The correct use of urea
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Urea has a high nitrogen content, and the application rate should not be too large, so as to avoid unnecessary waste and "fat damage".
Many farmers in the fruit-producing areas have used urea in large quantities, causing dead trees, and the consequences are very serious.
Urea has high nitrogen content, and has obvious effects after application. It has no side effects. It can be used as base fertilizer, top dressing, and root dressing. It is deeply loved by the masses of farmers. However, if the application method is not correct and the application period is not suitable, the utilization rate will be significantly reduced. In severe cases, the utilization rate is only 10% to 20%. The growers have spent both money and time, but they have not received the results they deserve. They may even cause “fertilization†and harm crops. Therefore, it is necessary to apply urea correctly and scientifically.
Ten rubies in urea use:
Mixing with ammonium bicarbonate After urea is applied to the soil, it must be converted into ammonia to be absorbed by the crop. The conversion rate is much slower under alkaline conditions than under acidic conditions. The ammonium nitrate is alkaline after being applied to the soil, and the pH is 8.2 to 8.4. Mixed application of ammonium bicarbonate and urea in farmland will greatly reduce the rate of conversion of urea into ammonia, which will easily lead to loss of urea and loss of volatilization. Therefore, urea and ammonium bicarbonate are not suitable for mixing or simultaneous application.
The second place is to apply urea on the surface, and it can be used after 4 to 5 days of transformation at room temperature. Most of the nitrogen is easily volatilized during the ammoniation process. The actual utilization rate is only about 30%. In the soil with high soil and organic matter content, the loss of nitrogen will be faster and more. Moreover, the shallow application of urea is easy to be consumed by weeds. Deep application of urea, melt fertilizer in the soil, so that the fertilizer is in the moist soil layer, is conducive to the performance of fertilizer. For the topdressing should be applied to the seedlings or the ditch on the side of the seedling, the depth should be about 10~15cm. In this way, urea is concentrated in the dense layer of the roots, which is convenient for crops to be absorbed and utilized. Tests have shown that deep application can increase the utilization rate of urea by 10% to 30%.
In the production process, a small amount of biuret is often produced. When the biuret content exceeds 2%, the seed and seedlings are poisoned. Such urea enters the seed and the seedling, which denatures the protein. It affects seed germination and seedling growth, so it is not suitable for seed fertilizer. If it must be applied as a seed fertilizer, avoid contact with seeds and fertilizers, and control the dosage.
Immediately after the application of the four bogey, the urea is an amide nitrogen fertilizer, which can be converted into ammonia nitrogen to be absorbed and utilized by the crop roots. The transformation process is different due to different soil, water and temperature conditions, and the time is long and short, generally after 2 to 10 The day can be completed. If the irrigation is done immediately after application or the dry land is applied before heavy rain, the urea will dissolve in the water and be lost. Generally, summer and autumn seasons should be watered 2 to 3 days after application, and water should be watered after 7 to 8 days after application.
When the five bogey and the alkaline fertilizer are mixed or simultaneously applied, the urea must be converted into ammonia nitrogen to produce fertilizer effect. Under the alkaline condition, most of the nitrogen will become ammonia gas, so the urea cannot It is mixed with or applied simultaneously with alkaline fertilizers such as lime, grass ash, calcium magnesium phosphate fertilizer. Generally speaking, in summer and autumn, urea and alkaline fertilizer should be staggered for 3 to 4 days, and winter and spring should be staggered for 7 to 8 days.
Six bogey on celery celery needs to apply a large amount of nitrogen fertilizer during the whole growth period, but not urea. Because of the application of urea, the celery fiber is thicker and thicker, the plant is aging, the growth is slow, and the taste is bitter and the quality is inferior. Celery is suitable for the application of ammonium bicarbonate, ammonia and organic fertilizers, which is beneficial to improve quality.
The amount of the seven bogey is too large. The nitrogen content of urea is high, and the application amount should not be too large, so as to avoid unnecessary waste and "fat damage". Generally, 5 to 15 kg per mu is applied, and 15 to 20 kg per acre is applied to the paddy field. Excessive application, can not be absorbed by the soil before conversion to ammonium bicarbonate, easily leached by rain, and easily damage crops. At the same time, too much urea is applied, most of which is lost, and entering the groundwater will cause nitrogen pollution in the water body, causing the deposition of nitrite, which seriously affects the safety of humans and animals.
Eight bogey high concentration foliar application In all nitrogen fertilizers, urea is the most ideal foliar fertilizer. Spraying urea, the amount and speed of protein synthesis in crops exceeds that of other nitrogen fertilizers. However, when the foliar spray is applied, the concentration of the urea solution should not be too large, otherwise the leaves will be burned and the plants will be poisoned. Generally, the concentration of corn, wheat, rice and cotton is 2%; vegetables and fruits are suitable for 0.5-1%; fruit trees are preferably 0.5-1.5%.
Jiuji application is too late. Urea application is too late, which is not conducive to the effect of fertilizer efficiency. It is easy to cause crops to be late and ripe, so it should be applied 4 to 7 days earlier than other nitrogen fertilizers.
Ten bogey single application The active ingredient of urea is nitrogen, nutrients are single, and crop growth and development requires a variety of nutrients. Therefore, urea should be applied in combination with organic fertilizers and phosphorus and potassium fertilizers to meet the needs of crops for various nutrients. Moreover, urea can be effectively mixed with organic fertilizer and chemical fertilizer, and its utilization rate can be effectively improved. For example, when urea is mixed with superphosphate, the unstable ammonium hydrogencarbonate can be converted into stable ammonium phosphate, so that the natural volatilization of nitrogen is greatly reduced. Urea is mixed with organic fertilizer to produce organic acid during fermentation. It can also accelerate the conversion and decomposition of urea, and is quickly absorbed by crops to improve the utilization of urea.
Second, the correct use of urea 1, balanced fertilization of urea is a pure nitrogen fertilizer, does not contain the phosphorus and potassium in a large number of elements necessary for crop growth, therefore, when doing topdressing should be based on soil testing, using formula fertilization technology Balance the application of nitrogen, phosphorus and potassium fertilizers. First, all the phosphorus and potassium fertilizers required for the whole growth period of the crop and some (about 30%) of the nitrogen fertilizer should be combined with the ground. The remaining 70% of the nitrogen fertilizer (which can be used as urea) is applied as a top dressing. The critical period of the fertilizer and the maximum efficiency period of the crop are about 60%, and the late stage is about 10%. Only the nitrogen, phosphorus and potassium fertilizers can be combined and scientifically applied to improve the utilization rate of urea.
2. Appropriate topdressing In the agricultural production, some unreasonable fertilization can often be seen: every year after the spring, the wheat is returned to the green period, and the farmers can pour or flush the urea into the wheat field by pouring back the green water; the corn seedling period, the farmers The urea is sprinkled into the field before the rain; the urea is washed with the watering in the seedling stage; the tomato is flushed with urea when the seedling is watered. This applies urea, although the fertilizer is used, but the waste phenomenon is serious (ammonia volatilization, urea granules are lost with water), and it will lead to excessive nutrient growth, wheat, corn late lodging, tomato "blowing", cabbage delay Other undesirable phenomena occur.
Each crop has a specific critical period for the absorption of nitrogen, phosphorus and potassium (ie, the period during which the crop is particularly sensitive to the absorption of certain elements). In this period, the lack of fertilizer (nitrogen, phosphorus, potassium), the yield of crops is reduced, the quality is reduced, and the impact is huge. 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, the fertilized crops can obtain higher yields in this period, and the crops have the highest utilization efficiency of fertilizers. It can be seen from the above analysis that only when the crop is in the critical period of nutrition and the maximum efficiency period, the utilization rate of fertilizer can be improved, and the crop can reach high yield and high quality.
When urea is used as top dressing, it should be applied one week before the critical period of nitrogen demand and maximum efficiency of crops. Different crops require different fertilizer critical periods and maximum efficiency periods, and should be treated differently and rationally. For example, the critical period of nitrogen demand for wheat, corn and other gramineous crops is in the tillering stage, the ear differentiation stage, and the cotton in the bud and bell stage. The maximum efficiency of nitrogen is from jointing to booting stage, rice is tillering to jointing stage, corn is in the big bell stage, tomato is in the fruiting stage, cabbage is in rosette stage, sunflower is in flower bud stage, soybean is in early flowering stage, etc.
3. Appropriate topdressing urea is an amide fertilizer, which needs to be converted into ammonium carbonate adsorbed by soil colloid and then absorbed by crops. This process takes 6-7 days. During this period, urea is first dissolved by 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 nitrogen demand and the maximum efficiency of fertilizer, not too early or too late.
4, deep application of soil application method is not easy to cause urea loss with water, ammonia volatilization and other nitrogen loss phenomenon, wasting fertilizer, labor, and greatly reduced the utilization of urea.
The correct application method is: apply on crops such as corn, wheat, tomato, cabbage, etc., should dig a hole of 15-20 cm deep at a distance of 20 cm from the crop, apply the fertilizer to the soil and cover it with soil, and the soil is not too dry. In the case of watering after 7 days. When the soil is seriously dry and needs to be watered, it should be lightly poured once in small water. It should not be flooded with large water to prevent urea from being lost with water. When applied on rice, it should be applied. After application, the soil should be kept moist. It can not be watered within 7 days. After the fertilizer is fully dissolved and adsorbed by the soil, it can be poured once with water and then aired for 5-6 days.
5, foliar application Urea is soluble in water, diffusive, easy to be absorbed by the leaves, less damage to the leaves, suitable for root dressing, combined with crop pest control for foliar application. However, when topdressing is done outside the root, urea with a biuret content of not more than 2% should be selected to prevent damage to the leaves. The concentration of top dressing varies from crop to crop. The spraying time should be after 4 pm, at this time, the transpiration amount is small, and the leaf surface pores are gradually opened, which is beneficial to the full absorption of the urea aqueous solution by the crop.
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