Eight taboos on urea application

First, it should not be mixed with alkaline fertilizer or applied at the same time. Urea must be converted into ammonia nitrogen to produce fertilizer effect, and under alkaline conditions, most of the nitrogen will be volatilized into ammonia, so urea can not be mixed with alkaline fertilizers such as lime, plant ash, calcium magnesium phosphate fertilizer or at the same time. Generally speaking, urea and alkaline fertilizer should be staggered for 3-4 days in summer and autumn, and 7-8 days in winter and spring.

Second, it is not suitable to be mixed with seed fertilizer. In the process of urea production, a small amount of biuret is often produced, which will be toxic to seeds and seedlings when the biuret content is more than 2%. When such urea enters seeds and seedlings, it will cause protein denaturation and affect seed germination and seedling growth. therefore, it is not suitable to be used as seed fertilizer. If it must be used as seed fertilizer, the contact between seed and fertilizer should be avoided and the dosage should be controlled.

Third, irrigate immediately after unsuitable application. Urea belongs to amide nitrogen fertilizer, which must be converted into ammonia nitrogen before it can be absorbed and utilized by crop roots. the transformation process takes a long and short time due to different soil quality, water and temperature, and generally can be completed after 2 to 10 days. if irrigation and drainage is applied immediately after application or dryland is applied before heavy rain, urea will be dissolved in water and lost. In general, irrigation should be done 2-3 days after application in summer and autumn, and 7-8 days after application in winter and spring.

Fourth, it is not suitable to scatter on the surface. Urea is spread on the surface and can only be used after 4-5 days of transformation at room temperature. most of the nitrogen is easily volatilized in the ammoniation process, and the actual utilization rate is only about 30%. If it is applied in alkaline soil and soil with high organic matter content, nitrogen loss will be faster and more. And the shallow application of urea is easy to be consumed by weeds. The deep application of urea will melt fertilizer into the soil and make the fertilizer in the wet soil layer, which is beneficial to the exertion of fertilizer effect. Topdressing should be applied on the side of seedling or ditch on the side of seedling, and the depth should be about 10~15cm. In this way, urea is concentrated in the dense layer of root system, which is convenient for crop absorption and utilization. The experimental results show that deep application can increase the utilization rate of urea by 10% to 30% compared with shallow application.

Fifth, it should not be used too much. Urea has high nitrogen content and should not be applied too much, so as to avoid unnecessary waste and "fertilizer damage". Generally, 515kg / mu and 15kg / mu are applied in paddy field. If it is applied too much, it can not be absorbed by the soil before it is converted to ammonium bicarbonate, so it is easy to be leached by Rain Water and easy to hurt crops. At the same time, if urea is applied too much, most of it will be lost and enter the groundwater, which will lead to nitrogen pollution and nitrite deposition in the water body, which will seriously affect the safety of human beings and animals.

Sixth, it is not suitable for foliar spraying with high concentration. Among all the nitrogen fertilizers, urea is the most ideal foliar fertilizer. By spraying urea, the amount and speed of protein synthesis of crops are higher than that of other nitrogen fertilizers. However, when foliar spraying, the concentration of urea solution must not be too high, otherwise it will burn out the leaves and poison the plants. Usually the concentration of spraying corn, rice, etc., is 2%; the concentration of vegetables and melons is 0.5%-1.5%.

Seventh, it should not be applied too late. The application of urea too late is not conducive to the exertion of fertilizer efficiency, and it is easy to cause crops to be green and mature late, so it should be applied 4-7 days earlier than other nitrogen fertilizers.

Eighth, should not be applied to celery. Celery needs to apply a large amount of nitrogen fertilizer during the whole growth period, but not urea. Because topdressing urea will make celery fiber increase and thicken, plant aging, slow growth, bitter taste and poor quality. Wang Aiping