Questions re: Compost Teas, etc..

[Soiled]

Well, OK, if you don't want to discuss it, that's up to you. But let me help out others who are reading this and are more curious.

https://fieldreport.caes.uga.edu/news/compost-enriches-soil-but-doesnt-replace-fertilizer/
"Unfortunately, the nutrient value of compost is very low when you consider the average compost contains about 1.5% nitrogen, phosphorus and potassium." That's NPK, percentage by weight.

https://extension.umd.edu/resource/organic-matter-and-soil-amendments/
"Plant-based composts have an N-P-K analysis of approximately 1.0-0.5-1.0." That's about a tenth that of chemical fertilizers.

There are loads of other references. Compost offers minimal nutrients, though one advantage is that those minimal nutrients are available for a long period of time, unlike with chemical fertilizers.

 

[Oliver Buckle]

I think there is a misunderstanding here, and when Meadowlark says 'Compost' he means composted cow manure, whereas the usual UK meaning is composted general garden vegetable waste, or in this case leaves. That is good for friability and water retention, but low in nutrient quantity, manure is high in nutrients. Personally I use leaves, gerden compost, horse manure, wood, anything I can get for free.

 

[Soiled]

Composted manure is equally lacking in nutrients, but maybe a tiny bit higher than homemade compost. Vastly lower than chemical or "natural" fertilizers.
https://www.allotment-garden.org/composts-fertilisers/npk-nutritional-values-animal-manures-compost/

It is a common gardening myth that composted anything is high in NPK. UNcomposted manure will be rich in N, however, which is why it is kind of dangerous. Compost is a lovely amendment for soil friability and water retention. It does add nutrients, but not much. Manure is basically just vegetable waste, processed in a digestive system, with some acid and urea added.

 

[Meadowlark]

Composted manure is equally lacking in nutrients, but maybe a bit higher than homemade compost. Vastly lower than chemical or "natural" fertilizers.

Another completely false generalization. My lab tests prove it, and my veggies confirm it. My compost is NOT lacking in nutrients.

In fact, the lab recommends No N P K be added. It tests out at a 94% nutrient density probability.

Falsehood after falsehood after falsehood.

 

[Soiled]

Again, your tests are being compared to SOIL. Your compost has nutrients that compare well with SOIL that has plenty of nutrients. So yes, you could grow stuff in your compost. But as a soil amendment, compost is not a strong fertilizer. Your veggies don't "confirm" anything about your compost's NPK, but rather that your soil is good. My veggies grow great and never whisper NPK to me, though lab tests of my SOIL say that I need not add any NPK to it. I add lots of compost, but at least the P and K in my soil is largely coming from the minerals in it. Not the compost. I do add ammonium nitrate for N.There are many expert sources referenced above that assert that compost is a weak fertilizer. You're welcome to argue with them. I'll look forward to hearing how those arguments turn out. Keep us posted. But let's not bother arguing here. I'm just presenting facts. Unversity ag extensions aren't noted for making "false generalizations".

 

[smitty55]

Composted manure is equally lacking in nutrients, but maybe a tiny bit higher than homemade compost. Vastly lower than chemical or "natural" fertilizers.
https://www.allotment-garden.org/composts-fertilisers/npk-nutritional-values-animal-manures-compost/

It is a common gardening myth that composted anything is high in NPK. UNcomposted manure will be rich in N, however, which is why it is kind of dangerous. Compost is a lovely amendment for soil friability and water retention. It does add nutrients, but not much. Manure is basically just vegetable waste, processed in a digestive system, with some acid and urea added.

That's a myth I've never heard. Most knowledgeable gardeners are aware that compost isn't high in nutrients, it's best use is to supply beneficial bacteria and as a soil conditioner.

 

[smitty55]

Dr. Elaine Ingham is a world renowned expert on soil biology and the soil food web. If you really want to learn a lot watch her five part series on how and why to use compost teas in the garden.

 

[Soiled]

That's a myth I've never heard. Most knowledgeable gardeners are aware that compost isn't high in nutrients, it's best use is to supply beneficial bacteria and as a soil conditioner.

True point. But most UNknowledgable gardeners are not aware. There are some around here, it would seem.

Dr. Elaine Ingham is a world renowned expert on soil biology and the soil food web. If you really want to learn a lot watch her five part series on how and why to use compost teas in the garden.

With all due respect to Dr. Ingham, it would seem commercial farmers don't want to learn from her, and their careers depend on productivity. Compost teas are by no means a part of commercial produce farming. If compost tea makes a difference, it evidently doesn't make much of a difference.

 

[smitty55]

True point. But most UNknowledgable gardeners are not aware. There are some around here, it would seem.



With all due respect to Dr. Ingham, it would seem commercial farmers don't want to learn from her, and their careers depend on productivity. Compost teas are by no means a part of commercial produce farming. If compost tea makes a difference, it evidently doesn't make much of a difference.

Commercial farmers are the main reason that most of the soils around the world are almost dead when it comes to soil biology and are totally dependent on chemical fertilizers to sustain plants that end up being very deficient in nutrition. Organic farming is becoming more popular all the time and they depend on soil biology. I've seen videos where farmers use compost teas on a large scale and the difference in fields using them compared to chemical ferts is substantial specially when it come to nutrient values. Besides, I don't think there are many commercial gardeners in this forum.

 

[Soiled]

We're not talking about organic farming. We're talking about compost tea. I suspect some farmers have tried compost tea, but most don't use it. They don't use it because they have not been convinced that the difference in using it is substantial or worth the effort. Yes, there aren't many commercial gardeners in this forum, but I'm not speaking to them. I'm speaking to home gardeners who don't want to waste their effort doing gardening strategies that don't make a big difference. It's the commercial gardeners who are teaching us what makes a difference and what doesn't.

I should add that when it comes to nutrition, compost tea provides a sudden jolt of nutrients, much like chemical fertilizers (see below). Those ferts are often not taken up by the plant and are water soluble and easily leached away. So if you want to use compost for fertilizer, compost tea is not the best way to do it.

Of course, you've probably seen this. Speaking of world-renowned experts.

https://wpcdn.web.wsu.edu/wp-puyallup/uploads/sites/403/2015/03/compost-tea.pdf

Look, if people get enjoyment about making compost tea, more power to them.

P.S. Speaking of composting myths, try this on for size - https://www.planetnatural.com/composting-101/soil-science/myths/. Now you've heard of it.
"1. 'Compost is a fertilizer.'
This one dies hard, and its persistence points to our cultural ignorance about plants and what sustains them. It persists because there is some truth in it as reluctantly acknowledged in the section revealingly entitled 'Adds (a few) Nutrients.'
As admitted in that section, albeit through gritted teeth, compost does contain low levels of primary and secondary nutrients and important quantities of micro-nutrients. However, composts do not usually contain enough of the primary nutrients to qualify as a fertilizer or to satisfy the needs of most plants."

 

[PolycarbonateGreenhouse]

Great point . A lot of people assume compost fertilizer, but really, it’s more of a soil conditioner that helps structure, moisture, and microbes. The nutrient boost is pretty mild compared to actual fertilizers. That’s why a mix of compost plus a balanced fertilizer usually works best for structure + nutrients.

 

[Oliver Buckle]

Could it be that most commercial farmers don't use compost tea not because it doesn't work, but because the effort to result ratio is much lower using commercial fertilizer? That could greatly affect the economics of a farm operation, but be quite sustainable for a gardener.

 

[Soiled]

Could it be that most commercial farmers don't use compost tea not because it doesn't work, but because the effort to result ratio is much lower using commercial fertilizer? That could greatly affect the economics of a farm operation, but be quite sustainable for a gardener.

I suspect that's largely correct. Making compost tea commercially would be a big operation, requiring lots of tankage, plumbing (including bubblers for proper aeration), and individualized attention. But again, since compost itself is not a rich source of nutrients, derivatives from it, like compost tea, aren't going to be a lot better. So there is no question that compost tea can be a fertilizer. Just not a very good one. Now, as to tankage and plumbing, a home gardener will face those challenges as well. It's vastly easier to fork compost onto a bed and dig it in than it is to brew and irrigate the bed with compost tea. Nutrient-wise, compost tea can't have any more than the compost it came from. You don't create N, P, and K by making tea. True that compost tea extracts these nutrients into plant-usable form faster than compost itself does, but it's all going to be released eventually. As noted above, that fast release can be a disadvantage, since plant-usable N, P, K can be leached. That is, overloading the soil with water-soluble nutrients just invites their disappearance.

 

[Oliver Buckle]

You don't create N, P, and K by making tea. True that compost tea extracts these nutrients into plant-usable form faster than compost itself does,

And in a more concentrated form I would guess, which could make it useful for things like feeding tomatoes as they start to flower, and if, like me , you grow them in containers and water judicially you won't flush them out. Not that I make compost tea, but I wash through horse manure to produce a 'tea' for such things.

 

[Soiled]

True that there might be some advantage in using compost tea for containers. That's a situation where you're not going to be forking piles of compost in.