One is suitable for top dressing. Urea is a neutral fertilizer, less damage to crop leaves, but also easy to dissolve in water, strong diffusion, easy to be absorbed by the leaves, after entering the leaves is not easy to cause plasmolysis phenomenon, it is very suitable for extra-root fertilizer. However, urea with a biuret content of not more than 2% should be used to prevent damage to the leaves. Generally, the amount of fertilizer applied outside the urea root per acre is 0.5 to 1.5 kg. The spraying time is suitable after 4 pm, when the amount of transpiration is small, the leaf pores gradually open, and the diluted urea solution can be absorbed completely at one night, which greatly improves the utilization rate of urea.
The second is to apply early and deep. One must apply early. Urea must be applied to the soil to have a conversion process that can be absorbed and utilized by crops. Therefore, if urea is applied for the same time as other nitrogen fertilizers, the maximum effect period of crops on nitrogen nutrient absorption will be delayed. The second is to deepen. Urea, regardless of basal or topdressing, should be deeply buried. Deep application can control the rate of hydrolysis of urea to make it evenly release nitrogen nutrition, prevent and control the loss of nitrogen volatilization, and improve utilization.
Third, it is not appropriate to express, dip, and apply seed immediately after application. First, it is inappropriate to express. In particular, saline land is less suitable for spreading on the surface. This is because ammonium carbonate, ammonium hydrogen carbonate, and ammonium hydroxide produced after the decomposition of urea are all unstable compounds. The second is not suitable for dipping and seed dressing. Urea contains a small amount of biuret, which has a toxic effect on crops. Soaking and mixing seeds with urea can destroy the protein structure of the seed, denature the protein, and affect seed germination and root growth of seedlings. Third, it is not suitable to apply water immediately after application. After the urea is applied to the soil, it is dissolved in the soil solution in a molecular state before being converted into ammonium bicarbonate, which is not easily adsorbed by the soil. If irrigation is performed immediately, the fertilizer will be lost along with the water, and the irrigation water is applied every several days after the application.
The second is to apply early and deep. One must apply early. Urea must be applied to the soil to have a conversion process that can be absorbed and utilized by crops. Therefore, if urea is applied for the same time as other nitrogen fertilizers, the maximum effect period of crops on nitrogen nutrient absorption will be delayed. The second is to deepen. Urea, regardless of basal or topdressing, should be deeply buried. Deep application can control the rate of hydrolysis of urea to make it evenly release nitrogen nutrition, prevent and control the loss of nitrogen volatilization, and improve utilization.
Third, it is not appropriate to express, dip, and apply seed immediately after application. First, it is inappropriate to express. In particular, saline land is less suitable for spreading on the surface. This is because ammonium carbonate, ammonium hydrogen carbonate, and ammonium hydroxide produced after the decomposition of urea are all unstable compounds. The second is not suitable for dipping and seed dressing. Urea contains a small amount of biuret, which has a toxic effect on crops. Soaking and mixing seeds with urea can destroy the protein structure of the seed, denature the protein, and affect seed germination and root growth of seedlings. Third, it is not suitable to apply water immediately after application. After the urea is applied to the soil, it is dissolved in the soil solution in a molecular state before being converted into ammonium bicarbonate, which is not easily adsorbed by the soil. If irrigation is performed immediately, the fertilizer will be lost along with the water, and the irrigation water is applied every several days after the application.