A suitable for root dressing. Urea is a neutral fertilizer, which has less damage to crop leaves, is soluble in water, has strong diffusibility, and is easily absorbed by leaves. It is not easy to cause separation of the walls after entering the leaves, so it is very suitable for top dressing. However, urea with a biuret content of not more than 2% should be used to prevent damage to the leaves. Generally, the amount of top dressing per urea is 0.5 to 1.5 kg. The spraying time is preferably carried out after 4 pm. At this time, the amount of transpiration is small, and the leaf pores are gradually opened. The diluted urea solution can be absorbed in one night, which greatly improves the utilization rate of urea.
The second is to apply early and deep application. One must apply early. Urea is applied to the soil to have a transformation process that can be absorbed and utilized by the crop. Therefore, if the application of urea is the same as the application of other nitrogen fertilizers, it will delay the maximum effect period of crops on nitrogen nutrient absorption. Second, we must apply it deeply. Urea should be applied to the soil in depth, whether it is base fertilizer or top dressing. The deep application can control the hydrolysis rate of urea, so that it can release nitrogen nutrition evenly, prevent the loss of nitrogen volatilization, and improve the utilization rate.
It is not appropriate to apply water, water, and water immediately after application. First, it is not appropriate to apply. In particular, saline-alkali soils are less suitable for spreading on the surface. This is because ammonium carbonate, ammonium hydrogencarbonate, and ammonium hydroxide which are produced after the decomposition of urea are unstable compounds. Second, it is not suitable for dip and seed dressing. Urea contains a small amount of biuret, which is toxic to crops. Using urea to soak and mix seeds will destroy the protein structure of the seed, denature the protein, and affect the seed germination and root growth of the seedling. Third, it is not appropriate 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 carbonate, and is not easily adsorbed by the soil. If the water is immediately poured, the fertilizer will be lost with the water, and the water will be poured every few days after the application.
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