The Myth of Foliar Feeding

Roguejim

Roguejim

This is information that was emailed to me by Dr. Nigel.  I've read this paper before, but, couldn't remember where I had seen it.  Anyway, what I'm hoping for is good discussion, and perhaps, some science that might challenge the information in the pdf file linked to below.  Anecdotal claims for foliar feeding abound, and, I take them seriously, especially when the source of the claim has particular expertise.  But, I wouldn't mind seeing some good science behind the claims.  No fighting, now!  Oh, and by the way, Dr. Nigel himself describes foliar feeding as "bullsh--", I think, largely based on the pdf file below.
 
http://puyallup.wsu.edu/~linda%20chalker-scott/Horticultural%20Myths_files/Myths/Foliar%20feeding.pdf
 
I foliar feed because it is easier for me to do that over spraying the roots and my hopes are enough drips off onto the root system :) As for the science, I have read plenty of conflicting stories on the pros and cons. I personally do not by into it but also do not have the science behind my statement. 
 
JoynersHotPeppers said:
I foliar feed because it is easier for me to do that over spraying the roots and my hopes are enough drips off onto the root system :) As for the science, I have read plenty of conflicting stories on the pros and cons. I personally do not by into it but also do not have the science behind my statement. 
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Looking at your square foot raised beds, you probably can't even get to the roots!  Do you foliar feed, exclusively?
 
Roguejim said:
Looking at your square foot raised beds, you probably can't even get to the roots!  Do you foliar feed, exclusively?
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I amend prior to planting out in hopes that I am required to do very little throughout the grow season. I do fish fert every other week when I can remember just because it STINKS so bad and drives people away ;) 
 
JoynersHotPeppers said:
I amend prior to planting out in hopes that I am required to do very little throughout the grow season. I do fish fert every other week when I can remember just because it STINKS so bad and drives people away ;)
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That's right.  I'd forgotten about the chicken manure. 
 
Now, back to our topic...Anyone else?
 
So I read the article. It seems a human analogy might be appropriate…. One could feasibly shove small food particles up the nostrils, selectively close off the passages to the lungs, and get nutrients into the body by this alternative method to the mouth. You'd have to have extreme process control to ensure no food got into your lungs, but it's possible. Similarly, we could all bypass the mouth and instead take all of our nutrients through IV. 
 
We could…. but should we? 
 
The article seems to draw the same conclusion about feeding via foliar spray vs. the roots - that foliar is not the best option. Still, if your mouth was sewn shut, the nostril or IV method might seem rather attractive, though I personally enjoy eating sometimes, enough to prefer to stay away from both of those if at all possible….  ;)
 
Is this a valid analogy? It seems to me that marketers of soluble fertilizers would want to tout newer research than from the 1950's, if such supporting research were available. While not a scientific observation from a plant's perspective, it seems to me this is a good observation of human marketing behavior and, hence, a good indication that more current scientific research doesn't support foliar feeding as being superior. I tend to like researching the research, but this time I'll take a pass. My plants are happy, being soil-fed, and that's what is most important to me.
 
I foliar feed with AACT because I buy into the concept of applying a surplus of "beneficial" microorganisms to the surface of the plant foliage as a measure to offset the presence of "bad" microorganisms,  The same idea as having competing bacterial or mold colonies in a petri dish; there is only a limited amount of geography available and selectively manipulating the environment for "the good" leaves less for "the bad".
 
When I feed with a foliar of Epsom salts the benefits may be diminutive but the costs for doing the feed are negligible; 1 Tbsp of Epsom salts, 2 gallons of  dechlorinated tap water and 15 minutes of my time.  The results may end up being purely imaginary but so long as there are no deficits and my time is my own to spend... where is the problem?
 
:D
 
hmm that pdf makes very good points, and at the same time these marketers of the foliage sprays and feeding "seem" to make a good point,  but then again we can all make a good point about something if we believe it enough, the true test would be to take two identical plants, feed one the good ol traditional way via dirt and roots, and the other only by foliage and see which one survives and is healthier, but you would have to make sure that none of the spray drips down to the dirt and roots or what ever medium you have the plant growing in. i mean to be honest if plants could take up enough nutrients to survive via their leafs then why is it when you take a cutting of a tree or rose or any other plant you have to make sure that the bottom of the cutting (end closest to the trunk or base) has to go into the dirt so it will root and actually grow, if you put it in upside down you end up with a stick in the dirt and nothing more.  thats just my two cents on that 
 
magicpepper said:
hmm that pdf makes very good points, and at the same time these marketers of the foliage sprays and feeding "seem" to make a good point,  but then again we can all make a good point about something if we believe it enough, the true test would be to take two identical plants, feed one the good ol traditional way via dirt and roots, and the other only by foliage and see which one survives and is healthier, but you would have to make sure that none of the spray drips down to the dirt and roots or what ever medium you have the plant growing in. i mean to be honest if plants could take up enough nutrients to survive via their leafs then why is it when you take a cutting of a tree or rose or any other plant you have to make sure that the bottom of the cutting (end closest to the trunk or base) has to go into the dirt so it will root and actually grow, if you put it in upside down you end up with a stick in the dirt and nothing more.  thats just my two cents on that 
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To do a "true test" you would need a MUCH larger sample size, let's say 1000 plants and your conditions for all other aspects would have to be consistent.
 
Also, the assertion is not that "plants can survive by leaf feeding alone" but whether foliar feeding yields any appreciable or measurable benefit.  My *belief* is that it does (so I do it, it also helps that there are no notable negatives do doing it).  The science is contradictory and possibly not done to exacting standards.
 
Anyone who has seen yellowing leaves start getting green back into them within hours of an epsom salt spray has to question a claim like this.  Other than a bacterial rubdown with AACT I have never seen the point in trying to actually feed the plants with a foliar spray, I think it's common sense that the roots would be the absolute best method...I mean, they're roots
 
I had a guy at the hydro store try to tell me I should foliar spray with fulvic acid...I quietly thought in the back of my mind...this guy is smokin some serious sh-t...

geeme said:
So I read the article. It seems a human analogy might be appropriate…. One could feasibly shove small food particles up the nostrils, selectively close off the passages to the lungs, and get nutrients into the body by this alternative method to the mouth.
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Case in point, people shouldn't swallow cocaine because it will become available all at once to the body in the stomach and can very easily cause an overdose where the same amount in the nose wouldn't.  This is a major reason why internal cocaine muling is so dangerous.
 
KingLeerUK said:
 
To do a "true test" you would need a MUCH larger sample size, let's say 1000 plants and your conditions for all other aspects would have to be consistent.
 
Also, the assertion is not that "plants can survive by leaf feeding alone" but whether foliar feeding yields any appreciable or measurable benefit.  My *belief* is that it does (so I do it, it also helps that there are no notable negatives do doing it).  The science is contradictory and possibly not done to exacting standards.
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good point, that is what i took from the pdf though, and you are right, there does not seem to be any negative results to foliar feeding, but at the same time i honestly dont see the benefits of it either, other then keeping the leafs cooler then the ambient temperature thus resulting in less water loss to the plant through evaporation, weather they actually use the nutrients that you apply via foliage is hard to say, i spray my plants with a mist of pure tap water, because it keeps the leafs cool and they dont lose water, i figure if it helps cuttings grow for that reason then why wouldnt it help the plant retain its moisture and result in less watering for me.
 
ikeepfish said:
Anyone who has seen yellowing leaves start getting green back into them within hours of an epsom salt spray has to question a claim like this.  Other than a bacterial rubdown with AACT I have never seen the point in trying to actually feed the plants with a foliar spray, I think it's common sense that the roots would be the absolute best method...I mean, they're roots
 
I had a guy at the hydro store try to tell me I should foliar spray with fulvic acid...I quietly thought in the back of my mind...this guy is smokin some serious sh-t...
Case in point, people shouldn't swallow cocaine because it will become available all at once to the body in the stomach and can very easily cause an overdose where the same amount in the nose wouldn't.  This is a major reason why internal cocaine muling is so dangerous.
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Also the crazy craze where certain folks were doing shots of vodka through a funnel into their anus and dying from alcohol poisoning :) 
 
There are some benefits to foliar spraying fulvic, mostly in regards to chelating nutrients in the foliar solution and making them more available. I believe it also has a similar effect on amino acids but memory rarely serves me well :D Much like foliar feeding though, I think it is just another way of temporarily alleviating a deficiency in the soil.
 
Edit: Clarity and removing my nonsense :D
 
so what is up with this epsom salt spray? isnt salt bad for plants, as in it dries things out, i can see some of the salt soaking into the leafs then drawing water into them thus turning the leaf from yellow back to green, possibly?, but what are the benefits of doing this on a good healthy plant, i have had a few people tell me i should try it,(their plants are dead now) but i am reluctant to spray salt onto my plants, specially when salts build up in the dirt (potted plants usually) and you have to give them a good soaking to get rid of it, so it seems redundant to me that we try to keep salt away from the roots but we are spraying it onto the foliage of the plant. maybe there is something i am missing here? help me understand the salt bath
 
All salts are not created equal.  Epsom salt is magnesium sulphate which is essential for chlorophyll production; thus the impetus to apply it directly to the foliage.  The concentrations used for foliar spray have a negligible drying effect, I tend to use 1 Tbsp to 2 gallons of water, which if you tasted it you would barely even register it as "salty" because it's not like sodium chloride (table salt) in flavour or detrimental effect to plants.
 
KingLeerUK said:
All salts are not created equal.  Epsom salt is magnesium sulphate which is essential for chlorophyll production; thus the impetus to apply it directly to the foliage.  The concentrations used for foliar spray have a negligible drying effect, I tend to use 1 Tbsp to 2 gallons of water, which if you tasted it you would barely even register it as "salty" because it's not like sodium chloride (table salt) in flavour or detrimental effect to plants.
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ok thank you for educating me on that, i knew all salts were different but most have the same effect, anyway now i know and kind of understand the reason for it
 
miguelovic said:
There are some benefits to foliar spraying fulvic, mostly in regards to chelating nutrients and making them more available. I believe it also has a similar effect on amino acids but memory rarely serves me well :D Much like foliar feeding though, I think it is just another way of temporarily alleviating a deficiency in the soil.
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Fulvic acid in and of itself has no nutritional value, as an acidic component of humus it's beneficial as a chelating agent in soil because it can carry 60x its molecular weight in nutrients.
 
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