Fish fertilizer is very popular. It is reported to be a good source of nutrients and a good source of proteins, amino acids, and oils—for your plants. Can plants use fish proteins and oils? Is fish fertilizer a good source of nutrients?
Before I go any further, let me say that there is nothing wrong with using fish fertilizer. It will help make your plants grow. I have two problems with fish fertilizer: it is extremely expensive compared to other sources of fertilizer, and many of the claims for it have no basis.
Fish Emulsion vs Fish Hydrolysate
What is the difference between fish emulsion and fish hydrolysate? The difference from a plant’s point of view is minor, but if you are trying to sell product, there are big differences.
Fish emulsion and fish hydrolysate start with dead fish. In some cases this is leftover bits from the fish industry, and in other cases, this is whole fish specifically caught to make fertilizer. These are then treated with various chemicals and enzymes to break down larger organic molecules into nutrients and other small organic molecules. Further treatment can take one of two paths; it is either heated or cold processed. Fish emulsion is the end product if the heating process is used. Fish hydrolysate is the result of using cold processing.
There is great debate between the benefits of emulsion vs. hydrolysate—which is better? The reality is that plants can’t use most of the large or even small organic molecules from either process. Normally microbes in the soil degrade these to nutrients plants can use. So the argument that heat in the emulsion process is detrimental makes no sense. It is true that heat will denature proteins, but they need to be denatured for the plants to use them.
I think the arguments for or against either process are just marketing hype. I have seen no scientific evidence to support the superiority of either process.
Fish Fertilizer Benefits
Fish fertilizer is an organic product—for the most part. So it does have the benefits other organic soil additives have. It feeds plants and microbes and improves soil structure.
But proponents of fish fertilizer make claims that do not apply to other organic fertilizers. Most seem to be centered around the fact that the liquid fertilizer contains proteins and oils. We all know fish oils are very important for our health, so they must be good for plants, right? Wrong!
Plants can’t make use of large molecules such as oils and proteins; see Organic Fertilizer—What Is Its Real Value? for more details. When these molecules are added to soil, microbes digest them and turn them into small molecules like nitrate and phosphate. It is only then that plants can make use of these molecules.
Since the large molecules need to be degraded before plants can use them, there is little difference—to the plant—between proteins and oils from fish, cows (manure), or even plants. I have found no support for the claim that fish fertilizer is better than any other organic fertilizer.
The main thing plants need from fertilizer is a source of nitrogen. Garden soils usually have enough P and K and the other minor nutrients. Nitrogen is the thing that is missing in soils. Given this fact, fish fertilizer is no better or worse than other types of fertilizer.
Fish fertilizer has about 2% nitrogen, which is the same as most organic fertilizers: compost, manure, and coffee grounds.
Is Fish Fertilizer Organic?
This probably seems like a dumb question—fish are organic, so why would fish extracts not be organic? Here’s why. In the process of turning fish scraps into fertilizer, companies add a number of chemicals, including phosphoric acid and odor inhibitors. Apparently, as long as these ingredients form less than 1% of the finished product, the product can still be called organic. Who knew—organic fertilizer only needs to be 99% organic!
Cost of Nitrogen
I checked several fish fertilizers, and a common analysis is 2-4-2, and if you buy in large containers, you can get 9 lb (3.8 kg) for $25. Small quantities are even more expensive. This fertilizer has 2% nitrogen, and so the cost for the nitrogen is $33 for 100 g of nitrogen. Wow! Even fresh-caught Atlantic salmon doesn’t cost that much!!
What is the cost of 100 g of nitrogen if you buy a commercial fertilizer? Scotts sells a 30-0-9 at $17 for 6.2 kg, or $0.91 for 100 g.
Fish fertilizer is 35 times more expensive than commercial fertilizer, and plants can’t tell the difference between the two sources of nitrogen.
I can hear your objection, BUT … fish fertilizer is organic. That is true, and organic fertilizers do more than just provide nutrients. They also help build better soil by feeding microbes. Fish fertilizer is about 14% protein, which is the same as manure. A 30 lb bag of manure will cost you $4 compared to $75 for the same amount of fish protein. Manure bought in bulk is even cheaper.
I really can’t think of any good reason to buy fish fertilizer if other sources of fertilizer are available.
References:
1) Photo Source: Cheryl’s Garden Goodies
….Meant to say that the plants require less insecticide/fungicide input grown w/fish& kelp vs synthetic NPK in last paragraph. But sheeeeewt. Since it’s been established that the amino acids in the hydrolysate (fish, whey, soy, poultry litter/feather meal, whatever the source) act as chelators in the soil for the sequestered & otherwise unavailable nutrients, the plants DO require less actual fertilizer input from the farmer when grown with fish hydrolysate vs ammonium or calcium nitrate.
🙂
It is true organic mater added to soil, helps hold nutrients in soil. And higher organic levels means that you need to fertilize less over time.
But plants still use the same amount of nutrients no matter the source.
As someone who has done multiple side by side comparisons of very high value consumable crops, I will say that fertilizing with hydrolyzed fish & kelp meal improve product appearance, aroma, flavor, fruit/flower size, fruit/flower shelf life, & provides a MEASURABLE increase in the plant resins & aromatic oils. My flowers test 10-15% higher for essential aromatic compounds when grown with fish hydrolysate & mechanically dried kelp meal VS when grown in sterile medium with with synthetic fertilizers. If my crop nets me an additional $1-2000 versus using scotts or miracle gro (or even an expensive ‘hydroponic’ bottle of mineral salts – one with multiple chelates), AND I can reuse my medium because it is not all locked up with mineral salt imbalances, it seems to be a smart $50 investment for the fish & kelp.
Feed the soil, not the plant. Plants fed fish and kelp also require less fertilizer input. Higher brix levels in the plants ensure that the plants will be more able to fight off any possible pests by themselves without me spraying them with pesticides/fungicides.
Please provide to support your findings.
Re”Plants fed fish and kelp also require less fertilizer input” – that is clearly not true. The amount of nutrients a plant takes out of soil is exactly the same no matter where the nutrients come from.
Do higher brix ward off pests?? I’d like to see the data on that. In fact, if anything, I would expect a higher brix to invite more pests like aphids due to the higher sugar levels. You might be growing your plants well which can lead to higher brix, and less pests. But that does not mean that there is a causation relationship between high brix and number of pests. The plant that is able to produce higher brix is usually healthier and therefore also able to produce more natural pesticides.
All I have to say is that you should read teaming with microbes and teaming with nutrients. It will educate you on how you feed the soil and not the plant.
Synthetic nutrients destroy the natural life of the soil, especially nitrogen.
Teaming with Microbes has some good points in it, but also has several incorrect statements in it.
You can’t feed the soil – soil is not living! Soil is the mineral part of what is in the ground plus organic matter. None of this is living. Soil does have a lot of things living in it.
The statement “synthetic nutrients destroy the natural life of the soil, especially nitrogen” does not make sense for two reasons:
1) Synthetic fertilizers when used appropriately do not destroy the natural life forms in soil – that is a commonly held myth.
2) Nitrogen is not a natural life form!
There is absolutely no difference between nitrogen from synthetic fertilizer and nitrogen from an organic source. to better understand this have a look at https://www.gardenmyths.com/what-is-organic-fertilizer/
Quote: “You can’t feed the soil – soil is not living! Soil is the mineral part of what is in the ground plus organic matter. None of this is living. Soil does have a lot of things living in it.”
You have just changed the definition of life. This applies to every living thing. You have alot of living things in you, without the bacteria you would not last very long.
No I didn’t.
Humans are living because we grow, we reproduce, our bodies consume compounds that get turned into larger compounds etc. Soil does none of the things we associate with life.
So in summary, fish fertilizer is a myth because you find it too expensive? Even though people have been using it before your time?
If you took the time to read the post you would know that what I said was “Before I go any further let me say that there is nothing wrong with using fish fertilizer. It will help make your plants grow. I have two problems with fish fertilizer; it is extremely expensive compared to other sources of fertilizer and many of the claims for it have no basis.”
People before my time used real fish that they collected – not the over priced, over hyped products being sold today.
There is good evidence (fully replicated scientific trials) which show that fish (and some other widely used organic preparations), have a significant affect on biological activity in soil. Since microbes are extremely important in nutrient cycling, plant access to nutrient, biological control of pests and diseases (to mention a very small number of their functions) I find it extraordinary that people continue to look at this only from the point of view of nutrient supply. I also find it extraordinary that a microbiologist or an entomologist or even a soil scientist, will have a completely different viewpoint than what is promoted by mainstream fertiliser companies who only promote one aspect of soil health (that of soil chemistry).Growth of healthy plants is a result of a complex interaction between soil physical characteristics, soil biology and soil chemistry.(all modified by climate, altitude and multiple other environmental factors). ie limitation comes from any factor which is limiting. There is no magic solution. If there is a shortage of nutrient to a plant, then either the nutrient needs to be supplied or the farmer needs to improve the ability of that plant to find the nutrient that the plant needs. There is more than one way to skin a cat! Since farmers have different values and goals, their choices on how to achieve this will be different. What is needed is an open minded approach from both ends of the debate, so that farmers are able to get the information that they need, in order to be able to make sensible, sustainable decisions, without the vested interest of those who supply products (both organic and mainstream) getting in the way……end of rant 🙂
No one doubts that fish fertilizer will have an effect on soil. Any fertilizer, organic or synthetic will have such an effect.
But does a fish extract perform better than another source of nutrients? That is a different question, and I don’t think there is good evidence that this is true, for the ‘fish extract’ products on the market. If it is, I would like to see a reference. You say that “fish (and some other widely used organic preparations), have a significant affect on biological activity in soil” – Ok so what. I don’t doubt this. I can throw almost any organic material on soil and get increased biological activity.
To be of value to gardeners, these studies need to show that when fish extracts are applied to a garden, they produce better plant growth than other sources of nutrients. People are trying to equate biological activity to better plant growth, and that is incorrect. That does not mean that some types of biological activity does improve plant growth – it does in some cases. But the one does not necessarily follow the other. In fact increased biological activity can harm a plant if the microbes being stimulated are pests.
I also think there is a big difference between adding real organic matter like raw fish, and adding extracts. Extracts are much closer to synthetic chemicals as far as their value to soil goes.
Your statement “There is no magic solution. If there is a shortage of nutrient to a plant, then either the nutrient needs to be supplied or the farmer needs to improve the ability of that plant to find the nutrient that the plant needs. There is more than one way to skin a cat! ” is absolutely true.
Hello Robert Pavlis,
Thanks for writing a nice blog. The section “Is Fish Fertilizer Organic?” could use some clarification.
1) Most commercially available hydrolysates and emulsions do not use odor inhibitors and which are very benign. Examples of odor inhibitors are: Tea tree oil, Lavender, Mint extract. These odor covering solutions are organic. Some are even organic certified in their own right. I don’t add them to my own hydrolysate because they are expensive.
2) The blog is correct, phosphoric acid or H3O4P is an inorganic acid. It is important to know what that means. H3O4P comes from minerals (salts) and it is not going to hurt you, or your plants, or the microbes near your plants. The potential harm from this acidic salt is that it is corrosive. How corrosive? Very corrosive at 85% (typical liquid state for H3O4P) and hardly corrosive at all at 1% (the amount in fertilizers). The pH for fish protein hydrolyses and most emulsions is about 4. For perspective, this is less acidic than tomato or orange juice.
3) We should add this information for your more interested readers. Some emulsions use mold inhibitors, like sodium propionate. These are mold inhibitors that are used in things like bread and grain storage. That white powder on a bun from a fast food burger or a pack of twelve white bread hot dog buns. That is sodium propionate, and some of it gets on your plants. In the fertilizer, it can make up about half a tenth of a percent volume (.05%).
For your really interested readers have provided some additional information.
General info about organic acids – http://www.differencebetween.com/difference-between-organic-acid-and-vs-inorganic-acid/
Nitty gritty on the three main types of Phosphoric acid –
http://pubchem.ncbi.nlm.nih.gov/compound/Phosphoric_acid#section=Top
Trailing wheels version – http://blog.fooducate.com/2009/06/30/11-quick-facts-about-phosphoric-acid-yes-that-chemical-in-coca-cola/
For our graduate student research readers – http://www.tandfonline.com/doi/abs/10.1080/10408690091189266
4) Also… I agree there is a lot of hype by fertilizer companies about the differences between hydrolyses and emulsions. The significant difference is that emulsions are heated. The heat kills many important microorganisms. Your microorganisms are hugely important! Do not roast your protozoans, do not fry your endomycorrhizal fungi, do not endanger your endogenous bacteria. If, as you claim, you have been having trouble finding articles on the topic from unbiased sources try some of these:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722406/
http://www.jifro.ir/files/site1/user_files_eb12be/eng/rabbanihamahnaz-A-10-600-9-a76695f.pdf
http://www.scribd.com/doc/233468891/Fish-Protein-Hydrosates#scribd
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1999.tb12268.x/abstract
5) Also some clarification about the fish oil… The argument for fish fertilizers is that the oils present in fish protein based fertilizers act as a spreader sticker, or an agent to help adhere the nutrients to the plants. This is a benefit to the plants as it increases the uptake of available Nitrogen. Plus we could re-work your math all day with other fish based fertilizers that have higher percentages of available Nitrogen. Many are closer to 5%. For me a 3.8% N fertilizer with higher uptake (thanks fish oil) and longer amino chains on the proteins (thanks cold-process hydrolysate) to feed my endomycorrhizae is far superior to the chemical alternative.
Last thing. Be careful making your own fish fertilizers at home with salt water fish. They can be salty. I also do not recommend using waste from commercial aquaculture unless you are sure they do not use antibiotics. The same goes with cow manure. My absolute preferred fertilizer over time is fish protein hydrolysate with some cow or chicken poo every now and again to balance your P and K. A mixture like this is wonderful for developing organic matter %.
Okay, I got carried away. Cheers.
-Thomas
Thanks for all the great info.
Re: your #4. You say “The heat kills many important microorganisms” – that is true. However I don’t think this is a bad thing. The microbes in and on fish are going to be quite different from the ones in the soil – completely different environments. There is no value in adding microbes on fish to your soil.
After heat treatment, the resulting material is food for soil microbes – this is true if heated or not.
The links are about hydrolyzing protein. None of them look at the effects of different processes on plants. I was looking for a study that compared different processes on actual plants grown in the field.
Re: 5. “oils present in fish protein based fertilizers act as a spreader sticker, or an agent to help adhere the nutrients to the plants”. Do you have proof of this? Sure oils would stick to plants, but that does mean it is good for plants. Nutrients need to go into soil and be absorbed by plants. Having nutrients ‘stuck’ to oil in the soil is no benefit to plant roots.
Re: “increases the uptake of available Nitrogen” – I find that hard to believe. Nitrogen is absorbed as nitrate and ammonia in water around the roots. Oil would not help. But if you have a reference to support this I’d be interested in seeing it.
Re:”longer amino chains on the proteins (thanks cold-process hydrolysate) to feed my endomycorrhizae is far superior to the chemical alternative” – do you have proof? all of these proteins need to be degraded to simple nutrients like nitrate before plants can use them. Having longer chains of amino acids is not going to be of any benefit. Ans organic nutrients are not far superior to chemical alternatives. Once they are converted to nitrate molecules – plants can’t tell them apart. See https://www.gardenmyths.com/what-is-organic-fertilizer/
To Thomas Lansing: “Be careful making your own fish fertilizers at home with salt water fish. They can be salty. I also do not recommend using waste from commercial aquaculture unless you are sure they do not use antibiotics.”
I agree with you on the antibiotics—they can attack the very bacteria in the fish and soil that you need. However, the ocean fish comment is probably inaccurate.
First of all, nearly all commercial fertilizer derived from fish, whatever its form, comes from ocean fishes. In my earlier post, I discussed the sources of fish-based fertilizer. It is not a sustainable source and should be avoided if possible.
Second, the “saltiness” of fish tissues (or any animal tissue) is about the same across fresh and salt water. Fish kidneys are very efficient at removing excess salt from the body, so there is little or no difference between fresh water and ocean fish when it comes to the salt content of their tissues. You may, however, want to wash off the sea water still clinging to the fish’s skin and mouth.
Antibiotics will decompose just like any other organic chemical. I do agree we want less in the environment, but I don’t see it as a concern in fertilizer.
You are still talking about amounts of nutrient and its direct effect on the plants that grow within that system. The most productive ecosystems on earth grow with no applied fertiliser. I agree with you, when you say that any input must produce an economic benefit for farmers (or gardeners). I also believe that the soil ecosystem of our farms and gardens is hugely disrupted compared to those natural ecosystems. I believe that the way of the future is efficient use of fertilisers which have minimum impact on soil biological systems and use of products which help to activate or enhance natural systems in the soil. There is scientific evidence that use of a number of products including fish hydrolsate and fish emulsion produce a measurable increase in both numbers, and activity of soil micro organism, and that use of high rates of high analysis fertilisers, particularly nitrogen fertilisers, produce the opposite, over time. So the question remains, is this of economic benefit?
The statement “most productive ecosystems on earth grow with no applied fertiliser” is not true. It is true for commercial fertilizers, but fertilizer is still applied, and plants can’t distinguish between the two.
The statement “There is scientific evidence that use of a number of products including fish hydrolsate and fish emulsion produce a measurable increase in both numbers, and activity of soil micro organism:, is certainly true. Adding nutrients of any type to soil will have this effect.
The statement “use of high rates of high analysis fertilisers, particularly nitrogen fertilisers, produce the opposite, over time” us also true, if by “high” you mean amounts in excess of recommended amounts. However, when commercial fertilizers are applied in amounts that make sense to replace deficiencies, the evidence is clear, that they do NOT destroy soil structure or affect soil life in a detrimental way.
I do agree with one point you make. We should not apply nutrients, as commercial or organic products unless we know there is a need.
I am really enjoying the debate, so I hope you don’t mind more questions. Are you saying that the only stimulation of microbial activity is from nutrient supplied? That there is no such thing as an activator? Are you also saying that no harm is done to any soil microbes by commercial fertilisers if they are applied at the required rate? There is then a whole argument about required rates vs recommended rates, when these are driven by commercial interests. It is a minefield out there!
Microbes are just like other living things. Food stimulates their growth. they need nutrients to grow, but they also need the right temperature, and the right amount of oxygen.
Activators are usually a mixture of bacteria and nutrients. For more info on this see https://www.gardenmyths.com/compost-accelerators-starters-and-activators/#more-2770
“Are you also saying that no harm is done to any soil microbes by commercial fertilisers if they are applied at the required rate? ” – correct. a bacteria or plant can’t tell if the nutrient molecule is from a commercial fertilizer or an organic source, because they are identical.
“There is then a whole argument about required rates vs recommended rates, when these are driven by commercial interests. It is a minefield out there!” a farmer bases their nutrient application on soil tests, so this is not a problem – they don’t follow package instructions. Howe owners don’t get soil test done and just guess – many times based on folklore or something stupid they were told on social media. If you don’t know what nutrient is missing from your soil – how can you expect to add the right nutrient, in the right amount???
hi,
well,I a afraid I dont understand your mathematical or financial explanation of the fish emulsion. You claim it is very expensive and poor in nitrogen. I have a 3 x 1 square meters of cranberry plot and I make my own fish fertilizer. I buy 500 grams of fresh fish for 1 dollar and a half plus other ingredients and that is enough for the whole year.Even other plants benefit from this fertilizer.
That is cheap fish – $3 per Kg. How much does your nitrogen cost? Fish meat is 15-20% protein. Assuming you are buying whole fish, it would be at the low end of this range. 1Kg of fish is 150g of protein. But only part of the protein is nitrogen – 16%. So the 1 Kg of fish contains 24 g of nitrogen. So you are buying 24 g nitrogen for $3. So you are paying $12 for 100 g of nitrogen, compared to commercial fertilizer at $0.91 for 100 g.
You are adding 500 g of fish to your garden plot for $1.50 – that is 12g of nitrogen (500 x .15 x .16). As commercial fertilizer this would cost you just $0.11.
trying to read the articles (below this box on https://www.gardenmyths.com/fish-fertilizer-worth-buying/ and they keep moving before I can finish reading them. Is there a fee to be able to actually read the article?
You must be talking about the promotions at the bottom of the post. Just click on the one you want to read and it twill take you to the page. Everything on this web site is free.
I have been terribly neglectful with my blog and just ran across your article using my picture. I am so flattered. Thank you!
Cheryl
Perhaps the benefit is in the fact that it is processed by a microbe. ie it is a food source. These are the same microbes which are cycling nutrient, and converting it to plant available forms. Without microbes, ever increasing amounts of the nutrient our plants need will have to come out of a bag. I agree with you if all we are looking at is NPK etc, but we all know that it is a lot more complex than that.
I am sorry–I don’t understand your comment. I did not say fish fertilizer has no benefits. I agree that microbes will use the nutrients and yes they are very important to healthy soil. The point of the post is that fish fertilizer is a very poor and expensive choice. Most other options are less expensive and also feed the microbes.
Well here in the tropics it is a sustainable soil amendment.Heavy rain fall, That oil helps leaching,Cold process has living enzymes doesn’t matter NPK your chemical only feeds your plants and runs off to destroy more ground water. When making fish 50gal of shredded fish makes 1000-1 dilution rate which = teaspoon a gal .. Protein in your soil is food, They have been using it way before us and way after.. Fish is the most amazing soil amendment i have ever used and consider your blog a insult to Fish fertilizer and people making the world a better place without chemicals.
I think you missed the point of the post. I never said fish were not sustainable, nor that it was not a good fertilizer. I also did not discuss the situation where you live near available fish and can make a 50 gal batch for yourself at low cost.
Most gardeners need to buy the material in small containers – and then it is a very expensive choice.
Living enzymes are just proteins, and there is no evidence that they are beneficial to plants except for the addition of the nutrients. Protein in your soil is NOT food for plants. It first needs to be broken down into basic nutrients and then it becomes food for plants. Once that happens there is no difference between protein and commercial fertilizer. to understand this you might want to read Organic Fertilizer – What is its Real Value.
Fish are chemicals! Plants can’t grow without chemicals.
To solve this for everyone.
Mr.Robert says fish based nutrients are the same as synthetic salts as far as your plants are concerned. They are also cheaper.
Everyone else says, so what?
We will pay more for (or make our own) fish based fertilizer (or any other organic amendment) because it is more friendly to the ecosystem and doesn’t support the petro-chemical industry.
Which is worth every penny spent. (or unspent!)
The End.
That is a valid point. Supporting an organic industry is a good reason to buy fish fertilizer. Lots of people decide to pay higher prices to buy organic. And if the fish fertilizer industry or its proponents were using this as the reason to buy I would have no problem with it. Unfortunately they chose to make up false claims about their product instead.
As far as not supporting the ‘petro-chemical industry’, your point is incorrect. Fertilizer production is not petro-chemical based – something that is on my list of things to write about.
Thank you the information, it gas opened up a good and important conversation… I would like to what do you think about adding sugar to the soil since sugar will feed the microorganisms? I hope this is not a stupid question.
No question is stupid and lots of web sources promote the addition of sugar to soil. Microbes like sugar and can use it as a food source. It will increase the population but only until the sugar is used up. Then the population crashes.
Although sugar is organic it does not provide many of the benefits of adding more complex organic molecules that you get from plant material, manure or compost.
Thank you for answering my 1st question. Hopefully this second question will be my last, but I want to know if compost, manure and plant material is all plants need to get all their nutrients? Of course beside water, sun etc…
Or better yet, how do YOU grow your plants successfully w/o the use of expensive fertilizers?
Plants need basic nutrients. It does not matter where they get them from. Many are naturally in soil. Others come from decomposing organic matter.
Think of nature. Who fertilizes the plants in the woods? No one. So clearly plants don’t need to be fertilized provided that the organic matter they produce stays whee they grow.
I mulch with wood chips which provides some nutrients, and I leave organic matter in the garden. I don’t fertilize.
In a veg garden you remove produce, and therefore you need to add some nutrients back. I like to use straw for nutrients and weed suppression.
Thank you.
Return your pee and poop to the soil …
Does a bear “fertilise” in the woods?
Not really. Bear droppings will decompose and add nutrients to the soil, but consider this. If the bear was not there, the food it eats would fall to the ground and decompose providing the same nutrients. So the bear is not needed to add nutrients to the soil.
what about fish blood,,,that left while cutting n cooking,,,have found benifit in my roof garden,,,what r the cons…
Anything organic will benefit the plants. If you have a cheap source use it. If you are suggesting paying high prices for fish blood – don’t do it.