What should be paid attention to in the process of using urea?

What should be paid attention to in the process of using urea? Please guide that urea is applied to the soil and can be absorbed and utilized by crops only after it is converted into ammonium bicarbonate. Due to the process of transformation, the fertilizer effect is slow and should be applied 4-6 days in advance. At the same time, it is also required to apply deep covering soil, and do not irrigate immediately after application, so as to prevent nitrogen from dripping into the deep layer and reduce the fertilizer effect. When topdressing urea outside the root, especially foliar spraying, the nutrients in urea can be absorbed quickly, the utilization rate is also high, and the effect of increasing yield is obvious. When spraying urea, the concentration requirements are relatively strict. Generally, the concentration of Gramineae crops is 1.5%-2.0%, that of fruit trees is about 0.5%, that of open-field vegetables is 0.5%-1.5%, and that of greenhouse vegetables is 0.2%-0.3%. For crops in the peak growth period, or for adult fruit trees, the concentration of urea can be appropriately increased. The following problems should be paid attention to in the use of urea: (1) generally, it is not used as seed fertilizer directly. Because urea contains a small amount of biuret, which is generally less than 2%, biuret is harmful to seed germination and growth. If you have to make seed fertilizer, you can separate the seeds and urea into the field, and you must not soak or mix seeds with urea. (2) when the biuret content is more than 0.5%, it can not be used as extra-root topdressing. (3) after urea is converted to ammonium bicarbonate, it is easy to decompose and volatilize on calcareous soil, resulting in nitrogen loss. Click to get more nitrogen, phosphorus, potassium application techniques click to get more fertilizer application techniques