Slow-Release vs. Quick-Release Fertilizer

person fertilizing a lawn

It’s not a question of which is better between slow-release vs. quick-release fertilizer because they’re both necessary for maintaining healthy lawns. When choosing between these fertilizers, you need to consider the type of lawn you have and the state it’s currently in.

However, the key to learning how to juggle these two types of fertilizers is knowing when to use which one, depending on your lawn’s growth stage. But before you know how to use them effectively, you must understand how each of them works.

Quick comparison of slow-release vs. quick-release fertilizer

Here’s a quick overview of the differences between slow-release vs. quick-release fertilizers:

Slow-release fertilizerQuick-release fertilizer
Mostly organicMostly inorganic or synthetic
Less concentratedHigh concentration of formula
Provides nutrients long-termGives a quick boost of nutrients
Great for beginnersIts application requires expertise
Feeds the soilFeeds the plant
Less frequent applicationsMore frequent applications
Less chance of fertilizer burnHigher risk of over-fertilization
Nutrients take time to become availableNutrients are readily available
It can take longer to see the resultsResults are more immediate

You may find a slow-release fertilizer with a similar formulation and nutrient content as that of a quick-release fertilizer. But even with the same N-P-K (nitrogen, phosphorus, and potassium) ratio, the effects on your lawn will be significantly different due to how they deliver these nutrients.

How slow-release fertilizer works

urea fertilizer in farmer hands.
iamporpla | Adobe Stock | License

A slow-release fertilizer delivers nutrients in a slow and steady manner. But what it lacks in speed, it makes up for being consistent. Depending on the brand, formula, and lawn conditions, the nutrients can stay in the soil for around six to eight weeks.

The science behind the slow delivery is the coating, which is usually made of semi-permeable polymer or resin. It acts as a barrier that holds the nutrients inside and releases them in a controlled manner when it meets a specific condition, such as watering or soil microbial activity.

There are different methods in regulating the release but most of them fall on these three approaches: diffusion, osmosis, and microbial decomposition. The first two methods use water to break down the coating or allow the nutrients to pass through. On the other hand, the third method relies on soil microbes to dismantle the coating.

When you apply a slow-release fertilizer, expect the granules to dissolve within 48 hours, depending on the brand. However, with the nutrients available for up to eight weeks, this slow release time is negligible if your turf doesn’t need the supplements right away.

Examples of slow-release fertilizers include the following:

  • Bone meal
  • Compost
  • Milorganite
  • Sulfur-coated urea
  • Urea formaldehyde

How quick-release fertilizer works

Also known as a fast-acting or soluble fertilizer, a quick-release fertilizer is a sort of pick-me-up for your lawn and plants when they’re in dire need of specific nutrients.

Water plays an important part when using a quick-release fertilizer, whether made with a water-soluble formula or inorganic salts. When mixed with water, the fertilizer quickly releases the nutrients so the grassroots can immediately consume them. There’s no long wait for any coating to break down.

This type of fertilizer usually has a higher concentration of the macronutrients nitrogen, phosphorus, and potassium, and is also packed with micronutrients. As such, quick-release fertilizers can rapidly boost your lawn’s health and even that of malnourished plants. Due to its high concentration, though, applying the wrong formulation can lead to overfertilization.

Using a fast-acting fertilizer also has several drawbacks. Since the nutrients are delivered rapidly, they only last up to two weeks in the soil. Because of this, you’ll need to apply it more frequently if you want a steady boost. Due to its dense concentration, a quick-release fertilizer can have adverse effects on your lawn, plants, and the environment if you apply it incorrectly.

Examples of quick-release fertilizers include the following:

  • Ammonium nitrate
  • Ammonium phosphate
  • Calcium nitrate
  • Potassium nitrate

When to use slow-release vs. quick-release fertilizer

feeding lawn with granular fertilizer for perfect green grass
Shutterstock

From the time you seed your lawn to its regular maintenance, you will have to use both slow-release and quick-release fertilizers. Which of the two to use and when will just depend on your lawn’s current condition or the result you want to achieve.

The table below highlights which lawn conditions, situations, or fertilization goals call for slow-release vs. quick-release fertilizer.

Lawn condition or fertilization goalWhich fertilizer to use and why
Newly seeded lawnQuick-release helps boost the nutrients needed by your new lawn
Stable and established lawnSlow-release provides a steady supply of nutrients for a longer period
Dying lawnQuick-release replenishes the supplements necessary to save a lawn from dying
Lawn winterizationSlow-release consistently provides nutrients without stressing the grass during its dormant period
Bringing a lawn back to life in springCombination of both: Mostly slow-release for a constant supply of nutrients and only add quick-release if you need to quickly compensate for lacking nutrients.
Environmental safetySlow-release is not as harmful because of its lower concentration and minimal chances of leaching
Slow grass growthQuick-release can provide soluble nitrogen your lawn can consume rapidly for faster grass growth
Occasional fertilizer applicationSlow-release fertilizer applications can be applied less frequently since they last up to eight weeks in the soil
Reduce mowing timeSlow release doesn’t encourage growth burst, which means you won’t have to mow your lawn often
Uniform grass growthSlow-release fertilizers release nutrients over time, resulting in a steady supply of nutrients

Additionally, you must choose the type and formulation of fertilizer based on your current soil test result. According to Robert F. Polomski, associate extension specialist at Clemson University, it’s crucial to test your soil so you can choose the fertilizer that will benefit your lawn and plants.

FAQ about slow-release and quick-release fertilizers

Can I use a lot of slow-release fertilizers on my lawn?

No, there’s still a risk of overfertilization even when using slow-release fertilizers. While these fertilizers have lower concentrations of salt, they can still cause fertilizer burn if you apply too much, too often. Apart from consulting your soil test report, also refer to the instructions on the fertilizer’s packaging label for proper application.

Here are a few resources to help you understand more about fertilizers and how you can use them to make your lawn more beautiful and healthy:

Will it be better to have a pro apply quick-release fertilizers?

Yes, it’s better to let a pro apply fast-release fertilizers since they are experts in using these chemicals. If you choose to hire a lawn care company, professional lawn fertilization costs around $0.02 to $0.07 per square foot.

Can my pets play on my newly fertilized lawn?

Whether you’re using a slow-release or a quick-release fertilizer, you must wait around 24 to 72 hours after application before allowing your pets to run around and play on the lawn. To be safe, ensure you’re using a pet-friendly lawn fertilizer.

Leave fertilization to the pros

While the best option is to use a mix of slow-release and fast-release fertilizers, you must apply them at the right time for optimal results. However, it can be confusing since numerous factors, like seasonal changes, can influence your turf’s condition. So, instead of fertilizing your lawn yourself, hire a lawn care pro who can safely and properly handle the job.

Main Image Credit: evgenyb | Adobe Stock | License

Melanie Joseph

After discovering her passion for writing through her beauty blog, Melanie left her engineering job in California, became a writer, and never once looked back. When she isn't writing, she loves dipping in the pool, tending to the garden, or doing simple home improvement projects.