Following a suggestion on how to keep cats from using my garden beds as a litter box, I have liberally sprinkled used coffee grounds over the soil. I know that some people add coffee grounds to their composting, but does adding coffee grounds directly to the soil have any effect on the chemistry of the soil? eg. the pH? By the way, the cats seem to be staying away.
I'd just suggest that any seed meal, which coffee grounds would be one, will be a fairly good nitrogen source once the protein in the material is decomposed. I've often noticed the fungal growth on my coffee grounds left in the compost or anywhere else for a few days. The fungi would tend to create a more acidic environment for themselves...which is probably where the "coffee grounds make the soil more acidic" saying arises. I consider coffee grounds a good resource, and hate to see them go in the garbage...especially if the homeowner turns around and buys fertilizer to replace what the coffee "waste" could have provided for free and in a more eco-sensible way! Cat deterrence...if it works for ya, great!
Urgh, it hasn't worked for the cats here, they like my gravel driveway. I put a whole bunch down where they like to poop and it didn't seem to help a bit. Glad you're having better luck! Usually I just compost them. I haven't tried adding them directly to the soil but I'd think the pH change would be negligible.
I've heard of coffee grounds sprinkled on the soil being used to increase the soil acidity, so based on that I'd say yeah they probably do affect the PH. I guess it would depend on how much you used and how often it gets rained on...
