As a gardener and homeowner, I know that proper fertilization is key to a great yard, but finding the right fertilizer has been frustrating. Recently, I stumbled across slow-release fertilizer, and, y’all, it’s a game changer.
Slow-release fertilizer is a type of plant food designed to gradually supply nutrients to plants over an extended period — typically 2 to 9 months — rather than all at once. Unlike conventional fertilizers that dissolve quickly when watered, slow-release fertilizers discharge essential nutrients like nitrogen, phosphorus, and potassium a bit at a time.
In this article, we’ll talk about what lawn care experts have to say about slow-release fertilizers and how they differ from other fertilizers.
How do slow-release fertilizers work?
Slow-release fertilizers release nutrients over weeks or even months, ensuring plants enjoy a consistent supply of food, says David Liu, professor of horticultural sciences at the University of Florida. Slow-release fertilizers can be inorganic, like N-SURE, or organic, like manure, bone meal, or compost.
The nutrients in many slow-release fertilizers are coated with polymers, resins, or sulfur, which slow down the release process. Temperature, moisture, and microbial activity in the soil slowly break down the coatings and release the nutrients little by little.
That is also the downside of slow-release fertilizers: how long they last and how consistently they fertilize depends on those factors. Or as Liu puts it, “the rate, pattern, and duration of release are not controlled (our emphasis) because they depend on microbial organisms whose effectiveness is dependent on soil temperature and moisture conditions.”
Read more:
- Organic vs. Inorganic Fertilizer
- Fertilizer Basics: What to Look for in Your Fertilizer
- How to Fertilize Your Lawn
How are slow-release fertilizers different from other fertilizers?
There are three basic kinds of fertilizer: slow-release, controlled-release, and quick-release fertilizer. As we’ve already discussed, slow-release fertilizers rely on microbes in the soil to break them down and release nutrients little by little.
Controlled-release fertilizers are typically coated with inorganic or organic materials that control the rate, pattern, and duration of nutrient release. As water gradually penetrates, the fertilizer slowly dissolves, releasing the nutrients. The nutrient releases are well-known and controllable.
Quick-release fertilizers are water-soluble, and the nutrients are available for plants when they hit the soil. They are ideal for pre-plant applications and are available in liquid or granular form, while most slow-release and controlled-release fertilizers are granular or natural.
Here’s an easy breakdown of the differences between slow-release and quick-release fertilizers.
| Slow release | Controlled release | Quick release | |
| How it works | Microbes decompose fertilizer over time to release nutrients | Water slowly penetrates the encased fertilizer to release nutrients | Nutrients are immediately available |
| Cost | Moderate | High | Low |
| Drawbacks | Unpredictable release of nutrients | Cost and can cause low pH, calcium, and magnesium in soil. | A high risk of burn and runoff, and multiple applications may be necessary |
| Benefits | Longest lasting and releases more fertilizer during the growing season and less in the off-season | Long-lasting, predictable release of nutrients | Produces immediate results |
Read more: Slow-release Vs. Quick-Release Fertilizers
Why use slow-release fertilizers?
Compared with conventional, quick-release fertilizers, slow-release fertilizers have many benefits.
- Decreases nutrient losses: The slow-release rate keeps available nutrients in the soil, reducing runoff and leaching losses.
- Minimizes environmental risks: The slow-release rate prevents fertilizer runoff that pollutes water.
- Minimizes fertilizer burn of your grass and plants: Fertilizer burn occurs when plants get too much fertilizer and can’t absorb it properly. Slow-release fertilizer doesn’t discharge enough nutrients to cause burn.
- Reduces risk of lawn diseases: With nutrients available for an extended period, you can significantly reduce the stress on your grass, which in turn helps lessen the occurrence of lawn diseases.
- Reduces number of applications: Quick-release fertilizers last about 2 to 4 weeks, while slow-release fertilizers last 8 weeks or longer. Often, you only need one or two applications per growing season.
- Boosts lawn’s aesthetics: The slow and steady delivery of nutrients helps promote balanced growth across the lawn. As a result, you can get a more aesthetically pleasing appearance.
- There are low-cost options: Professor David M. Kopec at the University of Arizona recommends low-cost SRFs like activated sewage sludge (Milorganite) and processed turkey manure (Sustane). “Other organic products can include wheat germ, soya, poultry manure, seed meals, other manures, or tank residues,” he says.
Read more:
- Best Type of Fertilizer for Your Grass
- 8 Best Lawn Fertilizers of 2025
- The Best Type of Fertilizer for your Grass
FAQ about fertilizing
The best time to fertilize your lawn depends on your grass type–cool-season or warm-season. For cool-season grasses, fertilize in late summer or early fall once the grass is green after the summer heat. For warm-season grasses, the best time to apply fertilizer is late spring or early summer once the grass is green after the winter freeze. Another round of fertilizer should be applied in late summer/early fall.
Read our complete guide: When is the Best Time to Fertilize Your Lawn?
Yes, you can over-fertilize your lawn. Overfertilization damages your grass, sometimes killing it. A few telltale signs of over-fertilization include yellowing, wilting, brown tips, and excessive grass growth.
Read more: How Do You Know You Over-Fertilized Your Lawn?
Professional lawn fertilization costs typically range from $103 to $343 per visit, with an average of $289. This includes the necessary fertilizer, equipment, and labor. This works out to be $0.02 and $0.07 per square foot. However, the total cost of fertilizing your lawn will depend on your project size and other factors.
To learn more, check out our lawn fertilization pricing guide.
Professional lawn care at your fingertips
If you have the equipment and know-how, fertilizing your lawn is an easy DIY task. But you still need to purchase the fertilizer and expend the time and labor to do the job. That’s why so many homeowners are turning to Lawn Love. We have affordable, vetted, local lawn care pros who’ll care for your fertilization needs without you breaking a sweat or the bank.
Sources:
- Easing the Roller Coaster Ride With Slow Release Fertilizer: Dr. David M Kopec, University of Arizona
- Controlled-Release and Slow-Release Fertilizers as Nutrient Management Tools: Dr. Guodong “David” Liu et. al., University of Florida
Main Image Credit: Poramet | Adobe Stock Free | License
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