Fish emulsion, the result of cooking and processing fish waste, contains nitrogen, phosphorus, potassium and sulfur. Used as a form of organic fertilizer, fish emulsion is sold as a concentrated liquid. Although fish emulsion works quickly to promote root growth and produce plant protein, some gardeners avoid it due to its characteristic fishy odor. According to the Organic Gardener, fish emulsion is processed from waste from the fish food industry. It does not involve harvesting fish simply to make fertilizer.
Mix one tablespoon of fish emulsion to a gallon of water. Some concentrates may require more or less emulsion; always check the application rate on the container. Too high a concentration can burn roots or damage plants, according to the University of Arizona Extension.
Pour or sprinkle the solution over foliage or on the soil at the base of plants in early spring to give them a boost. Apply in early morning or late afternoon. Avoid application during the heat of the day.
Repeat once or twice a month, or when plants show delayed or halted growth. For blooming or fruiting plants, apply a week or two before blooming or fruit set to encourage healthy blooms and abundant fruit.