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Urea vs Ammonium Sulfate: Nitrogen Fertilizers for Lawns & Turfgrass

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Written By: Mark Marino

a Massachusetts Core Applicator License holder and owner/operator of Lawn Phix,

Updated on

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Both urea and ammonium sulfate can give your lawn a fertilizing boost and are good alternatives to ammonium nitrate, which may be more difficult to procure and more costly. Each of these is a nitrogen fertilizer, but which one is better for your lawn? Considering the cost of nitrogen fertilizers, it makes sense to choose a product that’s destined to be most effective for your turfgrass. Nitrogen is essential for a healthy lawn; without it, your turf will appear dull and stunted as opposed to vibrant green and lush. In order to choose between nitrogen fertilizers like urea and ammonium sulfate, it’s important to understand how they differ to determine which is best for your turf. You may also need to conduct a soil test .

What Is the Difference Between Ammonium Sulfate and Urea?

Both ammonium sulfate and urea are nitrogen fertilizer sources that you can apply to your lawn and soil. Choosing one over another depends on soil pH and even your budget. Typically, urea containing 46% nitrogen, a high content of nitrogen, is less costly than ammonium sulfate, even though ammonium sulfate contains less nitrogen, 21%; however, it is also less effective as a nitrogen fertilizer. 

So why is more nitrogen-rich urea less effective in soil and for lawns? Urea isn’t always rapidly converted to nitrate that your lawn can use. So, nitrogen loss can result in more than 40% with urea. That means that ammonium sulfate offers more reliable total nitrogen for lawns; however, it is more expensive. 

What Is Urea?

Urea is one of the components of mammal urine. It’s a popular nitrogen fertilizer soil and lawns because it’s cheap. It has a high nitrogen concentration that is converted to ammonia in soil. Therefore, it is not as resistant to nitrogen loss as are other nitrogen fertilizers like ammonium sulfate or ammonium nitrate. Generally, gardeners apply urea for spring, fall, and winter fertilization but are increasingly using it during the summer months. However, atmosphere loss is a greater risk in summer, so it’s important to irrigate or apply within a few days of rainfall.

What Is Ammonium Sulfate?

Ammonium sulfate is a popular alternative to ammonium nitrate for lawns and plants. However, it can be a more expensive option than urea. Unlike urea, ammonium sulfate also contains sulfur, which is beneficial for soil. Sulfur can raise the acidity of soil, which may be needed to achieve a healthy pH. Ammonium sulfate promotes rapid grass growth. The best time to apply this nitrogen fertilizer is in spring and summer. Gardeners should avoid over-fertilizing their lawns because the ammonia can burn it out. 

Slow Release Nitrogen Fertilizers 

Slow release nitrogen fertilizers are ideal for lawns. They are more costly, but there is less risk that they will burn lawns. They are also associated with less leaching of fertilizer into ground water or surface water. Slow release nitrogen fertilizers also promote slower, more natural and consistent grass growth. These fertilizers are generally available in pellet form. 

The main disadvantage of slow release fertilizers is that the nitrogen and other nutrients they contain are not available for turf right away. Consequently, it may take longer for your lawn to green up. These products are also more costly than liquid fertilizers. 

Other Forms of Nitrogen in Lawn Fertilizer

When it comes to the ideal nitrogen source, your grass needs enough but not too much. Nitrogen sources include both organic and synthetic materials. There are other fertilizer sources you may want to use. Common inorganic nitrogen lawn fertilizers aside from ammonium sulfate, include:

  • Ammonium Nitrate
  • Potassium Nitrite
  • Calcium Nitrite

All of these lawn fertilizers, including ammonium sulfate, are water soluble. They tend to provide grass with necessary nutrients quickly but come with an increased risk of lawn burning. 

Organic sources include:

  • Grass Clippings
  • Manure
  • Animal By-Products

There are also combination fertilizers like urea that include organic and synthetic compounds. 

Ammonium Sulfate vs Urea FAQs

Which is better–urea or ammonium sulfate?

Ammonium sulfate is generally preferred over urea when it comes to efficacy as a nitrogen source. However, urea is usually a cheaper fertilizer. Both are good alternatives to ammonium nitrate.

Why is urea better than ammonium sulfate?

Urea is sometimes preferred to ammonium sulfate if the soil is acidic as the sulfur in ammonium sulfate can increase the acidity of the soil. Ammonium sulfate also has a higher price than urea.

Is urea ammonium sulfate?

No. Both of these substances are different. They both contain nitrogen, but ammonium sulfate is a primarily synthetic nitrogen fertilizer while urea is a hybrid that contains organic and inorganic compounds.

Why is urea preferred over ammonium sulfate?

Urea is preferred over ammonium sulfate when weather conditions call for rainfall. It is more water soluble than ammonium sulfate. Both are effective alternatives to ammonium nitrate.

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Author's Note: this piece has been updated for accuracy since its first publication on
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Author: Mark Marino
My name is Mark Marino, and I am the founder, owner, and operator of Lawn Phix. With a passion for lawn care and turf nutrition for over a decade, I've dedicated countless hours to correcting soil and perfecting lawns. Today, my expertise, backed by formal courses at UMass Extension Pesticide Education, allows me to offer top-tier lawn care services and advice. I am a fully licensed and insured lawn care applicator in Massachusetts, specializing in comprehensive turf nutrition, weed control, and lawn pest control. My license number is AL-0053865. Contact me at [email protected] or +1 (508) 500-8402.

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