What are the precautions for applying urea to farmland?
What should be noted when applying urea to farmland? Please explain: urea is convenient to use and has high fertilizer efficiency, making it a nitrogen fertilizer much loved by farmers. It can be used as a base fertilizer, a topdressing, and also as a foliar topdressing. If applied improperly, it not only wastes fertilizer but can also cause "fertilizer burn" and harm crops. Therefore, when applying urea...
What should be noted when applying urea to farmland? Please explain
Urea is convenient to use and has high fertilizer efficiency, making it a nitrogen fertilizer much loved by farmers. It can be used as a base fertilizer, a topdressing, and also as a foliar topdressing. If applied improperly, it not only wastes fertilizer but can also cause "fertilizer burn" and harm crops. Therefore, when applying urea, you must observe the "eight don'ts."
First, don't mix it with alkaline fertilizers or apply them at the same time. Alkaline fertilizers include plant ash, lime, calcium magnesium phosphate fertilizer, steel slag phosphate fertilizer, and so on. If mixed with urea or applied at the same time, it will intensify the conversion of the nitrogen in urea into ammonia and cause volatilization. Therefore, in summer and autumn, urea and alkaline fertilizers should be applied 3 to 4 days apart, and in winter and spring they should be applied 7 to 8 days apart.
Second, don't use it as a seed fertilizer. When urea is used as a seed fertilizer, the toxic effect of the concentrated biuret will cause the seeds to lose their germination ability and endanger the seedlings. At the same time, because high concentrations of urea can destroy the protein structure of seeds, it is also toxic and inhibitory to seeds, so it is not suitable as a seed fertilizer. If it must be used as a seed fertilizer, avoid contact between seeds and fertilizer and control the amount used.
Third, don't water immediately after application. Amide-form nitrogen has a very low adsorption capacity with soil colloids, and its mobility and leaching loss in soil are no less than those of nitrate nitrogen fertilizer. In view of these properties of urea, after applying urea as a topdressing, do not water before it has completely transformed, otherwise there will be great waste. Generally, in summer and autumn, water 2 to 3 days after application, and in winter and spring, water 7 to 8 days after application. When topdressing rice with urea, the shallow water layer should also be controlled to a "flower-eye water" level, and after application, cultivate to blend soil and fertilizer; urea must not be applied before heavy rain.
Fourth, don't apply it shallowly. Shallow application of urea makes nutrients prone to volatilization and easy for weeds to consume. Deep application of urea incorporates the fertilizer into the soil, placing the fertilizer in a moist soil layer, which helps give full play to fertilizer efficiency. As a topdressing, it should be applied in holes beside the seedlings or in furrows at the side of the seedlings, with a depth of about 10 to 15 cm. In this way, through movement, most of the urea can be concentrated in the dense root layer, making it easy for crops to absorb and use.
Fifth, don't apply too much. Urea has a nitrogen content of 44% to 48%, and its nutrient content is high, so the application amount should not be too large, to avoid unnecessary waste and "fertilizer burn." Generally, the application amount is 5 to 15 kg per mu for dry fields and 15 to 20 kg per mu for paddy fields.
Sixth, don't spray foliar fertilizer at high concentration. For foliar spraying, be sure not to use too high a concentration of urea solution, otherwise it will burn the leaves and also poison the plants. Usually, for corn, wheat, rice, and cotton, a concentration of 2% is suitable; for vegetables and melons and fruits, 0.5% to 1% is more appropriate; for fruit trees, 0.5% to 1.5% is suitable.
Seventh, don't apply too late. Applying urea too late is not conducive to giving full play to fertilizer efficiency and easily causes crops to remain green and mature late, so it should generally be applied 4 to 7 days earlier than other nitrogen fertilizers.
Eighth, don't apply it alone. Urea should be applied in combination with organic fertilizer and phosphorus and potassium fertilizers, and so on, to meet the crops' needs for various nutrients. For example, mixing urea with superphosphate can transform unstable ammonium bisulfate into stable ammonium phosphate, accelerate the transformation and decomposition of urea, enable available nitrogen to be quickly absorbed by crops, and improve the utilization rate of urea.
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