What is the general total nitrogen content of soil, and the method of determining soil total nitroge

The time taken for soil test results varies depending on the test project and the actual situation of the laboratory, and in general, it takes 2-15 days for common soil test indicators to produce results.

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First of all, there are many types of soil testing indicators, including organic matter, total nitrogen, available phosphorus, available potassium, pH value, salinity, heavy metals, microorganisms, etc. These metrics vary in how they are measured and processed, so the time to results varies. For example, soil heavy metal testing usually takes 5-7 working days, while soil organic matter and pH testing is faster, usually taking 2-3 days.

In addition, the actual operation of the laboratory can also affect the time it takes to produce results. For example, the number of equipment in the laboratory, the number of samples, the skills and experience of the testing personnel, etc., can all have an impact on the testing time. If the number of samples is large or the equipment fails, it may lead to longer testing times.

To ensure soil testing.

For the accuracy and reliability of the results, laboratories need to follow certain operating procedures and quality control measures when carrying out soil testing. These measures include sample collection, preservation, processing, and analysis, which require a certain amount of time and manpower. Therefore, the time for the results of soil testing indicators is not fixed, but depends on the specific situation.

<>1. The total nitrogen content of soil will be different in different types of soil, among which the total nitrogen content of cultivated land is generally kilograms, and the total nitrogen content of undamaged natural vegetation soil is generally kilograms. 2. Soil total nitrogen determination method: prepare containers and samples, and do a good job of elimination, cooling and distillation.

An electric furnace with a voltage of 110V-120V should be used for elimination, the time should be controlled during cooling, and the liquid transfer during the distillation process should be non-destructive.

1. What is the general total nitrogen content of soil?

The total nitrogen content of different types of soil is different, and the total nitrogen content of soil in cultivated land is generally per kilogram, and the average total nitrogen content is per kilogram. In nature, the total nitrogen content of undamaged soil is generally per kilogram, on average. Soil total nitrogen content refers to all forms of nitrogen in the soil, which can reflect the level of nitrogen supply to the soil.

2. Methods for determining soil total nitrogen.

1. Prepare the container and air-dried sample, the container can be 50ml, and the sample should be weighed through the pore size sieve before it can be put into the container, and the sample should be shaken well after being put into the container.

2. Add 5ml of concentrated sulfuric acid, insert a small funnel with a curved neck into the mouth of the container, put it on the electric stove to eliminate the mood, the voltage of the electric furnace should be 110V-120V, wait until the sulfuric acid emits a large amount of white smoke, and there is no black carbon particles adhered to the bottle wall of the container when shaking well, and the whole process takes about 1 hour. After cooling, the saturated potassium dichromate solution should be added, the dosage is 5ml, and it should be placed on the electric stove, which should be kept at a low temperature and boiled slightly for 5 minutes.

3. Prepare the container retort, put the digested liquid to be tested into the distillation tank, to ensure that there is no loss during the transfer process, add the LNAOH solution to it after transfer, and the dosage is 30ml.

4. Place the triangular bottle with boric acid indicator mixed solution under the condenser tube of the nitrogen analyzer, the dosage of boric acid indicator mixed solution is 10ml20g per liter, and the capacity of the triangular bottle is 150ml, pay attention to the lower end of the condenser tube when placing the indicator mixed solution to ensure the completeness of absorption, suitable for distillate of about 75ml.

5. Carefully read the operating procedures of the nitrogen determination instrument, use the instrument in strict accordance with the regulations, and carry out the distillation work, wait until the distillation work is completed, remove the triangular bottle of the container, and use the hydrochloric acid solution for titration work, the amount of hydrochloric acid solution is per liter, pay attention to the titration end point is when the solution changes from blue to purple red, and do a blank test when participating in the measurement.

The general standard for cultivated soil is milligrams kg, nitrogen at 150-200, phosphorus 60-100, potassium 100-150.

The area of phosphorus-deficient soil in China is about 100 million mu, mainly calcareous soil in the north, white clay soil in the northeast, red soil, purple soil and low-yield paddy soil. The so-called phosphorus-deficient soil generally refers to the soil with less than 10mg kg of available phosphorus (p). It can be seen that the phosphorus-deficient soil area is greater than 75% of the cultivated land area of the province and the provinces are all over the southeast and northwest of China, which is the fundamental reason why phosphate fertilizer is the second largest fertilizer industry in China.

Soil total nitrogen content.

It decreases dramatically as the depth of the soil increases. Soil total nitrogen content is in a dynamic situation, and its growth and decline depend on the relative amount of nitrogen accumulation and consumption, especially on the bioaccumulation and hydrolysis of soil organic matter. For natural soils, when stable levels are reached, the equilibrium value of total nitrogen content is a function of climate, topography or landform, vegetation and organisms, parent material, and age or time of soil formation.

The general standard for cultivated soil is milligrams kg, nitrogen at 150-200, phosphorus 60-100, potassium 100-150.

Among them, nitrogen is divided into ammonium state and nitrate state, and most of the nitrogen in the soil exists in an organic state, and the organic nitrogen is converted into inorganic nitrogen for crop absorption and utilization under a series of conditions such as tillage and mineralization by soil microorganisms. The sum of organic and inorganic nitrogen in the soil is called soil total nitrogen. Most of the soil nitrogen comes from organic matter, so the content of organic matter is positively correlated with the total nitrogen content.

The total nitrogen content in the soil represents the total nitrogen storage and nitrogen supply potential of the soil. Therefore, total nitrogen content is one of the main indicators of soil fertility, along with organic matter. Alkali hydrolyzable nitrogen, also known as hydrolyzed nitrogen, includes inorganic nitrogen and organic nitrogen with simple structure that can be directly absorbed and utilized by crops, which can be absorbed and utilized by crops in the near future, so it is also called available nitrogen.

The level of alkaline hydrolyzable nitrogen content depends on the level of organic matter content, the quality and the amount of nitrogen fertilizer put into it. It is rich in organic matter, high in maturation, and high in alkaline hydrolyzable nitrogen, and vice versa. The content of alkali hydrolyzable nitrogen in soil is not stable enough and is susceptible to changes due to soil hydrothermal conditions and biological activities, but it can reflect the nitrogen capacity of soil in the near future.

The total nitrogen content will vary from region to region and from plot to plot.

The average value of total nitrogen content in different regions of the country is shown in the figure below

The nitrogen in the soil can be divided into organic nitrogen and inorganic nitrogen, and the sum of the two is called total nitrogen.

In general, the organic matter and nitrogen content of cultivated soil in China is not high, and the total nitrogen content (n) is generally g kg

Determination of soil total nitrogen: Semi-micro Kjeldahl method is commonly used.

Soil total nitrogen determination refers to soil total nitrogen, including organic nitrogen and inorganic nitrogen, and the determination is commonly carried out by semi-micro Kjeldahl method. The nitrogen-containing compounds in the soil are hydrolyzed and oxidized by concentrated sulfuric acid and mixed catalysts under strong thermal and high temperature treatment to convert nitrogen into ammonium ions.

Sodium hydroxide is added to the digested solution for distillation, and the distilled ammonia solution is absorbed by the boric acid solution, and then titrated with the acid standard solution (bromocresol green and methyl red are mixed indicators, and the end point is pink), and the total nitrogen amount is calculated from the consumption of the acid standard solution. Nitrous nitrogen, nitrate nitrogen and stationary ammonium are not included, as the content of these components is generally small, which will not affect the analysis results.

If it is necessary to determine the total nitrogen including nitrous nitrogen, nitrate nitrogen and fixed ammonium, it is necessary to add the step of reducing nitrous nitrogen and nitrate nitrogen to ammonium nitrogen and the step of adding hydrofluoric acid and hydrochloric acid to destroy clay minerals to extract fixed ammonium, that is, to modify the Kjeldahl cooking distillation semi-micro nitrogen determination method.

The parts of soil organic nitrogen that are relatively easy to decompose, or mineralizable organic nitrogen and inorganic nitrogen, are often regarded as available nitrogen for crops, including ammonium nitrogen, nitrate nitrogen, amino acids, amides and protein nitrogen that is easily hydrolyzed, which is called hydrolyzable nitrogen. Measuring the changes of hydrolyzable nitrogen in soil is of great significance for understanding soil fertility and guiding fertilization.

The determination of soil total nitrogen was carried out using the micro-Kjeldahl method.

The trace Kjeldahl method is to coheat nitrogen-containing organic matter with concentrated sulfuric acid, and finally convert organic nitrogen into inorganic nitrogen ammonium sulfate through a series of complex processes such as decomposition, carbonization and redox reactions, which is called the digestion of organic matter. In order to accelerate the decomposition of organic substances and shorten the digestion time, potassium sulfate, copper sulfate, mercury oxide, hydrogen peroxide and other reagents are usually added during digestion, adding potassium sulfate can increase the boiling point of the digestive juice and accelerate the decomposition of organic matter, in addition to potassium sulfate, it can also increase the boiling point of salts such as potassium chloride.

Reaction principle:1The nitrogen in organic matter is digested to form (NH4)2SO4 under the action of strong heat and CuSO4 and concentrated H2SO4

The reaction formula is: H2SO4==SO2+H2O+[O].

r.2nh3+h2so4==(nh4)2so4

2.In a Kjeldahl nitrogen detergent, it reacts with alkali and releases NH3 by distillation, which is collected in H3Bo3 solution.

The reaction formula is: 2NH4++OH-==NH3+H2O

nh3+h3bo3==nh4++h2bo3-

3.It is then titrated with a known concentration of HCI standard solution, and the nitrogen content is calculated based on the amount of HCI consumed, and then multiplied by the corresponding conversion factor to obtain the content of the acquired protein.

The reaction formula is: H2BO3-+H+==H3BO3

However, this method does not include nitrous nitrogen, nitrate nitrogen and fixed ammonium, which are generally low in content and do not affect the analysis results. If it is necessary to determine the total nitrogen including nitrous nitrogen, nitrate nitrogen and fixed ammonium, the step of reducing nitrite nitrogen and nitrate nitrogen to ammonium nitrogen and the addition of hydrofluoric acid and hydrochloric acid to destroy clay minerals to extract fixed ammonium must be added, that is, the semi-trace nitrogen determination of Kjeldahl decution distillation must be added.

Summary. Pro, the soil nitrogen content of 70 is also, pro, in addition, most of the nitrogen in the soil is in the organic form of bonding. The inorganic form of nitrogen generally accounts for 1 5 of total nitrogen.

The growth and decline of soil organic matter and nitrogen are mainly determined by the relative strength of bioaccumulation and decomposition, as well as the factors of climate, vegetation and farming system, especially hydrothermal conditions, which have a significant impact on soil organic matter and nitrogen content.

Pro, the soil nitrogen content of 70 is also, pro, in addition, most of the nitrogen in the soil is organically combined. The inorganic form of nitrogen accounts for 1 5 of the total nitrogen. The growth and decline of soil organic matter and nitrogen are mainly determined by the relative strength of bioaccumulation and decomposition, as well as the factors of climate, vegetation and farming system, especially hydrothermal conditions, which have a significant impact on soil organic matter and nitrogen dispersion.

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