I am looking for information on how to enrich my apple tree, not necessarily the grass under it. I was thinking of aerating and then spreading about 1 inch of compost under the tree. I don't care about the grass.
Certified GKH Gardening Expert
Aerating may help, but the compost certainly will help. Have your soil tested as well and see how your pH is. Apples like a pH of about 6.5-7. If you fall above this or below this, then adjusting for the pH will also be helpful. A soil test will also let you know what your soil is lacking so that you can amend for this too.
Here is more information on getting your soil tested: