When choosing nitrogen fertilizers or industrial nitrogen sources, two popular options stand out: urea and ammonium sulphate. Both deliver essential nitrogen to support plant growth or fuel chemical processes, but they differ sharply in nutrient composition, performance, cost, and environmental impact.
The question “which is better urea or ammonium sulphate?” depends on your specific needs—soil type, crop, application method, and budget all play a role. This article compares urea and ammonium sulphate across key factors to help you make an informed decision.
The fundamental distinction between urea and ammonium sulphate lies in their nutrient content and behaviour in soil:
In farming, “better” translates to nutrient availability, crop response, and soil compatibility. Here’s how the two stack up:
Urea: Requires conversion by soil microbes (urease) to ammonium before plants can absorb it. This process takes 2–7 days (depending on soil temperature: faster in warm soil, slower in cold).
Ammonium Sulphate: Releases ammonium immediately – no conversion needed. Ideal for crops with short growing cycles or those needing quick nitrogen uptake (e.g., leafy greens, strawberries).
Verdict: Ammonium sulphate wins for fast-acting results; urea is better for long-term, sustained nitrogen release.
Urea: Neutral initially, but breaks down to form alkaline byproducts (slightly raises soil pH over time). Suitable for acidic soils (pH < 6.0) to mitigate acidity.
Ammonium Sulphate: Acidifies soil as ammonium is nitrified (releases H⁺ ions). Perfect for alkaline soils (pH > 7.5) or crops that thrive in acidic conditions (e.g., blueberries, rhododendrons, tea). Avoid in acidic soils (risk of aluminum toxicity).
Verdict: Choose based on soil pH – urea for acidic soils, ammonium sulphate for alkaline soils.
Urea: Versatile for all crops, especially cereals (wheat, corn, rice), cash crops (cotton, sugarcane), and field crops. Its high nitrogen content makes it cost-effective for large-scale farming.
Ammonium Sulphate: Essential for sulphur-deficient soils or crops that require sulphur for protein synthesis and oil production (e.g., canola, soybeans, brassicas, onions). Also preferred for greenhouse crops and hydroponics (immediate nutrient release).
Verdict: Urea for general use; ammonium sulphate for sulphur-needy crops or deficient soils.
Urea: High volatility – up to 30% of nitrogen can be lost as ammonia if applied to the soil surface and not incorporated (via tillage or irrigation) within 24–48 hours.
Ammonium Sulphate: Low volatility – ammonium is held tightly by soil colloids, reducing nitrogen loss. Safer for surface application without incorporation.
Verdict: Ammonium sulphate is more efficient for surface application; urea requires careful incorporation to minimize losses.
Budget and ease of use are critical for farmers and industrial users:
Urea: Lower cost per kg of nitrogen (46% N means less product is needed to deliver the same nitrogen dose). For example, 1 ton of urea (46% N) provides 460 kg of N, while 2.19 tons of ammonium sulphate (21% N) are needed to match that – significantly increasing transportation and handling costs.
Ammonium Sulphate: Higher cost per unit of nitrogen, but the added sulphur can eliminate the need for separate sulphur fertilizers.
Verdict: Urea is more cost-effective for nitrogen-only needs; ammonium sulphate offers value if sulphur is also required.
Urea: Hygroscopic – prone to caking if stored in damp conditions. Requires sealed containers and dry storage facilities. Excellent flowability in prilled form, ideal for mechanical spreaders.
Ammonium Sulphate: Less hygroscopic – resists caking, easier to store in humid environments. Crystalline forms may have poorer flowability than prilled urea.
Verdict: Ammonium sulphate is more forgiving for storage; urea is better for automated spreading.
Urea: Suitable for broadcast spreading, side-dressing, and fertigation (dissolved in irrigation water). Avoid foliar application (high concentration can burn leaves).
Ammonium Sulphate: Works for broadcast spreading, side-dressing, fertigation, and foliar application (diluted). The acidic nature makes it effective for correcting iron chlorosis in alkaline soils.
Verdict: Ammonium sulphate offers more flexible application methods; urea is limited for foliar use.
Resin Production: Key raw material for urea-formaldehyde (UF) and melamine-formaldehyde (MF) resins (used in particleboard, adhesives, coatings).
Animal Feed Additive: Provides non-protein nitrogen (NPN) for ruminants.
Wastewater Treatment: Used for denitrification and flue gas desulfurization.
Deicing Agent: Mixed with salts to lower freezing points.
Chemical Manufacturing: Precursor for ammonium persulfate (oxidizing agent), dyes, and pharmaceuticals.
Textile Industry: Used in dyeing and printing processes (fixes dyes to fabrics).
Food Industry: Yeast nutrient in baking and brewing.
Mining: Used in mineral processing and flotation.
Urea is preferred for resin production and large-scale nitrogen-based processes; ammonium sulphate excels in specialty chemical, textile, and food applications where sulphur is a key component.
Sustainability depends on nutrient use efficiency and soil health:
Q1: Can I mix urea and ammonium sulphate?
A1: Yes – mixing them combines high nitrogen (urea) with sulphur (ammonium sulphate), reducing volatility. Avoid mixing in damp conditions (urea’s hygroscopicity can cause caking).
Q2: Which is better for lawns?
A2: Ammonium sulphate is better for alkaline lawn soils (greens up grass faster) and sulphur-deficient lawns. Urea works for acidic lawns but requires immediate watering to prevent volatilization.
Q3: Which is safer for organic farming?
A3: Neither is allowed in certified organic farming (both are synthetic fertilizers). Organic alternatives include composted manure, blood meal, or fish emulsion.
Q4: How long does each fertilizer last in soil?
A4: Urea lasts 4–8 weeks (sustained release); ammonium sulphate lasts 2–4 weeks (fast-acting, may require more frequent applications).
There’s no one-size-fits-all answer to “which is better: urea or ammonium sulphate.” Here’s a quick decision guide:
Choose Urea If:
Choose Ammonium Sulphate If:
By aligning your choice with soil conditions, crop needs, application method, and budget, you’ll maximize performance and sustainability. Both urea and ammonium sulphate are valuable tools – the “better” option is simply the one that fits your specific requirements.
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