To kill grass and weeds unwanted there.

We recomend just placing the mulch on top of the turf.

Mulching - http://home.ccil.org/~treeman/sub3.html
and
http://www.treedictionary.com/DICT2003/M/ Look up "Mulch"

Sincerely,
John A. Keslick, Jr.
Arborist
http://home.ccil.org/~treeman
and www.treedictionary.com
Beware of so-called tree experts who do not understand tree biology.
Storms, fires, floods, earthquakes, and volcanic eruptions keep reminding us
that we are not the boss.