Here is a link to an article from Sunset magazine. They sent coffee grounds to a lab for analysis. HTH!

Here is a link that might be useful: Sunset Coffee Grounds Analysis

The main problem I know of with UCG is that if you layer them too thick they can form a crust and repel water. I'm not sure if that would happen when they're under the soil or not. I would still be a little reluctant to have a layer more than about 1/2 inch thick, but if you mix them well with the soil, you can probably use more than that.

My guess that by putting the coffee grounds underground the worms in the area will think they died and went to worm heaven.

bpgreen is correct with the crusting issue. You can use at least 25% of the volume of the garden bed with coffee grounds as long as you mix them in really really well with the other soil. Soak it all, then mix again! Cover with mulch, light water, leave for a week to settle and you are ready to plant.

Here is a link that might be useful: The Ground to Ground website

A planting bed across the parking lot from the church kitchen has gotten a lot of coffee grounds added to it over the years and there has never been any problem with crusting of those grounds inhibiting water flow. Of course the grounds have never been thicker than about 1/4 inch in any one place. I am not sure anyone has yet put more coffee grounds on their soil then the soil could use.

kimmsr - When I just started out with coffee grounds, I dumped 80kilos of it into a smallish garden bed and didn't mix it in well. Took about 9 months for it to resemble soil, and when I dug deeper it was always dry. That was with the grounds about 1 foot thick above the soil.

I would be careful about using coffee grounds as a significant More than 10-15% fraction of a raised bed soil. 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 old coffee or tea on my plants; nor would I add tea bags/coffee grounds to my container soils, or use them as a significant fraction of RB soils.

I had left similar commentary on the Sunset site, but I see they recently deleted it - apparently they only allow people who agree with their views to comment.

Al

I remember reading that post of yours tapla. It is important that we get as many voices on this as possible, so sad to hear they pulled it.

Al,
I learn something new every time you talk, you are the man ;-)

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I have not read that, AL.
I Have used raw( not even run though water)pure ground & whole bean coffee, as well as coffee chaff as mulch on vegetables, blueberries, 2-3 inches deep. I have turned it into the raised beds for collard,onion & Sun chokes 4 inches deep. I have composted it with out any other C/N,4'X4'X8'pile.
I get two side affects: 1) fruit green beetle grubs.
2) More fruits then I can put up & have to give them away.
Lucky, I have a big family.
If you have a link, I would like to read it.
Thanks, jolj

I have collected some links on Allelopathic, autotoxic Chemicals in Coffee:. The one down about Dec 5th is most interesting. I think that a prolific poster above has some fibers that might be woven into a thread of truth but since none of the above is referenced we can only assume that, without more information, this is just the ranting of another old, howbeit knowledgeable, curmudgeon.

Thanks for the links, albert.
I am more confused then ever.
It this very minute, I have grass pulling up though pure undiluted ground coffee & coffee chaff.
This is the hated Bahia grass, though 12 inches in some places, when I dig it out, I find a mass of new roots.
Six weeks or so ago I covered the land with 6-12 inches of this coffee, also coffee chaff.
As great as it is on my tomatoes & Blueberries, I wish it would kill the Bahia grass.

My link above dated March 29, 2011 no longer works.

Still using Chaff from coffee & ground coffee.

Still getting lots of food.