Urea is a high-concentration, fast-acting nitrogen fertilizer with 46% pure nitrogen. It has high nitrogen efficiency and is therefore very popular among farmers. Topdressing is a period of rapid growth during the growth period of the crop, that is, a large number of growth stages in which vegetative growth and reproductive growth go hand in hand, and the crop is supplemented with a certain amount of quick-acting nitrogen or nitrogen-potassium fertilizer to meet the high yield of crops. At this time, it is the period of high nutrient absorption efficiency of crops, and the utilization rate of nitrogen fertilizer can be more than 50%. The main reason is that the nutrients in the top dressing can be quickly and efficiently absorbed by the crops that are being flowered, and converted into yields in time. Therefore, the fertilizer used for topdressing must have the characteristics of easy dissolution and quick-acting, and urea is often used as the fertilizer of choice for farmers. It is considered to have high nitrogen content and quick effect.
At present, most people directly engaged in agricultural production are often not comprehensive enough about the “quick fixability†of urea. Although urea is an organic small molecular nitrogen fertilizer that dissolves quickly after application to the soil, crops cannot absorb it directly in large quantities. Because urea is applied to the soil and then decomposed by urease, it can be quickly and widely absorbed and utilized by the roots of the crop after it is converted into ammonium nitrogen. This shows that the fertilizer effect of using ammonium sulfate, ammonium chloride and ammonium bicarbonate as the top dressing is definitely faster than that of urea. They can be directly absorbed and utilized without conversion, which is in line with the purpose and effect of top dressing.
Since urea requires a conversion process to be widely absorbed by crops, how long does it take to convert? What are the factors that affect the speed of conversion? Is it a few days ahead of other ammonium nitrogen fertilizers to use urea as a top dressing? Scientific experiments have long proved that the urea conversion process is affected by various factors such as soil temperature, moisture, organic matter content, pH and other factors. In general farmland, when soil moisture and pH are basically adapted to the normal growth of crops, soil temperature is urea conversion. The main influencing factor of speed. For example, in the early Spring and winter wheat seasons in the north, the ground temperature is about 10 °C, and it takes about 7 to 10 days for the urea nitrogen to be converted into ammonium nitrogen; the local temperature rises to 20 °C, the spring corn trumpet stage top dressing, and the cotton bud stage top dressing When the wheat is topdressed at the booting stage, the conversion of urea to ammonium nitrogen takes about 5 days, while the local temperature rises to 25 °C and only takes 3 days.
In short, because the purpose of top dressing is to require fertilizer application as soon as possible after urea application, to provide a large amount of absorbable nutrients for the flourishing crops, it is better to use urea top dressing a few days earlier than other ammonium nitrogen fertilizers. As for the specific days in advance? It is necessary to master the seasons according to local conditions, and it is also the season of spring and summer. It takes a few days for the soil temperature in the northeast to rise very slowly. In the south of China, the soil temperature is high, and urea should be applied one to two days earlier. In other words, because the rice field temperature is slightly lower than the dry land, it should be treated differently.
In addition, when urea is used as top dressing in summer, it is necessary to pay attention to timely soil or irrigation. Because of the high temperature, urea conversion is fast, and urea is converted to produce a large amount of ammonia. If urea is not buried in the soil, or it is scattered on the surface, it is not immediately When watering, the consequences of ammonia volatilization will cause the leaves to burn. In severe cases, the leaves of the plants will be boiled like boiled water.
Source: Agricultural Resources Report, No. 1, 2009
At present, most people directly engaged in agricultural production are often not comprehensive enough about the “quick fixability†of urea. Although urea is an organic small molecular nitrogen fertilizer that dissolves quickly after application to the soil, crops cannot absorb it directly in large quantities. Because urea is applied to the soil and then decomposed by urease, it can be quickly and widely absorbed and utilized by the roots of the crop after it is converted into ammonium nitrogen. This shows that the fertilizer effect of using ammonium sulfate, ammonium chloride and ammonium bicarbonate as the top dressing is definitely faster than that of urea. They can be directly absorbed and utilized without conversion, which is in line with the purpose and effect of top dressing.
Since urea requires a conversion process to be widely absorbed by crops, how long does it take to convert? What are the factors that affect the speed of conversion? Is it a few days ahead of other ammonium nitrogen fertilizers to use urea as a top dressing? Scientific experiments have long proved that the urea conversion process is affected by various factors such as soil temperature, moisture, organic matter content, pH and other factors. In general farmland, when soil moisture and pH are basically adapted to the normal growth of crops, soil temperature is urea conversion. The main influencing factor of speed. For example, in the early Spring and winter wheat seasons in the north, the ground temperature is about 10 °C, and it takes about 7 to 10 days for the urea nitrogen to be converted into ammonium nitrogen; the local temperature rises to 20 °C, the spring corn trumpet stage top dressing, and the cotton bud stage top dressing When the wheat is topdressed at the booting stage, the conversion of urea to ammonium nitrogen takes about 5 days, while the local temperature rises to 25 °C and only takes 3 days.
In short, because the purpose of top dressing is to require fertilizer application as soon as possible after urea application, to provide a large amount of absorbable nutrients for the flourishing crops, it is better to use urea top dressing a few days earlier than other ammonium nitrogen fertilizers. As for the specific days in advance? It is necessary to master the seasons according to local conditions, and it is also the season of spring and summer. It takes a few days for the soil temperature in the northeast to rise very slowly. In the south of China, the soil temperature is high, and urea should be applied one to two days earlier. In other words, because the rice field temperature is slightly lower than the dry land, it should be treated differently.
In addition, when urea is used as top dressing in summer, it is necessary to pay attention to timely soil or irrigation. Because of the high temperature, urea conversion is fast, and urea is converted to produce a large amount of ammonia. If urea is not buried in the soil, or it is scattered on the surface, it is not immediately When watering, the consequences of ammonia volatilization will cause the leaves to burn. In severe cases, the leaves of the plants will be boiled like boiled water.
Source: Agricultural Resources Report, No. 1, 2009
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