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Does Lawn Fertilizer Go Bad? How Long Does It Last?

Does Lawn Fertilizer Go Bad? How Long Does It Last?

If you are new to gardening, you are probably wondering does lawn fertilizer go bad.

The answer to this question is both yes and no. Fertilizers aren’t supposed to go bad if you store them properly and use them within the first year. This is because nutrients do not break down over time, nor do they lose their effectiveness. However, they can be affected by microbes.

In this article, we will review the shelf life of certain fertilizers and how to best store them for maximum results.

How long do fertilizers last?

How long do fertilizers last

All fertilizers can be categorized as liquid and dry fertilizers. Companies can make them by only using organic substances or adding pesticides and herbicides to them. Depending on the composition, they may or may not lose potency over time.

Dry fertilizer

The most common type of fertilizer is organic dry fertilizer. It usually consists of phosphorous, nitrogen, and potassium, which are crucial for healthy soil. The proportion of nutrients can vary to accommodate the plant’s needs.

An important thing to note is that these chemical ingredients are stable and won’t change their properties over time. The main advantage of these products is that they slowly dissolve into the soil. This makes them ideal for large fields. Also, dry fertilizer is less likely to burn the plants, unlike liquid one. 

Liquid fertilizer

Liquid fertilizer’s shelf life will vary based on the substances that are used for the mixture. We differentiate two main subtypes of liquid fertilizer: mineral and organic.

Companies create mineral fertilizers through a chemical process. They are easily soluble and are independent of the soil quality. A mineral fertilizer can last anywhere from eight to ten years. The only thing you need to remember is to shake it before use.

Organic fertilizer, on the other hand, has various organic matters. Depending on ingredeints, a fertilizer’s shelf life can vary significantly from product to product. This is why you need to be very careful when using a new product and check its life expectancy.

Liquid fertilizers provide much quicker results than dry fertilizers. However, they won’t last as long.

Weed and feeds fertilizer

Weed and feed fertilizer is a type of dry fertilizer. They have various herbicides and pesticides on top of the manure. These products have a limited shelf life, and they usually last up to four years. Unlike some other substances, they will lose potency over time.

These fertilizers may also have chemicals meant to eliminate weeds and insects. They also last for up to four years. Weed and feed fertilizers are illegal in various countries. You can’t buy them in Australia, Canada, or most of Europe.


Compost is a type of fertilizer that never goes bad as long as you properly store it. However, over time, it might decompose into small bits. But, the potency of its nutrients will remain intact. So, even if you use it after several years, you should achieve similar results.

The most important thing you need to consider when storing compost is the climate. If the weather is hot and humid, it will have a major impact on the substance, causing it to degrade much faster.

You can easily determine if compost has gone bad based on its smell. You will notice a strong odor, and when you touch it, the pile will be wet. Besides humidity, this can result from an imbalance between nitrogen and carbon and a lack of aeration.

How long do fertilizers last in soil?

How long do fertilizers last in soil

Once you place fertilizer in the soil, it will remain there for a variable period. The duration will depend on the type of fertilizer that you use. Among others, you should consider other factors such as the quality of the soil and the number of plants you want to feed.

Here is how long different fertilizers last in soil:

  • Organic dry fertilizer lasts from 4 to 6 weeks
  • Organic liquid fertilizer lasts from 2 to 4 weeks
  • Synthetic dry fertilizer lasts from 4 to 36 weeks
  • Synthetic liquid fertilizer lasts from 1 to 2 weeks

On average, organic fertilizers will need some time to break down into useful nutrients that a plant can utilize. Synthetic products provide much quicker results, as plants can utilize these chemicals almost immediately. Depending on the synthetic substance that you’re using, they won’t last more than a week.

Granule synthetic products have a bit different traits due to their surface coating. These binders envelop active nutrients, thus reducing the rate at which the ground absorbs them. As a result, they last much longer.

The best methods for storing fertilizer

Here are some of the things you need to do to maximizing fertilizer’s shelf life and prevent clustering:

  • Start by finding the right place to store your fertilizer. Ideally, the area shouldn’t have any moisture or sources of water. According to experts, humidity levels should be well below 70%.
  • It is also much better to put it in a cold room without direct exposure to the sunlight. You should have a ventilation system or, at least, the ability to open windows. The area should be closed off so that your kids and pets cannot reach it.
  • Fertilizer should be kept in its original packaging. This is especially important if you’re using several different types of products or bought them at different times.
  • You need to put toxic substances away from organic ones. In particular, they need to be separate from seeds, grains, agricultural products, and foods.
  • It is a good idea to place pallets or linoleum on the ground. This would prevent potential damping.
  • Every bag and packaging should be closed off tightly. By doing so, you will reduce exposure to humidity.
  • Liquid fertilizers are prone to freezing during winter. So while the room temperature shouldn’t be too high, you should find a way to control the climate so that the product doesn’t freeze.
  • Make sure to read the product label. You can also refer to storage instructions.

What will happen if you don’t store fertilizer properly?

What will happen if you don’t store fertilizer properly

There are several signs that fertilizer has gone bad:

  1. The substance will smell differently
  2. It will change the texture
  3. The bottle might bulge
  4. It will become infested with bugs and mold
  5. The product will change its color

If you notice one of these issues, that doesn’t necessarily mean that you should throw away fertilizer. The integrity and potency of nutrients will remain intact. But, you will need to address the issue before you can use it for the plants.

How to determine if a liquid fertilizer has gone bad?

Liquid fertilizer that relies on organic ingredients will go bad rather quickly because it doesn’t have stabilizing chemicals to prevent degradation. In addition, once you open the original packaging, you won’t be able to control the degradation process.

Liquid fertilizer can be affected by microbes such as bacteria, fungi, and mold. The shape of the bottle might change due to the gasses that mold produces. Over time, the liquid will slowly start changing its thickness and will produce a nasty smell.

Unlike some other fertilizers, expired liquid substances can be very harmful to plants.

How to determine if a granular fertilizer has gone bad?

Granular fertilizer that has gone bad will become much harder. This happens due to high humidity, but luckily, you can resolve the issue by simply drying and breaking up the substance.

Organic granular products might also be affected by insects and small barn animals. When they get ahold of the substance, they leave feces and bacteria that are dangerous to plants. If you notice any surface waste or anything else that might seem suspicious, avoid using the fertilizer.

Mold might also start growing on top of granular fertilizer but, this isn’t as concerning as bacteria. You can easily address the problem by leaving fertilizer in a dry room for a couple of days, thus killing the microbes.

How to determine if a microbial inoculant has gone bad?

These fertilizers are very susceptible to environmental conditions. Therefore, you need to keep them at temperatures between 60 to 80 degrees Fahrenheit to maximize their shelf life. Microbial inoculants rely on a mixture of nutritious substances and microbes to provide a boost to the plants.

When you open the packaging, warm air will activate microbes causing them to start feeding on nutrients. As a result, there will be nothing remaining for your crops. At the same time, if you put the bottle in a room at a high temperature, it will kill off bacteria, which is also something you don’t want.

Given that it’s hard to determine if microbial inoculant has lost its potency, just make sure to keep it at the right temperature all the time.

Last thoughts

The best way to protect your fertilizer is by keeping it sealed within the original packaging, controlling the temperature, and preventing microbes from affecting the substance. In most cases, it is easy to tell if a fertilizer has gone bad as it will change its physical properties.

Has your fertilizer ever gone bad? What was your issue? Make sure to share it in the comments below!

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