What are the benefits of coffee grounds in soil?

https://www.thespruce.com/using-coffee-grounds-in-your-garden-2539864

they acidify soil. Before using, have your soil tested in a few different areas.

My Mamaw Woods used to throw eggshells and coffee grounds in her kitchen garden (garden that started just outside the porch from the kitchen door, in which she only grew sunflowers, tomatoes and cucumbers). She didn’t wash the egg shells and just threw them and the coffee grounds out helter-skelter so some rows got lots, some none. He kitchen garden produced Long into the fall. ☺️

Coffee grounds aerate the soil and keep moisture in longer. Also absorbs and releases good nutrients

There is a distinction to the coffee grounds theory, if you use the coffee grounds before you brew it, it is acid and that is the coffee grounds that acidifies the soil.

If you use brewed "washed" coffee grounds they are pretty neutral and won't have much effect making the soil acidic. These do help keep the soil loose, but are lacking in nutrients so you will have to add compost or nutrients another way.

Grounds are also good for azalea bushes.

Grounds are used to acidify the soil for acid-loving plants like azaleas, rhododendrons, and irises.