia nitrogen content and the blank water-soluble ammonia nitrogen content value is calculated as the first difference. The first difference is multiplied by the fixed volume of the soil sample to obtain the first product. Then, the ratio of the first product to the mass of the dry soil sample is calculated to obtain the ammonia nitrogen hydrolyzable nitrogen content. The difference between the water-soluble nitrate nitrogen content and the blank water-soluble nitrate nitrogen content is calculated as a second difference. The second difference is multiplied by the fixed volume of the soil sample to obtain a second product. The ratio of the second product to the mass of the dry soil sample is then calculated to obtain the nitrate hydrolysable nitrogen content. The difference between the water-soluble nitrite nitrogen content and the blank water-soluble nitrite nitrogen content is calculated as the third difference. The third difference is multiplied by the fixed volume of the soil sample to obtain the third product. The ratio of the third product to the mass of the dry soil sample is then calculated to obtain the nitrite hydrolyzable nitrogen content.
3. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The step of processing the soil sample to obtain a dried soil sample specifically includes: After drying, the soil samples were ground and crushed, and then filtered through a 100-mesh sieve to obtain dried soil samples with a particle size of no more than 0.15 mm.
4. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The step of mixing the dried soil sample with ultrapure water and extracting it by shaking to obtain a soil mixture, and then filtering the soil mixture to obtain a soil extract solution, specifically includes: Place 2.0g of the prepared dry soil sample into a graduated 100mL stoppered colorimetric tube, add 70-100mL of experimental ultrapure water, and extract the soil mixture by horizontal shaking. The soil mixture is transferred into a vacuum filtration device for filtration, and then filtered through a filter membrane. The filtered soil mixture is then transferred into a 100 mL volumetric flask and diluted to volume to obtain a soil extract solution.
5. The rapid test method for hydrolyzable nitrogen in soil according to claim 4, characterized in that, The conditions for the oscillation extraction are: oscillation frequency of 300-500 rpm and extraction time of 30-45 min.
6. The rapid test method for hydrolyzable nitrogen in soil according to claim 4, characterized in that, The filter membrane is a 0.45-micron pore membrane.
7. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The steps for obtaining the blank water-soluble ammonia nitrogen content value, blank water-soluble nitrate nitrogen content value, and blank water-soluble nitrite nitrogen content value for the blank control specifically include: Take 2g of quartz sand as a blank control sample of soil. Perform the same shaking extraction, vacuum filtration, filtration treatment, water-soluble ammonia nitrogen test, water-soluble nitrate nitrogen and water-soluble nitrite nitrogen test on the quartz sand as on the dry soil sample to obtain blank water-soluble ammonia nitrogen content value, blank water-soluble nitrate nitrogen content value and blank water-soluble nitrite nitrogen content value.
8. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The steps following obtaining the soil hydrolyzable nitrogen content also include: Based on the detection results of the hydrolyzable nitrogen content in the soil, the mass or volume of the dried soil sample is adjusted accordingly, so that the concentration of the water-soluble ammonia nitrogen content is within the test range of the Nessler's reagent spectrophotometric method, and the water-soluble nitrate nitrogen content and the water-soluble nitrite nitrogen content are within the test range of the ion chromatography method.
9. The rapid test method for hydrolyzable nitrogen in soil according to claim 1, characterized in that, The method further includes: Multiple standard soils with different hydrolyzable nitrogen contents were collected as quality control samples. The entire process of hydrolyzable nitrogen testing was carried out simultaneously with the soil samples to be tested to obtain the corresponding quality control test results.
10. The application of a rapid testing method for hydrolyzable nitrogen in soil as described in any one of claims 1-9 in soil nitrogen supply capacity evaluation technology.