What should be paid attention to when applying urea?

What should be paid attention to when applying urea? There are no netizens who know to help introduce that urea is an indispensable fertilizer in agricultural production, but improper operation of urea in the application process will cause the opposite effect, so the farming net has sorted out the unsuitable application method of urea. The following is listed in detail for netizens' reference. First, urea cannot be mixed with alkaline fertilizer or applied at the same time, because urea must be converted into ammonia nitrogen to produce fertilizer effect, and under alkaline conditions, most of the nitrogen will be volatilized into ammonia. therefore, urea cannot 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. Note that urea is not suitable for seed mixing fertilizer, because urea often produces a small amount of biuret in the production process, 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 denature protein and affect seed germination and seedling growth, so 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, it should not be watered immediately after the application of urea, because 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 conditions such as soil quality, water and temperature. Generally, it can be completed after 2-10 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, urea should not be spread on the surface, because 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 spread 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. Note that the amount of urea should not be too large, because the nitrogen content of urea is high, and the application amount should not be too large, 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. Note 6, urea foliar spraying concentration should not be too high, because in all nitrogen fertilizer, 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%. Note that urea should not be applied alone, because the effective component of urea is nitrogen, the nutrient is single, and the growth and development of crops need a variety of nutrients. Therefore, urea should be applied in conjunction with organic fertilizer, phosphorus and potassium fertilizer to meet the needs of crops for various nutrients. Moreover, the reasonable mixed application of urea, organic fertilizer and chemical fertilizer can effectively improve its utilization rate. For example, the mixed application of urea and calcium superphosphate can transform unstable ammonium bicarbonate into stable ammonium phosphate, so that the natural volatilization of nitrogen is greatly reduced. The mixed application of urea and organic fertilizer can not only produce organic acids in the process of fermentation, but also accelerate the transformation and decomposition of urea, which can be quickly absorbed by crops and improve the utilization rate of urea. Note 8. Urea should not be applied to celery, because 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. Celery is suitable to apply ammonium bicarbonate, ammonia and mature organic fertilizer to improve the quality. Effects of nitrogen, phosphate and potash fertilizers on large granular urea