Does Fertilizer Cause Metal to Rust?

Fertilizer generally consists of chemicals and other materials, and it’s common for them to come into contact with different metal materials. Because of this, you may be wondering if fertilizer can cause the metal to rust.

Fertilizer can cause metal to rust because it’s a corrosive material. Although some fertilizers will cause more rusting, it’s safe to assume that all of them can corrode metal. To avoid rusting from fertilizer, you should keep it away from metal as much as possible.

The rest of this article will discuss why fertilizer causes metal to rust. It will also discuss the best ways to prevent fertilizer from rusting metal, whether rust is bad for plants, and how to prevent rust in general (not related to fertilizer).

Why Does Fertilizer Cause Metal to Rust?

Fertilizer causes metal to rust because it contains corrosive ingredients. When these ingredients come into contact with oxygen and metal, they can eventually cause rusting. Nitrophosphate is an example of a corrosive element of fertilizer.

According to a study in the Journal of Taibah University for Science, two of the most corrosive agents in fertilizers are nitrophosphates and ammonium sulfates. So fertilizers with these agents are more likely to cause rusting.

The scientific study on agricultural vehicle corrosion also named mineral fertilizer the most significant causal factor in metal corrosion, primarily through these nitrophosphates and ammonium sulfate. 

Prolonged contact with these mineral fertilizers caused pitting, cracks, and enlarged gaps in metal joints. 

Thus your garden fertilizer can and will rust your metal implements, so you should take care with your storage and implements metals in your garden. 

Ways To Prevent Fertilizer From Rusting Metal

Although fertilizers can cause rusting, there are some ways to prevent it from being an issue. Allowing metal to rust from fertilizer will cause you many problems. You’ll have to spend money on new metal equipment, or you’ll need to spend a lot of time trying to remove rust from the objects.

Read the sections below to learn the best ways to prevent fertilizer from rusting metal.

Dry All Metal Equipment After Fertilizer Contact

If you leave the fertilizer to sit on anything metal, it will eventually corrode the material. Therefore, you should try to dry all metal equipment after being subjected to contact with fertilizer.

Of course, this isn’t possible if you’re storing the fertilizer in a metal container. However, if you have any metal tools or other objects around your garden that may have come into contact with fertilizer, dry them thoroughly.

Clean Metal Equipment Regularly To Prevent Rust

As mentioned above, leaving fertilizer sitting on metal for extended periods will eventually cause rust. While it’s essential to dry metal after fertilizer contact, cleaning everything regular cleaning practices are also a must. Cleaning prevents rust from fertilizer, but it also prevents rust from other things like rain and moisture.

However, you should always ensure you thoroughly dry your metal tools after cleaning them. Leaving them wet, especially in a garage or moist environment, could cause rusting. This moisture is what you want to avoid, so keep this in mind when cleaning your tools!

Use Galvanized Steel To Prevent Fertilizer Corrosion

To avoid rust as much as possible, you should consider using galvanized steel. This option is essential if you store your fertilizer in a metal container. Galvanized steel is less susceptible to rust than other metals. However, it will eventually rust. It just takes longer.

Even still, it’s better than using materials that rust quickly. Using galvanized steel as much as possible in your garden and storing fertilizer in this metal should significantly reduce the chance of severe rust.

Avoid Materials That Are Subject to Rusting

You should avoid materials that are highly susceptible to rusting as much as possible. For example, use the original bag or a plastic container to store your fertilizer instead of a metal container.

If you need to use a broadcast spreader to apply your fertilizer, try to use one made of a non-rusting material like plastic. While you can use a metal spreader, it will rust over time and is generally a bad idea.

Additionally, it’s good to ensure no metal tools are on the soil when applying the fertilizer. These items might include small metal cutting and pruning tools you may have left on the soil.

Apply Oil to Metals To Prevent Fertilizer-Based Rust

Oil is an excellent thing to use on metal materials because it keeps them lubricated and prevents rusting. The oil creates a protective barrier over the metal, making it difficult for rust to form. 

So if you have plenty of metal tools often in contact with fertilizer, you may want to consider oiling them every so often.

Is Rusty Metal Bad for Plants?

Rusty metal is not bad for plants in small amounts. For example, if a rusty garden tool brushes off a plant, it likely won’t cause any harm. Since the rust isn’t soluble in water, the plant won’t absorb the rust.

You could even use a rusty tool to prune your plant, which would likely not negatively impact its health. However, rusty tools are generally more difficult to use and cut with because the rust blocks them from moving correctly. 

Because of that, it’s best to remove any rust from your tools, primarily if you use them to cut things. Plus, rusty tools are undoubtedly unsightly. 

Fertilizer-Rusted Implements and Plant/Human Health

It is safe to use rusty implements such as watering cans for plants. Thankfully, the plants won’t absorb the rust because the iron is not soluble. Even so, you should avoid it because it looks unsightly and will continue to worsen if you don’t treat it.

Allowing a watering can or any garden tool to become rusty is bad. The rustier it becomes, the more difficult it will be to clean and restore it. And you certainly want to avoid touching a rusty implement.

Some of the rust will get onto your hand and give it an orange tinge, but it’s also not healthy if you already have a cut on your hand, as you may get an infection. Although the rust itself won’t be harmful, the bacteria present on the rusty object can cause tetanus.

Can Fertilizer Cause Stainless Steel to Rust?

Fertilizer can cause stainless steel to rust, but it is less likely to rust than other metals. The main reason stainless steel doesn’t rust easily is that it contains chromium. 

So if you want to prevent rust as much as possible, using stainless steel tools is undoubtedly better than regular steel or other types of metal. If you need to choose between stainless steel and galvanized steel, stainless steel is the least likely to rust. 

To further prevent fertilizer from rusting your stainless steel tools, you should apply oil regularly. This lubrication will help protect the surface.

Alternatives to Metal Implements in Handling Fertilizer

Fertilizer does not cause damage to plastic. Since plastic can’t rust, you don’t have to worry about leaving your fertilizer stored in a plastic container. This lack of susceptibility to damage is why it’s always best to use plastic tools such as a plastic spreader when applying fertilizer.

The primary material that fertilizer can damage is metal due to the rusting. But as you now know from reading this article, you can do plenty of things to prevent this from being an issue, including avoiding metal materials and using oil to protect the metal.

Preventing Rust in General

Although it’s possible for fertilizer to be the leading cause of rust in metal garden tools, other things could be causing issues. For example, leaving tools out in the rain is sure to let rust grow on metal. 

Another thing to consider is humidity. If you keep your tools in your garage and the humidity is high, they are more likely to rust.

Here are some ways to prevent general rusting in metal:

Don’t Leave Tools Outside

You shouldn’t leave tools outside, especially if it’s humid or it rains. When you’re not using your tools, you should keep them in a safe, sheltered area of your home or garden. However, if the weather is sunny and dry with low humidity levels, it should be safe to leave your tools outside.

Clean and Dry Tools After Use

Earlier, I mentioned the importance of cleaning and drying metal tools after they’ve been in contact with fertilizer. But it’s also essential to clean and dry tools after you’ve used them in general. 

This cleaning is essential if you’ve used a metal tool to touch the soil or if the tool has been in direct contact with water. Since soil is moist, it can eventually lead to rusting in metal tools and materials—washing and drying them after each use prevents this issue.


Fertilizer causes metal to rust because it’s corrosive, so you should be careful when using it around metal objects. If you get fertilizer on a metal object, dry it right after. You should also try to clean and oil metal tools regularly to avoid rust.

When storing fertilizer, it’s best to keep it in its original container. You can also store it in a plastic container, but you should avoid using a metal container. While all metals are subject to rusting from fertilizer, stainless steel is the most resistant.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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