Fish fertilizer is used primarily for its nitrogen content, but it is also helpful as a mineral supplement, since it contains appreciable amounts of Calcium (Ca), Magnesium (Mg), Sulfur (S), Chlorine (Cl) and Sodium (Na).
There are a few kinds of fish fertilizers,
Fish meal: It’s made from dried fish waste. Oils that become rancid are removed, preservatives are added and the material is spray dried. The nutrient analysis of fish meal is around N : P : K = 10 – 12 : 6 : 2 .
Fish Emulsion: Most fish emulsion products are made by baking, pressing and processing fish parts. I used it only once and it really smells, so I can’t talk about it, but these few site have good pages on the subject:
Neptune Harvest is a fish fertilizer producer, on there site they have a good there fish Fertilizer ( mainly hydrolized ) vs Emulsions fish fertilizers.
Hydrolyzed Fish: made from whole fish waste which is minced and digested with enzymes. To prevent further degradation this fish ‘soup’ is acidified with phosphoric acid at a lower ph than fish emulsion. It preserves more micro-nutrients, vitamins and proteins than the emulsion.
Pacific Natural company has developed a process using enzyme accelerated hydrolysis that helps lock in the enriching nutrients in the fish organic material, allowing them to deliver superior nutritional value to the plant and soil. The process is completely organic. That’s from there web site: Pacific Natural
And they have research results on different field trials.
Organic fertilizer found economically feasible in tests with squash, collards, an Auburn University researchers studied published on the American Society for Horticultural Science