1. Urea is a kind of fertilizer with the highest content of nitrogen in the solid nitrogen fertilizers, with nitrogen content up to 46%. As a kind of high-concentration nitrogen, urea belongs to intermediate quick-acting fertilizer. Without any harmful substance residing in the soil, it has no influence after long-time application.
3. Urea is a kind of organic nitrogen fertilizer, and it can be absorbed by crops only after the urease action in soil and hydrolysis into ammonium carbonate or ammonium bicarbonate. Therefore, urea should be applied 4-8 days before the pre-fertilization period of the crops.
3. A small portion applied in the soil is solved in the soil solution in the form of molecular state, and is absorbed by the soil through the hydrogen-bond interaction, and most of the remaining is hydrolyzed into ammonium carbonate with the action of urease, so as to generate hydrogen carbonate and ammonium hydroxide. Then NH4+ can be absorbed by plants and soil colloid, and NCO3- also can be absorbed by crops, so no harmful component will reside after urea is applied in the soil.
4. It is easily soluble in water, and has relatively stable physical and chemical properties before applied in the soil and has relatively small moisture absorption, being a quick-acting nitrogen fertilizer with stable commercial form.
5. The grains are excellent, even and glossy and are easy to be applied.
It applies to all crops and soils, can be used as base fertilizer and top dressing fertilizer, and is suitable for both dry land and paddy field.
When used as top dressing fertilizer, urea can be acted on the root of the crops through soil, and is also suitable for the foliage spraying. When urea needs to be used as the top dressing fertilizer during the vigorous growth period of crops, note that it should be applied in advance of such quick-acting nitrogen fertilizers as ammonium sulfate and ammonium carbonate during the fertilization period depending on the season and temperature, generally 6-8 days in early spring (below 10℃), 3-4 days in late spring and early summer (16-20℃) and 1-2 days in summer. Used as foliage top-dressing fertilizer, urea is suitable for the foliage spraying of various crops, with a concentration generally 0.1%-0.5%, so it varies depending on the crop species and growth period. When urea is used for the foliage spraying, note that the content of the auxiliary component biuret must be lower than 0.5%.
In addition, when the mixed solution of urea and monopotassium phosphate is used as the foliage top-dressing fertilizer and sprayed on the foliages of wheat or crops, it is beneficial for their filling and to improve the thousand seed weight. The urea contained in the foliage fertilizer is beneficial for the absorption of phosphate and potassium.