How to use urea?

How to use urea? Please introduce a large number of field fertilizer efficiency, but the actual investigation shows that the nitrogen utilization rate of urea as topdressing is not high, and it is not as good as ammonium sulfate, ammonium chloride and ammonium bicarbonate. So how to make good use of urea please continue to look down: first of all, we should understand the purpose of crop topdressing and the requirements for fertilizer. Topdressing is in the rapid growth stage of crops, which is generally a large number of growth and development period in which nutrients and reproductive bodies go hand in hand at the same time, which is the stage when crops need the most nutrients. In order to meet the stage needs of high-yield crops, it is necessary to supplement a certain amount of available nitrogen fertilizer or nitrogen-potassium compound fertilizer. Because of the high root absorption efficiency at this time, as long as the amount and method of topdressing are used correctly, the utilization rate of nitrogen fertilizer will be very high, up to more than 50% and 70%. According to the purpose and demand of topdressing, fertilizer varieties must have the characteristics of easy dissolution, easy absorption and fast fertilizer efficiency. Urea is often used by farmers as the first choice of nitrogen fertilizer varieties, it is generally believed that it has the characteristics of high nitrogen content and quick effect. The actual fertilizer supply characteristics of urea: at present, most people who are directly engaged in agricultural production often do not have a comprehensive understanding of the "quick availability" of urea. In fact, urea is a kind of organic small molecular nitrogen fertilizer, although it dissolves quickly on the surface after being applied to the soil, but the molecular urea crop root system can not directly absorb and utilize it. Urea must be converted into ammonium nitrogen through the decomposition of urease before it can be quickly and massively absorbed and utilized by crop roots. This shows that the fertilizer effect of using ammonium sulfate, ammonium chloride and ammonium bicarbonate as topdressing fertilizer must be faster than urea, they can be absorbed and utilized directly without transformation, and they are more in line with the purpose and function of topdressing. How long will it take to complete the conversion of urea? What factors affect the speed of transformation? As a result, it is determined that urea as topdressing is several days earlier than other ammonium nitrogen fertilizers. Scientific experiments show that the process of urea conversion is affected by many factors, such as soil temperature, moisture, organic matter content, acidity and alkalinity, etc. In general farmland, when soil moisture and pH are basically suitable for the normal growth of crops, soil temperature is the main factor affecting the conversion rate of urea. For example, in the northern early spring winter wheat topdressing season, when the soil temperature is about 10 ℃, it takes about 7 to 10 days for urea nitrogen to convert into ammonium nitrogen; when the local temperature rises to 20 ℃, it takes about 5 days for urea to convert to ammonium nitrogen when topdressing at spring corn trumpet stage, cotton bud stage and wheat booting stage, but only 3 days after the local temperature rises to 25 ℃. Therefore, it is better to apply urea topdressing a few days earlier than other ammonium nitrogen fertilizers. As for a few days in advance, it is also the season at the turn of spring and summer that the soil temperature rises slowly in Northeast China, while the soil temperature in South China is high, and urea should be applied 1-2 days in advance. For the same area, because the temperature of the paddy field is slightly lower than that of the dry land, it should also be treated differently. When using urea as topdressing in summer, we should also pay attention to timely covering soil or irrigation. because the temperature is very high and the conversion of urea is fast, the product after urea conversion is ammonium carbonate, which is more unstable than ammonium bicarbonate, which is commonly known as "gas fertilizer". Will produce a lot of ammonia. If urea is not buried in the soil, or sprinkled on the surface and not immediately watered, then the consequences of ammonia volatilization will burn the leaves, and in serious cases, the leaves of the plant will be boiled like boiling water, even if the volatilization of ammonia does not burn seedlings and leaves, the nitrogen loss will also pollute the environment and reduce the utilization rate. In a word, the application skills of urea as topdressing fertilizer: first, apply it in advance, and second, cover the soil. Click to get more nitrogen, phosphorus, potassium application techniques click to get more chemical fertilizer application techniques