Reply to Crandrew:
I love both dogs and cats but I know how bad it is to find "Kitty Almond Roca" where you grow your food.
My solution was to buy a device that links a water sprinkler to a motion detector.........(I can hear your sinister giggling already).
This device is highly effective against cats but not squirrels (they apparently appreciate a random shower much more than the cats do).
This unit is called Scarecrow (model cro-101).
Contech Electronics Inc.
P.O. Box 115
Saanichton B C V8M 2C3
I think they still sell on Ebay.
Another solution could be a dog
or a good neighbor/cat owner
who would place a pile of sand (as a enticing cat box) on their own property to keep their critters off of yours.
Good luck!
Tom Attilla