Urea has a high nitrogen content, and most of it is used for crop topdressing except for some of it. How can we improve the topdressing effect of urea? You can start from the following aspects: 
First, determine the amount of topdressing according to soil fertility. Practice has proved that increasing the amount of fertilization for medium and low-yield fields can significantly increase production; high-yield fields should maintain general fertilization levels. 
Second, topdressing in the crop nutrition period. The key to improving the utilization rate of topdressing is to grasp the critical period and maximum efficiency period of nutrient absorption of various crops, and try to topdress the fertilizer during the nutrient period of crops, which can improve the utilization rate of fertilizer. 
Third, the soil should be applied in depth. Practice has proved that after applying urea to the surface of the ground for 4-5 days, its utilization rate is only about 30%, especially on the surface of calcareous and alkaline soils, and the ammonia volatilization loss is more serious. Therefore, it should be applied deep in the field of topdressing, which is beneficial to the conversion of urea and reduce the loss of volatilization. 
Fourth, to maintain a certain distance from the crop. Because urea has a great hygroscopicity, it must be kept at a certain distance from the crop during top dressing. 
Fifth, early application. Urea is a low molecular organic compound that has an ammoniation process after being applied to the soil to be absorbed by the roots of the crop. Therefore, urea should be topdressed about 7 days earlier than other nitrogen fertilizers.
6. Do not mix with alkaline fertilizer. When urea is topdressed, it should not be mixed with alkaline fertilizer to prevent reducing fertilizer efficiency. If it is necessary to mix it with alkaline fertilizer, the date of fertilization should also be staggered. 
7. It is not advisable to fill the water immediately after the application. After urea is applied to the soil, it cannot be adsorbed by the soil before it is decomposed and converted. If it is immediately poured, it will cause a large loss of urea. Soil water shortage is serious, non-irrigation is not time, but also to do small water and dip irrigation, avoid flooding. 
Eight, it is advisable to do topdressing. Urea has less damage to crop leaves, is soluble in water, is highly diffusible, and is easily absorbed by leaves. It is not easy to cause separation of the walls after entering the leaves. Therefore, it is suitable for top dressing, but the biuret content should not exceed 2%. High quality urea to prevent damage to the leaves. Generally, the amount of top dressing per urea is 0.5-1.5 kg. The spraying time should be carried out around 4 pm. At this time, the transpiration is small, the leaf stomata gradually open, and the diluted urea solution can be absorbed overnight, which greatly improves the urea utilization rate.
First, determine the amount of topdressing according to soil fertility. Practice has proved that increasing the amount of fertilization for medium and low-yield fields can significantly increase production; high-yield fields should maintain general fertilization levels. 
Second, topdressing in the crop nutrition period. The key to improving the utilization rate of topdressing is to grasp the critical period and maximum efficiency period of nutrient absorption of various crops, and try to topdress the fertilizer during the nutrient period of crops, which can improve the utilization rate of fertilizer. 
Third, the soil should be applied in depth. Practice has proved that after applying urea to the surface of the ground for 4-5 days, its utilization rate is only about 30%, especially on the surface of calcareous and alkaline soils, and the ammonia volatilization loss is more serious. Therefore, it should be applied deep in the field of topdressing, which is beneficial to the conversion of urea and reduce the loss of volatilization. 
Fourth, to maintain a certain distance from the crop. Because urea has a great hygroscopicity, it must be kept at a certain distance from the crop during top dressing. 
Fifth, early application. Urea is a low molecular organic compound that has an ammoniation process after being applied to the soil to be absorbed by the roots of the crop. Therefore, urea should be topdressed about 7 days earlier than other nitrogen fertilizers.
6. Do not mix with alkaline fertilizer. When urea is topdressed, it should not be mixed with alkaline fertilizer to prevent reducing fertilizer efficiency. If it is necessary to mix it with alkaline fertilizer, the date of fertilization should also be staggered. 
7. It is not advisable to fill the water immediately after the application. After urea is applied to the soil, it cannot be adsorbed by the soil before it is decomposed and converted. If it is immediately poured, it will cause a large loss of urea. Soil water shortage is serious, non-irrigation is not time, but also to do small water and dip irrigation, avoid flooding. 
Eight, it is advisable to do topdressing. Urea has less damage to crop leaves, is soluble in water, is highly diffusible, and is easily absorbed by leaves. It is not easy to cause separation of the walls after entering the leaves. Therefore, it is suitable for top dressing, but the biuret content should not exceed 2%. High quality urea to prevent damage to the leaves. Generally, the amount of top dressing per urea is 0.5-1.5 kg. The spraying time should be carried out around 4 pm. At this time, the transpiration is small, the leaf stomata gradually open, and the diluted urea solution can be absorbed overnight, which greatly improves the urea utilization rate.
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