Deep Application and Covering: This is the most effective way to reduce nitrogen volatilization, leaching, and denitrification losses. Urea, ammonium bicarbonate, and ammonium nitrogen fertilizers should all be applied at a depth of 10-15 cm.
Multiple Applications: Based on the crop's nutrient requirements, distribute the total nitrogen amount in a ratio of "base fertilizer: top dressing = 30-60% : 40-70%" to avoid excessive vegetative growth in the early stages and nutrient deficiency in the later stages due to a single application.
Combined Application: Nitrogen fertilizer should be used in combination with phosphorus, potassium, and organic fertilizers. Organic fertilizers improve soil structure and enhance nutrient retention capacity; phosphorus and potassium fertilizers promote nitrogen absorption and utilization, achieving "phosphorus promotes nitrogen, potassium promotes nitrogen."
Summary: There is no "best" nitrogen fertilizer, only the "most suitable" nitrogen fertilizer. Urea is the most widely used "all-purpose fertilizer," but calcium ammonium nitrate is suitable for rapid topdressing, ammonium sulfate is the preferred choice for sulfur-loving crops, while ammonium chloride should be used with caution. It is essential to make a scientific choice based on your specific crop, soil, and climate conditions.
