Fish emulsion is a quick-acting organic liquid fertilizer made from byproducts of the fish oil and fish meal industry. It is also called fish fertilizer. It is a thick concentrate that you dilute with water and apply to your lawn or garden. It can have a strong fishy odor, but deodorized fish emulsion is commonly available as well.
Fish emulsion is appropriate for many uses in the garden but is especially useful as a lawn fertilizer in early spring and to feed leafy green vegetables due to its higher nitrogen content. Be careful when applying too much of it, though. If your soil already contains high levels of nitrogen, applying too much fish emulsion can cause nitrogen "burn" and affect growth. If you are not sure what condition your soil is in, contact your local Cooperative Extension Service to arrange a soil test, use a home soil test, or hire a professional to examine the soil.
To use fish emulsion, you first need to dilute it. Add just 1/2 ounce (about two tablespoons) of fish emulsion to 1 gallon of water. The odor may be strong but will dissipate in a day or so. Then water the plants using that fish water. Because fish emulsion works quickly, you may want to apply it more frequently. In fact, North Carolina State University researchers report that applying it twice a week gives plants the most significant growth compared to other frequencies. You can continue to apply it if the frequency seems to be working. You may consider fertilizing your lawn every spring with fish emulsion using a hose-end sprayer.
Make Your Own
Commercial fish emulsion can be pricey, plus it lacks bacterial microorganisms important for soil and plant health. You don't have to buy fish emulsion as you can make your own fish emulsion if you have fish scraps available. All you need is a bucket with a lid, mesh screen, sealable bottle, dried leaves, sawdust, or other brown material, fish scraps, and water. (An optional addition of molasses can help build up microbes that speed decomposition.) It is important to note that with any homemade fertilizer the ratio of nitrogen, potassium, and phosphorus will be unknown. Here is how to make it:
- Designate a five-quart bucket for the emulsion. It will always smell like fish after this, so you likely won't want to reuse it for something else.
- Get fish scraps from a store, or put your own in.
- Layer them in with leaves until the bucket is two-thirds full. The "browns" help control odor.
- Top the layers with a fish layer.
- Cover the mixture with water, leaving a few inches of space on top of the bucket.
- Seal the bucket and tuck it away. Check it each day for a week, and then every few days, to see if the gas is building up. When you notice gasses begin to form, you should stir the mixture once a week.
- It should sit for about a month. If you live in a warmer climate, it may tend to break down faster.
- To use the homemade fish emulsion, strain out leaves and fish bits by using a fine metal screen (an old window screen works well). Avoid smelling like a fish by being careful not to allow it on your skin or clothing. Place the strained emulsion into a sealable bottle. Dilute about 5 ounces of the emulsion into 1 gallon of water, or dilute 30 ounces of it into a 5-gallon bucket. Apply to the garden.
- Don't get rid of the leftover scraps. Add more water to the bucket and start the process again. You can typically use used material about three times.
Tenenbaum, Frances, et al. Taylor's Master Guide to Gardening. Houghton Mifflin, 2001
Fertilizer From the Sea. North Carolina State Cooperative Extension