Ammonium Sulfate Fertilizer 21-0-0
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Ammonium Sulfate Fertilizer 21-0-0
Premium nitrogen and sulfur fertilizer for professional results. Fast-acting, 100% water-soluble formula provides rapid nutrient delivery and supports soil acidification for alkaline conditions—perfect for lawns and acid-loving plants like blueberries.
See the Difference in Days
Day 1💧Apply & Water
Day 3-5🌱First Signs
Day 7-10🌿Visible Greening
Day 14+🌾Full Results
Perfect For These Applications
Lawns
4 lb/1000 sq ft
Vegetables
2-3 tbsp/plant
Blueberries
1/4 cup/bush
Houseplants
1 tbsp/gallon
Solves These Common Problems
😟 Yellow, patchy lawn
✅ 21% nitrogen → 7-10 day greening
😟 Blueberries not thriving
✅ Acidification creates ideal pH
😟 Slow plant growth
✅ 24% sulfur boosts chlorophyll
😟 Alkaline soil issues
✅ Gradual pH reduction improves nutrients
What Does 21-0-0 Mean?
Fertilizer numbers are always in the same order: N–P–K = nitrogen – phosphorus – potassium. Ammonium sulfate 21-0-0 contains:
- 21% Nitrogen (N): Fuels leafy green growth and recovery from yellowing.
- 0% Phosphorus (P₂O₅): No added phosphorus – ideal if your soil already tests high.
- 0% Potassium (K₂O): No added potassium – pair with a complete fertilizer if needed.
Plus: 24% Sulfur (S) – not shown in the NPK numbers, but essential for chlorophyll production and protein synthesis.
Use it as a targeted nitrogen + sulfur boost, or combine with a complete formula when your soil also needs phosphorus and potassium.
Why Choose Greenway Ammonium Sulfate
Third-Party Lab Tested
Every batch tested for purity and heavy metals. Certificate of Analysis available for complete transparency.
Guaranteed Low Heavy Metals
Exceeds EPA safety standards. Safe for edible crops, lawns, and gardens with verified low contaminant levels.
CDFA Registered
Official registration with California Department of Food & Agriculture ensures regulatory compliance and quality standards.
American Manufacturing
Manufactured in California since 1989. Strict quality control and environmental standards at our Madera facility.
💪 21% Nitrogen
Fast-acting water-soluble nitrogen for rapid green growth and vigorous development
🔬 24% Sulfur
Essential sulfur supports chlorophyll formation and helps acidify alkaline soils over time
⚡ 100% Soluble
Dissolves quickly for immediate availability through soil or foliar application
⚠️ Important Safety & Storage Information
- Keep off concrete/pavement (may stain - rinse immediately if spilled)
- Store in cool, dry place away from moisture in original sealed container
- Keep away from children and pets during application
- Water thoroughly after application to prevent burn and ensure nutrient uptake
- Never mix with urea in storage (creates cement-like substance when wet)
- Wear gloves when handling; avoid breathing dust
SOIL pH GUIDE & TESTING
Understanding pH & Ammonium Sulfate's Role
Ammonium sulfate helps acidify alkaline soils over time through the conversion of ammonium (NH₄⁺) to nitrate (NO₃⁻), which releases hydrogen ions. The exact pH change depends on soil type, buffering capacity, application rate, and time. Always test your soil before and after application to monitor pH changes.
📊 Soil Testing Recommendation: Test soil pH before first application, then retest 4-6 weeks after each application to track changes. Aim for 0.2-0.5 pH unit reduction per application season.
4.05.57.08.510.0
Blueberries: 4.5-5.5 | Most Plants: 6.0-7.0 | AMS helps lower pH
| Plant Type | Optimal pH | AMS Benefit | Application Notes |
|---|---|---|---|
| Blueberries | 4.5-5.5 | Excellent | Creates ideal conditions; test every 6 months |
| Azaleas/Rhododendrons | 5.0-6.0 | Excellent | Maintains acidity in alkaline regions |
| Lawn Grass | 6.0-7.0 | Good | Provides N + slight acidification if needed |
| Vegetables | 6.0-6.8 | Good | Supplies needed nitrogen; monitor pH quarterly |
FEATURES & QUALITY GUARANTEE
- High Nitrogen: 21% ammonical nitrogen (NH₄⁺) for rapid uptake and utilization
- Sulfur Rich: 24% sulfur (S) for protein synthesis and enzyme function
- 100% Water Soluble: Quick dissolution and easy application - no residue
- Versatile Use: Lawns, vegetables, fruits, flowers, houseplants, and commercial crops
- pH Support: Helps acidify alkaline soils; always verify with soil testing
- Professional Grade: Used by commercial growers and turf managers worldwide
- CDFA Registered: Official registration #2014005 with California Department of Food & Agriculture
- Lab Certified: Third-party tested for nutrient content and purity
- Very Low Heavy Metals: Exceeds EPA standards for cadmium, lead, and arsenic safety
- Made in USA: Manufactured at our California facility since 1989
- Quality Tested: Certificate of Analysis (COA) available for every production batch
- 90-Day Guarantee: Full refund if not completely satisfied with results
APPLICATION RATES & TIMING
Mix into topsoil or dissolve in water. Always water thoroughly after application to prevent foliar burn and ensure nutrient movement into root zone.
💡 Quick Conversions: 1 cup ≈ 8 oz ≈ 227g | 1 tablespoon ≈ 0.5 oz ≈ 14g | 1 teaspoon ≈ 0.17 oz ≈ 5g
📅 Seasonal Application Guide
Spring
Begin when grass greens (Mar-Apr). Apply when soil temp >55°F.
Summer
Apply early AM/PM when temps <85°F. Water immediately.
Fall
Last app 6 weeks before first expected frost date.
Winter
No apps for dormant lawns. OK for greenhouse/indoor plants.
🌾 Lawn Application
| Area | AMS Rate per Application | Actual N Provided | Frequency |
|---|---|---|---|
| Per 1,000 sq ft | 3-5 lb | 0.63-1.05 lb N | Every 4-6 weeks |
| Per Acre | 120-200 lb | 25-42 lb N | As needed based on soil test |
🥬 Vegetables
| Type | Per 1,000 sq ft | Per Plant | Timing |
|---|---|---|---|
| Leafy Greens (lettuce, kale) | 1-2 lb | 1-2 tbsp | Every 3-4 weeks |
| Fruiting (tomatoes, peppers) | 2-3 lb | 2-3 tbsp | At transplant, then flowering |
| Root Crops (carrots, beets) | 1.5-2.5 lb | 1.5-2.5 tbsp | At planting, avoid later apps |
🫐 Acid-Loving Plants
| Plant Type | Rate per Application | Frequency | Target Soil pH |
|---|---|---|---|
| Blueberries (mature) | 1/4-1/2 cup per bush | 2x per year (early spring + fall) | 4.5-5.5 |
| Azaleas/Rhododendrons | 1/4 cup per foot of height | 2x per year | 5.0-6.0 |
| Camellias | 1/3 cup per plant | 2x per year | 5.5-6.5 |
| Hydrangeas (blue flowers) | 1/4 cup per plant | Monthly during growing season | 5.2-5.5 |
🪴 Houseplants & Containers
| Container Size | Rate (dissolved in water) | Frequency |
|---|---|---|
| 4-6" pots | 1/2 tsp per gallon | Every 4-6 weeks during active growth |
| 8-10" pots | 1 tsp per gallon | Every 4-6 weeks |
| 12"+ pots | 1-2 tbsp per gallon | Every 4-6 weeks |
FERTILIZER CALCULATOR
COMPARE WITH OTHER NITROGEN FERTILIZERS
| Feature | Ammonium Sulfate (21-0-0) | Urea (46-0-0) | Calcium Nitrate (15.5-0-0) |
|---|---|---|---|
| Nitrogen % | 21% | 46% | 15.5% |
| Nitrogen Form | NH₄⁺ (ammonical) | CO(NH₂)₂ (converts to NH₄⁺) | NO₃⁻ (nitrate) |
| Sulfur % | 24% | 0% | 0% |
| Secondary Nutrient | None | None | 19% Calcium |
| Water Solubility | 100% (instant) | 100% (converts in soil) | 100% (instant) |
| pH Effect | Acidifying | Acidifying | Alkalizing |
| Speed of Action | Fast (3-7 days) | Moderate (7-14 days) | Very Fast (2-5 days) |
| Best For | Acid-loving plants, alkaline soils, sulfur deficiency | Quick green-up, high N needs | Calcium deficient soils, neutral/acid soils |
| Burn Risk | Moderate (water in well) | Low | Moderate |
| Cost per lb N | Moderate | Low | High |
Bottom Line: Choose Ammonium Sulfate when you need both nitrogen and sulfur, or when lowering soil pH is beneficial. Choose Urea for maximum nitrogen efficiency in neutral soils. Choose Calcium Nitrate when you need calcium or have acid soils.
DOCUMENTS & CERTIFICATIONS
Access complete technical documentation, safety information, and quality certifications:
FREQUENTLY ASKED QUESTIONS
What is ammonium sulfate and what does 21-0-0 mean?
Ammonium sulfate is a water-soluble fertilizer providing 21% nitrogen as ammonium (NH₄⁺) and 24% sulfur as sulfate (SO₄²⁻). The 21-0-0 designation indicates 21% nitrogen, 0% phosphorus, and 0% potassium. The nitrogen is immediately available to plants, and the sulfur helps with protein synthesis and chlorophyll formation.
Does it lower soil pH? How much and how fast?
Yes, ammonium sulfate helps acidify alkaline soils over time as the ammonium converts to nitrate, releasing hydrogen ions. The pH change varies based on soil type, buffering capacity, and application rate. Expect 0.2-0.5 pH unit reduction per application season in most soils. Always test soil pH before and after application to monitor changes and adjust rates accordingly.
Can I use it on blueberries and other acid-loving plants?
Absolutely! Ammonium sulfate is excellent for blueberries, azaleas, rhododendrons, camellias, and hydrangeas. Apply 1/4-1/2 cup per blueberry bush twice yearly (early spring and fall). The acidifying effect helps create and maintain the ideal pH range of 4.5-5.5. Monitor soil pH every 6 months with a soil test to ensure optimal conditions.
How quickly does it work?
Very fast - as a 100% water-soluble fertilizer, it dissolves within 24-48 hours when watered in properly. Visible greening typically appears within 7-10 days. Effects last 4-6 weeks before another application may be needed. Always water thoroughly after application to move nutrients into the root zone.
Can I mix it with other fertilizers?
Yes, ammonium sulfate mixes well with most phosphorus and potassium fertilizers. However, avoid mixing with lime or other alkaline materials as they counteract the acidifying effect. Critical: Never mix with urea in storage - when these two come in contact with moisture, they form a cement-like substance that is extremely difficult to remove.
Is it safe for vegetable gardens and edible crops?
Yes, when used as directed. Our ammonium sulfate is third-party tested and meets EPA standards for heavy metals, making it safe for vegetable gardens. Apply as a side-dress 4-6 inches from plant stems, water in thoroughly, and reduce or stop applications 2-3 weeks before harvest for leafy greens and fruiting vegetables.
What's the difference between this and urea?
While both provide nitrogen, ammonium sulfate (21-0-0) offers immediate availability and includes 24% sulfur, whereas urea (46-0-0) must first convert in soil and contains no sulfur. Ammonium sulfate is 100% water-soluble and works faster, while urea provides more nitrogen per pound but requires soil bacteria for conversion. Choose ammonium sulfate when you need sulfur or want to lower pH; choose urea for maximum nitrogen efficiency.
Will it stain my concrete or pavement?
Yes, it can. Ammonium sulfate may cause rust-colored stains on concrete, pavers, and stonework. If spilled, rinse immediately with plenty of water. To prevent staining, sweep any granules off hard surfaces promptly and avoid applying near walkways or driveways. Water applications thoroughly to dissolve and move nutrients into soil.
How should I store it?
Store in a cool, dry location in the original sealed container. Keep away from moisture, as ammonium sulfate is hygroscopic (attracts water) and will clump if exposed to humidity. Keep sealed and away from lime, urea, and alkaline materials. Properly stored, it has an indefinite shelf life. Store away from children and pets.
HAVE QUESTIONS?
Our fertilizer experts are here to help you achieve the best results. We can assist with application rates, soil testing interpretation, and product selection.
📞 Call: (562) 351-5168
📧 Email: info@greenwaybiotech.com
🕒 Hours: Monday-Friday 8:00 AM - 5:00 PM Pacific Time
📧 Email: info@greenwaybiotech.com
🕒 Hours: Monday-Friday 8:00 AM - 5:00 PM Pacific Time