Is Fish Oil a Good Fertilizer for Tomato Plants?
Commercial fish fertilizer isn't fish oil at all; it's called fish emulsion and is a mild, liquid fertilizer made from fish byproducts and waste that provide nitrogen, enzymes and other essential nutrients for plant growth. The chocolate-brown liquid emits a strong odor, but it strongly benefits both tomato (Solanum lycopersicum) seedlings and transplants. When fertilizer is applied to a tomato plant at the right time with the correct ratio of liquid concentrate to water, growers can achieve greater yields and better-tasting fruit.
One technique that is used during the transplanting process is to first flood a planting hole with the diluted fish fertilizer solution; then, the tomato plant's root ball is inserted and covered with soil. This technique assures that young and vulnerable roots receive immediate moisture and nutrients. Fish emulsion can be applied right after transplanting as well by using a watering can at ground level around the base of the plant. The liquid should not be splashed on the foliage.
Starting From Seed
Most fish emulsion recipes call for 1 to 3 tablespoons of concentrated liquid fertilizer diluted in 1 gallon of water. However, when you are caring for delicate seedlings, the solution should be diluted even more. Too much concentrated fertilizer might "burn" or kill a young plant. When high levels of fertilizer are applied, concentrated salts damage roots leading to decreased water intake.
Choosing the Right Fertilizer
A consistent supply of nitrogen helps tomatoes maintain healthy, green leaves. Yellowed leaves often indicate nitrogen deficiency. Fish emulsion contains high levels of nitrogen. The trace minerals and additional nutrients vary from brand to brand. Growers with an organic philosophy might steer toward products made from wild-caught ocean fish rather than farm-raised fish. Others might see geography as a selling point, preferring brands that boast North Atlantic or Alaskan fish ingredients.
Fish emulsion should be applied in cool weather, preferably in the early morning or evening. Avoid applying it in the midday heat or to any heat-stressed plants. If fertilizer is applied at the wrong time -- or if too much of the concentrate is applied at once -- it might prevent tomato plants from forming fruit. A sure sign of too much nitrogen fertilizer in tomato plants is lush and healthy plants with few flowers and fruit.
- Organic Gardening for Dummies; Ann Whitman, Suzanne DeJohn
- Washington State University: Common Cultural Fertilizer Burn
- Tomato Dirt: Preparing Your Soil for Planting Tomatoes in the Home Garden
- Mother Earth News: Free Homemade Liquid Fertilizers
- The Veggie Gardener's Answer Book; Barbara W. Ellis
Sally Wenczel has been writing professionally since 2004. Her articles have appeared in "Traverse City Business News," "Traverse Magazine," "The Chaldean News," "Garden Design Magazine" and "Ferndale Friends." She is program director for Growtown.org at the Penrose Art House & Art Garden in Detroit. Wenczel holds a Bachelor of Arts in English from Albion College and is a certified clinical massage therapist.