Types and Application methods of nitrogen Fertilizer

1. Rational application of nitrogen fertilizer 1. Fertilization according to soil conditions: (1) the content of organic matter in soil is high, the content of soil organic matter is also high, and there is little or no application of nitrogen fertilizer in limited fertilizer distribution. (2) the soil texture is light and the fertilizer conservation is poor, so it is necessary to apply a small amount of nitrogen fertilizer, especially nitrate nitrogen fertilizer, to prevent nitrogen leaching, while heavy soil can apply a large amount of nitrogen fertilizer at one time. (3) soil acidity alkaline soil applies physiologically acidic or chemical acidic fertilizer, acidic soil applies physiological alkaline and chemical alkaline fertilizer to regulate soil acidity. (4) do not apply Cl-fertilizer and Na + fertilizer in saline soil to avoid the increase of soil salt content. (5) the application effect of nitrate nitrogen fertilizer in arid area is better, and that of ammonium nitrogen fertilizer in rainy season is better. 2. According to crop fertilization: (1) different crops have different nitrogen requirements and sensitivity, leafy vegetables, mulberry, tea and other crops need more nitrogen, and legume crops only apply nitrogen fertilizer at the initial stage. (2) different crops have different responses to nitrogen types: the fertilizer efficiency of ammonium nitrogen fertilizer is higher than that of nitrate nitrogen in paddy field, and that of ammonium nitrogen fertilizer = nitrate nitrogen fertilizer or slightly smaller in dry land. For carbohydrate-rich crops, ammonium nitrogen fertilizer > nitrate nitrogen fertilizer; ammonium nitrogen fertilizer in the early stage of sugar beet

Nitrate nitrogen; tobacco ammonium nitrate is the best. (3) do not apply Cl-containing fertilizer to chlorine-avoiding crops. (4) nitrogen requirements are different in different growth stages. (5) pay attention to fertilization in two key periods of crop nutrition. 3. Fertilizing according to the nature of fertilizer: (1) ammonium nitrogen fertilizer is volatile and should be applied deeply. (2) nitrate nitrogen fertilizer is easy to leach, do not flood irrigation, and nitrate nitrogen fertilizer has fast effect and should be used as topdressing fertilizer. (3) fertilizers containing alkaline substances, volatile substances, toxic substances, salts, etc., should not be used as topdressing. 4. Fertilization according to climatic conditions: the efficiency of nitrogen fertilizer is greatly affected by climatic conditions, such as rainfall, temperature, light and so on. In general arid areas or dry years, the fertilizer efficiency of nitrogen fertilizer is poor, and the fertilizer efficiency is better in humid areas or humid years. 5. Pay attention to balanced fertilization: advocate the combined application of nitrogen, phosphorus, potassium and organic fertilizer to achieve the balance of nutrients and improve the economic benefits of fertilizers. 6. Fertilization combined with agrotechnical measures: (1) adhere to the principle of "deep covering soil". (2) avoid the loss of nitrate leaching and denitrification. (3) adopt reasonable comprehensive management of water and fertilizer. The nutritional effect of nitrogen fertilizer: because nitrogen nutrition plays an important role in crop growth, development and yield formation, most farmland soils in China are nitrogen deficient. Under reasonable application, standard nitrogen fertilizer (ammonium sulfate) per kilogram can increase grain yield by 3-5 kg, and the economic benefit is very significant. Improper application, the increase in yield is not obvious, and even lead to a reduction in yield. Rational application of nitrogen fertilizer is of great significance in agricultural production. Nitrogen is one of the main components of many important organic compounds in plants. Nitrogen is found in proteins, chlorophyll, enzymes, nucleic acids, vitamins and alkaloids. Some people call it the "element of life". When nitrogen supply is sufficient, plants can synthesize more protein, promote cell division and growth, increase leaf area and enrich chlorophyll, which is beneficial to dry matter accumulation and yield formation, and can improve crop yield quality. the remarkable characteristic of crop nitrogen deficiency is that the lower leaves lose green and yellowing at first, and then gradually expand to the upper leaves, and the plant growth process is slow. At the seedling stage, the plant growth was blocked and appeared short and thin, and the leaves were thin and small; Gramineae crops showed few tillers and slender stems; dicotyledons showed few branches; if nitrogen deficiency continued, Gramineae crops showed panicle and small grain shrunken premature senescence. When the nitrogen supply is excessive, the plant is too luxuriant, greedy green lodging, and easy to cause disease, delay ripening, but the yield decreases. 2. Types, properties and application methods of nitrogen fertilizer: there are many kinds of nitrogen fertilizer, which can be divided into four types: ammonium, nitrate, amide and long-acting nitrogen fertilizer. 1. Ammonium nitrogen fertilizer: including liquid nitrogen (NH 3), ammonia water (NH 3.H 2O), ammonium bicarbonate (NH 4 HCO 3), ammonium sulfate [(NH 4) 2 SO 4] and ammonium chloride (NH 4 Cl). Their nitrogen exists in the form of NH 4 + and NO 3 -. Their common characteristics are as follows: (1) it is soluble in water and is an available nutrient, which can be absorbed and utilized directly by crops. (2) NH 4 + can exchange with various cations on soil colloidal particles to form exchangeable nutrients, so that NH 4 + is not easy to disappear in soil, and the fertilizer efficiency is longer than that of NO 3 -. Ammonium nitrogen fertilizer can be used as both base fertilizer and topdressing fertilizer. (3) NH-3 will be decomposed in the presence of alkaline matter, and the volatilization loss of NH-3 will be caused by the application of ammonium nitrogen fertilizer on calcareous soil. Deep application of soil cover can improve the fertilizer efficiency. (4) in well aerated soil, NH 4 +-N can be nitrified into NO 3 -. Although both of them are absorbed and utilized by crop roots, NO 3-is easy to be lost and denitrified. Nitrate nitrogen fertilizer: including calcium nitrate [Ca (NO 3) 2], sodium nitrate (NaNO 3), ammonium nitrate (NH 4 NO 3) and potassium nitrate (KNO 3), their nitrogen exists in the form of NO 3 -. Its common characteristics are: (1) easy to dissolve in water, rapid fertilizer effect, high solubility and strong hygroscopicity, especially Ca (NO 3) 2 and NH 4 NO 3, which can absorb moisture and dissolve themselves in the rainy season, so they are strictly moisture-proof during storage. (2) NO 3-is a negatively charged ion, which exists in the soil solution due to negative adsorption after being applied to the soil. It has high mobility, large rainfall or paddy field is easy to be lost. (3) NO 3-under anaerobic condition, nitrogen is lost due to the formation of gaseous substances such as N 2 or N 2O by denitrifying bacteria. Therefore, it is not easy to use this fertilizer in the paddy field and use NH 4 +-N fertilizer instead. (4) nitrate nitrogen fertilizer can decompose into oxygen when heated, and its combustion-supporting property is extremely strong, and explosion will occur under strong impact, so it is necessary to prevent both moisture and heat during storage. From the commonness of nitrate nitrogen fertilizer, it can be seen that they are not suitable to be used as base fertilizer and seed fertilizer, nor to be applied in paddy field, but it is most suitable to be topdressing in dry field. 3. Amido nitrogen fertilizer: those that contain amide group (- CONH 2) or produce amide group during decomposition fall into this category, and urea [CO (NH 2) 2] is its representative. Urea is a neutral organic compound, which exists in the soil in molecular state and adsorbs with soil colloidal particles by hydrogen bond, and its adsorption power is slightly less than that of charge adsorption. Urea is transformed into ammonium carbonate by urease in soil to form NH 4 +-N, which is the same as NH 4 +-N fertilizer. Urea has strong moisture absorption and is easy to be used as base fertilizer and topdressing fertilizer, but not easy to be used as seed fertilizer. 4. Long-acting nitrogen fertilizer: most of the commonly used nitrogen fertilizers are quick-acting fertilizers, which are released quickly after being applied to the soil, and the fertilizer effective period is short, which is easy to cause nutrient loss. The new long-acting nitrogen fertilizer has the characteristics of slow nutrient release, long fertilizer efficiency and high fertilizer use efficiency. One application can meet the nutrient needs of crops during the whole growth period, and does not burn seedlings and poison crops. The main varieties are organic synthetic long-acting nitrogen fertilizers (such as urea formaldehyde, urea acetaldehyde, etc.), coated fertilizers (such as sulfur-coated urea, polymer-coated urea, slow-acting inorganic nitrogen fertilizer, long-acting ammonium bicarbonate, etc.). The above four types of nitrogen fertilizers have their commonness and are the basis for rational fertilization, but they also have their individual characteristics, such as: 1. Ammonium sulfate and ammonium chloride are physiologically acidic nitrogen fertilizers. Long-term use of this fertilizer will cause soil acidification, which is disadvantageous to crop growth. two。 Ammonia, liquid ammonia and ammonium bicarbonate are all alkaline fertilizers with strong volatility, also known as volatile nitrogen fertilizer, but after being applied to the soil, they become NO 3-by nitrification, and the alkalinity disappears. They have no residue in the soil and will not adversely affect the soil. Ammonium nitrate and urea also belong to the list of no residual nitrogen fertilizer. 3. Although urea is very soluble in water, it can not be absorbed and assimilated by roots before it is decomposed into ammonium carbonate. Therefore, it should be applied several days earlier than other nitrogen fertilizers. 4. Most of the long-acting nitrogen fertilizers are short of nutrients in the early stage, and sometimes need to be combined with a small amount of available nitrogen fertilizer. In addition, the cost of organic synthesis or coated nitrogen fertilizer is high, which is often suitable for cash crops, ornamental plants and so on.