[dcarch]

I don't have access to coffee grounds. Maybe someone can give this a try.

Coffee grounds decompose and eventually disappear in your soil.

What if you first bake them to charcoal, carbonize them and then put them in your soil.

Reasons for trying this:

1. Carbon does not decompose so it becomes permanent part of your soil.
2. Activated charcoal is the most porous material known. Although this is not the way activated charcoals are made, you may still end up with some very porous charcoal, may be much better then Perlite to help retain moisture.
3. The baking process will turn some grounds into ash, perhaps releasing more nutrients.
4. Darkening you soil to absorb more solar heat to warm up your soil.

dcarch