Can urea be used as foliar fertilizer? (How many times should urea be diluted to be used for foliar spraying?)

The effect of fertilizer application on crops depends on the utilization rate and the amount of loss. The lower the utilization rate, the greater the loss and the worse the effect of fertilization.

For gray soil, the utilization rate of nitrogen fertilizer is only about 30%. The main reason for its low utilization rate is the volatilization of ammonium nitrogen and the leaching and denitrification of nitrate nitrogen.

Urea is an amide nitrogen fertilizer and a synthetic organic nitrogen fertilizer that can be applied as a basal fertilizer, as a topdressing, or as a foliar spray .

In terms of the effects of foliar spraying of urea and soil application of urea, foliar application can indeed improve the effect, but there is no problem of doubling the effect .

First, although foliar spraying of urea is more easily absorbed and utilized by leaves, the amount used is too small to meet the crop's demand for nitrogen fertilizer throughout its entire growth period, so it is impossible to have a very good effect.

Foliar fertilization is only used in emergencies or when crops are deficient in nutrients. It is an auxiliary fertilization method and cannot completely replace soil fertilization.

It can be said that soil fertilization is absolutely essential, while foliar fertilization is optional. Can they be compared?

Second, although foliar spraying of urea can improve its utilization rate, it is affected by factors such as natural conditions, urea variety, and concentration.

The time for spraying foliar fertilizers such as urea should be appropriate, and it should be around the evening when it is sunny and windless, or on cloudy days. This will maximize the time for the fertilizer liquid to stay on the leaves for a while, thereby extending the absorption time of the leaves and improving the utilization rate.

If the time we choose is under high temperature and scorching sun, or the concentration is too high, it is easy to cause leaf burns and the utilization rate will be greatly reduced.

The concentration of urea for foliar spraying is generally 0.5%-1%, with a maximum of 2%. 2% can be used for field crops such as wheat, corn, rice, and cotton.

Urea itself contains biuret components. If it exceeds 2%, it cannot be used as foliar fertilizer, otherwise it will become toxic and its utilization rate will be greatly reduced. However, application in the soil will have little effect.

Third, in terms of the way crops absorb nutrients, they mainly rely on the root system. Although nutrients can also be absorbed through leaves and stems, it is only an auxiliary absorption method.

The nutrients absorbed by crop leaves and stems are similar to those absorbed by roots, and can all be converted and utilized within the crop body. However, when the crop is growing vigorously, the leaves absorb nutrients more intensely, and less at other times.

Especially when the soil is well-nourished, spraying urea on the leaves will have the opposite effect, causing excess nitrogen and leggy growth. The effect will decrease instead of increase.

For example, in medium fertility soil, 20 kg of urea per mu can meet the high yield requirements of corn. We can apply 1/3 as base fertilizer and 2/3 as topdressing, or apply it all at once during the flaring period. Based on a 30% utilization rate, 6 kg of urea can be used by corn.

When we spray urea, even if its utilization rate is 100%, based on a concentration of 2%, 150 kilograms of water are sprayed per acre, and 1.5 kilograms of urea are used, then we have to spray 4 times to meet the needs of corn.

I want to ask you, are you tired? You may not be able to meet the requirements of corn even if you try your best, because it still has the problem of peak fertilizer demand. When the demand is the highest, we can't meet the requirements by spraying urea on the leaves, and eventually the yield will be reduced due to nitrogen deficiency. What effect can we talk about? It's a thankless job.

Therefore, although spraying urea on leaves can improve its utilization rate, that is because the amount used is small and there is sufficient water, so there is no problem of doubling the effect.

If we can have such enough water, we can use it to drip urea. The utilization rate will definitely be greatly improved and the effect will be really good.

How to improve the effect of urea application?

First, urea itself has a certain degree of toxicity. Excessive application will affect seed germination and seedling growth, so it is generally not suitable for use as seed fertilizer and seedling fertilizer.

Second, determine the amount of fertilizer based on soil fertility, and try to apply fertilizer during the crop's peak fertilizer demand period or growth period.

Third, apply the fertilizer deeply and cover the soil, preferably below 10 cm, in a moist soil layer, which is conducive to transformation, reduces volatilization, and improves utilization rate.

Fourth, apply it in advance. Because crops can only absorb a limited amount of urea directly, it must first be converted into ammonium carbonate before it can be absorbed in large quantities, which takes some time. Therefore, it must be applied a few days earlier than other nitrogen fertilizers, about 7 days earlier.

Fifth, urea is a neutral fertilizer and should not be mixed with alkaline fertilizers to avoid reducing the fertilizer efficiency.

Sixth, it is not advisable to water immediately after applying urea, otherwise it will cause loss.

Seventh, when spraying urea on leaves, pay attention to the concentration, spraying time, and biuret.

In short, the effect of applying fertilizers such as urea is closely related to its utilization rate. How to improve the utilization rate of fertilizers and minimize losses is the goal of increasing crop yields and achieving higher efficiency.

Therefore, reasonable fertilization or coordinated fertilization is the key. Foliar spraying cannot double the effect, but it can improve the utilization rate.