Fertilization with urea, how to use it correctly? What are the contraindications to use?

Urea, also known as carbaamide, is a white crystal, one of the simplest organic compounds, and currently the nitrogen fertilizer with the highest nitrogen content. As one of the neutral fertilizers, urea is suitable for a variety of soils and plants. It is a kind of chemical nitrogen fertilizer that is easy to preserve, easy to use, has little effect on soil destruction, and is currently used in large amounts.

Ammonia and carbon dioxide are used industrially to synthesize urea under certain conditions.

Urea has high nitrogen content, the effect is obvious after application, no ***, in addition to base fertilizer, top dressing, can also be top dressing outside the roots, deeply loved by the majority of farmers. However, if the application method is incorrect and the application time is not suitable, its utilization rate will be significantly reduced, and only 10% 20% can be used in severe cases. Planting is expensive and time-consuming, but the effect is not good, and it may also cause fertilizer damage and harm crops, so urea needs to be studied accurately and scientifically.

Urea is sprayed on the surface, after 4 to 5 days of conversion at room temperature, most of the nitrogen is volatile in the process of ammoniation, the general actual utilization rate is about 30%, sprayed in alkaline soil and soil with high organic matter content nitrogen loss is faster. As the most widely used nitrogen fertilizer, urea has a nitrogen content of up to 46%, but the utilization rate is not high, only about 30%.

Excess urea can lead to growth, deficiency, and even lodging loss. In order to improve the utilization rate and effect of urea, we have also taken many methods, it is known that urea only urea mold and digestive enzymes produce ammonia nitrogen and nitrate nitrogen are absorbed and utilized by crops, ammonia nitrogen is easy to volatilize into the air, and nitrate nitrogen penetrates below the root layer with water. However, we have a speed of absorption of crops, and the fertilizer shelf life is also short, and if we can't absorb it, it will be wasted.

Therefore, only by solving the urea conversion rate and giving crops enough time can the urea utilization rate be improved and the effect doubled. Scientists have come up with many ways to improve urea utilization. For example, making small particles of urea into large particles can reduce the rate of release and allow for a slow release.

Just like when we eat rock sugar, even if it's the same sugar, the large pieces dissolve more slowly than the small pieces, so the sugar water we suck for a longer time.

When urea is used as the base fertilizer, it needs to be combined with an appropriate amount of phosphorus and potassium fertilizer, and urea fertilizer needs to be applied deeply. Urea fertilizer as top dressing should pay attention to the time, urea fertilizer is mainly nitrogen fertilizer, to promote the growth of plant branches and leaves, flowering and fruiting period can not be applied in large quantities, responsible for affecting plant yield.

Use it according to the role and efficacy of urea, and understand the planting and fertilization of crops. Do not pee on the surface, nor can you use it with reactive fertilizers, pay attention to the method of urea, do not gather urea in the roots, pay attention to the amount of watering, and balance the fertilization technology, so as to ensure the correct use of urea.

Be sure to choose the right brand according to the variety of crops, pay attention to the ingredient ratio of urea, and pay attention to the time of use, which can be used as a base fertilizer, do not use urea when the temperature is relatively high or when it rains heavily, and do not use too much at one time.

The contraindication of this fertilizer is that it cannot be used too much, otherwise it is easy to burn the plant. Fertilizer should be applied according to the dosage of about 50 kg per mu.

The role of urea fertilizer

1. Adjust the amount of flowers. To overcome the apple tree.

In large and small years, in small years, 5 to 6 weeks after flowering (the critical period of apple flower bud differentiation, when the growth of new shoots is slow or stopped, and the nitrogen content of leaves is declining), foliar spraying urea aqueous solution, spraying twice in a row, can improve the nitrogen content of leaves, accelerate the growth of new shoots, inhibit the differentiation of flower buds, and make the flower amount of the big year suitable.

2. Thin flowers and fruits. The flower of the peach tree is more sensitive to urea but the response is more slow, therefore, urea is used abroad for peaches and nectarines.

The flower and fruit thinning test was carried out. The results showed that the flower and fruit thinning of peach and nectarine required a large concentration ( to show good effect, and the most suitable concentration was 8 12%, and the purpose of flower and fruit thinning could be achieved within 1 2 weeks after spraying. However, under different soil conditions, the response of different periods and different varieties needs to be further tested.

3. Rice seed production. in hybrid rice.

In seed production technology, in order to improve the outcrossing rate of the parent parent and increase the seed yield of hybrid rice or the number of sterile lines, erythoxin is generally sprayed with the female parent to reduce the degree of neck wrapping of the female parent or to make it completely withdrawn, or the parent is sprayed to regulate the growth of the two and synchronize the flowering period. Due to gibberellin.

**It is more expensive, and the cost of seed production is high. Urea was used instead of gibberellin for experiments, and urea was used at the peak of booting and the first panicle stage (20 heading), and the propagation effect was similar to that of gibberellin, and the plant height was not increased.

How to use:

1.Use in combination with other fertilizers.

Because urea is a nitrogen fertilizer.

Does not contain phosphorus and potassium.

Plant growth needs to be nutritionally balanced, so urea should be applied in conjunction with phosphate and potassium fertilizers. Thirty percent of urea is mixed with phosphorus and potassium fertilizer, then applied to the soil, and then the remaining urea is applied. The combination of three fertilizers can improve the utilization rate of urea.

2.Time for top dressing.

When using urea as top dressing, it should be used one week in advance. Because urea is an amide fertilizer, in order to be fully absorbed by plants, it must first be dissolved in water and then converted into ammonium carbonate during top dressing.

It is then adsorbed in the soil colloid, and this process takes about a week.

3.Urea is sprayed on the foliar surface.

Urea is less harmful to the leaves and is easily absorbed, if urea and potassium dihydrogen phosphate are sprayed on the foliar surface.

It can extend the life of functional leaves. To reduce damage to the leaves, urea with a lower biuret content should be used. Urea can be sprayed at 4 p.m. to allow the plants to absorb the fertilizer.

1. Do not mix with ammonium carbonate.

Once urea is applied to the soil, it is converted into ammonia before it can be absorbed by the crop, which is much slower in alkaline conditions than in acidic conditions. Ammonium carbonate reacts alkalinely when applied to the soil, and the pH value is. The mixed application of ammonium carbonate and urea in farmland will greatly slow down the conversion of urea into ammonia, which is easy to cause the loss and volatilization of urea.

Therefore, urea and ammonium carbonate should not be mixed or applied at the same time.

2. Avoid sprinkling on the surface.

Urea is sprinkled on the surface, at room temperature it takes 4 to 5 days to be utilized, most of the nitrogen is easy to volatilize in the process of ammoniation, the general actual utilization rate is only about 30%, if it is sprinkled in alkaline soil and soil with high organic matter content, the loss of nitrogen will be faster and more. Moreover, urea is shallow and easy to be consumed by weeds. Top dressing should be applied to the seedling side or dug or furrow applied on the seedling side, which is convenient for crop absorption and utilization.

Experiments have proved that deep application can increase the utilization rate of urea by 10% to 30% compared with shallow application.

3. Avoid seed fertilizer.

Urea in the production process, often produce a small amount of biuret, when the content of biuret more than 2%, it will poison seeds and seedlings, such urea into the seeds and seedlings, will denature the protein, affect the germination of seeds and seedling growth, so it is not suitable for seed fertilizer.

Fourth, do not irrigate immediately after application.

Urea is an amide nitrogen fertilizer, it needs to be converted into ammonia nitrogen in order to be absorbed and utilized by crop roots, the transformation process is different due to soil quality, moisture and temperature and other conditions, the time is long and short, generally after 2 10 days to complete, if the application is immediately irrigated and drained or dry land is applied before heavy rain, urea will be dissolved in water and lost. Generally, irrigation should be carried out 2 to 3 days after application in summer and autumn, and 7 to 8 days after application in winter and spring.

When applying urea or base fertilizer to crops, it is recommended to apply deeply, and cover the soil after deep application, which can greatly improve the loss and waste of urea, and greatly improve the utilization rate and fertilizer efficiency of urea.

Urea, the scientific name diammonium carbonate, has a nitrogen content between 44% and 46%, and biuret should be reduced.

At present, it is the fertilizer with the highest nitrogen content in China's solid ammonia fertilizer, the physical and chemical properties are relatively stable, the pure product is white or slightly yellow crystals or small particles, with anti-humidifiers, less hygroscopic, soluble in water, and neutral nitrogen fertilizer. The urine content is high, suitable for all kinds of soil and a variety of crops, and is most suitable for top dressing, especially the effect of root topdressing.

Urea is late when applied to the soil, and can only be absorbed and utilized by crops after it is converted into ammonium bicarbonate. Due to the process of transformation, the fertilizer efficiency is slower and is generally applied 4 to 6 days in advance.

At the same time, it is also required to apply deep covering soil, and do not irrigate immediately after the number of keys is applied, so as to prevent nitrogen from drenching deep and reducing fertilizer efficiency. When topdressing outside the root of urea, especially on the foliar surface, the nutrients in urea are absorbed quickly, the utilization rate is also high, and the yield increase effect is obvious.

When spraying urea, the concentration requirements are stricter, and the concentration of gramineae is generally about fruit trees, open-field vegetables, and greenhouse vegetables. For crops at the peak of growth, or for mature fruit trees, the concentration of urea can be appropriately increased.

Attention should be paid to the following problems in the application of urea: 1. Generally, it is not directly used as seed fertilizer. Because urea contains a small amount of biuret, generally less than 2%, biuret is harmful to seed germination and growth.

If you have to make seed fertilizer, you can separate the seeds and urea into the ground, and you must not use urea to soak or dress seeds. 2. When the content of biuret is higher, it cannot be used as topdressing outside the root.

3. After urea is converted into ammonium bicarbonate, it is easy to decompose and volatilize on calcareous soil, resulting in nitrogen loss, so it is necessary to apply deep covering.

First of all, urine must be fermented for a few days before it can be used! Because urine contains trace elements such as nitrogen, phosphorus, urea, creatinine, and uric acid, if used directly, it will burn the root system of plants.

Urine as a metabolite of the human body can be used as fertilizer, but now we are using water from the high brigade, itself lacks the necessary nutrients for plants, so it is recommended that the tap water is also placed for a few days and then mixed with urine to water the plants, so that those delicate plants will not be over-fertilized and cause harm!

It is best to leave the urine to ferment for more than two or three days and mix it with three to five times the water, so that the urea in the urine can be diluted! Thus achieving normal fertilization.

The correct fertilization method of urea starts from balanced fertilization, appropriate topdressing, deep soil covering, and foliar spraying.

1. Balanced fertilization.

Urea fertilizer is a pure nitrogen fertilizer, rich in phosphorus and potassium elements, as a base fertilizer should be used with organic fertilizer to meet the nutrients required by crops in the growth cycle, to avoid the use of a single fertilizer to grow or grow poorly, and according to the corresponding proportion of the allocation of Wu Shu.

2. Appropriate follow-up.

Urea fertilizer is rich in nutrients, but the crop has a certain critical period for the absorption of nutrients, so there will be a weak growth when there is a lack of fertilizer, but too much dosage will also cause fertilizer damage, it is best to apply urea fertilizer during the crop growth period, when it is in the critical period of nutrition, it plays a role in improving quality and increasing yield.

3. Deep soil covering.

When urea fertilizer is deeply buried in the soil, it is suitable for corn, wheat and other crops and cabbage and other vegetable crops in the field, it is best to dig a 15 cm hole at a distance of 20 cm from the crop, and apply the urea fertilizer into the hole pit to cover the thick soil, and water properly when it is too dry.

4. Spray foliage.

Urea fertilizer can be soluble in water, has a certain diffusivity, is easy to be absorbed when used for root topdressing, and has almost no damage to the leaves, suitable for the vigorous period of crop growth, combined with the control of pests and diseases for spraying, foliar topdressing is best carried out after 16 o'clock in the afternoon, at this time the transpiration is weakened, the stomata of the leaves are opened, and the nutrients can be well absorbed.

The effect of urea on plants

1. Adjust the amount of flowers.

Urea can regulate the lack of flower cavity in plants, the most typical example of which is the problem of apple size. When the apple encounters a small year, spray urea solution to the foliar surface 5-6 weeks after flowering, and spray twice in a row to increase the nitrogen content of the leaves, which can accelerate the growth of new shoots and inhibit the differentiation of flower buds.

2. Thin flowers and fruits.

Spraying plants with a certain concentration of urea can also play a role in thinning flowers and fruits. According to foreign experiments on peaches and nectarines with urea, after spraying urea with a concentration greater than 1-2 weeks, the purpose of thinning flowers and fruits can be achieved, but this effect is also different in different regions, and the appropriate concentration needs to be adjusted according to different varieties.

3. Pest control.

Urea also has the effect of preventing and controlling plant diseases and insect pests, with urea, laundry detergent, water in a ratio of 4:1:400 stirring and mixing after spraying plants, you can control fruit trees, vegetables, cotton and other plants on aphids, red spiders, cabbage insects and other pests, the sterilization effect of this mixed solution is more than 90%.

The main role of urea is to supplement nitrogen fertilizer, and the main role of nitrogen fertilizer is to strengthen the leaves, make the leaves dark green and healthy!

If you apply it, the principle is to apply thin fertilizer diligently, fertilizing a large area is not as good as a line, root application and hole application are the best, and the soil should be kept moist after application!

If the soil is dry after application, it will not take long for the soil to be solidified, which is also the reason why the soil with chemical fertilizer is easy to compact!