I'm not sure I understand the need to know NPK if the material is just going to be added to compost - seems like it would be far more important to determine the nutrient content of the end product, not the ingredients.

NPK is not calculated for many materials or potential compost ingredients because they are not intended specifically as a source of plant nutrients. You can rather easily find the nutrient content of various edible products as these are required to be disclosed per the same sort of labeling requirements plant fertilizers are subject to.

N is not measured in most consumable food products, often because it is not present in any measurable concentration.

Both tea and wine do contain an array of minerals including P and K but these are presented on a per serving basis. 1 fl oz of wine (red) contains 6.7mg of P and 37.1mg of K. Sweetened tea contains 25.5mg of P, 395mg of K per cup (8 oz)

Ash is the non-combustible residue, primarily minerals, that is left after the material is burned. It is detailed on a lot of nutrient calculations for consumable products but like water, does not need to be disclosed on the label.

Thanks for the detailed and thoughtful answer. My compost has overflowed the big barrel I use, and I wanted to leave it alone for a month or so at this time so it will finish & I can empty it. During this time, I want to put some materials directly onto various beds, sheet composting, 'tis the season for too many greens & not enough browns. I want to have some idea of the n-p-k for some things because I'm having a problem with a bed I piled too many oak leaves on and don't want to inadvertently make it worse. Thought those leaves were aged enough...

Also have a gallon jug I dump glasses into before washing, a inch of tea here, a little wine there. It's about full and I was just wondering what kind of "fertilizer" it might make if used directly. Seems like it would just run out of the hole at the bottom of the barrel and be wasted if I poured it into the compost. Are you saying there's no nitrogen in either wine or tea?

I still don't understand about the ash. Why would somebody burn their materials before composting them?

I've been gardening & composting for a long time and am trying to understand more of the science behind it. I'm pretty confident about what I'm doing but just don't know why it works or what is going on sometimes in scientific terms. The list I found was interesting but it is an odd assortment of things most people never encounter, and the selection of foodstuffs that most home gardeners have available to compost seemed extremely incomplete.

First, this is by no means my area of expertise! I'll try to explain my understanding of the issues but if I blow it, I hope someone more versed in nutrition will chime in and set us both straight :-)

I think some of the confusion is created by attempting to compare plant nutrient analysis (NPK) with animal/human food nutrient analysis. They are of course very different organisms and metabolize and use different nutrients differently. What is tested for and analyzed in one (i.e. fertilizers) is not tested for in the other (foods and other consumables) and/or other, different tests are required or considered necessary for these.

That's probably why you are not seeing as many food products on that list as you would like......they are not routinely tested for NPK because they are not directly considered to be fertilizers or good sources of plant nutrients :-) The nutrient content of processed human food stuffs (and many animal foods) are required to be as carefully labeled as are plant fertilizers but the labels disclose different properties.

There could be N in the wine and tea but humans process N through proteins and amino acids so these are what are disclosed in a detailed nutritional analysis of foods. And some foods just don't contain any significant or measurable amounts of proteins also. I didn't check specifically for the two liquids but I'd be surprised if there were much.

And the process of testing food or other materials for their chemical or nutrient content does include incinerating the material to determine exact nutrient content of specific minerals. The proteins, starches and water are burned off and what's left - the ash - is analyzed for various minerals.

I ended up using the bag on the mower to add grass to the oak leaves, and all is well there.

Never did find an answer of the n-p-k of tea but unless my gallon jug was more than 20% tea (which I just poured on compost pile) I used it to water potted plants... Occasionally there was a bit of Mt. Dew and/or fruit juice also - whatever was left in cups when washing dishes.

Some plants have done extremely well such as spider plant, parlor palm, Sanseviera, coleus, heart-leaf Philodendron vine, and 3 different Dracaenas. Plants that seemed to be adversely affected were lime green sweet potato vine (Ipomoea batatas,) Caladium, Dahlia, and Persian shield (Strobilanthes dyerianus.) Many" of the SP vine's leaves turned purple, an interesting trick but not a healthy color.

So now I know what happens, but still don't know why...

I would guess that the pH of that liquid was rather on the acidic side, since wine, soda pop and tea are all acidic. So it might have shocked some of your plants a bit. It's not a bad thing to do, I know people who put coffee and tea on certain house plants with good results.

The solution to the concentration is to dilute it with water. Just as a wild guess, I'd say 10-25% would make it dilute enough that few plants would mind.

I usually throw this kind of stuff in my kitchen compost collection bucket, and it goes into the compost in small amounts, so it doesn't ever run out the bottom.

But wine - did you say LEFTOVER wine? Hmm. Never heard of that. :-]

Acidity. Now that's something I didn't know to consider. Thanks! Will dump the next jug at the base of Hydrangea.

Wine - IKR! Not usually a factor but when I first asked the question, I had a big bottle that we thought had been put in the frige but got left out all night. I just dumped it in the compost although it was suggested that it would help make some really good-tasting tomatoes.

Part of the motivation I failed to express before is that there doesn't seem to be a need to compost liquids first if you know the plants you're putting it on won't mind or get some kind of benefit. My compost had no trouble staying moist even in a drought due to being mostly kitchen scraps and pulled weeds all summer. We're pretty heavy-hitters on tea, so that's the liquid being used without composting. When I have it, I also use water from boiled veggies to water plants. And ok, yeah, the "that's compostable" wacko in me being bothered by seeing that stuff go down the drain.

One thing I can say from this summer's experiment is that if you have a Dracaena, give it a little diluted sweet tea (which we make with about 1/3 the sugar as your typical southern restaurant.) One I just bought this spring but the other 2 are older trees and both have sprouted multiple new tops late this summer. And my parlor palm's leaves are growing faster and are a darker green than they've ever been.

Full circle :)

From a previous post, so it might not be dead on the mark, but you might find it interesting nonetheless:

Forum discussions frequently center on the question of adding dilute coffee/tea or grounds to plants as a 'tonic', but Arabica (coffee) and Camellia (tea) are known for their toxic alkaloid (caffeine) content and their allelopathic affect on plants as well as autotoxic (poison to their own seedlings) effects on future generations. Caffeine interferes with root development by impairing protein metabolism. This affects activity of an important bio-compound (PPO) and lignification (the process of becoming woody), crucial steps for root formation.

We also know that the tannins in both coffee and tea are known allelopaths (growth inhibitors). There are ongoing experiments to develop herbicides using extracts from both coffee and tea that cause me to want to say they might serve better as a nonselective herbicide than as a tonic. I would not use either (stale coffee or tea) by applying directly to my plants - especially containerized plants; nor would I add tea bags/coffee grounds to my container soils.

Al

I think too, we could chase the question in another direction. What if we asked and answered what's in the soda/juice/sweet tea that offers a potential benefit to the plant and is there anything in the leftovers that is potentially limiting??

In the juice & soda, we know there might be natural or artificial flavorings, neither of which are likely to be beneficial. There is water, which we know isn't a plus. We already know that some of the bio-compounds in tea are potentially limiting. So, we're left with the primary consideration, which is the sugar content. Let's clear the way by saying if the drinks are artificially sweetened, it's almost a certainty that it would have a limiting effect, or at best would offer no advantage to the plant.

Even if it was needed and could be used by the plant, sugar couldn't be absorbed by the plant in molecular form. The hydrocarbon chain would need to be cleaved. Sugar (CnH2nOn [n is a number from 3-7]) hydrocarbon chains contain carbon, hydrogen, and oxygen, which are never deficient under normal circumstances, so nutritionally it looks like the leftovers are a bust.

What does sugar actually DO when it becomes part of the soil solution? It increases the level of TDS (total dissolved solids and EC (electrical conductivity). What this does is make it more difficult for the plant to take up water and the nutrients dissolved in water. The goal of a good nutritional supplementation program should be to keep TDS/EC as low as possible w/o the level of nutrients being so low it causes nutrient deficiencies. From this, we can see that ANYTHING in the soil solution that is not nutritional is going to be limiting.

To illustrate why non-nutrients in the soil solution are limiting, lets say that in a plant growing strongly, 800 ppm fertility is perfect when only the nutrients essential to growth are present in the soil solution, and they are there in the same ratio in which plants use them. Anything lower than 800 ppm carries the potential for deficiencies, and anything above 800 ppm makes it more difficult to absorb water & nutrients. Skewing the RATIO of nutrients in the soil solution even when the total ppm remains at 800 is also limiting. Adding sugar or any soluble substance the plant can't use has to be limiting. At 800 ppm with sugar being 100 ppm, there can be nutritional deficiencies even if the nutrient ratio is perfect. At 900 ppm with sugar being 100 ppm the effect is limiting because it makes it unnecessarily difficult for the plant to take up water - the primary cause of spoiled foliage in houseplants.

I'm done. ;-)

Al

Well it sounds like the results of my quasi experiment are anomalous and probably just lucky. I rescind my endorsement and will stick to putting these things in the compost.

Thanks again, Al, for sharing your info!

Somebody please pass the wine?