Urea is applied to the soil and can only be absorbed and utilized by the crops after being converted into ammonium bicarbonate. Due to the process of transformation, the fertilizer efficiency is slow, and it is generally applied 4 to 6 days in advance. At the same time, it is also required to apply soil cover deeply, and do not immediately irrigate the water after application to prevent nitrogen from drenching into the deep layer and reducing fertilizer efficiency.
When the urea root is topdressed, especially the foliar spray, the nutrients in the urea are absorbed quickly, the utilization rate is also high, and the yield increase effect is obvious. When spraying urea, the concentration requirements are stricter. Generally, the concentration of grass crops is 1.5%-2.0%, that of fruit trees is about 0.5%, that of open vegetables is 0.5%-1.5%, and that of greenhouse vegetables is between 0.2%-0.3%. For growing crops, or adult fruit trees, the concentration of urea applied can be appropriately increased.
The following problems should be noted when using urea:
(1) Generally not directly used as seed fertilizer. Because urea contains a small amount of biuret, generally less than 2%, biuret is harmful to seed germination and growth. If the seed fertilizer has to be used, the seed and urea can be separated from the ground, and the urea can be used for seed soaking or seed dressing.
(2) When the biuret content is higher than 0.5%, it cannot be used as a top dressing.
(3) After the urea is converted into ammonium bicarbonate, it is easily decomposed and volatilized on the calcareous soil, causing nitrogen loss. Therefore, it is necessary to apply the soil deeply.
Metallographic Polishing Cloth
Cloth wheel polishing the main material is cloth, used for polishing the mechanical wheel. Polishing cloth wheel, material linen, cotton, non-woven cloth, flannelette, denim, miscellaneous cloth and linen wheel, nylon wheel, emery wheel, used for all kinds of polishing tools.
Performance: this kind of product is generally made of cotton twill and cotton cloth cut, strong sewing force, strong grinding force. Specification: according to the size provided by customers. Usage: this kind of product is usually used for grinding, even polishing, but also need to depend on the workpiece material and product quality requirements, can not be generalized. For example: the workpiece material hardness is low can also be rough grinding, polishing quality requirements are not very high, can also be used as polishing, etc..
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