Fish scraps in your garden… not the most glamorous of neatly placed mulch, right? You might wonder how they will smell, how easy they will be to work with, and whether you will attract every raccoon within a 5-mile radius. Can you imagine raccoons all over your yard? But fish scraps can be very beneficial for your soil! They nourish your plants, create organic matter, and get a waste product away from the landfill. It is one of those little tricks gardeners have been using for eons, and if you can deal with some of the management of the downsides, it still works today.
What Fish Scraps Provide to the Soil
When fish breaks down in soil, it doesn’t just disappear, it is basically a feast of nutrients. You are adding nitrogen (when in fresh fish, about a 4-1-1 NPK ratio), which plants love for growing leafy parts, along with additional minerals such as calcium, potassium, zinc, and iron. Fish scraps are also pure organic matter, which will over time improve the structure of the soil. And if you dislike throwing things out, this is a cool way to see something that may have gone in the rubbish bin turn into a free fertilizer.
There are some trade-offs you have to think about, though. Raw fish can carry pathogens and parasites, so if you are growing edible crops, you need to be careful where you use it and how much you use. And the stink? Let’s just say every neighborhood cat might think your yard smells delicious. There is also the small but real risk of heavy metals like mercury that could be present, especially if it came from a sketchy waterbody.
Selecting Safe Sources
If you want to try it, you want to start with fish scraps that are safe and sustainable, specifically heads, bones, and guts from fish you would eat yourself and wishing you had more of. Do not use whole fish and do not use anything that is spoiled. It is also better if you know the source has not fished in heavily polluted waters. And just to be clear, once you have your fish scraps, you don’t want to just toss those scraps on the surface of your garden and walk away. Unless you want to be swarmed by pests and smell some pretty bad odors.
Why Some People Use Commercial Fish Fertilizer
If you are cringing at the thought of raw fish in your soil, there is an easier way to go about it. Commercial fish-based fertilizers (fish meal, fish emulsion, fish hydrolysate) are processed so they won’t carry pathogens and smell much less, and they will offer you many of the same nutrient benefits without the pesky pest risk. Disadvantages? You pay for something you could have made yourself for free, and depending on how the process is completed, some of them might not offer you an environmentally friendly product.
Four Methods to Use Fish Scraps Safely
If you’re going the DIY route, there are four well known methods gardeners use, each with some pros and cons and the various “ick” factors involved.
Bury Them Deep
This is probably the oldest method in the book, and I’ve read that Native American gardeners used to do this all the time for corn. Just choose plants that will appreciate the boost (fruiting plants seem to benefit most). Dig a hole that is at least 12 to 24 inches deep, put the scraps in the hole, and cover them back with soil. This keeps the scraps contained and the odors to a minimum, plus it makes it harder for animals to dig the scraps up. Over time, the scraps will break down and return nutrients to your soil where the plants can access them.
Blend and Pour
Yes, you read that right, a fish smoothie for your plants. You can put the scraps in the blender with some water and then pour it into your soil. This will hasten decomposition, and, full disclosure, the odor is strong, and it does not magically disappear when you bury it. Plus, using an emulsion probably is not the best method if you already have pest issues in your neighborhood.
Make Fish Emulsion
If you want to go a little less “homemade,” you can create your own fish emulsion. You mix fish scraps with sawdust or another carbon source, molasses, and water and let it break down into a liquid fertilizer you can use. This needs to be diluted prior to using, but now you have quick-acting feed for individual plants. Making fish emulsion is messier than just burying fish scraps, but it is more flexible and can be easier to apply.
Compost With Caution
You can add fish to a compost pile, but only if you are willing to manage the odor and ensure the pile gets hot enough, at least 145°F, to kill the pathogens present. You will probably have to go through multiple heating cycles to ensure it is safe. Nutrient-wise, fish hardly changes in compost, but it will contribute something to the overall combination of materials.
How to Decide
It comes down to how much of a mess and odor you can deal with and the risk for your plants. If you want the least amount of fuss, deep burying will probably be the easiest method. If you like a little bit of unpredictability, try the emulsion method. Composting is a viable option if you have a compost system already. Just remember: the deeper you bury it and the better you can mask the odor, the fewer pest problems you will have.
Not everyone can handle fish scraps in the gardens. Some gardeners are staunch fish scrap users, while others will not only shy away from it, but run as far away from it as fast as they can. With careful processes, fish scraps can be an environmentally sustainable and helpful method to enhance your soil fertility. In the end, whether you do it at home, or purchase something store bought, the end goal is nutrients for the plants, while aligning your efforts with the entire ecosystem in your garden system.
