I was surprised to learn that coffee grounds can ever contribute to a temporary Nitrogen deficit.
In the past, I just noted that coffee grounds are "greens" - they contain MORE nitrogen than is needed to decompose them. In a compost heap, they contribute N, they don't consume it.
If I understand your references, they suggest that there is a period of time when microbes can digest the "Carbon" parts of coffee grounds faster than they can extract usable N from the coffee grounds. That surprises me, but what do I know?
It's probably good for a compost heap to have some "slow-release-N" raw materials. That way, less N is lost to the atmosphere since the pile is "running lean" until it gets around to extracting and solublizing any slow-release N.
In the soil, that might not be a good thing, since you never want fungi and bacteria competing with plant roots for a limiting source of N.
I'll probably keep using coffee grounds as a top-dress mulch and scratch them into the surface a little. If a little temporary Nitrogen deficit is happening in the top few inches, I've still lightened the soil, attracted worms, added fast and slow OM, and added more N overall than I've added C.
But the point is well taken: I might NOT be adding as much QUICK Nitrogen as I used to think. Perhaps it is mostly slow-release N.
Maybe a better use would be mixing coffee grounds into a compost heap, or amending clay that mainly needs grit and OM to make it drain and aerated at all.
