Urea properties and application methods

1. Composition and Properties Urea nitrogen content is 46%, which is the highest amount of ammonia nitrogen in solid nitrogen fertilizer. Urea during the granulation process, if the high temperature (above 133 degrees Celsius) treatment, will produce biuret, biuret content of more than 2%, the crop seed and seedlings are toxic. Urea is easily soluble in water and can dissolve 105 kg of urea in 100 kg of water at 20 degrees Celsius.
2. The transformed urea in the soil is applied to the soil and dissolved molecularly in the soil solution, and can be adsorbed by the soil colloid. The mechanism of the adsorption is the combination of urea and clay minerals or hydrogen bonding with humus. Urea is hydrolyzed into ammonium carbonate or ammonium bicarbonate by the action of urease secreted by soil microorganisms in the soil. Neutral in the soil, moisture is appropriate, the higher the temperature, the faster the hydrolysis, at 10 degrees Celsius, it takes 7-10 days, 20 degrees Celsius 4-5 days, 3 degrees Celsius, only 2 days can be fully conveyed Into ammonium carbonate, ammonium carbonate is very unstable, so the application of urea should also be covered with deep soil to prevent loss of nitrogen. Urea is a neutral fertilizer, and long-term application has no destructive effect on the soil.
3. Application method Urea is suitable for various soils and various crops. It can be used as base fertilizer and topdressing. Because the nitrogen content of urea is high, the concentration of NH4+ in the vicinity of the fertilizing point in the hydrolysis process increases dramatically, making the PH in the soil rise in the short term. 1-2 units, it will affect the seed germination or seedling root growth, in severe cases, the seeds lose the ability to germinate, such as for fertilizer application, must be mixed with dry fine soil under a certain distance, to avoid direct contact of fertilizers and seeds , but also control the dosage, generally 2.5 kg / acre is appropriate.
Urea has a high nitrogen content and a small amount, and must be applied evenly. Whether as a base fertilizer or topdressing fertilizer, the soil should be deeply applied to prevent loss of nutrients. Urea fertilizer efficiency is about 3-4 days later than other nitrogen fertilizers. Should be applied earlier.
Urea is a neutral organic matter with very small ionization degree. It does not contain any secondary components. It has small burns to crops, and has small urea molecules and is hygroscopic. It is easily absorbed by the leaves and enters the leaf cells. Urea is therefore particularly suitable for top dressing of crops. However, the biuret content does not exceed 0.5%. Urea spray 0.5-1.5 kilograms per mu, spray once every 7-10 days, generally spray 2-3 times, spray time in the early morning or late evening is better.

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