4 Effective Ways To Use Fish Scraps as Natural Garden Fertilizer 1

There are many ways to fertilize your garden, some less smelly than others, and perhaps the smelliest is fish scraps.

Fish scraps have the benefit of building your soil, adding nutrients (especially nitrogen), and reducing garbage that often ends in the landfill or pollutes the environment.

The downsides, besides the smell, are that fish scraps can contain pathogens, parasites, and heavy metals, and they can attract unwanted animals into your garden.

Maybe you have a pile of fish scraps that you just can bear to see go to the landfill. Or maybe you have access to fresh fish guts and you want to give it a try adding fertility to your garden.

Whatever the reason, here are the four best ways to use fish scraps in your garden, and tips on how to do so safely.

What Fish Scraps Do For Your Garden

Fish have been used in the garden since antiquity. Fish scraps can provide many good benefits to soil and plants, but there can be some very dangerous results if it is not handled prudently. Here are the pros and cons of fish scraps for the home gardener.

Benefits

Here are some ways that fish scraps can improve your soil and help your plants grow.

  • Soil Building: As the fish scraps decompose, they will break down and build the soil by adding rich organic matter.
  • Nitrogen: Decomposing fish will provide nitrogen for your growing plants, which is important for healthy plant growth. Fish products will often fertilize your soil at a rate of 4-1-1 (N-P-K), corresponding to the amount of nitrogen, potassium, and phosphorus it adds to the soil. 
  • Other Nutrients: The fish scraps will also add lots of other nutrients such as iron, zinc, calcium, and potassium. Bear in mind, however, that these are not necessarily in a form that is readily available to plants and there has not been very much research into exactly which nutrients fish scraps provide the plants.
  • Reduce Waste: Using fish scraps in your garden means that those pieces of ‘garbage’ and offal won’t end up in the landfill. It is also better to fertilize your plants with it rather than dumping them back into the water.

Disadvantages Of Fish Scraps

Despite its advantages and long-standing history, using fish scraps in the garden should be done with care as there are several problems that can arise.

The Indigenous Peoples are well known to have long used fish scraps to grow their crops. However, while this can still be a viable agrarian practice, we must remember that our agricultural predecessors were not dealing with the polluted waters and contaminated fish that we are exposed to today.

(And they didn’t have nosey neighborrs complaining about the stinking smell fromyour yard).

Here are some of the dangers of using fish waste in your garden:

  • Pathogens: Raw fish can be full of harmful bacteria. Many of these pathogens can stay in the soil and contaminate any crops grown there, pathogens including salmonella and listeria to name a few.
  • Parasites: Raw fish has been known to carry parasites that are very bad for humans. If infected fish is buried in the soil, many of these parasites can remain behind, thereby infecting your soil and any future crops.
  • Attracts Pests: Many animals love to eat fish, including possums, rats, raccoons, skunks, bears, coyotes, and the neighbor’s dog or cat. Rotting fish in your garden can attract at least one of these critters unless it is buried deeply (and even then many animals will dig for it), which can be a health or safety hazard for the gardener. There are also many flesh-eating insects that will be drawn to fish at the expense of beneficial bugs in your garden.
  • Heavy Metals: No amount of heating or decomposition will remove heavy metals from the fish, and these will then make their way into our soil and ultimately into our food. Almost all fish contains mercury at some level, and eagles across North America are getting sick and dying from eating lead-laden fish.
  • Unpleasant Odor: Most people, especially your neighbors, will say that fish stinks. Especially fish left out to intentionally rot.

Where To Get Fish Scraps

Using fish in your garden should be done with consideration of the environmental and ethical impact. Where you source your fish is perhaps the biggest concern.

Most fish that you buy are from fish farms, and there is growing concern about the environmental impact of these aquaculture farms.

Buying or catching fish with the intention of using the whole creature in the garden is extremely wasteful.It is far more responsible to use the inedible remains including the head, bones, organs, feces, and other offal.

Also, using fish scraps on a large scale can pollute the soil and groundwater as dangerous bacteria builds up or washes away.

Is It Better To Buy Fish Fertilizer?

In terms of pathogens and other health concerns, it is probably better to buy fish fertilizers since they have been processed to remove these problems.

Purchased fish fertilizers come in several forms:

  • Fish Meal is the by-product of the fish oil industry. The remaining flesh and bones are cooked dried and ground in a powder to sprinkle on the garden.
  • Fish Emulsions are the by-product of fisheries where the unwanted offal is cooked down and strained.
  • Fish Hydrolysatetakes fish and ferments them into a thick, liquid fertilizer.

While purchased fish fertilizers can cause fewer health concerns than using your own fish scraps, they can have just as many environmental concerns.

Ways To Use Fish Fish Scraps In Your Garden

If you are turned off by the thought of using dead fish in your garden but still want the same results, consider using an alfalfa meal for a healthy dose of vegan nitrogen.

However, if you want to give fish scraps a try in your garden, here are the 4 most common ways to use fish waste for adding fertility to your soil.

1: Bury Fish Scraps Under Plants

Bury Fish Scraps Under Plants
@backwoodscrossing/ Instagram

This is probably the most common way to use fish scraps in the garden, and many Indigenous farmers used to bury a fish head under a corn seed to help it grow.

Here are some tips for burying fish scraps directly in the garden:

  • Grow Fruit Bearing Crops. Avoid growing roots and other crops that you eat the whole plant over fish scraps. If you grow a carrot on top of buried fish scraps, pathogens and parasites can infect the edible root itself, posing a health risk. If you grow a fruit bearing plant, however, such as a cucumber or tomato, the pathogens are far less likely to be present in the fruits themselves.
  • Bury it deeply. In most cases, you want to bury the fish scraps at least 30cm (12 inches) deep. If you are concerned about the smell, or about animals coming and digging it up, bury the fish scrap at least 45cm to 60cm (18-24 inches) deep. Of course, the deeper you bury it the less available the decomposing matter is to the plants, so it is a bit of a balancing act.

Fish scraps decompose relatively quickly compared to other meats or dead animals. At the end of the year, all that will be left of your fish scrap is a few clean bones.

Many gardeners notice a dramatic improvement in their plants when grown over a decomposing fish head, including healthier and stronger growth,

improved productivity, and longer growth for annuals.Here is an interesting video showing the results of growing tomatoes on top of fish heads.

2: Blended Fish Scraps

Another common way to use fish scraps in the garden is to simply blend them with water and spread them as a fertilizer. This is probably the least desirable way to use fish scraps in the garden.

First of all, it smells. Second, you are simply spreading a slurry on the ground where it will become a stinking rotten mess that attracts flies.

It can also be lightly incorporated into the soil, but this does not alleviate the smell nor keep insects and critters away.

It would be far better to blend your fish and then pour the mixture in a whole under your plants as mentioned above. Blending the fish first has the added advantage that the small pieces will decompose faster.

3: Make Your Own Fish Emulsion

Making your own fish emulsion creates a liquid natural fertilizer you can add to your garden. It is quite simple though it is smelly.

How to make Homemade Fish Fertilizer? 🐟 🐟 🐟

Materials You need

  • Fish scraps
  • Sawdust
  • 5 gallon bucket with lid
  • Molasses (unsulfured)
  • Water

Follow these simple steps to make DIY fish emulsion fertilizer.

  • Half fill the bucket with 50:50 fish scraps and sawdust
  • Add 1 cup of molasses
  • Cover the mixture with water
  • Mix well
  • Let it sit for about two weeks, giving it a stir every day
  • Once it has steeped, strain out the solids which can be mixed with fresh water and molasses for another batch, and the resulting liquid emulsion can be used as a liquid fertilizer.
  • Dilute 1 TBS of emulsion in 4 litres (1 gallon) of water, and use this to water your plants twice per week.

Fish emulsion is a fast-acting fertilizer that will provide nutrients for the individual plants but will not improve the garden as a whole.

4: Composting Fish Scraps

Composting Fish Scraps

I am largely against using any meat, dairy, eggs, and also fish in the compost. They are harbingers of pests and pathogens and should not be used lightly in the home garden. You can check this list of household waste items that you should leave out of your compost pile.

Fish may work fine in large composting facilities, but they generally do not have a place in the backyard heap.

If you do choose to compost fish, here are a few safety practices to follow:

  • Make sure the fish is added to the middle of the compost to smother any smell and (hopefully) keep animals from digging them up.
  • Heat the pile to at least 64°C (145°F) which is the minimum temperature required to kill pathogens in raw fish, and make sure it maintains that heat for 5 days.
  • Repeat the heating process three times.

It is important to remember that adding fish scraps does NOT increase the nitrogen content of your finished compost. Unlike burying fish scraps in the ground where the nutrients are released directly into the soil,

composting decomposes the organic matter and turns it into rich humus. Humus is a finished product and it has (roughly) the same nutrient composition whether it is made from plant or animal sources.

Conclusion

Using animal products in a garden is a bone of contention for many growers, as is the health and safety of using raw fish (either for eating or for growing food to eat).

I hope this article has presented enough information for you to make a wise decision for yourself. Whether you use fish or not, always be careful with what you put in your soil, and your soil will reward you with beautiful flowers and a bountiful harvest.

Cameron Jenkins

Written By

Cameron Jenkins

Cameron Jenkins moved from the city to a small farm where he lives with his wife and daughters. The farm is divided between the garden, pastures, hayfields, the start of an orchard, and 13 times as many pets as people. Their farm vision is to grow produce and raise animals in unison with nature. When Cameron is not farming (or writing about it) he spends his time playing with his children, reading, cooking, and napping with his pet pig.

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