Fish fertilizer is very popular. It is reported to be a good source of nutrients and a good source of proteins, amino acids, and oilsโfor 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. hydrolysateโwhich 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 productโfor 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 FertilizerโWhat 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 differenceโto the plantโbetween 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 questionโfish 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 knewโorganic 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
I discovered a free fertilizer which is readily available and high in nitrogen. I can get it on a daily basis. Don’t even have to leave the house, in fact. It’s urine!!! Diluted one part urine to about ten parts water. Please try it before you slam the thought! I use it on veggies and all. Every.single.plant loves it!!! Makes my veggies taste so delicous. Of course I thought it was weird too when I first heard of it. But if you try you will not be disappointed!!
I agree it is a good source of nitrogen. It does have high levels of salt but unless you apply a lot that should not be too big of a problem.
https://www.gardenmyths.com/the-full-scoop-on-composting-poop/
Hey, it’s a free source that Nature uses everywhere that there’s an animal that needs to pee!
I get your argument hereโa very focused, purely empirical, purely economic statement about the basic chemical value of plant nutrient sources vs cost. An ion is an ion is an ionโno matter its source, its all buffet to a plant. I also get your argument about false claims used by manufacturers to boost the desirability of their product, and kudos to you for busting their chops about it, especially at 25 bucks a gallon. However, the chemical industry makes all kinds of false claims, too, especially about the safety of their products in these safety-conscious times. Just sayin’.
Most of the respondents here seem to think that you are attacking fish as a source of fertilizer. You aren’tโI can see that. Unfortunately, in your efforts to reiterate your basic statement that plants can’t tell the difference between nutrient sources, some of your responses make you sound like a chemical industry shill, which naturally turns up the volume on opposing shouts. Interesting debate ensues.
Here is my problem with commercially available fish emulsions and fish meals: They do not come exclusively from scraps left over from processing human foodโwhich makes it sound like fish emulsion is this eco-friendly waste-not process that we should embrace as a small-footprint Good Thing. Instead, the vast majority of fish fertilizer comes from targeted fishing of species which are deemed undesirable as human foodโso-called “industrial” species. However, these fish are valuable food sources for other organisms. In some places, food-fish stocksโsuch as anchovy and sardine, as well as krillโhave been devastated by over-harvesting for the fertilizer and animal feed industries. The result, of course, are equally devastated losses of large fish, sea birds, pinnipeds, and cetaceans in the over-fished areas, as well as the overall ecological imbalance that always accompanies the wholesale loss of a key link in the chain.
So, while using fish fertilizers allows the organic gardeners and farmers to give a nice, satisfying, righteous middle-finger “screw you!” to BigChem, the use of these products carries its own heavy weight in terms of negative ecological burdensโsomething that the manufacturers don’t tell you in their promotional ads.
The best thing? Use the fish, yes, but don’t buy commercial versions which come from the industrial fisheries. If you are an angler, or just someone who eats fish regularly, use your own scraps and trash fish by-catch to make your own emulsion. You can also get fish waste from restaurants, grocery stores, butcheries, and if you live near a fishing town, straight off the docks there. All it really requires is a lidded container, fish parts, a carbon source, occasional stirring and patience. There are plenty of instructions and tips online on how to make your own emulsion.
You understood the post and the comments very well. Many of the comments are from people who did not read the post.
You said “Here is my problem with commercially available fish emulsions and fish meals: They do not come exclusively from scraps left over from processing human foodโwhich makes it sound like fish emulsion is this eco-friendly waste-not process that we should embrace as a small-footprint Good Thing. Instead, the vast majority of fish fertilizer comes from targeted fishing of species which are deemed undesirable as human foodโso-called โindustrialโ species. ”
I was not aware of this and have done some digging, and you are right. It is clear that many of the products on the market are NOT made from fish waste products. I find that very upsetting and will do a future post about this.
Please do! Gardeners of every stripe need to know the real costs of what they are using.
Hamakua Gold out of Hawaii uses waste of the fishing industry and ferments its product. It is like a probiotic for your plants and soil and a sustainable product!
If they use fish waste – that is a good thing, but it is not “a probiotic for your plants” – it is just nutrients like every other fertilizer.
Yes, this is exactly why I am reading all the comments in this forum. I live in Maryland and just recently the Atlantic States Marine Fisheries Commission did a disservice to the very important forage fish species “menhaden” and will not be managing them in an ecologically sound way or with a scientifically based method, all because of the powerful lobbyists that represent the Menhaden Fisheries Coalition (sounds like a group to protect the menhaden, but it’s just a group of companies that exploit this tiny yet very important fish). There is one BIG company headquartered in Virginia called Omega Protein that uses plane spotters to find the big schools and then nets them to make fish oil vitamins and pet food and fertilizer and is responsible for removing about 80% of the allowable catch annually. As the previous commenter said, it’s not actually “byproducts” from fish used for human consumption, which if that’s what people think, then using fish fertilizer sounds like a good thing that doesn’t let anything go to waste, but that’s far from the truth. This fish is in danger and because of corporate greed, striped bass and many other fish that depend on this species as an actual food source are at risk. If there’s no reason to use fish fertilizer over another kind of fertilizer, people should get informed and stop buying it.
Have you written a follow up post about this yet? Thank you!
What would the followup story be? Things have not changed – it is still a problem.
Fish fertilizer is no better than other forms of fertilizer. I talk a lot about fertilizer in my book https://www.gardenmyths.com/garden-myths-book-1/.
I have used fish emulsion and miracle-gro and have had positive results with both. From what i have gathered, people have either skimmed over the article or just looked at the headline and jumped to the comments section. This seems to be common and also enjoyable. People tend to cling to what they believe in, even with counter evidence. I have a small garden, so it would be no problem to go fishing on the weekend to supply it with some fresh fish if thats what i wanted, but a farm or larger garden would take some serious fishing. I am no expert, but my plants look healthy and grow well either way.
There is an indoor tilapia Aquaculture facility in my city that donates culls to our organization. We could get several hundred pounds a month what are your thoughts on turning farmed tilapia into fish hydrolysate?
Go for it. Any free organic matter for the garden is a good thing.
So I’m gonna put in my two cents. I don’t know enough to be like “oo this is the best or this is the best” but when I was trying to find something for my roses that was pesticide free and wouldn’t burn the roots fish fertilizer was the cheapest option, and I must say my roses are thriving!
I’d like to see your data. How much did you pay, how much volume did you get, and what was the NPK analysis of the product you bought. Product name would also be useful to have. I will be very surprised if it was a cheap source of nitrogen, but the data will show us.
I finally found a point I can totaly disagree on. Synthetic ferts are petro ( natural gas ) based. We frack the ground to release natural gas to burn and make fertilizer. Fracking and its waste water pollut ground water. Oklahoma is frack capital of the world and since we started fracking we are earth quake capital of the world.
Synthetic fertilizers are not petro based – that is another myth. It is true that making nitrates does require an energy input and natural gas may be used. But it also takes energy to make fish fertilizer.
You might be right that synthetic fertilizer is not the most environmentally friendly options.
Sorry, Robert. You’re wrong. The nitrogen in synthetic plant fertilizers are made with petroleum products–specifically natural gas. Look up the Haber process.
I am quite familiar with the Haber process. Petroleum products are defined as “materials derived from crude oil (petroleum) as it is processed in oil refineries”, Wiki.
The Haber process: “The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures:
N2 + 3 H2 โ 2 NH3 (ฮH = โ92.4 kJยทmolโ1) ”
No oil is used in the reaction, so the production of nitrogen is NOT a petroleum product.
If every product made, that used some type of energy, eg natural gas, was classed as a petroleum product, then every product in the work would be a petroleum product, including fruits and vegetables which require energy inputs.
Hi Robert,
For somebody concerned about long-term sustainability of non-renewable fertiliser sources (e.g. mined phosphate), what would you recommend for an initial indoor growing phase (under lights) on a largely inert substrate (think 1:1:1 perlite/vermiculite/coir)? From seed to seedling, and then establishing the young plants.
Some of the plants will be transplanted to a vegetable garden with quality soil, where we have access to local, free resources (some manure, lots of coffee grounds, comfrey tea etc.)
But for the container grown plants – likely to be mostly salad greens, basil, general leafy vegetables – which will remain indoors, what’s the best approach? I have no special attachment to the ‘organic’ label, I’m just sensitive to renewable and non-renewable resources.
My initial idea was to use prilled urea as a nitrogen source, although I’m concerned about acidifying the soil.
I’d really appreciate your input; my reading has brought me here and you seem like you actually know what you are talking about.
Thanks in advance,
Nick
When I grow seedlings for the garden under lights, I don’t normally fertilize them very much. I do grow them in a peat based mix, like Pro-mix. Near the end of the growth cycle I do apply some water soluble fertilizer, but I don’t use very much. A small pail lasts me 15 years.
The key to understand is that all nutrients are the same – no matter their source. If you want to be more sustainable, use any fertilizer made from waste material, compost or fish fertilizer that is really made from fish waste and not live fish – https://www.gardenmyths.com/fish-fertilizer-damaging-environment/
The problem with being sustainable is trying to figure out which product actually harms the environment the most. For example, composting produces CO2. Is that worse than mining phosphate? Probably, but maybe not – we just don’t have the data.
All we ever do around these parts is each fall we bury fish and then put kelp on top a bit of dirt to hold it all down.
all summer long we just water no need to buy anything.
If fish is cheap this is a good idea.
chemical fertilizers are solubilized with water.
at this point, the plant has NO CHOICE but to take it up…
this is why it is possible to over-fertilize plants and burn roots.
These chemicals kill the microbes in the soil, and these microbes are the basis for plant health.
Chemical fertilizers change the epidermal cells and guard cells, and keep the stomata open, which can make the plant more prone to disease.
When the plant takes up chemical salts, it needs more water,
so… it takes up more water than it needs to.
This makes it “bloat” and appear larger.
The cell walls are actually thinner and are more susceptible to disease and pests.
Pests can notice this , and will attack this plant, and leave other nearby plants alone.
The gardener will then blame something else, and go and buy pesticides which will further kill the microbes in the soil.
This is wonderful for chemical companies, but, not so much for the rest of us.
Your comments are not factually correct.
1) the ions absorbed by plants are the same no matter if they are snythetic or organic.
2) There is no evidence that fertilizers, when used correctly, kill microbes – another organic gardening myth.
3) Once absorbed, fertilizer nutrients or fish nutrients will have the same effect on stomata
4) You are confusing the term ‘salt’ with fertilizer. all nutrients taken up by plants are ions of salt – again fertilizer ones are identical to organic ones.
5) the whole story about taking up too much water, bloating, and thin walls is not true – if you beleive it is provide some scientific evidence to support your statement.
Since fertilisers have a salt rating which shows their effect on salt concentration in the soil (because of the risk of seed and root burn) it is not unreasonable to assume that at higher rates they will also be causing harm or change in the soil ecosystem. There are choices when a particular nutrient is needed. Some of these choices are organic. So in my opinion, all nutrient is not the same.
I don’t follow your comment at all?
What is a ‘salt rating’? Salt concentration is easily calculated – you don’t need a salt rating? Fertilizers only burn roots if too much fertilizer is added. Yes higher rates will cause damage, but nobody is recommending to use higher rates.
Whether you get your nutrients from commercial fertilizer, or from fish or from plant compost – they are all salts! A nitrate molecule from any of these sources is identical. See What is Organic Fertilizer for more details.
Refer
http://host.cals.wisc.edu/soilscienceextension/wp-content/uploads/sites/47/2015/04/Laboski_salt_2008.pdf
I was responding to the comment by Brad Mayex. I agree that ions are the same whether they come from fish of from synthetic fertilisers but fertilisers are not applied in the ionic form, they are applied as salts, and all fertiliser salts are not equal in their risk of change to osmotic pressure across plant membranes, and therefore risk of root or seedling burn. It is also my belief that the same risk extends to harm to soil microbes
Correct, fertilizer is usually applied as a salt. For it to enter the soil, it must dissolve in water and when it does this it becomes ions.
Ions do change osmotic pressure – all ions do this, both synthetic and organic.
i just came to this site in my search for why the cucumber i put in my stew kind of ruined it.
i bought it from an organic grocer and did not store it in my fridge which doesn’t have any fishy anything in it. but my stew smelled strongly fishy…my roommate thought i had put fish or cod liver oil into it. no.
i recalled an in-law telling how strawberries gave her a bad reaction that she had only gotten from sea food. she said she had a sensitivity to iodine. she told me that they use fish fertilizer on strawberries.
so i knew i wasn’t crazy when i tasted something fishy with the cucumber.
i have now just learned that both kelp meal and fish emulsion are used on some produce–especially organic.
so now i’ve decided to give up on some of the organic produce.
and for the above reason, i hope that Robert Pavlis is successful in discouraging the use of those fertilizers.
Fish smell and fish flavors will NOT be transmitted into plants. The complex organic molecules must be broken down in to simple nutrients before plants can absorb them. By that point they are no longer identifiable as fish molecules.
Why would you even put a cucumber in a stew it is a salad vegetable
And water the roots and ground and not spray direct onto the produce your going to eat
I don’t believe your argument just your bad cooking
…but it could come from surface residue on leaves or in this case fruit if they are not washed well before use, as any produce should be, whether organic or not.
To the Author: Do you suppose there would be a benefit / difference between store-bought and homemade fish-hydrolysate?
The cost pretty much goes out the window, ($0.80 ea. for a few cans of sardines and $4 for a reusable bucket), unless you like adding expensive additives such as kelp meal, etc.
It’s my understanding that this method allows you to introduce not only the macro-nutrients to feed the microbes, but the microbes and bacteria itself, to the soil, since you’re not treating it to remove the bacteria before packaging it (done with all store-bought versions, so the bottles don’t explode from the pressure of continued fermentation).
You can’t compare an 80 cent can of fish with a $4 bucket of fish emulsion without looking at the numbers. How much nitrogen does each product supply? Then compare the cost on a Kg basis.
A can of sardines is just a can of sardines. It is a few ounces/grams of organic matter. No matter what you do to it, it is still only a few ounces/grams of organic matter. compared to the size of a garden bed – that is nothing.
Your soil already has all the microbes it needs. You don’t have to add more. Your goal as a gardener is to feed the microbes you already have so they grow and prosper.
I have seen NO scientific evidence that adding microbes to garden soil makes any difference in plant growth. If you have a source i would love to see it.
I also think it is poor practice to take good food and dump it on the garden, when people are starving.
Bugman, do not even consider using tinned fish as a fertilizer source! They are usually packed in oil which simply turns into a waxy substance. The fish is cooked and sterilized, so lacks living bacteria that help with fermentation. Cooked flesh decomposes slowly. And tinned fish is loaded with added NaCl salt. It is also a deplorable waste of edible food.
If you want to make your own fish emulsion, use raw fish. Like I stated in my post before, you can get raw fish scraps from several sources. Just a note: When you do go fish scrap foraging, make sure you get the guts, too, if you canโthis is where most of the decomp bacteria come from.
Foraging for scraps is a little challenging, true. You have to cultivate contacts with people who can provide them to you, and you have to be conscientious in your commitment both to your DIY emulsion project and to your contacts. Note: If all you want is a small amount for a one-time emulsion project, let them know so that they will not be saving waste for you unnecessarily. Commercial sources generate the waste everyday, so they would not need to save it. You could probably collect a fair amount just by walking in early in the morning and asking for it on an as needed basis. Smaller producers, like a friend who fishes on weekends, would probably have to save the waste for youโhelp them out by giving them a plastic bucket with a good lid that they can take with them on their fishing trips and make arrangements to pick it up asap upon their return.
Asking for fish scraps from a stranger can be a little daunting, yes. The potential supplier stares at you, tilts their head like a puzzled cat, and says, “You want fish offal for what?” So, it may take a little patient explaining.
Almost everyone knows someone who fishesโask that person to save the scraps and trash by-catch for you. If you live in a seaport town with a commercial fishing fleet and local cannery, talk to the boat captains and the cannery manager. Talk to the restaurant managers and head chefs of your local restaurants (including big chains, though you may find them less cooperative than small indies). Talk to the meat managers and butchers of your local grocery stores who process raw fish themselves. If you buy and eat fish, save the uncooked waste portions (heads, fins, skin, raw bonesโwhatever you’ve trimmed out before cooking) and add them to your emulsion bucket. Heck, you could even approach pet and aquarium stores for their culls and dead fish. If you are fortunate enough, like Sam Fleming in an earlier post, to live near an aquaculture facility, you could approach the manager about getting their culls and dead fish. Hatcheries may be a another source.
The beauty of this approach is that, except for the gas you use to get to the sources, it is pretty much free to you. Way cheaper, anyway, than buying emulsion.