Ammonium Sulfate Fertilizer 21-0-0 
Ammonium Sulfate is a high nitrogen synthetic or non-organic fertilizer that provides additional sulfur to help plants overall health and protein synthesis. Ammonium sulfate is 21% nitrogen and 24% sulfur. The NPK value is 21-0-0.
Ammonium Sulfate provides 21% nitrogen via ammonia. The Ammonium decomposes when exposed to water and then is readily available to plant roots.
Ammonium sulfate is easily stored and more stable than ammonium nitrate.
Ammonium sulfate is human and pet safe.
Uses of Ammonium Sulfate
Ammonium sulfate is popular with rice farmers who apply it to flooded rice fields. Nitrate fertilizers like urea and ammonium nitrate are poor choices in this situation because of denitrification losses. These losses are caused when bacteria convert nitrates and nitrites into nitrogen gas which escapes into the atmosphere. Ammonium sulfate does not react this way.
Ammonium sulfate is especially beneficial for alkaline soils. It tends to acidify soils which is preferable for plants.
Ammonium sulfate is an excellent fertilizer for grass lawns. It will green up a lawn in a few days and increase growth rate and leaf production. It is pretty universal though and can be used for shrubs, trees and any ground cover. The nitrogen will green up foliage and produce more of it. The sulfur helps with overall plant health and protein synthesis.
Onions, garlic, shallots, leeks and other bulbing plants will benefit from ammonium sulfate. The nitrogen will increase foliage which in turn will increase the bulb or root size via more sugar production by photosynthesis. The more leaves, the more photosynthesis and sugar production. Most people think nitrogen is not needed for root vegetables but this is not true.
Other Crops that Benefit from Ammonium Sulfate
How to Apply Ammonium Sulfate
Ammonium sulfate is a crystal or granular fertilizer and is very easy to handle and spread. Use as directed to avoid burning.
Turf or Grass Lawns – use a broadcast or drop type spreader to apply ammonium sulfate to grass lawns or golf courses. Apply 5 lbs per 1000 square feet or 200 lbs per acre. Reapply every 4-6 weeks.
Shrubs and evergreens – sprinkle 1/4 cup around the drip line of shrubs and then mix in with the top 1 inch of soil. Then water.
Vegetable Plants – apply 1 tablespoon per plant and mix in soil. Ammonium sulfate is also great for blueberry bushes.
Foliar Spray Application – mix 1 gallon of water with 1-3 tablespoons of ammonium sulfate. Use a fine mist sprayer or watering can to apply to foliage. Do not spray plants while in direct sunlight as it may burn the leaves.
Liquid Application – mix 1 gallon of water with 1-3 tablespoons of ammonium sulfate and use to water vegetable gardens, grass and shrubs. Use once per week.
When to Apply Ammonium Sulfate Fertilizer
Apply ammonium sulfate in late spring or late summer for a boost in grass/lawn growth. If too much is applied, you will see an enormous amount of growth. It’s pretty amazing. Avoid using it in late fall to prevent disease or winter kill.
Ammonium sulfate is a fast release fertilizer and will need to be applied every 4-6 weeks. There are however slow release formulations available.
Pros and Cons of Ammonium Sulfate
Advantages – ammonium sulfate is easily stored, non-flammable and easy to apply via broadcast or drop type spreaders. It provides a relatively high amount of nitrogen to stimulate new growth. The added sulfur is necessary for overall health of plants and supports protein synthesis. It is a fast release fertilizer and will stimulate growth in a few days. Ammonium sulfate is an inexpensive fertilizer and can be blended with other fertilizers like urea.
Plant Benefits from Ammonium Sulfate
- Promotes root development which can reduce loss from droughts
- Promotes breakdown of organic matter in the soil
- Stimulates fruit/seed production and early plant maturity
- Helps nitrates convert into proteins
- Promotes dark green foliage coloration by increasing chlorophyll
- Promotes nodule formation on legumes
- Improves soil structure
- Increases water filtration
The main disadvantage is it increases acidity in the soil which could require lime at some point to correct the soil pH. Use a soil test kit to monitor soil pH.
Popular Ammonium Sulfate Brands
- Earthborn Elements
- Lilly Miller
- Greenway Biotech
- Alpha Chemicals or AC
- Pure Organic Ingredients
- Cesco Solutions
Where to Buy Ammonium Sulfate
You can buy ammonium sulfate at most nurseries and home improvement stores like Lowes, Home Deport and Ace Hardware. It is also available online with free shipping. It comes in a bag weighing from 1 lb to 50 lbs. It costs on average about $3/lb.
You can also use Scotts Turf Builder SummerGuard Lawn Food for grass lawns. It’s very similar to ammonium sulfate with a NPK of 20-0-8. It provides high nitrogen and medium amount of potassium.