8 wrong ways to use urea - have you fallen into any of them?

Urea is popular with farmers because of its high nitrogen content, long-lasting fertility and ease of use. However, to give full play to the role of urea, you need to master the correct method of use, and pay attention to the following 8 points during use:

1. Avoid mixing or applying it together with alkaline fertilizers.

After application, urea must be converted into ammoniacal nitrogen before it produces a fertilizing effect, and under alkaline conditions most of the nitrogen in ammoniacal nitrogen will turn into ammonia gas and volatilize away, so urea cannot be mixed or applied together with alkaline fertilizers such as lime, plant ash, and calcium magnesium phosphate fertilizer. Generally speaking, in summer and autumn, urea and alkaline fertilizers should be applied 3-4 days apart, and in winter and spring they should be applied 7-8 days apart.

2. Avoid using it as a seed dressing fertilizer.

During production, urea often produces a small amount of biuret. When the biuret content exceeds 2%, it will poison seeds and seedlings. When such urea enters seeds and seedlings, it will denature proteins and affect seed germination and seedling growth, so it is not suitable as a seed fertilizer. If it must be applied as a seed fertilizer, contact between seeds and fertilizer should be avoided and the amount used should be controlled.

3. Avoid irrigating immediately after application.

Urea is an amide-form nitrogen fertilizer. It must be converted into ammoniacal nitrogen before it can be absorbed and used by crop roots. The conversion process varies in duration depending on soil quality, moisture and temperature, and generally takes 2-10 days to complete. If irrigation or drainage is carried out immediately after application, or if it is applied on dry land before heavy rain, the urea will dissolve in water and be lost. In winter and spring, water should be applied 7-8 days after application, and in summer and autumn, water can only be applied 2-3 days after application.

4. Avoid broadcasting urea on the soil surface.

When broadcast on the surface, at room temperature it takes 4-5 days of conversion before it can be used, and most of the nitrogen is likely to volatilize during ammonification. Generally, the actual utilization rate is only about 30%. If broadcast on alkaline soil and soil with high organic matter content, the loss of nitrogen will be faster and greater. In addition, shallow application of urea makes it easy for weeds to consume it, while deep application of urea blends the fertilizer into the soil, keeping the fertilizer in a moist soil layer, which is conducive to giving play to its fertilizing effect. As a topdressing, it should be applied in holes beside the seedlings, or in furrows at the side of the seedlings, at a depth of about 10-15 cm. In this way, urea is concentrated in the dense root layer, making it easy for crops to absorb and use. Experiments have shown that deep application can increase the utilization rate of urea by 10%-30% compared with shallow application.

5. Avoid using too large an amount.

Urea has a high nitrogen content, and the application amount should not be too large, so as to avoid unnecessary waste and “fertilizer damage”. Generally, 15-20 kg is applied per mu. If applied excessively, it cannot be absorbed by the soil before being converted into ammonium bicarbonate, is easily leached away by rainwater, and easily harms crops. At the same time, if too much urea is applied, most of it will be lost into groundwater, which will lead to nitrogen pollution of water bodies, cause the deposition of nitrites, and seriously affect the safety of humans and livestock.

6. Avoid high-concentration foliar spraying.

Among all nitrogen fertilizers, urea is the most ideal foliar fertilizer. The amount and speed of protein synthesis by crops sprayed with urea exceed those of other nitrogen fertilizers. However, when spraying on leaves, never use too high a concentration of urea solution, otherwise it will burn the leaves and also poison the plants. Usually, the suitable concentration for spraying wheat and corn is 2%, and for vegetables and melons it is 0.5%-1.5%.

7. Avoid applying too late.

Applying urea too late is not conducive to giving play to its fertilizing effect and easily causes crops to remain green and ripen late, so generally it should be applied 4-7 days earlier than other nitrogen fertilizers.

8. Avoid applying it to celery.

Celery needs a large amount of nitrogen fertilizer as topdressing throughout its growth period, but urea must not be applied. This is because topdressing with urea will increase the fiber in celery and make it coarser, and the plant will age and grow slowly. It also tastes bitter when eaten and has poor quality. Celery is suitable for application of ammonium bicarbonate, ammonia water and decomposed organic fertilizer, which helps improve quality.