sallyg said:
. "Nitrogen rich compounds.. break down quickly, releasing plant available nitrogen.." Why not let that happen right around the plants I want to grow?
Well you could do that , but you can also do both. Split your bounty of coffee grounds in half and use some around your plants and place the rest in your compost pile(s). That way your compost pile will get some added goodness plus with the grounds being high in Nitrogen, it can speed up the composting process and you could get your finished product sooner.
sallyg said:"Be sure to allow coffee grounds to cool.." Seriously? How hot can my filter full of grounds be by the time I drop it in my compost? (Or are we talking about the WAWA folks dropping 2 pounds of fresh brewed grounds right on their compost bin out back lol)
If you haven't noticed by now, there seems to be an influx of warning labels and other forms of cautions on most everything we come in contact with nowadays. This is just another example of one of them. I teach composting classes in my community and during the pandemic, these classes moved online to reach the large number of new gardeners taking up the gardening hobby . During one of the Q&A sessions at the end of my presentation, a new gardener asked the question, "Do I have to wait for the grounds to cool before I put them in my compost pile?" So yes, I can see why sometimes a warning like this might be necessary.
sallyg said: ' .. no more than half an inch.." Has this really been studied experimentally, versus an inch? Probably not, it sounds hard to get a decisive result.
While I couldn't find any studies done about an appropriate layer of used grounds to lay on the soil, I can take from my own experiences over the past few decades of utilizing grounds in my gardens. I experimented with using grounds as a mulch but found the thicker you apply them one major issue surfaces. The grounds will dry out and become hydrophobic as a crust tends to form on the surface, making it impervious to water. My recommendation would be to keep the thickness of any layer of grounds to a minimum, or be prepared to go through any areas where it is applied thickly and break it up to keep it permeable. ( Side note: I had planned on including that information about not applying the grounds too thickly in my original comment but left it out to keep my response shorter. Seeing your reply made me realize maybe I should have included it originally.)
