If your idea of a fun afternoon is reading academic research papers, just Google “Salmonella in compost.” You’ll get titles like Cascading effects of composts and cover crops on soil chemistry, bacterial communities, and the survival of foodborne pathogens. To be fair, there is some pretty interesting information in the paper; I’m even using some of it in what you’re about to read. But reading about E. coli, Salmonella, Listeria, and other pathogens is not really what I might call “fun.” 

As gardeners, though, we can’t ignore the possibility of Salmonella in compost. Don’t get too stressed out! It’s not all that common. Still, I’m guessing it’s not something most of us want to contend with. But does compost hide a dastardly bacteria that is out to make us sick?

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What is Salmonella?

As far as bacteria go, Salmonella is kind of notorious. Certain strains of the bacteria cause typhoid fever! Don’t worry, though. That’s not what you’re going to find in your backyard garden. 

Your “basic” Salmonella can cause diarrhea, fever, stomach cramps, nausea, vomiting, or headaches. Salmonellosis, as the illness is known, may appear anywhere between six hours to six days after infection, and symptoms generally last less than a week. The Centers for Disease Control and Prevention (CDC) says that most people recover with rest and plenty of fluids, though more severe cases may require hospitalization. 

Where does it come from? You might not like this answer. It’s kind of gross. The CDC says that “Salmonella live in the intestines of people and animals,” and that it is “usually transmitted to humans by eating foods contaminated with small amounts of animal feces.” 

I told you it was gross! This is why it’s important to wash your hands like 7 billion times while you’re cooking. In all seriousness, hand-washing and keeping your food prep areas clean are two of the best things you can do to prevent contamination. Let’s get back to the garden, though. 

Yikes! Is there Salmonella in compost? I’m about to put that in my garden!

There’s a lot I could say about compost. There’s even more I could say about using manure as compost. Compost can do wonders for any garden. And when you cure it and compost it correctly, some kinds of manure can be nutrient-rich amendments to your soil. The trick with either of these, however, is that they need to be fully composted or cured. 

Back to that research paper I mentioned…, it appeared in the Journal of Applied Microbiology, and there is a lot of information in there. I’d recommend reading it if you want to take a deep dive into soil chemistry, pathogens, and farming practices. Here’s the very abridged conclusion: 

Adding compost to your soil, including manure, can improve soil health to the point of inhibiting the growth of pathogens. “Proper composting techniques are known to reduce pathogen populations in biological soil amendments of animal origin, which can reduce the risks of introducing pathogens to farm fields in soil amendments.”

In other words, when your compost “cooks” for long enough and gets hot enough, that can kill much of the Salmonella in compost. And as you add compost and improve soil health, it becomes more and more resistant to these dangerous bacteria. 

The University of Arizona Cooperative Extension Program agrees that compost and animal manure can be “exceptional organic soil amendments and fertilizers.” They offer a few tips to ensure the safety of any manure you may use.

• Don’t use fresh manure in your food garden, as it often contains E. coli, Salmonella, and other pathogens.
• Let your manure cure for two to four months before you use it. 
• Incorporate any manure into the soil, so it doesn’t come into contact with plant leaves, fruits, and vegetables. 
• Try to add manure after the harvest, or at least 120 days before you harvest any vegetables. 

Of course, you can always skip the manure and compost your vegetable scraps, egg cartons, coffee grounds, tea bags, and eggshells. 

The point is that Salmonella in compost, at least for home gardens, isn’t terribly hard to avoid. Use care in deciding where to get your compost, especially if it contains manure. If you do your own composting, make sure it gets hot enough to kill any bacteria and be sure it’s finished before you use it. 

Have you had any issues with your compost or other problems with pathogens in your garden? How did you handle it?

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