Fertilizer Basics [Date: 2005-4-22] Source: Author: [font: medium and small] 1. What is fertilizer? The substances that are applied to the soil to increase crop yield and product quality and increase soil fertility are called fertilizers. Those fertilizers that directly supply essential nutrients to the crops are called direct fertilizers. Nitrogen fertilizers, phosphate fertilizers, potash fertilizers, trace elements, and compound fertilizers belong to this category. Others, mainly for the purpose of improving soil physical, chemical and biological properties, thus improving the growth conditions of crops, are called indirect fertilizers such as lime, gypsum and bacterial fertilizers. However, these two types of fertilizers can sometimes not be completely separated, such as organic fertilizers are both direct and indirect fertilizers. 2. What nutrients are necessary for crops? The essential elements for the normal growth and development of plants are called essential nutrients. More than 70 elements have been found in plants, but not all of them are essential nutrients. According to research, there are 16 kinds of essential nutrients, they are: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium ( Mg, S, S, Fe, Mn, Zn, B, Mo, Cu, and Cl. 3, which nutrients are called a large number of elements? Which are called trace elements? What is called "the three elements of fertilizers"? The above 16 elements are required for the growth and development of plants, but their requirements are very different. It is customary to include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur as a large number of elements; The remaining 7 elements with a content of 0.01% or less are called trace elements. Plants need more nitrogen, phosphorus, and potassium, and the soil often fails to meet the needs of crops. They often need to supply crops through fertilization, so they are called "three elements of fertilizers." 4. What are beneficial elements and ultra-trace elements? Although some elements are essential elements, they have a certain nutritional effect on plants. These elements are called beneficial elements, such as cobalt (Co), which is a non-essential element, but it is an essential element in the fixation of nitrogen in leguminous rhizobia. Therefore it has a good influence on the growth of legumes. Sodium (Na), silicon (Si), iodine (I), selenium (Se), strontium (Sr) nickel (Ni), vanadium (V), and the like are also beneficial elements. Ultra-trace elements are those non-essential elements that are rarely found in plants (under a few hundred thousandths), and some of them are beneficial elements such as selenium, cadmium, and mercury. 5. Where do the necessary nutritional elements of the crop come from? Carbon, hydrogen, and oxygen needed for plants come from air and water. Nitrogen comes mainly from the soil and the rest comes from the soil. Therefore, in addition to carbon, hydrogen, and oxygen, plants mainly rely on roots to absorb these nutrients from the soil. 6. What form of nutrients does crops absorb from the soil? Crops mainly absorb inorganic ions in the soil, such as K+, NH+4, NO-3, Ca#, etc.; but they can also absorb certain soluble organic substances such as urea, amino acids, amides, nucleic acids, and phosphoglycerate. Fertilizers mainly supply inorganic ionic nutrients, which are easily dissolved in water, and the fertilizer efficiency is fast. Organic fertilizers can supply both ionic nutrients (after decomposition) and some organic nutrients. 7. How does the crop absorb nutrients? Crops absorb nutrients in the soil through the roots, but first the roots and nutrients must be in contact, ie nutrients can be absorbed into the roots on the root surface. How can nutrients reach the root surface? One way is to extend the root directly to promote nutrients. This method is usually called interception. The nutrients intercepted by the root system are few; the other is diffusion, in which the nutrients move from low concentrations to high concentrations. When the nutrient concentrations near the roots are higher than the roots, the nutrients spread to the root surface; The pathway is mass flow, which is the flow of plastids, which is caused by the role of leaf transpiration. As transpiration consumes a large amount of water near the root surface, it causes the surrounding water to move toward the root surface, and the nutrients in the water also move to the root surface. The absorption of root nutrients by crops has two processes: active absorption and passive absorption. Passive absorption is a chemical and physical process that does not require energy. For example, nutrients enter cells through diffusion or charge balance; active absorption is a process that requires energy consumption and is selective. Some people think that nutrients pass through passive absorption into free space (between the cell wall and the plasma membrane) and meet a substance called a carrier on the plasma membrane. The carrier contains ionic nutrients in the cytoplasm, and the carrier needs energy to work. of. Just as cars are carriers, cars need gasoline to move around. Therefore, if the plant supplies less energy to the roots, or some conditions affect the respiration of the roots, and the lack of phosphorus, it will affect the plant's absorption of nutrients. 8, what is called rational fertilization? Reasonable fertilization is the requirement that fertilization can achieve the following three purposes: 1 fertilization can make plants get high yield and high quality; 2 get the best economic benefits with the least investment; 3 improve soil conditions create a good foundation for high and stable production, that is to use land Combine with the cultivation of land. 9. What is the main basis for rational fertilization? The main target of fertilization is crops. Therefore, the fertilization must first consider the nutritional characteristics of the crop. The nutrition of various crops is different, and the requirements for nutrition of the same crop at different growth periods are also different. That is to say, different crops or crops have different requirements for the types, quantities, and proportions of nutrient elements at different fertility stages. For example, to produce 100 kg of corn, 2.57 kg of nitrogen (N), 0.86 kg of phosphorus (P2O5) and 2.14 kg of potassium (K2O) are needed to be drawn from the soil, while potato 100 kg of bodhi only requires 0.5 kg of nitrogen (N ), 0.2 kg of phosphorus (P2O5) and 1.06 kg of potassium (K2O). Cereals and leafy vegetables require much nitrogen, but legumes require less nitrogen. Because they have root nodules, they fix nitrogen in the air. For example, bananas require a lot of potassium, but less phosphorus is needed. Therefore, the nutritional characteristics of crops are the most important basis for fertilization. Secondly, fertilization is mainly through soil supply to crop nutrition, so the nature of the soil will inevitably affect the effect of fertilization. Therefore, fertilization must also be carried out according to the nature of the soil. Among these considerations are the content of various nutrients in the soil, and the ability to retain fertilizer and provide fertilizer. Whether there is obstacle factor, etc. Once again, it is to consider the relationship between climate and fertilization, how to fertilize dry season or dry seasons, areas and seasons where there is much rain, low temperature and high temperature seasons. In short, the climate affects the effect of fertilization and fertilization affects the adaptation and utilization of crops to climatic conditions. In addition, fertilization must be considered in conjunction with other agricultural technical measures. 10. What is the Critical Period, Critical Value, and Maximum Nutritional Efficiency Period for Crop Nutrition? The critical period and the maximum efficiency period of crop nutrition have the closest relationship with the effect of fertilization. Nutritional criticality refers to the requirement for nutrients for a crop during a certain growth period. Although the number is not large, if there is a lack or excess or imbalance between nutrient elements, it will have a significant adverse effect on crop growth and development. For most crops, the critical period generally occurs at the beginning of growth, and the critical period of phosphorus appears earlier, followed by nitrogen and potassium later. Therefore, phosphorus fertilizer is often used as a seed fertilizer in production to ensure that sufficient phosphorus is obtained at the beginning of crop growth. The critical period of nitrogen nutrition, rice in the three-leaf stage and spikelet differentiation period; wheat, corn in the early stage of tillering and spikelet differentiation period. Critical period of potassium nutrition, rice in the early stages of tillering and young ear formation. According to the research, tillering at the tillering stage of rice with potassium content below 1.0% stops the tillering; in the spikelet formation stage, if the potassium content is below 1.0%, the number of grains per panicle significantly decreases. The critical value is when the nutrient in the crop body is lower than a certain concentration, its growth amount or yield is significantly reduced, and shows the symptoms of nutrient deficiency. At this time, the nutrient concentration is called the “critical nutrient valueâ€. For example, the critical value of potassium in the rice tillering stage and spikelet formation period is 1.0%. Fertilizers used in different periods have great differences in the effect of increasing yield, and one of them has a good nutritional effect. This period is called the period of maximum nutrient efficiency. That is, the highest economic output was obtained from nutrient units. Maximum efficiency is often consistent with the period when the crop needs the most nutrients. According to research, the maximum efficiency period of peas is during its 15-40 days of growth; eggplant is from the beginning to the full fruit period; corn is the maximum efficiency period of nitrogen and potassium from the formation of the trumpet to tasseling, and it is phosphorus from flowering to milk-cooking. Maximum efficiency period. The period of maximum nutrient efficiency for various crops is different and we can determine this through field trials. The method is to divide the growth period of the crop into several distinct stages, and then apply the same amount of fertilizer at each stage to see which stage has the highest economic output, and that stage is the period of maximum nutrient efficiency. 11, what is called fertilizer utilization? Fertilizer utilization refers to the percentage of nutrients absorbed by fertilizers in the current season from the fertilized materials. The utilization rate can be calculated by field test and indoor chemical analysis according to the following formula: Absorption of this element in the crop area in the fertilization area - Mid-absorption amount of this element in the crop-free area Fertilizer use efficiency (%)=--- ─────────────────100 The total amount of this element in the fertilized materials is under the current management level of cultivation techniques. The utilization of chemical fertilizers is roughly in the following range: nitrogen fertilizer is 30-50%, Phosphate fertilizer 10-15%, potassium 40-70%. 12. What is the minimum nutrient law? The minimum nutrient rate was proposed by the German chemist Libice. He once said that if there is an insufficient nutrient in the soil, or if it is lacking, even if other nutrients are present, the soil will become a barren land. In other words, the factor limiting yield in some soil is one of the most deficient nutrients. The law of minimum nutrients reminds us that when fertilizing we should find out the lack of nutrients that affect the yield of crops, and the relationship between the proper proportions of various nutrients. The minimum nutrient is not fixed, after solving some kind of minimum nutrients, another certain nutrient may rise to the minimum nutrient. 13. What is the law of diminishing returns? The pay-reduction rate was first proposed by European economists Durco and Anderson, and it reflects the relationship between input and output under the same technological conditions. It means that the remuneration received from a certain land increases with the increase of labor and capital invested in the land, but the amount of remuneration per unit of labor or capital decreases as the input increases. For example, in the fertilization, the effect of a certain nutrient is greater when it is insufficient in the soil, but if the application amount of this nutrient is gradually increased, the increase in the yield per unit of nutrients gradually decreases. Therefore, the amount of fertilizer that yields the highest yield is not necessarily the best amount of fertilizer, because the decline in economic benefits will not increase production. So do not blindly increase the amount of fertilizer. Some people estimate based on experiments that the optimum amount of fertilizer is about 5% less than the amount of fertilizer that yields the highest yield. 14. What is the factor comprehensive law? The growth and development of crops are affected by various factors (water, fertilizer, gas, heat, light, and other agricultural technological measures). Only under the premise that the external conditions guarantee the normal growth and development of crops can the full effect of fertilization be exerted. The central meaning of factor comprehensive rate is: Crop yield is the result of the comprehensive effect of various factors that affect the growth and development of crops, but there must be a dominant limiting factor, and crop yield is constrained to a certain extent by this limiting factor. Therefore, fertilization should be coordinated with other agricultural technical measures, and fertilizers should be used in conjunction with each other. For example, the control of fertilizers for water, fertilization and irrigation is very important. 15. What is the positive interaction effect and negative interaction effect between molecules? If the soil lacks two or more nutrients, supplementing only one of them alone will have no significant effect on the growth or yield of the crop, while applying both nutrients at the same time may have a large impact. When the effect of the simultaneous application of two nutrients on the yield increase is greater than the sum of the effects of the two crops when the two nutrients are applied separately, there is a positive interaction effect between these two nutrients, or a positive conjoint effect. . When the simultaneous application of the two nutrients in the crop is less than the sum of the effects of the two crops when the two nutrients are applied separately, it is said that there is a negative interaction between the two nutrients. If the simultaneous effect of the increase in production is equal to the increase in yield when applied alone, there is no interaction effect between the nutrients. For example, the nitrogen and potash fertilizers applied to rice were tested in the following manner: XML:NAMESPACE PREFIX = O /> Treatment yield (kg/mu) (1) Non-fertilizer (CK) 500 (2) Single application of nitrogen (N) 600 (3) Single application of potash ( K) 580 (4) Nitrogen and potassium fertilizers (NK) 750 The relationship between nitrogen and potassium is: NK=(NK-CK)-(N-CK)-(K-CK) Substituting the yield into the formula: NK= (750-500)-(600-500)-(580-500) = 250-100-80 =70 The effects of nitrogen and potassium on the yield increase are greater than the sum of the effect of the individual application of the increase in yield. Therefore, there is a positive link between nitrogen and potassium. Should effect. If there is a positive effect, the nutrients should be applied as far as possible while fertilizing; on the contrary, simultaneous application is avoided. If there is no relevant effect, it does not matter how it is applied. 16, what is the antagonism between ions? As mentioned above, the roots that draw nutrients from the soil are mainly inorganic ionic nutrients in the soil. The presence of a certain ion inhibits the absorption of another ion. This relationship is called antagonism between ions. It is now known that there is an antagonistic effect between K+ and Mg#, potassium is strongly antagonistic to magnesium, and magnesium is weaker to potassium; Ca# and Mg#, K+ and Ca# are also antagonistic, and K+ and NH+4 are considered to be antagonistic. Some people think that there is no antagonism, and opinions are not yet reached. There are also antagonistic effects between anions such as Cl-, NO-3, and H2PO-4. So pay attention to this relationship in production. For example, applying lime or more potassium fertilizer on acid soil may induce magnesium deficiency in crops. 17. What is the role of ion assist? The presence of a certain ion can promote the absorption of another ion, which is called ion-assisted interaction. According to studies, calcium ions can promote the absorption of monovalent cations such as K+ and NH+4 at low concentrations. However, if the concentration is too high, it has an inhibitory effect. Anions generally have an assisting effect on cations. If Cl- can promote the absorption of K+, NO-3 can promote the absorption of Mg#. 18, what is base fertilizer, seed fertilizer and top dressing? Basal fertilizer is fertilizer applied to the soil before or before transplanting. The role of basal fertilizer is mainly to supply the nutrients needed for the whole growth period of the crop. Fertilizers applied to improve the soil are generally also applied as basal fertilizers. Fertilizer refers to fertilizer that is applied at the same time or mixed with seeds. The role of seed fertilizers is mainly to supply seedlings with nutrients. Because the fertilizer is in the vicinity of the seed, the seedling root system can quickly absorb nutrients. Top dressing refers to fertilizer applied to the growth of crops. The role of topdressing is mainly to supply a large amount of nutrients for a certain period of the crop needs, or to be filled with deficiencies. The production is usually a combination of basal fertilizer, seed fertilizer and topdressing fertilizer. Generally, base fertilizer is mainly used as top dressing. 19, what is outside fertilization? What are its advantages? In addition to nutrients in the roots of plants, leaves and green shoots can also absorb nutrients. Spraying the nutrient-containing solution onto the aerial parts of the crop (mainly the leaves) is called extra-root fertilization. The advantages of fertilization outside the roots are: (1) Directly supply crops with effective nutrients, prevent them from being fixed or transformed in the soil and reduce fertilizer efficiency. (2) When the absorption force to be lined is weak, the roots are fertilized and the crop is easily absorbed into nutrients. For example, the spraying of urea and potassium dihydrogen phosphate in the later stage of rice growth will have a good effect. (3) The absorption and transformation of nutrients by leaves are faster than roots, and they can timely supplement the needs of crops for nutrients. For example, it usually takes 4-5 days for urea to be applied to soil, but it usually works after 1-2 days. Therefore, the use of external root fertilization is effective in preventing deficiency diseases. (4) Root-fertilization is suitable for mechanization and is economical and effective. The amount of fertilized roots is usually only about 10% of the soil. Many fertilizers, especially urea, can be sprayed together with many pesticides. Save time and labor; such as the use of mechanical spray high efficiency and quick. The use of extra-root fertilization in the cultivation of fruit trees, tea plants and vegetables is most suitable. Nowadays, mechanical fertilization in pineapple is widely used abroad. 20, what problems should pay attention to the application of root fertilization? To obtain good results when applying fertilizers to the roots, note the following: (1) Keep the leaves moist for as long as possible. The longer the leaf wets after the root spray, the more nutrients the plant absorbs. Therefore, it is generally better to spray after 4 o'clock in the afternoon, or before 9 o'clock in the morning. It is not suitable for the sun to be violent and windy and rainy at noon. If it is cloudy, it can be carried out all day. (2) The solution should adhere well to the blade. In order to do this, generally better performance sprayer is used; it is best to mix a small amount of "humectant", such as neutral soap or seagull detergent (not suitable for strong alkaline), the concentration is generally 0.1-0.2% To promote nutrient penetration into the leaves. (3) The concentration of nutrient solution and pH should be appropriate. The greater the concentration of the solution in the permissible concentration range, the more beneficial the absorption of the leaves is, and the less the preparation of too much solution, the too high concentration will burn the leaves and hinder the absorption. The concentrations tolerated by various crops are different. In general, cereal crops can be thicker, and dicot crops such as beans and fruit trees can be thinner; young plants can be thicker. Generally, the concentration of salt solution in macronutrients is approximately 0.2-2%, and the salt solution of trace elements is approximately 0.01-0.1% (or 0.01% in pure nutrient concentration). Please refer to chemical fertilizer section for details. The pH of the nutrient solution is generally close to neutral, and overacidity is not conducive to crop absorption of nutrients. The solution is superacidity and alkali is adjusted to near neutrality by dilute acid or dilute alkali. If the main nutrient in the solution is cation, the solution can be adjusted to be slightly alkaline. If it is an anion (such as nitrate and phosphate, etc.), it can be slightly acidic. Because it is beneficial to the absorption of these ions by crops. (4) The solution should be sprayed on the back of the leaf. Due to the stomata on the back of the leaves, the tissues are looser and the nutrients are easily infiltrated, and the solution of the leaves is dried slowly. If the cereal crops can also be sprayed on both sides, the leaves also have many pores. If some nutrients such as boron, calcium, iron, manganese, molybdenum, and zinc that are not easily moved in the plant body are sprayed, it is generally necessary to spray on new shoots. Since root fertilization should be performed twice or more, it can be sprayed every 7-10 days. Each mu can spray 50-70 kilograms of water solution. Finally, it must be pointed out that although there are many advantages in the application of root fertilizers, the amount of crops absorbed by them is still very small, and given that China’s current level of mechanization is not high and energy is insufficient, the use of rootless fertilization instead of soil rhizosphere fertilizer is not Appropriate, especially a large number of nutrient elements, or should be based on soil fertility, external fertilization to assist the combination of methods is appropriate. 21. What are quick-acting fertilizers and delayed-effect fertilizers? Fertilizers that are applied to the soil and can be immediately or quickly absorbed by crops are all fast-acting fertilizers. Like most chemical fertilizers. All fertilizers that cannot be absorbed or utilized by crops immediately or very quickly, and which can only be absorbed and utilized by crops after a period of decomposition or conversion, are considered to be delayed fertilizers. For example, the vast majority of organic fertilizers, phosphate rock, etc. are delayed fertilizers. 22. What kind of fertilizer is suitable for base fertilizer, seed fertilizer and top dressing? Late-effect fertilizers, fertilizers that are not easily lost in the soil, and those that use soil-based fertilizers are all suitable as base fertilizers; quick-effect fertilizers that are harmless to seeds or seedlings can be used as seed fertilizers; and quick-acting fertilizers and energy can convert quickly. Fertilizers suitable for crops to absorb fertilizers are suitable for top dressing; fertilizers used for top dressings are generally water-soluble quick-acting fertilizers, and some trace element fertilizers are not necessarily fast-acting. 23. What is physiological acid fertilizer, physiological alkaline fertilizer and physiological neutral fertilizer? Some chemical fertilizers dissociate into cations and anions after being applied to the soil. Because the crops absorb more cations than anions, more acid ions remain in the soil, thus increasing the acidity of the soil (or soil solution). Fertilizers that increase soil acidity after nutrient absorption by crops are called physiological acidic fertilizers, such as ammonium sulfate, where the crop absorbs more NH4 than SO4, and SO4 remaining in the soil is released by crop substitution and absorption. H+ (or dissociated H+) combines with sulfuric acid to increase the acidity of the soil. Therefore, ammonium sulfate and ammonium chloride are all physiological acidic fertilizers. Similarly, some fertilizers absorb more cations in the soil because of the absorption of more anions than cations in the soil, which results in increased alkalinity of the soil. This fertilizer, which absorbs nutrients through crops and increases alkaline properties of the soil, is called physiological alkaline. Fertilizers such as sodium nitrate, the crop absorbs more nitrate (NO-3) than nano (Na+), and the sodium ions combine with the bicarbonate (HCO-3) exchanged from the crop to form sodium bicarbonate, sodium bicarbonate. The hydrolysis is basic, it can also be that the crop consumes certain acid in the process of absorbing nitrate in the body and reducing to ammonia in the body. The crop excretes excess hydroxide (OH-) from the body in order to maintain the balance of cell pH. Increases soil alkalinity. So sodium nitrate is a physiological alkaline fertilizer. The so-called physiological neutral fertilizer means that the cations and cations in the fertilizer are the main nutrients absorbed by the crop, and the two are absorbed by the same amount, and those fertilizers that do not change the pH of the soil after the crop absorbs nutrients such as ammonium nitrate. Ammonium bicarbonate, although ammonium ions are absorbed by the crop more than bicarbonate (HCO-3), the soil contains more bicarbonate, and it exchanges with the crop and H+ combines with carbonic acid (H2CO3). Arguably, ammonium bicarbonate is physiological. A generalized fertilizer, but because of carbonic acid instability, it decomposes into water and carbon dioxide, and the acidity of carbonic acid is very weak, so ammonium bicarbonate is also generally a physiologically neutral fertilizer. The physiological response of fertilizers has a certain influence on soil properties and fertilizer efficiency. Therefore, it is best to use physiological alkaline fertilizers for acidic soils, and physiological acidic fertilizers for calcareous or alkaline soils. We can also make use of the physiological acidity of the fertilizer's physiological acidic fertilizer to dissolve some non-water-soluble fertilizers to increase its fertilizer efficiency. For example, the calcium-magnesium phosphate fertilizer or the phosphorus-based ore-fertilizer can increase the fertilizer efficiency of the phosphate fertilizer. 24. What are the fertilization methods for field crops? Field crop fertilization generally has the following types: (1) Spreading spreads fertilizer uniformly in the soil. The appalaching can be deep or form (shallow). The technique of deep application is to use a plough to plunge into the soil after spreading. Application applies to dense crops and fertilizers. The advantage of the application is that it is simple and the nutrients are absorbed by crops in all parts of the soil; the disadvantage is that the fertilizer is not used in a high efficiency because the fertilizer cannot be used by all crops and the weeds are fattened. The water-soluble phosphate fertilizer is in contact with the soil and is easily exposed to it. Fixed to reduce fertilizer efficiency, fertilizer dosage. (2) Shi He points the application of fertilizer in the sowing ditch and sowing hole, or in the transplanting line and hole, called the Shi He points. Fertilizers can be applied under the seeds and can also be applied on one or both sides of the seeds. The following conditions are suitable for planting and planting: 1 less fertilizer; 2 large crop spacing; 3 fertilizers that are easily fixed by soil, such as phosphate fertilizers; 4 poor crop root development, and low soil fertility. The advantages of this method of fertilization are: the near roots of fertilizers, which are easily absorbed and utilized by crops, and therefore have a higher utilization rate of fertilizers; the contact surface between fertilizers and soil is small, the degree of fixation of nutrient elements is low, and the effective time is longer than the application. (3) Spraying is external root fertilization. Please see question 20.
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