Fertilizers are essential for plant growth, and most gardeners tend to buy them in bulk. Buying in bulk saves them frequent trips to the gardening store, and sometimes, it’s also cheaper in the long run. So, if you prefer to buy fertilizer in large quantities like many other gardeners, you may wonder if it can go bad.
Fertilizer can go bad if it is not stored correctly or if it is kept past its expiration date. High humidity and temperatures can make a fertilizer go bad quickly. In addition, certain factors like a fertilizer’s form and composition can also determine its shelf life.
In the rest of this article, I will explain the different types of fertilizers, how their differences may affect their sell-by date, and whether it is possible to prolong the shelf life of your fertilizer. I will also share tips on identifying fertilizer that has gone bad and the results of using expired fertilizer.
How Life Span of Fertilizer Varies According to Its Type
Fertilizers can generally be categorized based on composition or form. Regarding composition, fertilizers can either be organic or mineral. In terms of form, fertilizers can be liquid, dry, or granular.
Let’s dig into how a fertilizer’s composition and form may contribute to its potency or shelf life.
How Composition of a Fertilizer Affects Its Shelf Life
Organic vs. Mineral Fertilizers
Both organic and mineral fertilizers supply essential nutrients that aid plant growth. However, they differ in the type of nutrients they provide and how they supply the nutrients to the plants.
Organic fertilizers are made from natural materials like animal, plant, or human waste. Because they tend to work slowly, organic fertilizers are most suitable in cases where plants need a consistent supply of essential nutrients over a long period. While you can easily make organic fertilizers by composting organic waste from your home, you can also opt for manufactured organic fertilizers from your local gardening store.
In storage, organic fertilizers tend to degrade faster than mineral fertilizers. However, this doesn’t mean that they become unusable. Instead, when organic fertilizers degrade, they lose their potency over time. If this happens, a gardener may be forced to increase the quantity they use.
On the other hand, mineral fertilizers, also known as synthetic fertilizers, are made with chemicals. Some synthetic fertilizers are made from petroleum products, while some others are made with beneficial compounds like potassium chloride, magnesium sulfate, and ammonium nitrate. When gardeners need a quick supply of nutrients for their plants, they often choose mineral fertilizers.
Mineral fertilizers tend to last longer than organic fertilizers because they are manufactured with chemicals that have a long shelf life of their own. However, the form in which organic or mineral fertilizer is produced may also affect its shelf life. In the next section, I will explain how a fertilizer’s form may affect its longevity.
How the Form of a Fertilizer Affects Its Shelf Life
Liquid vs. Dry Fertilizer
Dry fertilizers can last several years, provided that you store them under the right conditions. Once you open a bag of dry fertilizer, ensure that you keep it sealed. If you damage the original package while opening it, consider transferring the product into another sealable container.
Liquid fertilizers often come in bottles or kegs that have sealed covers. If you keep your liquid fertilizer in its original container and close it whenever it is in storage, it will last for as long as the manufacturer states on the label.
How Long Do Fertilizers Last?
So far, it is clear that fertilizers generally have a long shelf life, and their longevity will depend on their type and how they are stored.
Dry fertilizers can last many years if stored under the right conditions. However, the lifespan of dry fertilizer may be shorter if it contains insecticides and herbicides. Granular fertilizers containing these pest or weed-control chemicals will last only about four years.
The shelf life is slightly different for liquid fertilizers.
Liquid chemical fertilizers can last up to ten years, whereas liquid organic fertilizers last for about five to eight years. If you use liquid concentrates that require you to dilute some of it with water, ensure that you use up the mixture as soon as possible. Mixing liquid fertilizer with water without using it will reduce its potency and shorten its life span.
In addition, whenever you use liquid fertilizer, ensure that you shake the product thoroughly before applying it to the soil. This is because when you leave liquid fertilizer in storage, the solid and concentrated portion of the product settles at the bottom of the bottle or keg. So, if you use it without shaking it, the dispensed dose may not be as effective as you expect.
Here is a table that summarizes the life span of different fertilizer types:
| Fertilizer Type | Life Span |
| Dry and granulated fertilizer | Indefinite |
| Dry fertilizer (with insecticides and pesticides) | One to four years |
| Liquid fertilizer (organic) | Five to eight years |
| Liquid fertilizer (synthetic) | Up to ten years |
Can You Extend the Shelf Life of a Fertilizer?
Not all fertilizers come with expiry dates. But some do. If a manufacturer lists an expiration date on the fertilizer, don’t use the fertilizer past the stated date.
You cannot extend the shelf life of fertilizer if it has an expiry date. Using fertilizers past the manufacturer’s expiration date may harm your plants and the soil. Instead, you can prolong the fertilizer’s shelf life by employing the best storage practices. I will share some helpful storage tips later in this article.
In addition, if you keep a good inventory and stick to an excellent fertilizing schedule, you will use nearly all, if not all, your fertilizer before its expiration date. So, ensure that you keep a record of every bag of fertilizer in your storage.
If your fertilizer doesn’t have an expiry date, at least you know that even if the label wears off and you can no longer read the manufacturer’s information, you won’t be causing any harm to your plants if you use it. However, as a general rule, you must ensure that you store any kind of fertilizer the right way. In the next section, I will share a few tips on how to store fertilizers properly.
Tips on How To Store Your Fertilizer
Storage plays a crucial role in the longevity of a fertilizer product.
Storing your fertilizer under the right conditions saves you the cost of having to throw it away because it has become unusable. Without proper storage, dry fertilizers may cake or clump up while liquid fertilizers may spill or leak, leading to product loss.
Here are a few tips on how to store fertilizers correctly:
- Store in a cool place. Avoid exposing your fertilizer to sunlight for an extended period, as some fertilizers may be affected by high temperatures. When in storage, keep your fertilizer in a location where the temperature is between 50°F and 80°F (10°C and 27°C).
- Keep in a low-humidity area. Fertilizers are highly hygroscopic, meaning they tend to absorb moisture easily. When dry fertilizer absorbs water, it becomes lumpy and difficult to use. So, avoid storing yours in high-humidity conditions. As a rule of thumb, keep your fertilizer in areas with about 30-40% relative humidity.
- Use original packaging. Keeping your fertilizer in its original packaging is helpful because you can retain the useful information on its label. Such information includes active ingredients, expiry dates, and storage information. If the original package is damaged, consider transferring the fertilizer into a new container and label the container with all the vital information.
- Keep fertilizer bags above the ground. Use pallets to keep bags and drums of fertilizer above the ground. This storage method keeps the fertilizer dry and prevents it from absorbing moisture. You can store smaller bags on shelves. In addition, keep fertilizers away from food, seedlings, tobacco, and any chemicals that may react with it.
- Create an inventory system. Creating an inventory of your fertilizer stock helps you monitor your usage and prevents you from storing fertilizers beyond their expiry date. An inventory system is also essential in the event of a fire outbreak, where firefighters will need information about chemicals in your inventory.
What Happens if You Use Bad Fertilizer?
Using a fertilizer that has gone bad can release too much or too little nutrients to your plants. Some gardeners believe that an expired fertilizer only loses its potency. So, they continue to use their fertilizers past the expiry date and increase the dose. By doing this, they risk oversupplying their plants with nutrients, which can be harmful to both the plants and the soil.
While many people get away with using a fertilizer that has gone bad, you may not be lucky. Consider the fact that you don’t know how much potency the fertilizer has lost. How then can you ascertain the correct dose to add? So, eventually, you may risk adding too much or too little nutrients.
If your fertilizer has expired, I advise you to replace it. Even better, when you shop for fertilizers, only buy the quantity you will need for a specific period. In addition, keep a record of your fertilizer stock to ensure that you use each product before it expires and loses its potency. So, if you have a stock-taking system in place, you won’t need to worry about using a fertilizer that has gone bad in the first place.
How To Know if Your Fertilizer Has Gone Bad
Since using fertilizer past its expiration date may be harmful to your plants and the soil, it is essential to know how to identify expired fertilizer.
Here are a few characteristics that can help you know if your fertilizer has gone bad:
Color
When you buy your fertilizer, take note of its color. A color change after a few uses indicates that it has gone bad. Bacterial growth may present as whitish streaks in your fertilizer. If you notice color changes, be wary of using such fertilizer on your soil. Since there is no way to tell if the bacteria is good or harmful to your crops, you are better off disposing of the fertilizer.
Texture
If you use dry or granular fertilizer, one way to know if it is still good for use is to assess its texture. The fertilizer may be bad if the texture is no longer as consistent as you’ve always known it to be. A bulge in your fertilizer bottle may also indicate that it is no longer suitable for use.
Odor
Sometimes, bad fertilizers are marked by a change in smell. So, if your liquid or dry fertilizer starts to smell funny, it is most likely contaminated. Discard any product with suspicious smells and get a fresh stock if you need some more fertilizer.
Other Common Signs Your Fertilizer Has Gone Bad
Other indications that your fertilizer may have gone bad include the presence of fecal waste from rodents and insects. Excrement from roaches, rats, or mice in your bag of fertilizer will harm your plants if you choose to use the fertilizer.
In addition, if you notice molds or signs of fungal or bacterial growth in your liquid or dry fertilizer, it may have gone bad. In that case, don’t use it. Instead, dispose of the product according to the manufacturer’s instructions and/or regulations by your local authority.
Conclusion
Storing fertilizers under the right conditions prevents them from going bad quickly. If there’s an expiry date on the product label, take note of it. Resist the urge to use fertilizers that have exceeded their expiry date.
Using expired fertilizer can be harmful to both your plants and the soil. So, occasionally check your fertilizer’s color, odor, and texture to know if it is still safe to use. If something seems off, then refrain from using the product.
When in doubt, call the manufacturer and share any suspicious signs with them to confirm whether your fertilizer is still usable.