The important role of soil analysis in assisting agricultural production fertilization

I. Preface In the process of scientific development, various disciplines are interrelated and mutually reinforcing. For example, chemistry, physics, and biological sciences have promoted the development of soil and fertilizer sciences, while soil and fertilizer research have also enriched the contents of chemistry, plant physiology, and environmental science.
Similarly, the development of science and the improvement of industrial and agricultural production are also closely related. For example, as early as 4,000 years ago, our people knew the role of manure (manure and soybeans) in fertilizer fields, and organic fertilizers were used very early in agricultural production. Another example is the chemical fertilizer industry, which was published in the book “Chemistry in Agriculture and Plant Physiology Applications” published by the German agricultural chemist Liebig in 1840, and proposed the theory of mineral nutrition. Subsequently, in 1842 the United Kingdom began to produce superphosphate, and in 1870 Europe produced potassium fertilizer for the first time. In 1919, it began mass production of synthetic ammonia. With the mass production and application of fertilizers, chemical fertilizers play an important role in improving soil fertility, regulating plant nutrition, and increasing agricultural yield and quality.
Therefore, whenever we take into account the bright future of agricultural modernization, we will think of how to speed up the role of chemical fertilizers in agricultural production in order to accelerate the rapid development of agriculture. Therefore, we must study the relationship among soil, fertilizer, and plants. In order to conduct in-depth research in this area, it is extremely important to master the use of soil analyzers and to use soil analysis methods.
Second, the importance of soil analysis on the use of chemical fertilizers As the world’s population continues to increase, so does the need for food and other products. In the past two decades, the area of ​​cultivated land in the world has only increased by 130 million. Ten thousand hectares, which is roughly equivalent to more than 9 of the current total cultivated area (1.5 billion public items), but the world population in the same period increased from 2.8 billion to 4 billion, an increase of 400,000. Therefore, the increase in the area of ​​arable land has increased. Grain can only feed 400 million people, and another 800 million people's food depends on increasing yields. Since food and other crops need to absorb various nutrients from the upper soil for growth and development, it is necessary to understand the status of nutrients in the soil and thus produce the corresponding chemical fertilizers. The industry can use reasonable fertilization to better utilize and transform the soil. To meet the needs of high crop yields. However, all kinds of nutrients in the soil are neither touched nor visible. This requires the use of laboratory tests for diagnosis. For example, before the Japanese farmer fertilizes, he must ask the soil fertilization agency to test the soil and prescribe a prescription to the fertilizer company to purchase the required fertilizer. Another example is Romania. If agricultural production units do not have soil nutrient maps, they will not receive fertilizer.
On the other hand, although chemical fertilizers can supplement the soil with the nutrients that plants need, it is an important measure for increasing agricultural production. In recent decades, the production and consumption of chemical fertilizers have been growing rapidly, and the pace of development has almost doubled in a decade. According to the long-term field experiments, it was found that the utilization rate of nitrogen fertilizer was only 30 to 70%, and the utilization rates of phosphate fertilizer and potash fertilizer (in the first year) were 6~25% and 40~70%, respectively. If we increase the utilization rate of more than 8 million tons of fertilizer (calculated on an effective basis) in China in 1978, it will increase the utilization of over 800,000 tons of fertilizer. If the grain yield is increased by one to two pounds per kilogram of fertilizer, it can increase grain production by two to three billion kilograms for the country. Therefore, increasing the utilization rate of chemical fertilizers has been urgently put on the agenda.
We know that fertilization in soil requires storage and transformation in soil for effective crop absorption and utilization, and these processes are closely related to soil properties and nutrient status. Therefore, through soil surveys and laboratory tests, we can understand the soil conditions and produce the chemical fertilizers needed for crops, and then apply the treatment to “diseases” because fertilization can increase the utilization rate of chemical fertilizers.
In recent years, international attention has been paid to soil census and analysis and analysis. For example, Romania conducts analysis and analysis every 2 or 3 years on soil throughout the country, and 200,000 D,000 soil samples are tested every year. North Korea's national soil survey has been carried out for the third time. They analyzed about 10 million samples of soil in the census, and the units that mobilized and analyzed the ability to carry out soil tests. They used laboratory data to fertilize properly, so that the basic seedlings of different soils grow in unison, achieving a large-area balanced yield increase. In addition, through soil surveys, they find out the soil resources, expand the area of ​​cultivated land, and improve the soil, so that the grain output can be rapidly increased. From food shortages, it can be developed to more than self-sufficiency.
As early as 1958, China had conducted a census on the national soil survey. This work has not been carried out for nearly two decades. In some areas, due to unclear soil conditions, a large amount of fertilizer is used, but the variety is single and cannot be used for soil fertilization. Due to soil cultivation, fertilization has great blindness, so it is impossible to achieve scientific farming, even improper fertilization, resulting in great Waste and production cuts. Recently, China is carrying out the second soil survey nationwide. This is a major event in the modernization of agriculture, and it is also a job that our comrades on the fertilizer industry front must care about and assist. 3. Analysis of soil entrenchment in soil census and fertilizer production applications, To test the physical and chemical properties of the soil? Why do you want to test these properties, and how are these nitrogen, phosphorus, and potassium nutrients in the soil? How to test? It is briefly described as follows.
(a) Soil texture The solid skeleton of the soil is basically composed of mineral particles of different sizes. Generally based on soil particles with a particle diameter of 2 mm or less, from coarse to fine, they are divided into three groups of sand particles (2, 0.02 mm), silt grains (0.02, 0.002 mm), and clay particles (less than 0.002 mm). Soil texture is often divided according to different proportions of these grains in the soil, such as sandy loam, loam or clay loam. Soil texture is an important agricultural production characteristic of soil. Because the size of soil particles is different, its physical and chemical properties are also different. According to calculations, 1 cubic centimeter volume of the object, subdivided into 1 cubic nanometer, its total area can be increased to 6000 square meters. Therefore, the finer the soil particles, the greater its surface area and surface energy, and the stronger the absorption performance. Therefore, there are many clay particles in the upper soil, and its adhesion, water absorption, and fertilizer retention are also strong. For example, if the content of sand in the soil is large, the texture is relatively coarse, and its adhesiveness, water absorption, and fertilizer retention are poor, and the permeability is strong. Nutrients are easily lost and cause lack of fertilizer, which is unfavorable to the late stage of crop growth. Therefore, it is necessary to Appropriate quantified fertilizer is applied in time for crop utilization.
The following is a brief description of a simple hydrometer method for measuring soil texture.
Weigh 50g on a 2mm mesh sieve, place a porcelain evaporating dish, add 0.6N sodium oxalate dispersant, stir for half an hour, and grind the glass rod with a rubber head for 15 minutes to fully disperse the soil particles. Then, pour into a 1000 ml sedimentation drum. Rinse the vessel and glass rod with distilled water so that all the soil particles are washed into the sedimentation drum. Then use distilled water to bring the volume to 1000 ml. Stir the stirrer up and down for one minute to evenly distribute the suspension. At the beginning of the time, select the specific hydrometer reading time (see Table 1), gently insert a pycnometer (soil hydrometer) into the suspension (put in 10 and 15 seconds before the reading), and each reading is bent Liquid surface edge prevail. Measured readings A of less than 0.02 mm pellets and readings B of less than 0.002 mm pellets, respectively.

Table 1 Calculating the hydrometer reading time table calculation:
Cohesion % = hydrometer reading B/dry soil weight × 100
Silica sand%=(meter reading A-meter reading B)/dry soil weight×100
Grit%=1-(Cement%+Sand%)
See Figure 1 for the percentage of content in each pellet group to determine the name of the texture. For example, a soil clay content greater than 45% belongs to clay.
Another example is another soil containing 6% clay, 41% sand, and 53% silt, which belongs to silt loam soil.
(b) Soil organic matter Organic matter is an organic compound component other than minerals in the solid phase of the soil. It is closely associated with minerals. Normal soil contains 1-3% organic matter, of which about 85% are mostly humic substances. It is a special polymer compound formed by microbial decomposition and synthesis of animal and plant residues in the soil.

Fig.1 Sketch map of soil texture in Tucheng The amount of organic matter in the soil is not large, but its role is very large. It is an important indicator to evaluate the level of soil fertility, and has a great relationship with the production of fertilizer varieties and fertilization. It is a major source of crop nutrients and a source of energy and nutrients for soil microbial activity. It can improve soil water retention and fertilizer performance, but also can promote crop growth and buffer the role of soil acidity and alkalinity. It also improves the soil's sand stickiness and promotes the formation of soil aggregates. Therefore, for soils lacking organic matter, organic manure (manure, green manure) and organic manure fertilizers should be applied to increase soil organic matter and increase crop yield.
The process of determining the content of organic matter in soil by potassium dichromate-sulfate oxidation is briefly described as follows:
Accurately weigh 0.1~0.5g of air-dried soil passing through No. 6D sieve in a rigid test tube, add 0.5N potassium dichromate 5ml, add 6ml of concentrated sulfuric acid, carefully shake, add a small funnel, and test tube Insert it into an oil bath at about 180°C and heat it to boil the solution for 6 minutes. After cold, wipe the oil on the outer wall. After cooling, wash the contents of the test tube with water into a 250 ml conical flask. Add water to make the total volume in the bottle to 70 ml. Left and right (solution acidity 2, 3N), and then add 3 to 5 drops of ophthalmia phthalein indicator, titration with 0.2N ferrous sulfate solution, the solution from the yellow through the green mutation to brown red, which is the end point. When testing samples, you must short the test, that is, use pure sand or burnt soil instead of soil samples. The steps are the same.
Calculation:
Organic matter%=(V.-V)N.times.0.003/dry soil weight.1.724*1.1.times.100
In the formula:
V. One for the titration blank test used to remove the ferrous sulfate milliliters V one for the titration of the soil sample solution used to remove ferrous sulfate ml N is a ferrous sulfate equivalent concentration of 0.003 to 1 milligram of carbon equivalent grams of 1.724 a by soil organic carbon The empirical constant converted to organic matter 1.1 The organic matter measured by this method is only 90% of the actual content, so it should be multiplied by 1.1 to correct it.
(3) Nitrogen is contained in amino acids, eggs, vitamins, chlorophyll, enzymes, and many metabolic compounds in nitrogen crops. Nitrogen is therefore called a living element and is necessary for various crops. If the amount of nitrogen fertilizer is not enough, it will affect the growth and development of the crop, but the amount is not appropriate, which will reduce the body of cellulose, pectin and other substances, resulting in soft tissue, easy lodging, resistance and stress resistance weakened, so nitrogen fertilizer The application should be reasonable.
The total nitrogen in the soil is called total nitrogen, accounting for about 0.1~0.2% in the soil, of which organic nitrogen dominates, accounting for about 98%~99% of total nitrogen. In organic nitrogen, the nitrogen in the humus and the egg is a delayed nitrogen that needs to be transformed by the microorganism before the crop can be used. Inorganic nitrogen in soil accounts for only 1-2% of total nitrogen, mainly including ammonia nitrogen and nitrate nitrogen. Although their contents are small, they are the most easily absorbed by crops. In addition, the amino acids in the organic nitrogen that can be used by crops in short-term use and the nitrogen in guanylamine are combined with available nitrogen. It is called alkaline hydrolysis nitrogen, and its content can reflect the level of nitrogen supply better.
The nitrogen in the soil is very important. In general, there are many organic matter in the upper soil, and the total nitrogen content is also relatively large. Therefore, the amount of organic matter can be used as a reference for rats containing total nitrogen. In addition, the content of alkaline dissolved nitrogen in soil can generally reflect the level of nitrogen supply, which can be used as a reference. The following is a brief introduction of a method for diffusive absorption of alkaline nitrogen.
Weigh 2 g of air-dried soil through No. 60 mesh and 1 g of ferrous sulfate powder and evenly spread it in the outer chamber of the diffusion dish (without adding ferrous sulfate to paddy soil), and add 2 ml of 2-tuoroboronic acid solution in the interior of the diffusion dish. Add 1 titration nitrogen mixing indicator, then apply special glue on the outer edge of the dish, cover with frosted glass, make the edge of the dish completely bonded, then slowly open the glass, expose a slit, quickly add 10 Add 1.5 ml of sodium hydroxide solution (Paddy soil plus 1.2 N sodium hydroxide) in the outer chamber of the dish and immediately tightly cover it. Rotate the diffusion dish gently in the horizontal direction to mix the solution with the soil sample, place it in an oven at 40°C, remove it after 24 hours, and use a 0.01N hydrochloric acid standard solution to titrate the boron acid in the inner chamber with a semi-microtiter tube. The amount of ammonia drops from blue to reddish.
Calculation:
Alkaline nitrogen (mg/100 g soil) N×V×14/ground weight ×100
In the formula:
N-normal hydrochloric acid equivalent concentration V-milligrams of milliliters of nitrogen equivalent to milliliters of nitrogen used in the titration of samples. (IV) Phosphorus and phosphorus are the main components of the nucleus composing the crop, such as nucleic acids, phospholipids, and nucleoproteins. . Nucleic acid is a very important substance in crops. Without nucleic acid, it cannot form proteins. It is not only involved in the composition of protoplasm and organelles, but also has a close relationship with various aspects of metabolism. Another example is nuclear protein, which is an extremely important component of living cells. It exists in the nucleus and protoplasm, and has a close relationship with cell division and growth. In addition, phosphorus is contained in the ATP stored in the body tissues and regulates energy, and many other important enzymes also contain phosphorus. Therefore, the synthesis and operation of proteins and carbohydrates in crops, the storage and transmission of energy, etc. cannot be completed without phosphorus participation. Only sufficient supply of phosphorus, nucleic acid, and nuclear proteins can form normally, and cell division and growth can proceed normally.
The total phosphorus content in the soil is called total phosphorus, which accounts for about 0.1 to 0.2 million in soil. Organic phosphorus accounts for about 25% of total phosphorus. It must be degraded and transformed by microorganisms before it can be absorbed and utilized by crops. Therefore, it belongs to slow-acting phosphorus. In addition, inorganic phosphorus accounts for about 75% of the total phosphorus in soil, most of which are insoluble phosphorus, crops can not be absorbed and utilized, also belong to slow-acting phosphorus. Only weak acid-soluble phosphorus and water-soluble phosphorus crops can be absorbed and used in inorganic phosphorus, which is called quick-acting phosphorus. Although the content of this phosphorus in the soil is small, but the crop is easy to absorb, it can reflect the level of soil phosphorus supply. Phosphorous in soil can be decomposed and converted into readily available phosphorus under the action of various acids and microorganisms.
The supply level of soil phosphorus mainly depends on the content of available phosphorus, so its testing is more important. A simple method for the determination of rapidly available phosphorus is briefly described.
Take 2 grams of air-dried soil into a conical flask, add 10 ml of 0.6N sodium bicarbonate extract, add a small amount of a half spoon of activated carbon (from the decolorization effect), plug tightly, shake vigorously for 10 minutes, filter, and take the filtrate into 4 ml Test tube, add 1 ml of platinum acid and hydrochloric acid solution, while developing with the standard solution, add 1 to 2 drops of stannous chloride glycerol solution, shake, 3 to 5 minutes after the color, with the standard color scale color reading . Or with a photometer color comparison (light source wavelength 660 nm, or with a red filter).
Calculation: Soil Available P (ppm) = Readings (ppm) × Dilution times (E) Potassium Potassium is generally an ion or soluble salt in crops and is the major cation in protoplasm and cell fluids, most of which are concentrated in active crop growth. In the meristem. Potassium acts as an activator for many enzymes in the crop and enhances photosynthesis. It is closely related to the synthesis and operation of protein and carbohydrates. In addition, it can also enhance the mechanical organization of crops, make the crop resistant to lodging and resistance to pests and diseases.
Therefore, potassium fertilizer can increase the content of starch in root tuber crops, increase oil content in oil crops, increase sugar content in sugar crops, and increase the yield and quality of fiber crops. In recent years, as the yield per crop area and the multiple cropping index have been increasing, the potassium available for crop use in soil has gradually become insufficient.
The total potassium content in the soil is called total potassium, which accounts for 1~3% in the soil. The mineral potassium accounts for more than 98% of the total potassium. It is insoluble in water and cannot be directly used by crops. It is a kind of delayed potassium. There are substitute potassium and water-soluble potassium in the soil, accounting for about 1-2% of total potassium. It can be directly used by crops and is a quick-acting potassium. It can generally reflect the level of soil potassium supply. Therefore, the simple process of assaying available potassium by sodium tetraphenylborate is presented.
Weigh 2 grams of air-dried earth in a conical flask, add 10% sodium nitrate extract solution 10 ml, plug tightly, oscillate for 10 minutes, filter, absorb 5 ml of filtrate into test tube, add 5 drops of formaldehyde-EDTA mixed masking agent and 10 drops Glycerol, shake, add 1 ml of tetraphenylboron sodium solution, the solution is about PH5, shaken (it can also be diluted 5 times to shake), after standing for 6 minutes, produce a white precipitate, with a standard color turbidity, readings. Or take a photoelectric colorimetric reading at a wavelength of 420, 450 nm or a blue filter and take a reading.
Calculation: Soil Effective Potassium (ppm) = Reading (ppm) × Dilution Factor In addition to the analysis items described above, the pH, salinity, and other nutrient elements of the soil can also be determined based on local needs. In recent years, with the continuous development of analytical techniques, in-depth analysis of soil and crop nutrient status has led to increasing production and application of trace elements (boron, copper, magnesium, manganese, platinum, iron, zinc, etc.) fertilizers. Pay attention. Similar to nitrogen, phosphorus, and potassium fertilization, whether trace element fertilizers are effective or not depends on the timely diagnosis of soils and plants. After finding out the deficiency, they choose to produce fertilizers of the appropriate varieties and subsidize fertilization. In addition, trace element fertilizers must also be applied on the basis of adequate supply of nitrogen, phosphorus, and potassium in the soil in order to increase production.
IV. Concluding remarks According to the above, chemical fertilizers are closely related to the analysis and analysis of soil, and are very important in the process of agricultural modernization. We must strengthen close cooperation in this area, combine soil conditions, combine the needs of crops, develop chemical fertilizers, produce chemical fertilizers, and apply fertilizers rationally to create favorable conditions for China's agricultural modernization.

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