Urea, also known as carbinamide, is a white crystal that is one of the simplest organic compounds and is currently the nitrogen with the highest nitrogen content. As a neutral fertilizer, urea is suitable for a variety of soils and plants. It is easy to store, easy to use, and has little effect on soil destruction. It is a chemical nitrogen fertilizer that is currently used in large quantities. Industrially, ammonia and carbon dioxide are used to synthesize urea under certain conditions.
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 "fertilizer damage" and harm crops. Therefore, it is necessary to properly and scientifically apply urea.
The following contraindications need to be remembered 1. 1. Avoid 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.
2. The second place is to apply urea on the surface, and it can be used after 4 to 5 days of conversion at room temperature. Most of the nitrogen is easily volatilized during the ammoniation process. The actual utilization rate is only about 30%. When applied in alkaline soils and soils with high 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%.
3. Three bogey as fertilizers in the production process, often produce a small amount of biuret, when the biuret content exceeds 2%, it will poison the seeds and seedlings, such urea will enter the seeds and seedlings, it will make Protein denaturation 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.
4. Immediately after application, the urea is amide-type nitrogen fertilizer, which is 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. It can be completed in ~10 days. 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.
5. Five bogey and alkaline fertilizer mixed application or simultaneous application of urea must be converted into ammonia nitrogen to produce fertilizer effect, while ammonia nitrogen under alkaline conditions, most of the nitrogen will become ammonia gas volatilization, so Urea cannot be mixed or applied simultaneously with alkaline fertilizers such as lime, grass ash, calcium magnesium phosphate. Generally speaking, in summer and autumn, urea and alkaline fertilizer should be staggered for 3 to 4 days, and should be staggered for 7 to 8 days in winter and spring. 6. Six taboos should be applied to celery and celery should be applied with a large amount of nitrogen fertilizer during the whole growth period, but No urea can be applied. 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 ammonium bicarbonate, ammonia water and organic fertilizer, which is beneficial to improve the quality. 7. The amount of urea is too large. The nitrogen content of urea is high, and the application rate 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. 8. Eight high-concentration foliar sprays are applied to 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%.
9. Jiuji application is too late. Urea application is too late, which is not conducive to the exertion 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.
10. 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.
The correct use of urea 1. Balanced fertilization: Urea is a pure nitrogen fertilizer, which does not contain phosphorus and potassium in a large number of elements necessary for crop growth. Therefore, based on soil testing, formula fertilization should be used when topdressing is performed. 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 application: In the agricultural production, some unreasonable fertilization can be seen: the wheat is returned to the green after the spring, and the farmers can pour or flush the urea into the wheat field by pouring back the green water; Farmers sprinkle urea into the field before the rain; the cabbage is washed with water by the watering of the cabbage seedling; the tomato is flushed with urea when it is watered during the seedling stage. 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. Timely topdressing: Urea is an amide fertilizer, which needs to be converted into ammonium carbonate adsorbed by soil colloids 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 carbonic acid. Ammonium, 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: improper application method is 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 spray: 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.
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 "fertilizer damage" and harm crops. Therefore, it is necessary to properly and scientifically apply urea.
The following contraindications need to be remembered 1. 1. Avoid 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.
2. The second place is to apply urea on the surface, and it can be used after 4 to 5 days of conversion at room temperature. Most of the nitrogen is easily volatilized during the ammoniation process. The actual utilization rate is only about 30%. When applied in alkaline soils and soils with high 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%.
3. Three bogey as fertilizers in the production process, often produce a small amount of biuret, when the biuret content exceeds 2%, it will poison the seeds and seedlings, such urea will enter the seeds and seedlings, it will make Protein denaturation 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.
4. Immediately after application, the urea is amide-type nitrogen fertilizer, which is 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. It can be completed in ~10 days. 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.
5. Five bogey and alkaline fertilizer mixed application or simultaneous application of urea must be converted into ammonia nitrogen to produce fertilizer effect, while ammonia nitrogen under alkaline conditions, most of the nitrogen will become ammonia gas volatilization, so Urea cannot be mixed or applied simultaneously with alkaline fertilizers such as lime, grass ash, calcium magnesium phosphate. Generally speaking, in summer and autumn, urea and alkaline fertilizer should be staggered for 3 to 4 days, and should be staggered for 7 to 8 days in winter and spring. 6. Six taboos should be applied to celery and celery should be applied with a large amount of nitrogen fertilizer during the whole growth period, but No urea can be applied. 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 ammonium bicarbonate, ammonia water and organic fertilizer, which is beneficial to improve the quality. 7. The amount of urea is too large. The nitrogen content of urea is high, and the application rate 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. 8. Eight high-concentration foliar sprays are applied to 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%.
9. Jiuji application is too late. Urea application is too late, which is not conducive to the exertion 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.
10. 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.
The correct use of urea 1. Balanced fertilization: Urea is a pure nitrogen fertilizer, which does not contain phosphorus and potassium in a large number of elements necessary for crop growth. Therefore, based on soil testing, formula fertilization should be used when topdressing is performed. 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 application: In the agricultural production, some unreasonable fertilization can be seen: the wheat is returned to the green after the spring, and the farmers can pour or flush the urea into the wheat field by pouring back the green water; Farmers sprinkle urea into the field before the rain; the cabbage is washed with water by the watering of the cabbage seedling; the tomato is flushed with urea when it is watered during the seedling stage. 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. Timely topdressing: Urea is an amide fertilizer, which needs to be converted into ammonium carbonate adsorbed by soil colloids 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 carbonic acid. Ammonium, 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: improper application method is 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 spray: 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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