Ammonium Sulfate Fertilizer 21-0-0
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- $ 24.99
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- $ 24.99
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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
FEATURES
- 21% Nitrogen: Fast-acting ammonium nitrogen (NH₄⁺) for rapid green-up and vigorous vegetative growth
- 24% Sulfur: Essential secondary nutrient supports chlorophyll production, protein synthesis, and enzyme activation
- 100% Water Soluble: Dissolves completely for immediate nutrient availability through soil drench or fertigation
- Acidifying Action: Gradually lowers soil pH over time—ideal for alkaline soils and acid-loving plants
- Dual-Purpose Formula: Provides both nitrogen nutrition and sulfur supplementation in one application
- Low Heavy Metals: Third-party tested to exceed EPA safety standards for garden and agricultural use
DERIVED FROM
Ammonium Sulfate (NH₄)₂SO₄
Manufactured through the reaction of ammonia with sulfuric acid, producing a stable crystalline salt. This synthetic process ensures consistent purity and nutrient content in every batch. Our ammonium sulfate is produced in the USA under strict quality controls, with each lot tested for nutrient analysis and heavy metal content to meet CDFA registration requirements.
PERFECT FOR THESE APPLICATIONS
COMMON PROBLEMS? WE HAVE SOLUTIONS
WHY GROWERS CHOOSE THIS FORMULA
💪 21% Fast-Acting Nitrogen
Water-soluble ammonium nitrogen for rapid green growth and vigorous development. Visible results in 7-10 days.
🔬 24% Essential Sulfur
Supports chlorophyll formation, protein synthesis, and helps acidify alkaline soils over time.
⚡ 100% Water Soluble
Dissolves quickly for immediate availability through soil application or fertigation systems.
🫐 Perfect for Acid-Lovers
Ideal for blueberries, azaleas, rhododendrons, and other plants that thrive in acidic conditions.
⚠️ 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
NPK FORMULA EXPLAINED
N-P-K: 21-0-0 - Targeted Nitrogen + Sulfur
Fertilizer numbers are always in the same order: N–P–K = nitrogen – phosphorus – potassium. This formula provides concentrated nitrogen with no phosphorus or potassium—ideal when your soil already has adequate P and K levels, or as a targeted nitrogen boost.
N - 21%
Nitrogen
As ammonium (NH₄⁺) for rapid uptake. Fuels leafy green growth and recovery from yellowing.
P - 0%
Phosphorus
Not included. Ideal if your soil already tests high in phosphorus.
K - 0%
Potassium
Not included. Pair with a complete fertilizer when potassium is also needed.
Plus: 24% Sulfur (S) – not shown in the NPK numbers, but essential for chlorophyll production, protein synthesis, and enzyme function.
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.
| 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 |
APPLICATION RATES & INSTRUCTIONS
Mix into topsoil or dissolve in water. Always water thoroughly after application to prevent foliar burn and ensure nutrient movement into root zone.
📅 Seasonal Application Guide
🌾 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⁺ (ammoniacal) | 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.
COMPLETE YOUR SYSTEM
Maximize your results with these complementary products
GROW WITH CONFIDENCE
Product Quality Guaranteed
- Third-party lab tested for purity and nutrient content
- Certificate of Analysis available for every batch
- Very low heavy metals - exceeds EPA safety standards
- CDFA Registered (#2014005)
- Manufactured in California since 1989
90-Day Satisfaction Guarantee
Not satisfied with your results? Contact us within 90 days for a full refund. We stand behind every product we sell because we know our quality delivers results.
FREQUENTLY ASKED QUESTIONS
Q 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.
Q 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.
Q 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.
Q 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.
Q 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.
Q 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.
Q 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.
Q 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.
Q 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.
DOCUMENTS & CERTIFICATIONS
Access complete technical documentation, safety information, and quality certifications:
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