When selecting nitrogen fertilizer, it is necessary to comprehensively consider the crop type, soil properties, climatic conditions, fertilization timing, and the physical and chemical characteristics of the fertilizer itself to achieve efficient and environmentally friendly fertilization. The following are key points for scientifically choosing nitrogen fertilizer:
According to Crop Requirements:
Ammonium-loving crops: Crops such as rice, wheat, corn, tea trees, mulberry trees, and leafy vegetables (cabbage, celery) should prioritize ammonium nitrogen fertilizers (such as ammonium sulfate, ammonium chloride, ammonium bicarbonate) or urea. These crops can effectively utilize ammonium nitrogen, and urea provides long-lasting fertilization effects.
Nitrate-loving crops: Crops such as vegetables (especially leafy and fruit vegetables), cotton, tobacco, and sugar beet, which require rapid nutrient supply during peak demand periods, should choose nitrate nitrogen fertilizers (such as ammonium nitrate, calcium nitrate) or calcium ammonium nitrate. Nitrate nitrogen is directly absorbable by crops and acts quickly.
Chlorine-sensitive crops: Crops such as grapes, watermelon, potatoes, tobacco, soybeans, and apples must avoid using ammonium chloride to prevent chlorine accumulation from affecting quality (e.g., reducing sweetness).
Sulfur-loving crops: Crops such as soybeans, peanuts, rapeseed, garlic, and onions prefer ammonium sulfate because it provides both nitrogen and sulfur elements.
According to Soil Conditions:
Acidic soil: Avoid long-term use of physiologically acidic fertilizers like ammonium sulfate or ammonium chloride, which can exacerbate soil acidification. Urea (physiologically neutral) or calcium ammonium nitrate (contains calcium, partially neutralizing acidity) may be chosen.
Alkaline soil: Avoid using fertilizers prone to volatilization, such as ammonium bicarbonate or ammonia water, to reduce ammonia loss. Urea and nitrate nitrogen fertilizers are better choices.
Sandy soil/poor nutrient retention: Follow the "small amounts multiple times" principle; choose slow-release/controlled-release urea or apply nitrogen in split applications to avoid nitrogen leaching.
Heavy/clayey soil/good nutrient retention: Single application doses can be appropriately increased, but it is still recommended to apply deep and cover with soil.
According to Climate and Irrigation:
Rainy/paddy areas: Prefer ammonium nitrogen fertilizers or urea, applied deep and covered with soil. Avoid nitrate nitrogen fertilizers as they are prone to leaching or denitrification loss under anaerobic conditions.
Arid/dry areas: Nitrate nitrogen fertilizers and urea are ideal. Nitrate nitrogen moves quickly and can be rapidly absorbed by roots; urea has long-lasting effects, suitable for base fertilization.
Low-temperature environments: The hydrolysis conversion of urea slows significantly (7-10 days below 10℃). Fertilizers that act quickly, such as ammonium bicarbonate or calcium ammonium nitrate, are more suitable.
According to Fertilization Timing:
Base fertilizer: Choose fertilizers with long-lasting effects and good stability, such as urea, ammonium sulfate, or ammonium bicarbonate (needs deep application). Nitrate nitrogen fertilizers are easily lost and should not be used alone as base fertilizer.
Top dressing: During the crop's peak nutrient demand, rapid nitrogen supplementation requires fertilizers that act quickly, such as calcium ammonium nitrate, ammonium bicarbonate, or urea (apply in advance). Water-soluble nitrate nitrogen fertilizers are particularly suitable for fertigation or drip irrigation.
