
Slow-release fertilizer is as literal as it gets — it’s a type of fertilizer that releases nutrients into the soil very slowly throughout a certain period. It’s what you would use for your lawn if you want to provide consistent nourishment.
Even if your turfgrass is healthy, the nutrients in the soil can get depleted over time. Applying a slow-release fertilizer can provide a steady supply of nutrients without over-fertilization. But this fertilizer is not for every lawn. If your lawn is in dire need of specific nutrients, it’s best to apply those nutrients first and wait for your lawn to recover before using slow-release plant food.
What makes slow-release fertilizers different?
Before we get into the details, remember that slow-release plant food is not the same as controlled-release fertilizer.
Slow-release fertilizers are dependent on the rate at which a microbial organism breaks down the fertilizer in your soil — which we have no control over.
Controlled-release fertilizers, on the other hand, involve controlling other external factors. But not everyone has the time and resources to create a controlled environment for the turf. So, for most homeowners, it’s better to go with slow-release fertilizers.
Peter Landschoot, professor of turfgrass at Pennsylvania State University, shared that “under certain conditions, some slow-release nitrogen fertilizers are less likely to leach into groundwater than soluble sources.”
The slow and natural way of breaking down nutrients into the soil is similar to nature’s decomposition process. Because of this, most people think that all slow-release plant foods are organic fertilizers.
However, slow-release plant food can either be organic or inorganic. In slow-release inorganic fertilizers, the coated granules are designed to slow down the breakdown process.
How slow-release fertilizers work

Coating plays a big part in the composition of slow-release fertilizers. Made with a semi-permeable polymer or resin, the coating acts as a barrier, which helps in controlling the release of nutrients from the granules. The actual rate of release depends on the method implemented by specific brands as well as other factors including soil microbial activity.
The different methods used to regulate the release of nutrients include:
- Osmosis: This method makes use of water to help break down the granules. Once the nutrients dissolve, they can be forced to pass through the coating.
- Diffusion: The process of diffusion moves the nutrients through the coating with concentration gradients.
- Microbial decomposition: With this method, soil microbes help dismantle the coating to release the nutrients.
Note: Most slow-release granular fertilizers can take up to 48 hours to dissolve, but the actual time will depend on the formula and the brand. It’s best to read the packaging label to get a more specific answer on how long it would take for the granules to dissolve.
Most common types of slow-release fertilizers

For organic fertilizers like bone meal or compost, it takes time before their nutrients are broken down. That’s why it’s easy to consider them as slow-release plant food.
When it comes to inorganic fertilizers, here are the four most common nitrogen compounds that help release the nutrients slowly:
- Polymer-coated urea: The release rate of polymer-coated urea is dependent on the temperature and the thickness of the coating. While it can be on the expensive side, it’s one of the most technologically advanced compounds suitable for most lawns.
- Sulfur-coated urea: Similar to polymer-coated urea, this compound also makes use of a coating to slow down the release of nutrients. It’s usually recommended for lawns with high pH levels.
- Methylene urea: The release of nutrients through water and soil microbial activity usually lasts around three to nine months. Best applied to actively growing turf, this fertilizer has no coating and up to 60% of its nitrogen is cold-water-insoluble.
- Urea formaldehyde: This compound has no coating as well. Microbial decomposition is responsible for releasing the nutrients, so environmental factors like moisture and aeration affect the rate of release. Keep in mind that this compound is best applied on flower beds instead of turfs.
Why use slow-release fertilizer?
Applying slow-release plant food offers a number of benefits, not only to the lawn or plants themselves but to the homeowner or gardener as well.
- 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, minimizing patches of overgrowth.
- Balances nutrient distribution: Instead of sudden bursts of nutrients, plants receive them slowly and safely, which helps prevent fertilizer burns. With a balanced distribution, there’s less possibility of over-fertilization or nutrient overload.
- 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.
- Minimizes environmental risks: Using slow-release plant food can help you be responsible when fertilizing. For one, you can avoid fertilizer runoff which pollutes the water, ultimately lessening environmental impact.
- Saves time and effort: The steady release of nutrients over time helps reduce the frequency of fertilizer application.
If your lawn is already established and doesn’t require an immediate boost of nutrients, you can apply slow-release plant food to maintain uniform growth. It can greatly benefit from a consistent supply of nutrients that can last six to eight weeks.
Tips for using slow-release fertilizer

Here are some tips to help you maximize the benefits of using this type of fertilizer:
- As with any fertilizer application, it’s always best to adhere to your current soil testing results. Check your soil’s pH and ratio of N-P-K (the three primary macronutrients needed for plant growth: nitrogen-phosphorus-potassium) and choose the slow-release fertilizer that would help you achieve a balanced nutrition for your turf.
- If you’re planning to apply fertilizer on your turfgrass, you can choose one with a high nitrogen ratio and combine it with herbicides for weed control. Flowering plants, on the other hand, usually require higher ratios of phosphorus.
- For a healthy boost, apply this type of fertilizer in early spring. This way, you can add the nutrients to your lawn before the grass starts to actively grow again.
- You can go with a slow-release plant food for your late summer fertilization. Since it’s essential not to stress your lawn before it enters dormancy, a slow and steady release of nutrients is the best approach.
- Remember to use a spreader when applying this fertilizer to get an even distribution across your lawn. And if you want to prevent uneven patches, don’t forget to do a second pass during application.
FAQ about slow-release fertilizer
How much does it cost to fertilize my lawn?
Most homeowners spend anywhere from $0.02 to $0.07 per square foot for professional lawn fertilization. The total cost of fertilizing your lawn will depend on your project size and other factors. To know more about the cost factors, you can check our lawn fertilization pricing guide.
Is slow-release fertilizer suitable for all lawns?
No, it’s not suitable for all lawns. For instance, lawns that are not yet fully established require an immediate boost of nutrients from a quick-release fertilizer. The slow and steady distribution of nutrients from this type of fertilizer will be detrimental to its growth.
Should I water my lawn after applying slow-release fertilizer?
Most slow-release fertilizers need water to activate it, but it’s always best to check the label for specific instructions. And since these fertilizers don’t dissolve quickly, you won’t have to worry about them getting washed away.
Hire a pro for a healthy and lush landscape
You won’t get instant gratification from a slow-release fertilizer. But when it comes to lawn care, it’s not always about quick results. The secret is to use the right kind of fertilizer at the right time. So, unless you’re a fertilizer expert, it’s better to hire a lawn care professional to handle all your fertilization needs.
Source list:
- https://edis.ifas.ufl.edu/publication/HS1255
- https://scholar.lib.vt.edu/ejournals/JARS/v55n3/v55n3-hammer.htm
- https://nrcca.cals.cornell.edu/nutrient/CA2/CA0209.php
- https://extension.soils.wisc.edu/wcmc/assessing-the-quality-of-polymer-coated-urea/
- https://aesl.ces.uga.edu/soil/fertcalc/
- https://extension.psu.edu/enhanced-efficiency-nitrogen-fertilizers-for-turfgrasses
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