Basic fertilizers "nitrogen, phosphorus and potassium fertilizers""

1． The types and properties of phosphate fertilizers are usually divided into three categories: water-soluble phosphate fertilizers, weakly acid-soluble phosphate fertilizers and poorly soluble phosphate fertilizers, based on the solubility and difficulty of crop absorption. Any phosphate fertilizer that can be dissolved in water (referring to the phosphorus-containing component) is called water-soluble phosphate fertilizer, such as superphosphate and double superphosphate. ； Any phosphate fertilizer that can be dissolved in 2% citric acid or neutral ammonium citrate or slightly alkaline ammonium citrate is called weakly acid-soluble phosphate fertilizer or citrus-soluble phosphate fertilizer. Such as calcium magnesium phosphate fertilizer, steel slag phosphate fertilizer, calcium metaphosphate, etc. ； Phosphate fertilizers that are neither soluble in water nor weak acids but only soluble in strong acids are called insoluble phosphate fertilizers, such as phosphate rock powder, bone meal, etc. Types and properties of phosphate fertilizers commonly used in production 2. Transformation of phosphate fertilizer in soil Transformation of superphosphate in soil: After superphosphate is applied to the soil, the main reaction is the dissolution of foreign components. That is, after fertilization, water gathers towards the fertilization point, causing monocalcium phosphate to dissolve and hydrolyze, forming a saturated solution of monocalcium phosphate, phosphoric acid and hydrous dicalcium phosphate. The reaction is as follows: 　　At this time, the concentration of phosphorus in the soil solution around the fertilization point can be as high as 10mg/kg-20mg/kg, causing phosphoric acid to continuously diffuse outward. At the fertilization point, the pH of the saturated solution within the micro soil range can reach 1-1.5. In the process of outward diffusion, it can dissolve iron, aluminum, calcium, magnesium, etc. in the soil, and interact with phosphate ions to form phosphates with different solubility. In calcareous soil, phosphorus reacts with calcium to form dicalcium phosphate and octacalcium phosphate, and finally most of them form stable hydroxyapatite. In acidic soil, monocalcium phosphate usually reacts with iron and aluminum to form iron phosphate and aluminum precipitates, which are then further hydrolyzed into basic iron aluminum phosphate. In weakly acidic soil, monocalcium phosphate is easily adsorbed and fixed by clay minerals. In neutral soil, superphosphate is mainly converted into CaHPO4·2H2O and dissolved Ca(H2PO4)2, which is the optimal state for supplying phosphorus to crops. CaHPO4·2H2O is weakly acid-soluble and remains at the fertilization point. Therefore, the mobility of superphosphate in the soil is very small, with a horizontal range of 0.5cm and a depth of no more than 5cm. Its annual utilization rate is also very low, usually 10%-25%. 　　Transformation of calcium, magnesium and phosphate fertilizers in soil: Calcium, magnesium and phosphate fertilizers can be dissolved under the action of acids secreted by crop roots and microorganisms, and can be absorbed and utilized by crops. 　　Transformation of phosphate rock powder in soil: After phosphate rock powder is applied to the soil, it gradually decomposes under the action of chemical, biochemical and biological factors, changes the original state and transforms into new phosphorus compounds (Figure 9-13). 　　The factors that affect this transformation are mainly soil pH, Ca2+ concentration and H2PO4- concentration. Obviously, acidic conditions are beneficial to this transformation of phosphate rock powder, so phosphate rock powder has higher fertilizer efficiency when applied to acidic soil. 　　3． Reasonable distribution and effective application of phosphate fertilizer Phosphate fertilizer has the lowest utilization rate among all chemical fertilizers, and crops in the current season can generally only utilize 10%-25%. The main reason is that phosphorus is easily fixed in the soil. At the same time, its mobility in the soil is very small, and the volume of contact between roots and soil generally only accounts for 4%-10% of the volume of the cultivated layer. Therefore, minimizing phosphorus fixation, preventing phosphorus degradation, increasing the contact area between phosphorus and roots, and improving phosphate fertilizer utilization are the keys to rational application of phosphate fertilizer and giving full play to the maximum benefit of unit phosphate fertilizer. 　　(1) Reasonable distribution and application of phosphate fertilizer according to soil conditions. Among soil conditions, factors such as soil phosphorus supply level, soil N/P2O5, organic matter content, soil maturity, and soil pH are most closely related to the reasonable distribution and application of phosphate fertilizer. 　　Soil phosphorus supply level and N?P2O5: There is little correlation between soil total phosphorus content and phosphate fertilizer efficiency, but there is a good correlation between available phosphorus content and phosphate fertilizer efficiency. It is generally believed that available phosphorus (P2O5) has a medium content in the range of 10mg?kg-20mg/kg (Olsen method). Applying phosphorus fertilizer can increase production. ； Available phosphorus >25mg/kg, phosphate fertilizer is ineffective ； When available phosphorus is less than 10 mg/kg, applying phosphate fertilizer will significantly increase yield. The critical range of phosphorus in vegetable soil is relatively high. When available phosphorus reaches 57mg/kg, phosphate fertilizer is still effective. The phosphorus content of Guoguang apple leaves is less than 0.14%, indicating phosphorus deficiency. The efficiency of phosphate fertilizer is also closely related to N/P2O5. On soil with low phosphorus supply level and large N?P2O5, the application of phosphate fertilizer can significantly increase the yield. ； On soils with high phosphorus supply levels and low N?P2O5, the effect of applying phosphate fertilizer is small. ； In soils with high nitrogen and phosphorus supply levels, the application of phosphate fertilizers is not stable in increasing yields. ； On soils with low nitrogen and phosphorus supply levels, only increasing the level of nitrogen application can help exert the fertilizer effect of phosphate fertilizer. 　　Soil organic matter content and phosphate fertilizer efficiency: Generally speaking, on soils with soil organic matter content >2.5%, the application of phosphorus fertilizers does not significantly increase yields, and only on soils with organic matter content <2.5% does it have a significant yield-increasing effect. This is because soil organic matter content is positively correlated with available phosphorus content, so phosphate fertilizer is best applied to soil with low organic matter content. 　　Soil pH and phosphate fertilizer efficiency: Soil pH has different effects on different varieties of phosphate fertilizers. Generally, weakly acid-soluble phosphate fertilizers and poorly soluble phosphate fertilizers should be distributed on acidic soil, while water-soluble phosphate fertilizers should be distributed on neutral and calcareous soils. 　　Before there is a specific evaluation of the quantitative index of soil phosphorus supply level, phosphate fertilizer can also be allocated to specific fields according to the degree of soil maturity. Generally, priority should be given to barren thin fields, dry fields, cold-soaked fields, newly cultivated land and newly leveled land, as well as soils with insufficient organic fertilizers, acidic soils or high amounts of nitrogen fertilizers, because these fields are usually deficient in phosphorus, and the effect of phosphorus fertilizers is significant and the economic benefits are high. 　　(2) Reasonably allocate and apply phosphorus fertilizer according to the phosphorus demand characteristics of crops and the crop rotation system. Different types of crops have different phosphorus absorption capabilities and amounts. On the same soil, all phosphorus-loving crops that are sensitive to phosphorus, such as leguminous crops, sugar cane, sugar beet, rape, radish, buckwheat, corn, tomato, sweet potato, potato and fruit trees, should be given priority in the distribution of phosphate fertilizer. Among them, leguminous crops, rapeseed, buckwheat and fruit trees have strong phosphorus absorption capabilities, so some insoluble phosphate fertilizers can be applied. Although potatoes are sensitive to phosphorus, their absorption capacity is poor, so it is better to apply water-soluble phosphorus. Some crops that are poorly responsive to phosphorus, such as winter wheat, need to be fertilized with phosphorus fertilizer because the soil temperature is low in winter and their phosphorus supply capacity is poor. They also require more phosphorus during the tillering stage. 　　In areas with a crop rotation system, the characteristics of the crop rotation should also be taken into consideration when applying phosphate fertilizer. In the paddy and drought crop rotation, the principle of "drought is heavier and water is lighter" should be grasped, that is, phosphorus fertilizer should be applied mainly to dry crops in the same crop rotation cycle. ； In dryland crop rotations, phosphorus fertilizers should be given priority to leguminous crops that require more phosphorus and have strong phosphorus uptake capabilities. ； When crops in the rotation have similar nutritional characteristics for phosphorus, phosphate fertilizer should be allocated primarily to overwintering crops. 　　(3) Reasonable distribution and application of water-soluble phosphate fertilizer according to the nature of the fertilizer is suitable for most crops and soils, but neutral and calcareous soils are more suitable. Generally, it can be used as base fertilizer, top dressing and seed fertilizer for centralized application. Weakly acid-soluble phosphate fertilizers and poorly soluble phosphate fertilizers are best distributed on acidic soils and used as base fertilizers. The effect is better when applied to phosphorus-loving crops with strong phosphorus absorption capabilities. At the same time, the crushing fineness of weakly acid-soluble phosphate fertilizers and poorly soluble phosphate fertilizers is also closely related to their fertilizer efficiency. The fineness of phosphate rock powder should be 90% through a 100-mesh sieve, that is, the maximum particle size is 0.149mm. The particle size of calcium magnesium phosphate fertilizer is in the range of 40-100 mesh. The content of citrus-soluble phosphorus increases as the particle size becomes finer. When the particle size exceeds 100 mesh, the citrus-soluble phosphorus rate does not change much. Different soils have different dissolving abilities of calcium-magnesium phosphate fertilizer and different types of crops have different abilities to utilize citrus-soluble phosphorus, so the requirements for fineness are also different. When applied on acidic soils where upland crops are grown, the size should not be smaller than 40 mesh. In neutral phosphorus-deficient soils and when planting rice, the size should not be smaller than 60 mesh. On calcareous soils lacking phosphorus, around 100 mesh is appropriate. 　　(4) Mainly use seed fertilizer and basal fertilizer, supplemented by external top dressing. Judging from the different growth stages of crops, the critical period of crop phosphorus nutrition is generally in the early stage. For example, rice and wheat are in the three-leaf stage, cotton is in the two to three-leaf stage, and corn is in the five-leaf stage. They are all early stages of crop growth. If sufficient seed fertilizer is applied, the demand for phosphorus in this period can be met. Otherwise, the supply of phosphorus nutrition during the critical period of phosphorus nutrition will be at least 15%. During the peak growth period of crops, the demand for phosphorus is very large, but at this time the root system is developed and the ability to absorb phosphorus is strong, so the phosphorus in the base fertilizer can generally be used. Therefore, when conditions permit, one-third is used as seed fertilizer and two-thirds is used as base fertilizer, which is the most appropriate phosphate fertilizer distribution plan. If there is insufficient phosphate fertilizer, seed fertilizer should be used first, which can be used both in the seedling stage and in the vigorous growth period. In the later stages of growth, crops mainly meet the needs of various organs through the redistribution and reuse of phosphorus in the body. Therefore, as long as most crops can fully meet their phosphorus nutritional needs in the early stages, their response to phosphorus in the later stages will be poor. However, some crops, such as cotton during the boll-bearing and flowering stage, soybeans during the pod-bearing and flowering stage, and sweet potatoes during the root expansion stage, all require more phosphorus. At this time, we use extra-root top dressing to meet their needs. The concentration of extra-root top dressing is 1%-3% for monocotyledonous plants such as rice, wheat, and fruit trees. For dicotyledonous plants such as cotton, rape, tomatoes, cucumbers, etc., 0.5%-1% (superphosphate) is appropriate. 　　(5) Deep and concentrated application of phosphate fertilizer. In view of the characteristics of phosphorus fertilizer being small in mobility and easy to be fixed in the soil, when applying phosphate fertilizer, it is necessary to reduce its contact area with the soil and increase the chance of contact with crop root groups to improve the utilization rate of phosphate fertilizer. Concentrated application of phosphate fertilizer is the most economical and effective application method. Because it is concentrated near the crop root mass, it not only reduces the contact area with the soil and reduces fixation, but also increases the concentration gradient of phosphorus between the fertilization point and the root soil, which is conducive to the diffusion of phosphorus and facilitates root absorption. 　　(6) Combined application of nitrogen and phosphorus fertilizers Combined application of nitrogen and phosphorus fertilizers can significantly increase crop yields and the utilization rate of phosphate fertilizers. In general, when there is no potassium deficiency, crops require a certain ratio of N and P. For example, the nitrogen to phosphorus ratio of grass crops is 2-3:1, and the nitrogen to phosphorus ratio of apples is 2:1. However, most soils in my country are deficient in nitrogen, so applying phosphorus fertilizer alone will not achieve high fertilizer efficiency. Only when N and P nutrients maintain a certain balanced relationship, can crops produce high yields. 　　(7) Used in conjunction with organic fertilizers. First of all, the crude humus in organic fertilizers can protect water-soluble phosphorus, reduce its contact with Fe, Al, and Ca and reduce fixation. ； Secondly, organic fertilizers produce a variety of organic acids during the decomposition process, such as citric acid, malic acid, oxalic acid, tartaric acid, etc. These organic acids form complexes with Fe, Al, and Ca, preventing the fixation of phosphorus by Fe, Al, and Ca. At the same time, these organic acids are also beneficial to the dissolution of weakly acid-soluble phosphate fertilizers and poorly soluble phosphate fertilizers. ； Thirdly, the above-mentioned organic acids can also complex Fe, Al, and Ca in iron phosphate, aluminum phosphate, and calcium phosphate in the original soil, thereby increasing the content of available phosphorus in the soil. 　　(8) The after-effect of phosphate fertilizer The annual utilization rate of phosphate fertilizer is 10%-25%. Most of the phosphorus remains in the soil, so its after-effect is very long. According to research, the annual cumulative performance utilization rate of phosphate fertilizers can reach about 50% for 5-10 consecutive years. Therefore, when phosphate fertilizers are insufficient, after several years of continuous application, they can be applied again every 2-3 years. By utilizing the after-effects of previously applied phosphate fertilizers, crops can meet their demand for phosphate fertilizers. 　　In short, the rational application of phosphate fertilizers must take into account not only soil conditions, characteristics of phosphate fertilizer varieties, nutritional characteristics of crops, and fertilization methods, but also the reasonable ratio with nitrogen fertilizers and the aftereffects of phosphate fertilizers. When there is insufficient potassium and trace elements in the soil, these elements must be fully taken into consideration so that they do not become the minimum limiting factor. Only in this way can the fertilizer efficiency of phosphate fertilizer be improved.

1． Types and Properties of Potash Fertilizers Commonly used potassium fertilizers in production include potassium sulfate, potassium chloride, plant ash, etc. Their main properties are shown in Table 9-3. The ash remaining after burning plant residues is called plant ash. For a long time, most rural areas in my country have used straw, fallen leaves, dead branches, etc. as fuel, so plant ash is an important source of fertilizer in agricultural production. The composition of plant ash is extremely complex and contains various ash elements in plants, including more potassium and calcium, followed by phosphorus, so it is usually regarded as potassium fertilizer. In fact, it plays a nutritional role of multiple elements. The main form of potassium in plant ash is potassium carbonate, followed by potassium sulfate, and potassium chloride is the least. Approximately 90% of the potassium in plant ash is soluble in water, making it highly effective and a quick-acting potassium fertilizer. Since plant ash contains K2CO3, its aqueous solution is alkaline and it is an alkaline fertilizer. Due to different burning temperatures, the color and potassium effectiveness of plant ash are also different. If the burning temperature is too high, potassium and silicic acid will form K2SiO3 with low solubility, which is gray-white and has poor fertilizer efficiency. Low-temperature burning plant ash is generally dark gray and has high fertilizer efficiency. 　　2． Conversion of Potassium Fertilizer in Soil After potassium sulfate and potassium chloride are applied to the soil, potassium is in an ionic state. Part of it is absorbed and utilized by plants, and the other part is adsorbed by colloids. In neutral and calcareous soils, Ca2+ is replaced to generate CaSO4 and CaCl2 respectively. CaSO4 is a slightly soluble substance that leaches downward with water and then settles down. It can block pores and cause soil compaction. CaCl2 is water-soluble and is easily leached with water, causing the loss of Ca2+ and also causing soil compaction. In arid and semi-arid areas, it will increase the content of water-soluble salts in the soil. Therefore, long-term application of potassium sulfate and potassium chloride on neutral and calcareous soils should be combined with the application of organic fertilizers. In acidic soil, both replace H+ to generate H2SO4 and HCl, which increases the acidity of the acidic soil. Lime and organic fertilizers should be applied together. 　　3． Reasonable distribution and effective application of potassium fertilizer. The efficiency of potassium fertilizer depends on soil properties, crop types, fertilizer mix, climatic conditions, etc. Therefore, in order to distribute and apply potassium fertilizer economically and rationally, it is necessary to understand the relevant conditions that affect the efficiency of potassium fertilizer. 　　(1) Soil conditions and effective application of potassium fertilizer. Soil potassium supply level, soil mechanical composition and soil aeration are the main soil conditions that affect potassium fertilizer efficiency. 　　Soil potassium supply levels: The level of soil available potassium is an important factor in determining potassium fertilizer efficiency. The index value of available potassium varies slightly due to different soil, climate, crop and other conditions in various places. Through multi-point experiments, Liaoning Province has set available potassium (K) 90mg/kg (equivalent to K2O108mg/kg) as the critical value for soil potassium abundance and deficiency. The available potassium content is less than 90 mg/kg, and the effect of potassium fertilizer application is significant. ； When the available potassium content is between 91 mg/kg and 150 mg/kg, the effect of applying potassium fertilizer is unstable, depending on the type of crop, the content of slow-acting potassium in the soil, and the combination with other fertilizers. ； When the available potassium content is greater than 150 mg/kg, potassium fertilizer application is ineffective. It should be pointed out that for soils with low available potassium and very different amounts of slow-acting potassium, it is not enough to judge the potassium supply level solely from available potassium. The storage capacity of slow-acting potassium must also be considered to more accurately estimate the potassium supply level. 　　Mechanical composition of soil: The mechanical composition of soil is related to its potassium content. Generally, the finer the mechanical composition, the higher the potassium content, and vice versa. Different soil textures also affect the potassium supply capacity of the soil, so some people have proposed critical indicators of potassium deficiency for different soil textures.: K2O is 85 mg/kg for sandy soil-sandy loam soil, 100 mg/kg for sandy loam soil-loam soil, and mg/kg for clay soil. Therefore, the effect of applying potassium fertilizer on coarser sandy soil is higher than that on clay soil. It is best to distribute potassium fertilizer first on sandy soil that is deficient in potassium. 　　soil aeration: Soil aeration mainly affects potassium absorption by affecting plant root respiration, so that the soil itself is not deficient in potassium, but the crops show symptoms of potassium deficiency. Therefore, in production practice, it is necessary to conduct a specific analysis of the potassium deficiency of crops, and take corresponding measures to address existing problems, in order to improve the potassium absorption of crops. 　　(2) Crop conditions and effective application of potassium fertilizer. Due to their different biological characteristics, various crops have different requirements for potassium and potassium absorption capabilities, so they respond differently to potassium fertilizer. Crops containing more sugar, such as potatoes, sweet potatoes, sugar cane, sugar beets, watermelons, fruit trees, tobacco, etc., require large amounts of potassium. These potassium-loving crops should be fertilized with more potassium fertilizer to increase yields and improve quality. Under the same soil conditions, priority should be given to potassium fertilizers on potassium-loving crops. In addition, the application of potassium fertilizer to leguminous crops and oil crops also has an obvious and stable yield increase effect. Of course, in potassium-deficient soils, potash fertilizers have good effects on a variety of crops, but in soils with moderate or rich potassium fertilizers, only potassium-loving crops have better fertilizer effects. 　　(3) Fertilizer properties and effective application of potash fertilizers. The types and properties of fertilizers are different, and their application methods are also different. 　　Potassium sulfate can be used as base fertilizer, top dressing, seed fertilizer and root top dressing, but potassium chloride cannot be used as seed fertilizer. Potassium sulfate is suitable for a variety of soils and crops, especially when applied to crops that prefer potassium but avoid chlorine and sulfur-loving crops such as the Brassicaceae family. Potassium chloride is suitable for fiber crops such as hemp and cotton. It can improve the content and quality of fiber. When applied on paddy fields, it can also prevent rice black roots. It is not suitable for use on chlorine-resistant crops and low-lying and saline-alkali lands with poor drainage. 　　Plant ash is suitable for use as base fertilizer, top dressing and cover seed fertilizer. When used as base fertilizer, it can be applied in ditches or holes with a depth of about 10cm and covered with soil after application. When topdressing, it can be spread on the leaves, which can not only supply nutrients, but also reduce or prevent the occurrence and harm of pests and diseases to a certain extent. Because plant ash is dark in color and contains a certain amount of carbon, it absorbs heat quickly and increases temperature quickly, and has a light texture. Therefore, it is most suitable to be used as seed fertilizer when raising rice and vegetable seedlings. It not only supplies nutrients, but also helps to increase ground temperature and prevent seedlings from rotting. Plant ash can also be used as top dressing. Generally, 1% water immersion solution is used for crops. Fruit trees can be sprayed with 2%-3% water immersion solution. In the late growth stage of wheat, 5%-10% water immersion solution can be sprayed. Plant ash is an alkaline fertilizer, so it cannot be mixed with ammonium nitrogen fertilizer or decomposed organic fertilizer, nor can it be poured into pig pens or toilets to avoid the loss of ammonia volatilization. Plant ash has a good response to a variety of crops on various soils, especially when applied to leguminous crops on acidic soils, the yield increase effect is very obvious. 　　(4) When potassium fertilizer is applied in conjunction with nitrogen and phosphorus fertilizers, crops have a certain proportion of N, P, and K requirements. Therefore, the fertilizer efficiency of potassium fertilizer is related to the supply levels of nitrogen and phosphorus. When the content of N and P in the soil is low, the effect of applying potassium fertilizer alone is often not obvious. As the amount of N and P increases, the application of potassium fertilizer can increase yields. The interactive effect (action) of N, P, and K can also make N and P promote the absorption of K by crops and improve the utilization rate of potassium fertilizer. 　　(5) Potassium fertilizer application technology Potassium fertilizer should be applied deeply and concentratedly: Potassium is easily fixed in the soil by clay minerals, especially 2:1 type clay minerals. Applying potassium fertilizer deeply can reduce this lattice fixation caused by frequent dry and wet alternations in the surface soil and improve the utilization rate of potassium fertilizer. Potassium is also an element with low mobility in the soil. Therefore, concentrated application of potassium fertilizer can reduce the contact area between potassium and soil and reduce fixation, increase the diffusion rate of potassium, and facilitate the absorption of potassium by crops. 　　Potassium fertilizer should be applied early: Usually, potassium fertilizer accounts for a larger proportion as base fertilizer and seed fertilizer. If potassium fertilizer is used as top dressing, it should be applied early. Because the critical period of potassium nutrition for most crops is in the early stages of crop growth, the crop's potassium uptake is intense in the middle and early stages, and significantly reduces in the later stages, and even some potassium overflows from the roots in the mature stage. Cereal crops require a large amount of potassium during the tillering and jointing stages, accounting for 60%-70% of the total potassium requirement. Cotton requires the greatest amount of potassium during the budding and boll-forming stages, vegetables, solanaceous fruits, and radish require the greatest amount of potassium during the budding stage, and the fleshy root expansion stage. As for perennial fruit trees, the appropriate fertilization period should be selected based on the characteristics of the fruit tree. For example, when pears are in the fruit development period and grapes are in the early stages of berry coloring, potassium is required the most. On sandy soil, it is not advisable to apply too much potassium fertilizer at one time. It should be applied in batches, that is, the principle of small amounts and multiple times should be followed to prevent potassium leaching. On clay soil, base fertilizer can be applied once or in larger amounts each time. 　　The amount of potassium fertilizer applied: The amount of potassium fertilizer applied should be determined based on the available potassium content of the soil, the potassium requirement of the crop and the mutual balance between various nutrients. Generally, it is advisable to apply potassium oxide per mu, 6kg-9kg for corn and 5kg-8kg for rice. For potassium-loving crops, it can be increased appropriately.

What is fertilizer? 　　We refer to substances that are applied to the soil or through other means to provide nutrients for plants, or to improve the physical and chemical properties of the soil, and to provide a good living environment for plants, as fertilizers. 　　Fertilizer is the food for crops and the material basis for increasing production. There is a Chinese agricultural proverb that "Farming without manure is equivalent to fooling around." According to statistics from the Food and Agriculture Organization of the United Nations, the role of chemical fertilizers in increasing grain production includes the fertilizer effect and subsequent effects in the season. The average production increase effect is 50%. my country's soil fertility monitoring results in recent years show that the contribution rate of fertilizers to agricultural product production is 57.8% on average nationwide. China feeds 22% of the world's population with 7% of the world's arable land, and it should be said that half of this is due to the role of fertilizers. 　　At present, there are still many problems in fertilizer application in our country. Heavy chemical fertilizers and light organic fertilizers ； Heavy nitrogen fertilizer, light phosphorus and potassium fertilizer, ignore micro-fertilizer ； Focus on output, light on quality ； Application methods are outdated and backward. This brings many adverse consequences: First, the decline in soil fertility affects the sustainable development of agriculture. ； Second, fertilizer utilization rate is low, waste is serious, and the environment and groundwater are polluted. ； Third, costs are high, benefits are low, and agricultural income increases slowly or even stagnates. ； Fourth, high yield but low quality directly affects the sales of agricultural products. Faced with the new situation of developing "three highs and one excellent" and advocating sustainable agricultural development, guiding rural cadres and farmers to update their concepts, reverse the "three heavy and three light" tendencies, adjust the fertilizer structure, and implement the integration of measurement, distribution, production, supply and application has become the focus of the current fertilizer work. 　　Chemical fertilizers refer to fertilizers that are manufactured or mined by chemical methods and processed. They are also called inorganic fertilizers, including nitrogen fertilizers, phosphate fertilizers, potassium fertilizers, micro-fertilizers, compound fertilizers, etc. They have the following common characteristics: Simple ingredients and high nutrient content ； Fast fattening effect, strong fattening power ； Some fertilizers have acid-base reactions ； Generally does not contain organic matter and has no effect of improving soil and fertilizing. There are many types of chemical fertilizers, and their properties and application methods vary greatly.