Eric K. writes Ask Gardenerd this week about using guinea pig poop in the garden: “Can I use guinea pig poop as fertilizer for tomatoes? And since we have a never-ending supply, can I keep dumping it into the soil all summer long, or is there a point at which it’s just too much? Also, when we sweep up the poop, it comes with spilled pieces of their feed hay (Timothy). Can I also dump the hay into the garden soil? I read somewhere that the hay may contain seeds, so perhaps I shouldn’t? Thanks.”
Great question, Eric. Guinea pig poop is similar to rabbit poop in that it doesn’t burn your plants. The carbon-to-nitrogen ratio (C:N) is around 12:1 so it’s mild. If you add urine-soaked bedding, the ratio is higher.
The difference is that guinea pigs can possibly carry giardia, which humans can contract. In my research, I found articles stating that sometimes the human discovers the infection in themselves before they detect it in their guinea pig.
What to Do?
To be on the safe side, it’s best to compost your guinea pig poop and bedding for a few months at least before applying it to food crops. You can probably apply the manure and bedding straight (uncomposted) around non-edibles and fruit trees. The risk is lower there.
If you have pets that eat other animal droppings, definitely compost your guinea pig manure and bedding. It will break down quickly and your garden will enjoy the benefits of that Timothy hay even more.
Hay has Seeds
We always need a refresher on hay vs. straw because it’s easy to forget the difference, so here goes: hay is the whole plant, including the seeds. Straw is just the biomass after the seed heads have been removed. So, yes, that Timothy hay has seeds that will most likely sprout in the garden. If you don’t mind weeding a little, go for it. Otherwise compost it first.
How Much Is Too Much?
Both the manure and the Timothy hay are nitrogen ingredients, so keep an eye on your garden. If you see a lot of green, leafy growth but not much fruiting and flowering, cut back on the manures. Add phosphorus and potassium ingredients to your compost and garden such as high-phosphorus sea bird guano and kelp meal respectively. It’s always good to do a soil test (for N, P, and K) to check levels once per year before amending.
We hope this helps you use that fantastic resource in your garden more effectively. Thanks for writing in.
Hey gardenerds, if you have experience with guinea pig poop in your garden post a comment below.