Hi Paul, thanks for the question.

Maple trees can rob lawns of water, nutrients, and sunlight.  Mulching done correctly is a good way to resolve the aesthetic problem but can also be beneficial to the tree. Two to four inches of mulch is adequate, less if you have poor drainage.  More is not better.  A coarser mulch allows for air and water to get to the roots.  Do not hide the root flair or allow the mulch to be in contact with the bark.  Mulch out to the drip line. Check out the following links:

Mulching Landscape Trees (psu.edu)

 Mulching Trees and Shrubs | University of Maryland Extension (umd.edu)

How to Deal with Surface Tree Roots – Wisconsin Horticulture

I hope this helps.