Agriculture Reference
In-Depth Information
Fish
Fish fertilizers come in different forms and qualities. According to the topic
Food Power
from the Sea
, fish was used as a fertilizer in Europe as far back as the Middle Ages. The
technology has changed — we now have liquid products that are easier to apply and more
efficient — but the principles are the same.
A fish emulsion is a liquid that's cooked to kill putrefying bacteria, filtered and stabil-
ized with sulfuric or phosphoric acid. The important oils, amino acids, vitamins, hormones,
and enzymes have either been separated for use in different products or denatured in the
high temperature manufacturing process. Some people prefer an emulsion over a hydrolys-
ate. My view is that it's often a lower quality product, but is still beneficial to use.
A hydrolysate is a liquid often made with by-catch, which is all of the unwanted fish that
were caught in the process of catching other more desirable fish. The whole fish is used in
this process. Instead of cooking, it's digested with enzymes at cooler temperatures, ground
up and liquefied. Phosphoric acid is used here, too, as a preservative. Many of the oils,
amino acids, vitamins, hormones, and enzymes remain in the product. The result is a
nutrient-rich product that has many trace minerals, is less prone to leaching than soluble
fertilizers, and is wonderful microbe food.
It's $20-$30 for a gallon of quality emulsion or hydrolysate. The application rates vary
widely, from approximately 1 ½ cups per 1,000 square feet for my hydrolysate to three
quarts per 1,000 square feet for some of the emulsions I've seen.
You can occasionally find either of these liquids without phosphoric acid as a preservat-
ive, which is okay as long as you use it before it spoils (or explodes). I don't mind the small
amount because it's a good source of phosphorus. It's still allowed in organics if it's under
a certain threshold.
Fish meals contain 5-12% nitrogen. The oils are removed to increase the nitrogen con-
tent and prevent it from spoiling. They're applied to the soil or mixed in a foliar spray. I
don't use them because I've always stuck to a really good hydrolysate I found early on, but
they are another option. It's $45-$70 for 50 pounds, which covers 500-1,500 square feet.
Fish fertilizers can be mixed with EM and water, and optional humic acids, and left to sit
for a few hours before application to decrease the odor of the fish. I had one client com-
plain that the fish attracted cougars, but mixing it with EM should cut that odor down tre-
mendously. Many people swear by this as a foliar feed. There's a golf course in the U.S.
that uses this as their only source of nitrogen.
Fish brings in many nutrients like the sea minerals, but it's particularly high in nitrogen,
available phosphorus and potassium. These natural, quite available forms of nitrogen and
phosphorus are especially useful when you don't have enough humus yet. Fish hydrolysate
