Free fertilizer and he's complaining?  I wish my life was so free of issues
I could worry about cat poop outside in the garden.

There are some plant types that seem to repel cats, try Googling this group
for discussions.

there is a spray that keeps cats from eating plants (you don't spray
directly on plants).  it smells really bad to cats.  what i would do is cut
strips of fabric and soak it in this repellant liquid (I bought it in cat
supply store).   wrap the scraps to the top of a stick like a giant q-tip
and stick it in the ground near the plants.  that should do it.  once the
cat is out of the habit of visiting the site, you won't have to keep doing
this.
good luck
Harriet

... just deal with the neighbours ...!

LOL  Leave it there, it's good for the garden.  I mean, really!! What harm
could it really do anyway?

You had to ask this same question in 2 different posts?