How is the availability of soil nutrients reflected? Can you design a test to illustrate?

Nutrient measurement index, (1) stability: absorbance drift within three minutes is less than ; (2) Reproducibility: absorbance is less than ; (3) Linearity error:

Red light measurement of copper sulfate is less than that of blue light measurement of potassium trichromate; 4) Wavelength range: red and blue light. pH measurement index, (1) Test range:

1～14 ；(2) Error: . Salt measurement index, (1) Test range:

2) The full-scale error of salt content is 5%. Technical indicators of moisture, measurement parameters: soil moisture volume percentage content (w%); 1. Range:

0－100% ；2. Measurement accuracy: 0 50% within the range of 2%.

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The agricultural technology department is now engaged in soil formula fertilization, which can be

**The procedure for soil composition is as follows:

Experimental requirements: Soil composition.

Experimental instruments: water, soil, beakers, glass rods, alcohol lamps, evaporation dishes, matches, tripods, asbestos nets, glass sheets.

The experimental procedure is as follows:

1.Place a piece of soil in a cup of water. You will see bubbles coming out of the soil. Indicate that the soil contains (air).

2.Stir the water into the clods with a glass rod and let it stand. After precipitation, the substance in the cup is divided into three layers, the upper particle (smaller) and the lower particle (larger). Indicates that the material of the soil layer is (clay) and the material of the lower layer is sand grains.

3.Put the clods of soil into an evaporation dish and use an alcohol lamp to cover them with a thin glass to extinguish them, and after a while you will see (water droplets condensed) on the glass sheets. Indicate that the soil contains (water).

4.Remove the glass and continue to heat, you can see that the soil is whitish and smells burnt. Indicate that the soil contains (humus).

Soil refers to a layer of loose material on the surface of the earth, which is composed of various granular minerals, organic matter, water, air, microorganisms, etc., and can grow plants. Soil is composed of minerals weathered from rocks, organic matter produced by the decomposition of animal and plant and microbial residues, soil organisms (solid substances), water (liquid phase substances), air (gas phase substances), and oxidized humus.

Solid matter includes soil minerals, organic matter and nutrients obtained by microorganisms through light sterilization. Liquid matter mainly refers to soil moisture. Gases are the air present in the pores of the soil.

These three types of substances in the soil constitute a contradictory unity. They are interconnected, mutually restrictive, provide the necessary living conditions for crops, and are the material basis of soil fertility.

Step 1: Wrap the soil clod with a paper towel and hold it firmly, and we will find that the paper towel is wet, which means that the soil contains (water).

Step 2: Put the soil in the water and find that there are bubbles, which means that there is air in the soil.

Step 3: Stir the soil in the water and let it stand for a period of time, we find that there is a stratification phenomenon in the soil accumulated by Shen Laonian, the large particles are in the (lower) layer, the small particles are in the (upper) layer, and the one floating on the water surface is (humus).

1. Moisture absorption.

Hygroscopic water is a thin layer of water formed by the surface molecules of solid particles in the soil directly absorbed by the water absorbed from the air. Its thickness and content depend on the saturation of water vapor in the air. In absolutely dry air, the amount of hygroscopic water is minimal, approximately zero.

Under saturated water vapor conditions, the hygroscopic water reaches its maximum. Hygroscopic water is greatly adsorbed by soil solid particles, so the content of hygroscopic water is related to soil texture, organic matter content and soil solute content. Because the hygroscopic water is tightly bound to the soil particles, it cannot move freely, and it is difficult to be absorbed and utilized by plants.

2. Thin film water.

After the adsorption of water vapor molecules by soil particles reaches the maximum moisture absorption, the soil particles adsorb more liquid water, and connect the water film between the particles to form a continuous water film, which is called membrane water wrapped in the outside of the hygroscopic water. The membrane water is adsorbed on the outside of the hygroscopic water, and is less adsorbed by the soil particles, so it can move freely between the membranes, and move from the place where the water film is thick to the place where the water film is thin. Membrane water is also known as the maximum molecular water holding capacity.

3. Capillary water.

When the soil water content reaches the maximum molecular water holding capacity, the soil moisture continues to increase and fill the capillary pores of the soil, and at the same time, it remains in the pores of the soil, becoming the soil moisture maintained by the capillary force, and is called capillary water. Capillary water is less stressed, has a strong ability to move freely, and can be absorbed and utilized by plants. At the same time, it has the ability to dissolve chemicals contained in the soil, so it is also a solvent and carrier for chemicals in the soil.

Depending on the degree of connection between soil moisture and groundwater, capillary water can be divided into capillary rising water and capillary hanging water.

When the groundwater is buried at a shallow depth, the groundwater can rise to a certain height along the capillary through the action of capillary force, and this soil moisture is called capillary rising water. Capillary rising water is a major form of groundwater replenishment of soil moisture. In the case of shallow groundwater, plants indirectly absorb and utilize groundwater through the action of capillary water lifting.

If the groundwater is buried at a large depth, the groundwater cannot rise to the surface through capillary action, and the water seeps down through the upper soil after rainfall or irrigation, and a part of the water moves from the macropores to the deep layer under the action of gravity, and a part of the water is maintained and suspended by the capillary force, which is called capillary hanging water.

4. Gravity water.

When the water in the soil exceeds the capillary force range, the excess water moves along the large capillary in the soil under the action of gravity. This moisture that moves under the force of gravity is called gravitational water. Gravity water has the basic characteristics of liquid water, so it can be absorbed and utilized by plants, but because it can move freely by gravity, it is not easy to remain in the root zone of crops, so most gravity water has no chance to be absorbed and utilized by plants.

Soil moisture types are divided into four types, each of which has different effectiveness and moisture absorption, and dry soil from the air.

The internal water guaranteed by the absorption of water vapor by DAO has no effect on plants.

Membrane water, the water adsorbed on the surface of soil particles, is weakly available water for plants.

Capillary water is the water adsorbed by the pores of the soil capillary, and it is divided into capillary hanging water (not connected) and capillary support water (connected to groundwater) according to whether it is connected to groundwater, which is the most precious for plants.

Gravity water, excess water, is water in the aerated voids of the soil, which will soon flow out and is largely ineffective against plants.

In addition, soil texture, soil structure, and organic matter content all have an impact.

Morphology of soil moisture:

Physical form: gaseous, liquid, and solid states are most closely related to plants in liquid water.

Soil moisture type: hygroscopic water, poor effectiveness, cannot be utilized; membranous water, which can be utilized; capillary water; Gravity water, due to easy loss, has a very low utilization rate;

Soil water availability: refers to the use of soil water cover plants. The withering coefficient is the lower limit of available water, and the field coefficient is the upper limit of small water.

The main objects of soil nutrient testing are nitrogen, phosphorus and potassium.

Soil nutrients are nutrients that are necessary for plant growth provided by the soil. Mineral nutrients in the soil that can be absorbed by plant roots, either directly or after transformation. It includes 13 elements such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, boron, molybdenum, zinc, manganese, copper and chlorine.

Nutrients are classified as macroelements, medium elements, and trace elements. In natural soils, soil minerals and soil organic matter are the main ones, followed by atmospheric precipitation, slope seepage and groundwater. In cultivated soils, fertilization and irrigation are also used.

According to the difficulty of absorption and utilization of nutrients by plants, they are divided into fast-acting nutrients and delay-acting nutrients. Generally speaking, available nutrients only account for a small part, less than 1% of the total amount, it should be noted that the division of available nutrients and delayed nutrients is relative, and the two are always in dynamic equilibrium.

In agricultural production, it is an important part of obtaining high-quality and abundant yields of crops to adjust the condition of soil nutrients and spring equinoxes to meet the nutrient needs of crops at different growth and development stages. Understanding the status of soil nutrients can provide a theoretical and scientific basis for scientific fertilization, zonal management of nutrients and effective control of farmland nutrient loss.

The main object of soil nutrient testing is soil

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OneSoil nutrient testing process

1.For the preparation of soil extractant, take a bag of soil extractant powder, pour it into a beaker, mix and dissolve, pour 500ml into a volumetric flask, and shake it well.

2.The preparation of the solution to be tested is called taking an air-dried soil sample, pouring it into a triangular bottle, adding 20ml of soil extractant in a triangular bottle, and shaking well. Pour a spoonful of soil decolorizer into a triangular flask, shake well, and filter the filtrate into another triangular flask with quantitative filter paper, which is the soil available nutrient to be tested.

3.Add the reagent dropwise, absorb 2ml of the soil test solution with a straw in a small test tube, and add 4 drops of soil available phosphorus 1 reagent to the test tube.

4.Drop soil available phosphorus 2 reagent, 1 drop soil available phosphorus 3 reagent, shake well, and let stand for 10 minutes. Two.

Pour the solution to be tested into the cuvette, put it into any channel of the instrument, close the lid, click on the physical and chemical analysis, and click on the box below the project name. Click to detect soil available phosphorus.

5.The test result is completed when the cursor stops rotating.

Soil fertilizer nutrient content tester can detect soil. Nitrogen, phosphorus, potassium, organic matter, soil pH, soil salinity, and trace element content such as calcium, magnesium, and zinc in nitrogen plants and fertilizers.

The soil fertilizer nutrient content tester adopts a rotating colorimetric cell design, equipped with multiple rotary detection channels, which can detect different samples at the same time, and the detection rate is greatly improved. Soil fertilizer nutrient content tester is used to ensure the stability and safety of agricultural production.

2. What are the soil composition testing items?

The third-party testing of soil mainly includes rock organic, ammonium nitrogen, nitrate nitrogen, phosphorus, nitrogen, potassium, calcium, magnesium, sulfur, iron, boron, molybdenum, zinc, manganese, etc.

Routine soil testing items include: arsenic, cadmium, chromium, copper, lead, mercury, nickel, carbon tetrachloride, chloroform, chloromethane, 1,1-dioxane, 1,2-dioxane, 1,1-dioxyethylene, cis-1,2-dioxyethylene, trans-1,2-dioxyethylene, dioxane, 1,2-dioxane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, tetrachloroethylene, 1,1,1-trichloroethane,

1,1,2-Trichloroethane, trichloroethylene, 1,2,3-trichloropropane, vinyl chloride, benzene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, ethylbenzene, styrene, toluene, m-xylene + paraxylene, o-xylene, nitrobenzene, aniline, 2-chlorophenol, benzo[ ]anthracene, benzo[ ]pyrene, benzo[ ] fluoranthene, benzo[k]fluoranthene, dibenzo[ , h]anthracene, indeno[1,2,3-cd]pyrene, naphthalene, etc.