The role and efficacy of agricultural urea are regulating flower volume, thinning flowers and fruit, rice seed production, and preventing insect pests. The floral organs of peach trees and other plants are more sensitive to urea, and the effect of thinning flowers and fruit can be achieved after urea is applied. The application of urea can increase the nitrogen content of plant leaves, speed up the growth of new shoots, inhibit flower bud differentiation, and control the number of flower buds. Urea is a neutral fertilizer, it can be used as fertilizer when facing different soils and plants.

The main functions of nitrogen fertilizer are: increase the total biomass du and economic output; improve the nutritional value of agricultural products, especially increase the protein content of dao in seeds and increase the nutritional value of food. Nitrogen is the main component of protein in crops. Without nitrogen, nitrogen white matter cannot be formed, and without protein, there can be no various life phenomena.

How to use urea:

1. Balanced fertilization

Urea is a pure nitrogen fertilizer and does not contain the phosphorus and potassium in the large elements necessary for crop growth. Therefore, when making top dressing, you should use formula fertilization technology on the basis of soil testing and chemical analysis to balance nitrogen, phosphorus, and potassium fertilizers. First, combine all the phosphorus and potassium fertilizers and some (about 30%) nitrogen fertilizer required for the whole growth period of the crops with soil preparation and bottom application.

Then put about 70% of the remaining nitrogen fertilizer as topdressing, among which about 60% of the crop’s critical period and maximum efficiency period are topdressing, and about 10% of the latter. Only when the three fertilizers of nitrogen, phosphorus and potassium are properly combined and applied scientifically, can the utilization rate of topdressing urea be improved.

2. Topdressing in appropriate time

Some unreasonable fertilization can often be seen in agricultural production: every year when the wheat returns to green after the beginning of spring, farmers use the opportunity of pouring the green water to spray or wash urea into the wheat field; in the corn seedling period, farmers spray urea before the rain Into the field; during the seedling stage of cabbage, urea should be flushed with water; during the seedling stage of tomato, urea should be flushed with water.

Applying urea in this way, although the fertilizer is used, the waste is serious (ammonia volatilizes and the urea particles are lost with the water), and it will also cause excessive nutrient growth, late lodging of wheat and corn, tomato “blowing”, and delayed cabbage filling And other bad phenomena occur. Each crop has a specific critical period for the absorption of nitrogen, phosphorus, and potassium (that is, the period when the crop is particularly sensitive to the absorption of certain elements).

Lack of fertilizer (nitrogen, phosphorus, potassium) during this period will reduce crop yield and quality, which has a huge impact. Even if sufficient fertilizer is applied later, the impact on crop yield and quality cannot be reversed. In addition, there is a maximum efficiency period, that is, during this period, fertilizing crops can obtain higher yields, and crops have the highest fertilizer utilization efficiency.

From the above analysis, it can be seen that only topdressing in the critical period and maximum efficiency period of crops can improve the utilization rate of fertilizers and achieve high yield and quality of crops.

3. Topdressing timely

Urea is an amide fertilizer, which needs to be converted into ammonium carbonate to be adsorbed by soil colloids and then absorbed by crops. This process takes 6 to 7 days. During this process, urea is first dissolved by the water in the soil and then slowly converted into ammonium carbonate.

Therefore, when urea is applied as top dressing, it should be applied about 1 week before the critical period of crop nitrogen demand and the maximum fertilizer efficiency period, not too early or too late.

4. Deep soil covering

Improper application methods can easily cause nitrogen loss such as urea loss with water and ammonia volatilization, waste fertilizer, consume labor, and greatly reduce the utilization rate of urea. The correct application method is: apply on corn, wheat, tomato, cabbage and other crops. Dig a hole 15-20 cm deep at a distance of 20 cm from the crop. After applying fertilizer, cover it with soil. The soil is not too dry. In case of watering after 7 days.

When the soil is severely dry and needs watering, water should be lightly watered once, not flooded with large water to prevent urea from losing with water. When applying on rice, it should be spreading. Keep the soil moist after application. Do not irrigate within 7 days. After the fertilizer is fully dissolved and adsorbed by the soil, you can pour small water once, and then dry it for 5-6 days.

5. Foliar spray

Urea is easily soluble in water, has strong diffusibility, is easily absorbed by leaves, and has little damage to leaves. It is suitable for extra-root topdressing and can be sprayed on foliage combined with crop pest control. But when doing extra-root top dressing, urea with a biuret content of not more than 2% should be selected to prevent damage to the leaves. The concentration of extra-root topdressing varies from crop to crop. The spraying time should be after 4 pm, when the amount of transpiration is small, and the stomata of the leaves are gradually opened, which is conducive to the full absorption of the urea aqueous solution by the crop.

The use of urea is contraindicated:

1. Avoid mixing with ammonium bicarbonate

After urea is applied to the soil, it must be converted into ammonia before it can be absorbed by crops, and its conversion rate is much slower under alkaline conditions than under acidic conditions. After ammonium bicarbonate is applied to the soil, it shows an alkaline reaction, with a pH value of 8.2 to 8.4. The mixed application of ammonium bicarbonate and urea in farmland will greatly slow down the conversion of urea into ammonia, which will easily cause the loss of urea and volatilization loss. Therefore, urea and ammonium bicarbonate should not be mixed or applied simultaneously.

2. Avoid surface spreading

Urea is sprayed on the ground. It takes 4 to 5 days to transform at room temperature before it can be used. Most of the nitrogen is easily volatilized during the ammoniating process. Generally, the actual utilization rate is only about 30%. If it is in alkaline soil and organic matter content When spreading in high soil, nitrogen loss will be faster and more.

And shallow application of urea, easy to be consumed by weeds. Urea is applied deeply to melt the fertilizer in the soil, so that the fertilizer is in the moist soil layer, which is conducive to the effect of fertilizer. For top dressing, it should be applied on the side of the seedling in the hole or in the furrow, and the depth should be about 10-15cm. In this way, urea is concentrated in the dense root layer, which is convenient for crops to absorb and utilize. Tests have shown that deep application can increase the utilization rate of urea by 10%-30% than shallow application.

3. Avoid making seed fertilizer

In the production process of urea, a small amount of biuret is often produced. When the content of biuret exceeds 2%, it will be toxic to seeds and seedlings. Such urea will enter seeds and seedlings, which will denature protein and affect seed germination and Seedlings grow, so it is not suitable for seed fertilizer. If it must be used as a seed fertilizer, avoid contact between seed and fertilizer, and control the amount.

4. Do not irrigate immediately after application

Urea is an amide nitrogen fertilizer. It needs to be converted into ammonia nitrogen before it can be absorbed and utilized by crop roots. The conversion process varies depending on the soil quality, moisture, temperature and other conditions. It takes 2 to 10 days to complete. If irrigated and drained immediately after application or applied in dry land before heavy rain, urea will be dissolved in the water and lost. Generally, water should be irrigated 2 to 3 days after application in summer and autumn, and 7 to 8 days after application in winter and spring.