Misunderstanding of urea application
1. Mixing of urea and ammonium bicarbonate: Since urea is applied to the soil, it must be converted into ammonia to be absorbed by the crop, and its conversion rate is much slower under alkaline conditions than under acidic conditions. After the ammonium bicarbonate is applied to the soil, it has an alkaline reaction with a pH of 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.
Second, the surface of the application: Urea is applied to the surface, at room temperature after 3 to 5 days of transformation process to be absorbed by the crop, most of the nitrogen is volatilized in the process of conversion of urea into ammonium, the utilization rate is only about 30%, If applied in alkaline soil, the loss of nitrogen is much faster. Therefore, nitrogen cannot be applied to the surface.
Third, urea as a seed fertilizer: urea in the production process, often produces a small amount of biuret. When the biuret content exceeds 2%, it will be toxic to seeds and seedlings. When urea enters seeds and seedlings, it denatures proteins, affecting seed germination and seedling growth.
4. Immediately after urea application: Urea is an amide nitrogen fertilizer, which must be converted into ammonium nitrogen after application to be absorbed and utilized by crops. The conversion process is different due to different soil, water and temperature conditions. The time is long and short. It usually takes 2~10 days to complete. If the urea is applied immediately after irrigation or the dry land is applied before heavy rain, the urea will dissolve in water and be lost. .
5. Mixed application of urea and alkaline fertilizer: After the urea is applied, it must be converted into ammonium nitrogen to be absorbed and utilized by the crop. Under alkaline conditions, most of the nitrogen will become ammonia gas volatilization. Therefore, urea cannot be mixed with or used with alkaline fertilizers such as lime, grass ash, calcium magnesium phosphate.
6. Urea is applied to celery: a large amount of nitrogen fertilizer should be applied during the whole growth of celery, but urea cannot 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 the application of ammonium bicarbonate, ammonia and organic fertilizers, which is beneficial to improve quality.