Urea nitrogen content between 44% to 46%, is the highest nitrogen nitrogen fertilizer nitrogen, the physical and chemical properties of relatively stable, pure white or slightly yellow crystal or small particles, plus moisture, moisture Small, soluble in water, neutral nitrogen. Urea nutrient content is higher, suitable for a variety of soil and a variety of crops, the most suitable for top dressing, Urea root top dressing effect is also very good. Urea into the soil, only after conversion to ammonium bicarbonate can be a lot of crop absorption. Due to the existence of the conversion process, so the fertilizer effect is slow. Generally 4 to 6 days in advance to apply. At the same time also requires deep casing, after the application should not immediately irrigation, Urea to prevent nitrogen leaching to deep, reduce fertilizer efficiency.
Urea is a high concentration of fast nitrogen fertilizer containing 46% pure nitrogen. With high nitrogen efficiency characteristics, so by the farmers favorite. Top dressing is in the rapid growth stage of crop growth period, that is, vegetative growth and reproductive growth at the same time into a large number of growth and development period, to crop a certain amount of quick-acting nitrogen or nitrogen and potassium fertilizer to meet the needs of high yield crops. At this time it is the crop nutrient demand, Urea the root absorption efficiency is high, the topdressing with nitrogen fertilizer utilization rate of up to 50% or more, the fertilizer in a large number of nutrients can be quickly flowering results of the crop absorption and timely conversion into Yield. Therefore, for the fertilizer fertilizer varieties must be easy to dissolve and quick-effect characteristics, Urea and urea is often the preferred fertilizer for farmers as fertilizer, that it has a high nitrogen content and quick effect.
At present, most people directly engaged in agricultural production for urea "quick" understanding, often not comprehensive. Although the urea is an organic small molecule nitrogen fertilizer, Urea applied to the soil quickly dissolved, but the crop can not directly absorb a lot of it. Because the urea into the soil after the urease involved in the decomposition of the role of conversion to ammonium nitrogen after the crop roots can be quickly and heavily absorbed. This also shows why the use of ammonium sulfate, ammonium chloride and ammonium bicarbonate to do fertilizer fertilizer is certainly faster than urea, they do not need to be directly converted by the use of conversion, Urea is in line with the purpose of the top dressing and role.
Since urea needs a transformation process can be a large number of crops can be absorbed, then the conversion takes a long time? The speed of conversion by what factors affect the use of urea as top dressing than other ammonium nitrogen fertilizer a few days ahead of scientific experiments have long proved In the general farmland, when the soil moisture and pH were basically adapted to the normal growth of the crop, the soil temperature was the main influencing factor of the urea conversion rate, and the soil temperature was the most important factor The For example, in the early spring of winter winter wheat seasoning seasoning, Urea the ground temperature of about 10 ℃, urea nitrogen into ammonium nitrogen need 7 to 10 days; local temperature rose to 20 ℃, spring corn cough bell top dressing, cotton Topdressing, wheat booting stage topdressing, urea conversion to ammonium nitrogen about 5 days, while the local temperature rose to 25 ℃ after only 3 days.
As for the specific few days in advance, due to local conditions. The same is the spring and summer of the season, Urea in the northeastern region of the soil temperature is very slow to take a few days, while the southern region of soil temperature is high, the application of urea corresponding 1 to 2 days in advance can be; the same area, Lower than dry land, but also differentiated treatment. In addition, in the summer with urea for topdressing, Urea but also pay attention to timely casing or irrigation, to prevent a large number of ammonia volatiles will burn leaves.