Seven points for attention in urea application

1. 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.

Third, irrigation immediately after it is not suitable for 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 or short time due to different soil quality, water and temperature, and generally can be completed after 2 to 10 days. if irrigation 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 spread 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 the seedling or ditch on the side of the seedling, and the depth should be 10-15 cm. The experiment shows that the deep application of urea in the dense layer of the root system is convenient for the absorption and utilization of crops, and the utilization rate can be increased by 10% and 30% compared with shallow application.

Fifth, do not use too much

The nitrogen content of urea is high, generally applying 515kg per mu in field and 1520kg per mu in paddy field. Too much application can not be absorbed by the soil before it is transformed into ammonium bicarbonate. On the one hand, it is easy to be leached by Rain Water, injuring crops, on the other hand, it will enter the groundwater, resulting in nitrogen pollution in the water body, resulting in nitrite deposition, seriously affecting the safety of human and livestock.

Sixth, it is not suitable for high concentration foliar spraying in all 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.

7. Do not apply it too late

Applying urea too late is not conducive to the exertion of fertilizer effect, 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.