Is freshwater fish compost as effective as saltwater fish compost on vegetable production?

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2014: $10,000.00
Projected End Date: 12/31/2015
Region: Southern
State: South Carolina
Principal Investigator:
Dale Snyder
Sweetgrass Garden Co-op


  • Vegetables: eggplant, peppers


  • Animal Production: aquaculture
  • Soil Management: composting


    The comparison of compost made with fresh fish carcasses and salt water fish carcasses found that fresh water fish compost was not inferior.


    A previous study from The Sweetgrass Garden demonstrated the efficacy of compost made with fish carcasses. The source of fish for the study was a commercial, off-shore fisherman and included a variety of wild-caught (not farmed), native coastal species.

    A subsequent grant proposal, which was not funded, involved a comparison of this fish compost with pluff mud, a rich, and abundant organic material. One criticism of this project was that fish carcasses are readily available on the coast, but not inland. Thus, results would not be universally applicable.

    However, on reflection, we realized that fresh water fish are widely available inland. But would compost made with fresh water fish carcasses be as effective as compost from salt water fish? It seems that the two would be equivalent, since the composition of all animal tissue is identical, including fish species. For example, intracellular and extra-cellular electrolyte levels are identical for humans, moles, birds, insects, and all fish species. Because a fish lives in salt water, its flesh contains no more sodium than other animals. On the other hand, it is possible that trace element concentrations are different with ocean fish.

    This study is a field comparison of two compost materials, one made with fresh water fish carcasses and the other, salt water fish carcasses. Essentially, it was a non-inferiority trial testing whether fresh water fish compost is non-inferior to that made with salt water fish , or compost that is plant based.

    Project objectives:

    We planted three 100 foot rows of eggplant with 50 plants in each row and three 100 foot rows of green peppers with 50 plants in each row. 

    We applied saltwater fish compost on one row of eggplant and one row of peppers.

    We applied freshwater fish compost on one row of eggplant and one row of peppers.

    We applied no compost on one row of eggplant and one row of peppers. 

    Our objective was to measure the yields of each row for a comparison of saltwater fish compost versus freshwater compost versus the control rows with no compost.

    The compost preparation was the same for both the saltwater fish compost and the freshwater fish compost.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.