Urea is a widely used and highly efficient nitrogen fertilizer that is popular among farmers due to its ease of application. It can be applied as a base fertilizer, top-dressing, or even as a foliar spray. However, improper use can lead to wasted resources, reduced crop yields, and even "fertilizer burn" that harms plants. To ensure optimal results, it's important to follow eight key guidelines when using urea.
First, avoid mixing urea with alkaline fertilizers such as wood ash, lime, calcium magnesium phosphate, or slag phosphate. When combined, the nitrogen in urea can convert into ammonia and volatilize, reducing its effectiveness. In summer and autumn, it's recommended to separate the application by 3–4 days, while in winter and spring, a gap of 7–8 days is advised.
Second, never use urea directly as a seed fertilizer. The biuret content in urea can be toxic to seeds, inhibiting germination and damaging young seedlings. If necessary, apply it separately from the seeds and in small amounts to minimize risk.
Third, do not water immediately after applying urea. Urea needs time to convert into a form that crops can absorb. Watering too soon can cause leaching and reduce efficiency. In summer and autumn, wait 2–3 days before irrigation; in winter and spring, wait 7–8 days. For rice fields, maintain a shallow water layer and avoid heavy rain after application.
Fourth, avoid shallow placement. Urea tends to volatilize quickly if placed too close to the surface. Deep application—around 10–15 cm—helps retain the fertilizer in the soil, where it can be better absorbed by plant roots. Apply it near the base of the plants or in furrows for best results.
Fifth, don’t over-apply. With a nitrogen content of 44% to 48%, urea is highly concentrated. Overuse can lead to waste and potential damage to crops. A typical rate is 5–15 kg per acre for dry land and 15–20 kg per acre for paddy fields.
Sixth, avoid high-concentration foliar sprays. Too strong a solution can burn leaves and harm plants. For crops like corn, wheat, and rice, a 2% solution is suitable. Vegetables and fruits should use 0.5–1%, while fruit trees can tolerate up to 1.5%.
Seventh, don’t apply urea too late. Late application may not provide enough time for the fertilizer to take effect, leading to excessive vegetative growth and delayed maturity. It’s best to apply urea 4–7 days earlier than other nitrogen sources.
Eighth, avoid using urea alone. It works best when combined with organic manures, phosphorus, and potassium fertilizers. Mixing with superphosphate helps stabilize the nitrogen, improving its availability and absorption by plants. This enhances overall fertilizer efficiency and supports balanced crop nutrition.
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