Keeping your fertilizer stock dry is essential to maintaining its shelf life. When properly stored, most fertilizers will last upwards of 10 years. However, if exposed to water, your fertilizer will be quickly rendered useless.
To keep fertilizer dry when stored, place it inside a raised, waterproof, air-tight container to protect it from rainfall, water spills, and moisture in the air. Fertilizers can be stored indoors or outside but must be securely protected from exposure to water.
Before storing your leftover fertilizer stock for the season, read on for some of the best ways to keep it dry when stored. I’ll also share tips for both indoor and outdoor storage, as well as a variety of storage techniques that work well for maintaining dry fertilizer.
1. Seal Plastic Bags Around Open Fertilizer Containers
Chances are, at the end of each fertilizing season, you’ll have leftover containers or bags of fertilizer. Whether the fertilizer is partially used or not, it’s still absolutely salvageable. Fertilizer can last for 10 years or longer with proper storage, but it must be kept dry.
To make sure fertilizer in previously opened containers is kept dry, use a large Ziploc bag to “reseal” it. Place the bag around the whole container and seal it completely. This will add an extra layer of protection when stored to prevent spills or unintended water exposure.
If your bag of fertilizer is too large to fit inside a Ziploc bag, you can label individual bags and split the leftover fertilizer up among them. Alternatively, you can use a larger one, like a garbage bag, secured with twisted elastic. You can also get creative and use large Christmas tree bags or other storage bags with zipper closures to store large amounts of fertilizer.
If you choose to split up your fertilizer into individual bags, it’s a good idea to save the original bag or take a copy of the important information printed on the packaging. You’ll want to have easy access to information such as usage amounts, ingredients, and manufacturer’s recommendations.
2. Use a Metal Trash Can for Storage
Metal trash cans are an excellent choice for protecting stored fertilizer. These storage vessels are great for preventing exposure to moisture, protecting the fertilizer from potential fires, blocking excessive exposure to the sun, and containing the fertilizer smell.
After sealing your fertilizer in a plastic bag, place the entire thing inside a metal trash can and put the lid securely on top. This will create a dark, safe environment for the fertilizer to live in until you need it again.
The best place to keep the metal trash can with fertilizer is inside a garage or a shed. You’ll want to control the temperature as much as possible to keep the fertilizer’s nutrients strong.
Remember that pets and pests are often attracted to fertilizer and can make a big mess of it if it’s not properly secured. A metal trash can covers the fertilizer entirely and will prevent animals from chewing their way in, unlike lighter storage solutions like cardboard boxes or bags.
If you have curious children around, it’s a good idea to lock the can to prevent them from getting into the fertilizer and exposing it to moisture. Protecting children from fertilizer is also important because some types can be highly toxic and can cause serious health problems if your kids don’t use precautions like gloves and masks.
Also, unless the trash can you’re using is made of stainless steel, you’ll want to watch out for signs of corrosion on it. If the container corrodes, it’s going to lose its protective properties against moisture, and you’ll have to move your fertilizer to another storage container.
There are other lightweight storage options out there, which are also excellent at keeping fertilizer dry. To best protect your fertilizer, you’ll want an air-tight and durable container.
Here are a few of the most dependable fertilizer storage options:
Food-Grade Plastic Bottles With Lids
Plastic bottles used to store food supplies, such as cereals and spices, also make excellent storage containers for granular fertilizers. These are specially designed to be airtight, which works well to preserve your fertilizers.
Also, they typically come in different sizes and are suitable for smaller volumes of fertilizer. Get one that’s big enough to store your fertilizer and has a screw-on lid to spill-proof the contents. For easier handling, you can also find one with a side grip.
Food-Grade Plastic Buckets
If you have larger packs of granular fertilizer, you can store them in plastic buckets with lids. Choose one with thicker materials to ensure pests like mice or rats won’t be able to gnaw through it.
These products usually have handles to make them easier to move around. However, a larger container with over 4-gallon (15 L) capacity can be too heavy to move around. Therefore, you must decide on a storage place before filling it in with fertilizer. Remember to keep the container away from direct sunlight and keep it shut to prevent moisture.
No matter what storage container you use, check them for signs of damage now and then. The moment you spot cracks, holes, or the like, replace the container as soon as you can.
3. Elevate Your Stored Fertilizer
Fertilizer storage bins, regardless of the type, should always be elevated. You should never leave a container of fertilizer lying directly on the ground.
The reason fertilizer should always be elevated is because of the potential for water exposure on the ground. Large amounts of precipitation, unexpected flooding, and accidental spills are just a few ways excess water can build up on the ground, potentially ruining your stored fertilizer.
To elevate stored fertilizer, use pallets. Depending on your flood risk, you can use one, two, or even three pallets stacked on top of one another to make a sort of foundation for your fertilizer storage.
Ensure that your pallets are completely clear of any nails, screws, or other obstructions that could puncture or damage your storage container.
4. Use Tarps for an Added Layer of Protection
Tarps are a waterproof, convenient, and simple way to add extra layers of protection to your stored fertilizer. If you’re elevating your fertilizer with pallets, try laying a tarp down on the pallets first to prevent any undesirable damage wood slivers might cause.
Additionally, you can use a tarp or two to cover the stored fertilizer from the top. This method is especially helpful if your fertilizer is being stored outside, as it can prevent excessive rainfall from damaging your fertilizer.
Be sure the tarps are covering the bags of fertilizer well. Use additional tarps to wrap the sides of the pile if necessary. You can secure the tarps with bungee cords or twine to ensure it stays in place even on the windiest days. For extra security, you can use locks around the cords or twine.
5. Choose a Level, Well-Draining Area for Storage
Before packing away your fertilizer for storage, scout out the best location for it to stay. It’s important that the area you choose to store your fertilizer has:
- Level ground: Uneven ground can cause spills, tipped containers, and level changes, increasing the fertilizer’s risk of water exposure.
- Well-draining soil: The soil in this area must drain adequately to prevent water build-up on the ground as well as excess moisture in the air.
- Minimal sun exposure: The ideal temperature for fertilizer storage is between 50°F and 80°F (10°C-17°C). Otherwise, the fertilizer’s quality may be adversely affected.
- Minimal rain exposure: Exposure to rain is best avoided altogether. If your stored fertilizer gets wet, it will become unusable.
Ideally, fertilizer should be stored inside a garage or garden shed to protect it from the elements and provide a somewhat temperature-controlled environment. However, if you must keep it outside, choose a level, well-drained area with a comfortable temperature. Use a hygrometer thermometer to measure the surrounding humidity and temperature, respectively.
6. Protect Your Fertilizer From Freezing Temperatures
Freezing temperatures are particularly dangerous for stored fertilizer. When fertilizer is exposed to freezing temperatures, it can lose the solidity of the chemical compounds that make it useful. Once the fertilizer thaws after the cold season, you might find that the fertilizer no longer works as well as it once did — or at all, for that matter.
To protect your stored fertilizer from freezing temperatures, keep it in a cool, dry, indoor location. Storing fertilizer outside in freezing temperatures can be done, but inside storage seems to work best for maintaining the integrity of the fertilizer compounds.
If you have access to a temperature-controlled space, like a heated garage or garden shed, this will be the best location for your fertilizer storage. Otherwise, try insulating the storage containers with tarps or towels. Ensuring that the storage containers are sealed completely and correctly will also help cut down on frost exposure.
Note that fertilizer doesn’t protect plants from freezing. I’ve written about fertilization in the winter in another article, where you’ll also learn a few techniques to protect your plants from the cold: Does Fertilizer Keep Plants From Freezing?
7. Clearly Label Fertilizer Storage Bins
When storing fertilizer, it’s extremely important to label every bin. If you have multiple types of fertilizer, clear labels will help you easily access whichever solution you need at any given time. Additionally, labeling storage containers can help to prevent any accidental mishaps, like opening a bin of fertilizer with wet hands or in the rain.
Be sure to keep the original packaging with the detailed fertilizer specifications inside the bin, and label the outside of the container with a clear, legible description of the type of fertilizer contained therein. It may also be helpful to note the date the fertilizer was opened so you can use the oldest fertilizer first in the coming seasons.
8. Do Not Store Fertilizer in Humid Environments
Fertilizers can get wet from more than just rain or water spills. Humidity, or high levels of moisture in the air, can be just as damaging to fertilizer as pouring a bottle of water into it. If stored in a humid space, the fertilizer will absorb the moisture from the area, causing clumps to form and nutrients to leak out.
Choosing a space with a dry atmosphere is absolutely essential to protecting fertilizer and keeping it dry. In agriculture, large, dry fertilizer storage buildings are often constructed for the sole purpose of creating a dry, temperature-controlled, humidity-free home just for fertilizer. These buildings are highly effective, although they’re not exactly practical when it comes to home gardening.
What Happens When Stored Fertilizer Gets Wet?
When fertilizer gets wet, it can create a bit of a mess. Not only does it get sticky and gooey, making an unsightly mess that you’ll have to clean up, but it also has the potential to render the fertilizer completely useless.
Once your fertilizer has been exposed to a good amount of water, it begins breaking down. Most fertilizers are water-soluble and immediately start to break down and release nutrients once watered. If your fertilizer is still in the bag, the nutrients have nowhere to go and are simply lost.
If storing compost or other microbial fertilizers, note that too much exposure to water can cause the microbes to die, creating a far less effective fertilizer.
Can You Still Use Fertilizer After It Has Gotten Wet?
If your fertilizer accidentally gets exposed to excess water, don’t fret. You can still use the batch, but you must keep in mind that the fertilizer will most likely not work as well as initially expected. Moreover, the sooner you can use the fertilizer, the better, as it will start to exponentially lose its quality as time goes on.
How To Save Fertilizer After Moisture Exposure
To use a fertilizer that has gotten wet, you first need to dry it out. Since it absorbed moisture, it may have gotten a little bit clumpy. You need to lay out a tarp and sprinkle the wet fertilizer all over. After that, you can go back through and break up the little clumps until all of the pieces are relatively back to normal.
If you place the tarp in a sunny area, the fertilizer granules should dry up fairly quickly. Once dry, you can repackage the fertilizer in a safely sealed and labeled container to prevent future water exposure.
Although wet fertilizer is usually still functional, albeit on a lower level after exposure to water, the fertilizer may fail to work at all and will need to be discarded. Unfortunately, there’s not really any way to know until you use it. If you see no results, it may no longer be functional. If, after application, your plants show notable improvements, your fertilizer is probably still working.
How Long Can Fertilizer Be Stored?
Fertilizers can be stored for many years. You may hear some say that fertilizer never expires, while others suggest it can last for around 10 or so years when maintained and stored correctly.
Technically, fertilizer does not have an expiration date. It can, however, become useless if damaged by excessive sun, cold, or water exposure.
The three main types of fertilizer are:
- Synthetic granular fertilizer
- Liquid synthetic fertilizer
- Organic fertilizer
To learn more about the differences between organic and synthetic fertilizer, you can check out this article: Organic vs. Mineral Fertilizer: The Differences Explained
Each type of fertilizer has a different shelf-life duration, which can increase or decrease depending on how well they’re insulated and protected from moisture.
- Synthetic granular fertilizers are thought to last the longest of all fertilizers with their strong chemical compounds and ability to remain intact even after long periods of storage. Usually, the expected shelf life of fertilizer is around 10 years, but these fertilizers can often last far longer than that.
- Liquid synthetic fertilizers typically last between 8 and 10 years on the shelf — an impressive shelf life compared to many other items.
- Organic fertilizers like homemade compost have the shortest life span, usually lasting up to about three to four years if maintained and stored properly. These fertilizers are stored a bit differently, as they do need some moisture to retain their living microbes.
As you can imagine, the fact that fertilizer has a long shelf life is beneficial. Although fertilizer can be pricey at times, the cost is much easier to endure when you know that it can last for years and years, depending on the volume of fertilizer you use and how carefully you use it.
For more information about why fertilizer is so expensive, check out my other article, where I discuss the forces driving up fertilizer costs. I also provide a few tips to help you minimize your costs. Why Does Fertilizer Cost So Much? 5 Reasons
Storing fertilizer doesn’t have to be complicated. The main goal is to ensure it doesn’t get exposed to any kind of moisture. To keep your fertilizer dry when stored, seal fertilizer in an air-tight storage bin that won’t leak or break down over time.
Keeping your fertilizer in its original container is ideal if it’s a hard-sided bin, but opened bags and cardboard boxes leave your fertilizer exposed to the elements. Your fertilizer and its original packaging should be stored in a waterproof container until it’s needed during the next fertilizing season.