Ammonium Sulfate

4897

April 15, 2025, 10:00 AM

Guide

Highlights at a glance

Ammonium sulfate ((NH₄)₂SO₄) is a widely used inorganic nitrogen-sulfur fertilizer, available in synthetic, by-product, gypsum-based, and pyrite-based forms, with by-product accounting for nearly half of global production. It is classified by particle form into crystalline, granular, and powder types, each suited to specific application methods. With 21.2% nitrogen (as ammonium) and 24% sulfur, it offers balanced nutrition, low hygroscopicity, and excellent storage stability. Compared to urea, ammonium nitrate, and ammonium chloride, it has moderate nitrogen content, low volatilization loss, and a strongly acidic physiological effect, making it ideal for neutral and calcareous soils. Granular and coated forms enhance mechanical application and nutrient use efficiency, with coated versions offering controlled release for high-value crops. Key quality standards require ≥20.5% N, ≤1.0% moisture, and strict limits on heavy metals. Its versatility supports broad agricultural use, especially where sulfur deficiency is a concern.

1.Product Characteristics and Properties

1.1 Definition and Classification

Ammonium Sulfate((NH₄)₂SO₄) is an important inorganic nitrogen fertilizer that also contains sulfur, being one of the earliest nitrogen fertilizers used worldwide. According to the international Fertilizer Association(IFA) standards, ammonium sulfate can be classified into the following categories based on production processes

Synthetic Ammonium Sulfate:
- Produced through direct neutralization of synthetic ammonia with sulfuric acid, featuring high purity and stable quality, accounting for approximately 35% globally.
By-product Ammonium Sulfate:
- Produced as a by-product in steel, coking, and other industries by recovering ammonia from waste gases, accounting for about 45% of total production.
Gypsum-Based Ammonium Sulfate:
- Produced through the reaction of gypsum with ammonium carbonate, with lower costs but inferior quality, accounting for approximately 10%
Pyrite-based Ammonium Sulfate:
- Produced using sulfuric acid from pyrite oxidation that reacts with ammonia, accounting for about 10%

Based on particle form, ammonium sulfate can be further classified as:

Crystalline Ammonium Sulfate:
- Crystal size 0.5-2.0mm, good flowability
Granular Ammonium Sulfate:
- Particle size 2-4mm, suitable for mechanical application
Powder Ammonium Sulfate:
- Particle size

1.2 Physicochemical Properties and Product Specifications

Major Physicochemical properties and international standard specifications of ammonium sulfate:

Basic Physicochemical Parameters:

Chemical Formula: (NH₄)₂SO₄
Molecular Weight: 132.14 g/mol
Nitrogen Content: 21.2% (all as ammonium nitrogen)
Sulfur Content: 24.0% (as S)
Crystal Form: Orthorhombic crystal system, typically colorless or white crystals
Solubility: 75.4g can dissolve in 100g water at 20℃, solubility increases with temperature
Density: 1.77 g/cm³ (crystal density)
Bulk Density: 0.90-1.10 g/cm³ (varies with particle form)
Critical Relative Humidity (CRH): 79.2% (at 25℃)

International Quality Standards:

Nitrogen Content: ≥20.5% (industrial grade); ≥21.0% (high-grade agricultural)
Moisture: ≤1.0% (bagged); ≤0.5% (bulk)
Free Acidity: ≤0.05% (as H₂SO₄)
Heavy Metal Content: Lead (Pb) ≤10mg/kg, Arsenic (As) ≤5mg/kg, Cadmium (Cd) ≤8mg/kg
Water Insoluble Matter: ≤0.5%
Particle Size Requirements (granular): 1-4mm proportion ≥90%
pH Value: 5.0-6.0 (10% aqueous solution)

1.3 Comparison of Ammonium Sulfate with Other Nitrogen Fertilizers

Ammonium sulfate has unique application value in the nitrogen fertilizer family

Characteristic	Ammonium Sulfate	Urea	Ammonium Nitrate	Ammonium Chloride
Nitrogen Content(%)	21.0-21.2	46.0-46.4	33.5-34.0	25.0-25.6
Nitrogen Form	All ammonium	Amide	Ammonium+Nitrate(1:1)	All ammonium
Sulfur Content(%)	23.5-24.0	0	0	0
Physiological Effect	Strongly acidic	Moderately Acidic	Weakly acidic	Strongly acidic
Hygroscopicity	Low	High	Very high	High
Soil Adaptability	Suitable for neutrla, calcareous soils	Wide adaptability	Wide adaptability	Suitable for neutral, clacareous soils
Nitrogen Fixing Effect	Strong	Weak	None	Moderate
Volatilization Loss	Low (	High (10-30%)	Low (	Moderate (5-15%)
Salt Index	69	75	105	102
Quick-acting Property	Moderate	Slow	Fast	Moderate
Storage Stability	Excellent	Good	Poor	Good

1.4 Ammonium Sulfate Product Forms and Application Characteristics

Characteristics and application scenarios of different forms of ammonium sulfate

Crystalline Ammonium Sulfate
1. Crystal Size: 0.5-2.0mm, crystallinity > 95%
2. Bulk Density: 0.96-1.05g/cm³
3. Flowability: Good, flow angle 30-35°
4. Application Characteristics: Easily dissolved, fast nutrient release
5. Application Range:Suitable for field crop basal and top dressing, especially sulfur-deficient crops
Granular Ammonium Sulfate:
1. Particle Size: 2.0-4.0mm, roundness > 90%
2. Bulk Density: 1.00-1.10 g/cm³
3. Strength: > 20N/granule, facilitating mechanical application
4. Application Characteristics: Moderate dissolution rate, strong anti-caking property
5. Applicable Range: Mechanized application, sulfur-deficient crops requiring long-term nitrogen supply
Coated Ammonium Sulfate Modified Products:
1. Coating Materials:Polymers, sulfur, or biomaterials
2. Nutrient Release Period: adjustable 30-90days
3. Nitrogen Use Efficiency: 10-15 percentage points higher than regular ammonium sulfate
4. Price premium: 30-50% higher than regular ammonium sulfate
5. Application Fields: High-value economic crops, facility agriculture

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