What is urea? What is good to use urea?

What is urea? What is good to use urea? Please introduce that urea belongs to amide nitrogen fertilizer, accounting for 35% of China's nitrogen fertilizer output, accounting for 40%, second only to carbamines. 1. The molecular formula of urea is CO (NH2) 2, which contains 46% nitrogen (N) and shows white or yellowish crystals. It is easily soluble in water, the aqueous solution is neutral and has strong hygroscopicity. Due to the addition of hydrophobic substances such as paraffin in urea production, its hygroscopicity is greatly reduced. Urea properties should be paid attention to: 1 urea contains a small amount of biuret, also known as biuret, which has an obvious inhibitory effect on crop growth when it is more than 1%, and should not be used as seed fertilizer, seedling fertilizer, foliar fertilizer or excessive and concentrated fertilizer. Urea is an organic nitrogen fertilizer, which is easily absorbed by crops after the transformation of urease in soil into ammonium carbonate or ammonium bicarbonate, which is generally applied 4-8 days in advance. (3) Urea is molecular before conversion and is not adsorbed by soil, so it should be prevented from losing with water; ammonia after conversion is also volatile, so it is necessary to cover soil deeply. 2. the application of technical urea can be used as base fertilizer and topdressing fertilizer, generally not directly as seed fertilizer or seedling head fertilizer, because of poor mastery, high concentration of urea will affect seed germination and root growth. If it is necessary to apply seed fertilizer, it should be separated from the seeds, and the amount of urea should not be high. The application of urea 5kg per mu of grain crops must first be mixed with dry and fine soil and applied to about 2cm under the seeds or lOcm on the side. (1) base fertilizer. Take grain crops as an example, 10-15 kg of urea is generally used per mu. First, when dry farming base fertilizer, urea can be sprinkled on the field, and then ploughed and raked. The soil temperature of spring sowing crops is low, so the amount of urea should not be too large, otherwise it is easy to cause local soil alkalization or biuret increase, resulting in seed burning. Second, in the case of basic fertilizer in the paddy field, urea can be sprinkled after draining the field water, and then ploughed, and then irrigated and raked after 5-7 days when urea is transformed into ammonium carbonate. It can also be applied in shallow water before raking after ploughing, and then ploughed with a tractor to make urea and mud mix evenly. In addition, when urea is used as flour fertilizer, the dosage per mu is 7-8 kg, which is evenly applied before transplanting rice, and water can not be released casually in the process of raking the field. (2) topdressing. 8-13 kg urea per mu of grain crops was applied at tillering stage or jointing stage. First, dryland crops can be applied by ditch or hole application, the depth of fertilization is 6-lOcm, and the soil is covered strictly after fertilization to prevent ammonia volatilization after hydrolysis. Second, when topdressing paddy crops, they should first drain water, maintain a thin water layer, weed and cultivate the field after application, and do not irrigate within two or three days, and then irrigate after most of the urea is converted into ammonium carbonate. Urea topdressing is several days ahead of other nitrogen fertilizer varieties. The leakage of water and fertilizer on sandy land is more serious, which can be applied in stages, and the amount of fertilizer should not be too much each time. Urea is easy to move with water, and can also be sprinkled on the soil surface on dry land, and then watered. In the first week, the fertilizer moves to the lower layer, and then due to water evaporation, the fertilizer moves to the upper layer again, and most of it is concentrated in the l0-20cm soil layer, which does not cause nitrogen volatilization loss. The amount of irrigation per mu should not be too large or too small, 20Mui 30 cubic meters for loam land and 15 Mel 20 cubic meters for sandy loam or sandy soil. When urea is applied to other crops, the amount and period of application are different, but the matters needing attention in application are the same. Click to get more nitrogen, phosphorus, potassium application techniques click to get more chemical fertilizer application techniques