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
Here in Philippines a lot of fish as raw material for Fish Amino Acid production at very low price. Fish scraps at free in our market.
I’m a commercial vegetable grower.
It’s probably worth noting that fish fertilizer is in fact very cost effective when compared only against other fertilizers suited for fertigation. The highly localized, “spoon-feeding” approach offered by fertigation can be cost effective relative to broadcast fertilization at prep or less frequent sidedressing, even if the fertilizer itself is more expensive, because you need much less if you only fertilize the root zone, and can dole out the plant’s and biome’s needs gradually over time.
Sure, it’s more expensive than granular fertilizers and manure, but it’s for a different job.
Why is it a different job?
Lets see your calculations to show it is cost effective?
Listen to John Kempf at Advancing Eco Agriculture for huuuge increases in quality, quantity, and anti-fragility by using the spoon feeding approach. Note also that he says that seed biocoats generate the highest ROI by far because they cost so little and create so much plant health.
Do you have a link to some scientific study to support these ideas? If not – its just a guy giving opinions.
I’ll go on to say though, that we have actually stopped using fish. Corn steep powder (byproduct of wet-milling corn) has become much more widely available recently and it matches or surpasses all of fish’s positives (as or more injectable, higher protein and amino basis, plant-based byproduct, fewer concerns as a nursery foliar spray) without the downsides (available dry and at a higher NPK concentration, not smelly, requires less agitation, about 30% cheaper). We used it on a trial basis this Fall and were pleased with the results. Planning a full switch for 2021. For people who see a niche for fish in their systems, I’d highly recommend they look into soluble corn powders as an alternative.
You know very little science. The nitrogen in fish fertilizer is organic, i.e. in the form of amino acids whereas the nitrogen in chemical fertilizer is in the form of NO3 which is a negative ion. The organic form releases over time and does not cause ionic water pollution whereas the ion form causes ionic water pollution. Fish fertilizer also contains trace minerals that plants need whereas chemical fertilizer does not.
I am a chemist. Until those amino acids are broken down into NO3, the exact same molecule provided by fertilizer, plants can use the nitrogen.
Organic nitrogen sources certainly do cause water pollution – it is a major problem with the spread of manure on fields.
Synthetic fertilizer can also contain trace minerals.
And plants create higher order amino acids with nitrogen…using precious solar energy. If those amino acids can be absorbed directly through the foliage, the plant needs not waste limited energy on the creation of complex amino acid molecules from simple nitrogen compounds.
Organic nitrogen does cause water pollution but the tiny amounts of fish fertilizer in foliar applications is almost certainly not going to cause water pollution. I have gotten Navels the size of grapefruit with regular foliar applications of fish, kelp (for growth hormones), yucca (for absorption) and Organic trace minerals tailored to address tissue test deficiencies. I begin before fruit bud initiation and continue every three weeks to the end of the cell division stage.
Bottom line, there is a lot more than just chemistry going on here. Physics, botany, and biology all play a role too.
Plants can’t get enough nitrogen from foliar feeding.
David, where did i say amino acid is absorbed directly into the plant? Are you hearing voices or seeing things? if organic nitrogen causes pollution, then why are you peeing into the drain which ends up in rivers and oceans?
Nitrogen from amino acid is slow release. Nitrogen from NO31- is quick release. Slow release form of nitrogen does NOT harm plants as much as NO31- which has affinity to water molecules. Organic nitrogen causes pollution? Are you kidding? How much are you dumping into the ocean? Organic nitrogen is plant food and will be absorbed by plants.
No such thing as organic nitrogen. Nitrogen tied up in large molecules gets released as nitrate. Then it is the same as nitrate from any source.
I can think of a reason:
Indoor gardening. You cannot really dump solid fertilizers like manure into your potted plants in large quantities and have it work out.
The particles clog the air holes in the soil and kill the roots over time. Also, the solid fertilizers start rotting and breeding flies.
Yes there are super cheap soluble fertilizers providing only npk but healthy plants need way more than just those three elements.
Liquid fertilizers are needed for indoor plants and high quality ones like dyna-fro foliage-pro that provide complete trace nutrients and calcium/magnesium are comparable in price to liquid fish fertilizers that also provide trace nutrients.
Then the fish fertilizers have the advantage of nourishing the soil biome. You can mix it with molasses, kelp, potassium sulfate to balance out the n/k ratio and further enhance the beneficial effect on soil bacteria.
For outdoor gardening? Sure pile on the manure, compost, etc.
“Liquid fertilizers are needed for indoor plants and high quality ones like dyna-fro foliage-pro that provide complete trace nutrients and calcium/magnesium are comparable in price to liquid fish fertilizers that also provide trace nutrients.” – I’d like to see some comparisons – the ones I looked at were all much more expensive.
“Then the fish fertilizers have the advantage of nourishing the soil biome.” – what exactly does that mean? Even soluble fertilizer is good for microbes.
Hello Robert
I have just found your web cite and love your banter, I just posted my first comment on Vitermin B you may give me you thourgts please. i see you like your grases and im fond myself.
I spent 10 pluss years working with compost teas and a biological system to promote fine grases and help prevent disease. I moved to Ireland around 3 years ago and work in the Amenity field doing just this.
I i use a lot of Leonardite and a range of microbes to help convert plant organic mater to soil organics. its working well but is there anything you have come across in your time working with grases that showed a good responce to plant heath. i kow its a long question but lets take out the NPK and micro and macro nutreints i have this covered. im thinking more left field .
Best regards
Andy
Hi Robert,
Your article is good except it conspicuously leaves out the most logical solution to all your complaints about cost namely “Free Fish”.
Sure, if I scroll down and read “every” comment, you do eventually touch on the subject, but- You don’t dig into the pro’s and con’s and “how-to’s” of using what you can reel in to feed your garden.
I just caught a 5 lb sail cat – largely considered a nuisance fish (I”m told “-nothing-” eats salt water catfish) and I took him home to feed my tomato’s.
(Luca Brasi sleeps with the fishes but at my house the fishes sleep with the tomato’s)
So why can’t I just bury this puppy (pun intended) in my garden?
What’s wrong with doing it that way?
I should also add: Instead of spending time writing a reply to me, why don’t you update your original article to include the information? (That i the most logical place for it.. don’t you think?)
Thanks again
P.S. Please check out our website
Whole fish are free if you catch them – but is that really a good way to use a natural resource? I guess you could catch birds and other small animals and do the same thing – but I would not recommend that.
Robert,
First I want to express my appreciation for what you’re doing here. A fellow green thumb can recognize a sustained effort when they see it.
I have searched this site and not yet found information on remedying calcium deficiencies. I have been growing under lights in no-till 30 gallon fabric containers for the last year with minimal imputes (mostly compost and a few soluble fertilizers, every other watering I also add unsulphered molasses to remineralize the RO water) I mulch with alfalfa hay and the remnants of plants I grow. This is creating the perfect environment for fungus gnats. And recently, for the first time I’m seeing what is widely accepted to be calcium deficiencies and I’m wondering if it’s not from the larva eating the roots?
A little more history might be helpful. I obtained an analysis from the compost I used to mix my loam and it had equal parts Nitrogen and Calcium-roughly 1% by dry weight. It seemed like a lot of calcium to me but it coincides with the high PH of 8.5. I mixed this compost with equal parts peat and a combination of aeration materials as well as worm castings, composted chicken manure, etc.
Initially this mix was light on nutrients, as observed by changing various environmental factors and then finally increasing feedings. occasionally I would see an excess of nitrogen manifest but the plants would quickly grow through it and be hungry again. I mention this because I’ve wondered if this particular strain of tomato is more sensitive to an N/C imbalance as it is the only, or first, to show a problem. Though it is not the strain that first demonstrates N excess.
Now, I know you’ve expressed the difficulty in knowing the nutrient levels by observing the canopy but surely patterns emerge allowing us to make adjustments with some success. So, without obtaining an expensive soil test, what would you suggest a person do to remedy a situation such as this? I should state that after failing to control the Gnats with predators, neem, and bacteria, I removed the mulch and layered sand on my containers to break the cycle of reproduction. Would you recommend waiting for a few months before adding something like gypsum if the symptoms of Calcium deficiency continue to progress? Obviously I’m leaning toward Gypsum versus lime being that the base is alkaline. I would prefer to do less, add less, be patient. But it pains me to see the plants struggling, and I always want to act as quickly toward a remedy as I can. Thank you for your consideration.
Jacob
Insects eating roots will not cause calcium deficiency. If a soil test shows a calcium deficiency – add some calcium. Calcium carbonate would work – crushed limestone.
The only way to know for sure you have a deficiency is to test the soil.
Thank you for the reply. The Fungus gnats are nearly gone. And the deficiencies seem to have stabilized. I’ll remain observent. In a month or so I’ll attempt to apply mulch again with predators, bacteria etc.
On a separate note: I’ve been considering this site you manage and the resistance that you frequently encounter regarding the information you present. I believe the objections go well beyond what is or is not healthy for soil and plants. I can feel in your reader’s resistance to the means of food production via modern agriculture, a more general objection to what this civilization has produced-namely depressed, anxious, obsessive consumers.
It seems to me that many of the objections come from this root of pain that we all share. As if your readers are expressing, How can you defend and even champion a system, or the products of a system, that clearly grow a culture of immense suffering?
Right or wrong there is something of this pain in the objections here. I know this because I can feel it in myself and recognize it in others. Any thoughts?
Your friend,
Jacob
Quite possible. I think that a lot has to do with a complex society and way too much information. People have not been taught to live in such a world. They can’t, or don’t have the time to properly filter information. This results in a lack of knowledge and yet people still have a need to reach conclusions quickly.
The objections to agriculture stem very much from a lack of knowledge. The general public has unrealistic impressions of the how and why of agriculture, which is after all a big business. It is easy for people to reach incorrect conclusions. I should do a post on the myths of agriculture?
Please do. I enjoy reading your posts, even if at times I can’t pin down exactly what my objection is to the information presented.
I do believe it is wisdom we are lacking, there is knowledge abound. Wisdom to me is: nature knows best. If we can agree on this point, the path forward is simple. As closely as we can we emulate nature’s most harmonious processes even while recognizing that part of the creation is in its destruction, a reality so personal few want to accept as we stare at the very real prospect of our self-induced annihilation.
Your friend,
Jacob
Hi Robert, Thanks for the interesting and thought provoking read. I guess my response to your well titled article was: “Is any fertiliser/input worth buying?” As I am sure you know, throughout the world there are different forms of low to zero input farming models proving to be effective. I’m really interested in applying that philosophy to a small suburban garden. I do make FAA and, as others have suggested, I try to harvest pest species. Many of the low/zero-budget farmers harvest fish from their own stocked dams. Both methods make it essentially free and sustainable. Which brings me back to my expansion of your question. Is it worth buying ANY gardening/farming input? I really don’t think so. Commercial gardening products are insanely expensive for home use. I am learning that there are viable alternatives that I can produce for zero to minimal expense. These days no kitchen or garden waste ever leaves my home and I even collect some from neighbours and friends. Sometimes I even forage for other supplies like nettles (which are an invasive species in my country). I convert these ingredients into a range of different products from compost and bio-char to fermented solutions and tinctures that support soil and plant health and deter pests and disease. So I think you are right. It’s not worth buying fish fertiliser. It’s not worth buying any gardening inputs – particularly chemical based ones. We can make what we need cheaply, ethically, and sustainable ourselves. 🙂
I agree that for home use you probably don’t need to buy any fertilizer. For farms it is worth buying fertilizer or they would not do it.
Most homeowners use way too much fertilizer, which not only costs a lot, but makes a lot of pollution.
I think this post is wrong and misleading my grandfather use fish guts in his garden and his food plants grew strong and healthy…He was best vegetable supplier in our community….My grandfather worked the fields all his life I have seen first hand that it works and it’s cost efficient.
I never said fish fertilizer does not work. If you have access to fish guts – they it will certainly be cost efficient. Most of use don’t have such access and buy highly price-inflated products in fancy bottles.
Robert, thanks for your simple explanation of the difference between emulsion vs hydrolysate. One aspect that I wanted to comment on is that myself and others have seen a big difference in microbial growth when using hydrolysate over emulsion.
Under a microscope, it’s pretty easy to test the two types and see what microorganisms are grown out. Fish hydrolysate has been proven to be a good bacterial and fungal food (Keep in mind I’m generalizing across brands here). Fish emulsion…..well not so much.
That may be true, but does it make any difference in soil?
I believe fish, seabird guano and kelp products add micro nutrients and trace minerals in an ideal balance. All life evolved from the sea. The sea contains mineral balances most ideal for the building blocks off life. Inland soils vary quite a bit in composition and most of them have imbalances of one sort or another. They imbalances are mostly micro nutrient in nature and are improved by using sea sourced fertilizers. I am a long time market farmer and I get better yields and higher quality produce than my farm neighbors by using sea based fertilizers.
Re: “All life evolved from the sea. The sea contains mineral balances most ideal for the building blocks off life”. The problem with this concept is that many organisms that live on land have developed genetically for a long time. As part of that development they have changed their requirements for the nutrients they need.
I am quite sure that even the organisms living in the sea do not all have the same requirements for this special balanced nutrient mixture.
Thanks for responding Robert. I live in the rich farming Willamette Valley in Oregon. I raise sheep and I know a lot of other sheep breeders. Why do we have to supplement our sheep with salt and Iodine? If as you say organisms have evolved to not require nutrients mostly found in the sea. It has also become common practice to feed our sheep kelp meal supplements as sheep farmers all over the country have recorded increased growth and health when adding kelp-meal to feed.
I did not say “organisms have evolved to not require nutrients mostly found in the sea”. They evolved to use a different ratio of these nutrients. So that the sea may or may not provide the right ratio.
Sheep may do well with added kelp to their diet, but kelp is a plant, and all plants contains thousands of chemicals. I doubt anyone knows which of these chemicals are helping the sheep.
Well we do know that whatever in the kelp is helping the sheep is adding something that is not found in Willamette valley soil pasture. In my trials growing fruits and vegetables for market I have noticed the same thing. Marine based fertilizers Kelp/fish add something that land based chicken/cow organic fertilizers are not. The performance is better in Willamette valley soils.