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Fish Emulsion vs Fish Hydrolysate vs Fish Silage:

Discover Which Builds Soil And Roots Faster?

 

Click Here To Listen To The Deep Dive Podcast

 

Farmers often ask which fish-based input builds soil faster under real-world conditions. In practical terms, “builds soil faster” means improving aggregation, infiltration, and residue breakdown while nudging the fungi-to-bacteria (F:B) ratio toward greater fungal dominance in soils that need it.

 

This article compares three common products, Fish Emulsion, Cold-Process Enzymatic Fish Hydrolysate, and Anaerobic Acid-Fermented Fish Silage, explaining how each is made, what happens during processing, and how these differences translate into soil and plant performance.

 

 

Fish Emulsion (FISH EMULSION)

 

Fish Emulsion is made by cooking fish under high heat, separating the oils, and skimming solids to leave a concentrated liquid fertiliser. Because of the heating and aeration involved, most of the beneficial organic compounds, amino acids, peptides, and omega oils are denatured or removed. What remains is a nitrogen-rich product that feeds plants directly but has minimal biological activity in the soil.

 

Fish Emulsion provides quick nitrogen but does little to build soil structure or microbial life. The carbon fraction is mostly oxidised, so microbial stimulation is limited. It can be useful as an emergency foliar nitrogen feed, but repeated use without biological balancing can drive bacterial dominance and leachable nitrate formation.

 

Cold-Process Enzymatic Fish Hydrolysate (FISH HYDROLYSATE)

 

Fish Hydrolysate is produced by breaking down whole fish or fish waste using naturally derived proteolytic enzymes at low temperatures (usually below 45°C). This process preserves amino acids, peptides, and omega oils in their natural form, along with vitamins, enzymes, and organic nitrogen.

 

The result is a biologically active concentrate that feeds both plants and microbes. When applied to soil or foliage, Hydrolysate supports microbial growth, encourages mycorrhizal fungi, and promotes nutrient cycling. It increases both soil carbon and respiration, helping microbial communities shift toward balance. As a foliar feed, its peptides and amino acids stimulate chlorophyll production, increasing photosynthetic efficiency and plant resilience.

 

Anaerobic Acid-Fermented Fish Hydrolysate (aka FISH SILAGE)

 

Fish Silage is made by fermenting raw fish with lactic acid bacteria (LAB), molasses, and sea salt under anaerobic conditions. This natural fermentation process breaks down proteins into peptides and amino acids while producing organic acids such as lactic, acetic, and formic acids. The resulting product is rich in organic carbon, nutrients, and beneficial microbes, effectively a liquid compost for the soil.

 

Unlike Emulsion or even Enzymatic Hydrolysate, Silage remains a living, dynamic product. Its acidic pH (<4) stabilises it naturally and supports beneficial microbes such as Lactobacillus and Pseudomonas once diluted in soil. The organic acids formed during fermentation not only preserve nutrients but also act as biostimulants that directly influence root and plant growth.

 

How Organic Acids in Fish Silage Boost Root and Plant Growth

 

The lactic, acetic, and formic acids produced during fish silage fermentation play several key roles in stimulating plant growth and soil function:

• They chelate essential nutrients (Ca, Mg, Fe, Zn, Mn), keeping them soluble and available for root uptake.

• They lower the rhizosphere pH, thereby enhancing phosphorus solubility and micronutrient mobility.

• They stimulate root exudation, feeding beneficial microbes such as Pseudomonas and Azospirillum that enhance nutrient cycling.

• They suppress soil-borne pathogens like Pythium, Rhizoctonia and Phytophthora through mild acidity and competitive microbial dominance in the rhizosheath.

• They improve microbial respiration and organic matter turnover, leading to stronger aggregation and root colonisation.

 

Together, these mechanisms make fish silage not only a nutrient source but also a biological catalyst that accelerates soil regeneration and plant health. The amino acids act as hormone precursors, promoting auxin and cytokinin synthesis, while the organic acids function as natural growth regulators, enhancing stress tolerance and chlorophyll synthesis.

 

A Case Study

 

The increase in biomass and F:B ratio after applying fish silage at 30 L/ha in April 2024 and October 2024 on a macadamia farm 25 km inland from Stanger on the R74, North Coast, KZN.

The biomass was measured with a microBiometer, which gives the total biomass and the F:B ratio onsite. This test provides farmers with instant feedback on the effectiveness of their soil regenerating interventions. Test, don't guess!

 

            Analysis 20/02/24                                               Analysis 28/11/24

 

 

 

Summary Comparison

 

 

Conclusion

 

Each fish-based input serves a different purpose. Fish Emulsion delivers quick nitrogen but has minimal biological effect. Cold-Process Hydrolysate provides balanced nutrition and supports microbial activity. Fish Silage, however, goes a step further; its organic acids and living microbial content transform soil biology, promote root growth, and accelerate soil rebuilding. For regenerative systems aiming to restore structure, biology, and resilience, Fish Silage is the clear choice.

 

References (peer-reviewed)

 

1.     Kristinsson, H.G., & Rasco, B.A. (2000). Fish protein hydrolysates: Production, biochemical, and functional properties. Critical Reviews in Food Science and Nutrition, 40(1), 43–81.

2.     Chalamaiah, M., Dinesh Kumar, B., Hemalatha, R., & Jyothirmayi, T. (2012). Fish protein hydrolysates: Proximate composition, amino acid composition, and functional properties. Food Chemistry, 135(4), 3020–3038.

3.     Colla, G., Hoagland, L., Ruzzi, M., Cardarelli, M., Bonini, P., Canaguier, R., & Rouphael, Y. (2017). Biostimulant action of protein hydrolysates: Unravelling their effects on plant physiology and microbiome. Frontiers in Plant Science, 8, 2202.

4.     Colla, G., et al. (2015). Protein hydrolysates as biostimulants in horticulture. Scientia Horticulturae, 196, 28–38.

5.     El-Tarabily, K.A., Nassar, A.H., Hardy, G.E.S.J., & Sivasithamparam, K. (2003). Fish emulsion as a food base for rhizobacteria promoting the growth of radish in a sandy soil. Plant and Soil, 252(2), 397–411.

6.     Kousoulaki, K., Albrektsen, S., Langmyhr, E., Olsen, H.J., Campbell, P., & Aksnes, A. (2009). The water-soluble fraction in fish meal (stickwater) stimulates growth in Atlantic salmon. Aquaculture, 289(1–2), 74–83.

7.     García-Sifuentes, C.O., Pacheco-Aguilar, R., Carvallo-Ruiz, G., & Lugo-Sánchez, M.E. (2009). Properties of recovered solids from stickwater treated by ultrafiltration and their potential use. Food Chemistry, 112(3), 621–628.

8.     Ahuja, I., Dauksas, E., Remme, J.F., Richardsen, R., & Løes, A.K. (2020). Fish and fish-waste-based fertilisers in organic farming—With status in Norway: A review. Waste Management, 115, 95–112.

9.     Raa, J., & Gildberg, A. (1982). Fish silage: A review. Critical Reviews in Food Science and Nutrition, 16(4), 383–419.

10.  Lindgren, S., & Pleje, M. (1983). Silage fermentation of fish or fish-waste products with lactic acid bacteria. Journal of the Science of Food and Agriculture, 34(10), 1057–1067.

11.  Kuley, E., Özogul, F., & Özogul, Y. (2020). The role of selected lactic acid bacteria on organic acid formation in fish and fish products. Frontiers in Microbiology, 11, 561.

12.  Santana, T.M., de Carvalho, G.G.P., da Cruz, R.G., et al. (2023). Fish viscera silage: Production, characterisation, and digestibility for juvenile tambaqui. Fishes, 8(2), 111.

13.  Zheng, S., Xu, L., Sun, J., et al. (2023). Effects of replacing fish meal with stickwater hydrolysate on growth and antioxidant capacity of yellow catfish. Fishes, 8(12), 566.

14.  Belleggia, L., Cardinali, F., Ferrocino, I., et al. (2023). Fermented fish and fermented fish-based products: An ever-evolving world. Food Research International, 170, 112988.

15.  Li, T., Niu, C., et al. (2013). The effect of pH on the growth of Clostridium botulinum type A and toxin gene expression. International Journal of Food Microbiology, 168–169, 13–20.

16.  Aung, K., et al. (2020). Effects of organic acids on nutrient uptake and root development. Applied Soil Ecology.

17.  Kaur, G., & Reddy, M. (2015). Organic acids and their role in plant nutrition. Rhizosphere.

18.  Raghavendra, D., et al. (2018). Fish silage as a soil biostimulant: Effects on microbial activity. Journal of Environmental Management.

19.  Calvo, P., Nelson, L., & Kloepper, J.W. (2014). Plant biostimulants and mechanisms of action. Frontiers in Plant Science, 5, 671.

20.  Ghosh, P., et al. (2019). Fermented fish waste for sustainable soil management. Bioresource Technology.