Animal Control will quite definitely not simply come out and shoot the cat. It scares the straights, and it’s not done. They may come out and try to trap it, and if they do trap it, they will take it back to the pound (or whatever they call it in your city), and if it isn’t adopted within whatever the deadline is, it will be euthanized. And since adult cats are a dime a dozen, and since this isn’t a “free to good home, won’t someone please take my kitty” adult cat, this is a full-grown feral cat, it is, to all intents and purposes, unadoptable.
Really, there are very few answers for this that don’t involve the cat dying. If it isn’t going to recognize the various deterrents, and if it is going to continue shitting in your garden, then it needs to be removed. In order to remove it, you can:
[ul]
[li] kill it. [/li][li] trap it.[/li]
[list]Who will trap the cat?
[li]You.[/li][list]Where will you get a trap?
[li] Buy one.[/li] [li] Borrow one.[/li] [list][li]From Animal Control.[/li] [li] From some humane society.[/li][/ul][/list]
What will you do with the cat once you have it?
[ul][li] Adopt it.[/li] [li] Find a home for it.[/li] [li] Give it to Animal Control. Cat most likely dies.[/li][li] Take it out into "the country" and release it. Cat probably survives, but is still a public nuisance, albeit "somebody else's problem". And assuming it doesn't simply come right back.[/li] [li] Give it to some humane society. Cat possibly dies.[/li]
[/ul][/list][ul]Someone else will trap the cat.
[list][li] Animal Control. Cat most likely dies.[/li] [li] Your landlord. Cat certainly dies.[/li] [li] Some humane society. Cat possibly dies.[/li][/ul][/list]
[/list]
The only option in this flow chart that has a 100% guarantee that the cat will not die is for you to trap it yourself, and then either adopt it or find a home for it. Every other option–including having it trapped by, and/or giving it to some humane society, unless you can find a no-kill shelter to take it–let’s face it, basically ends with the cat dying. So, really, there aren’t a lot of options here.
Except that you can explore deterrents more fully. But you’re constrained by your budget; hardware cloth or chicken wire to cover the soil’s surface (which was actually the best suggestion from your GQ thread), and cosmetic mulch to put on top of it to appease your landlord, all cost money.
So. You have a problem.
But, if you change your priorities to include “Cat possibly dies”, then your problem goes away. Your decision-making process is affected by your stipulation that the cat survives. But if you can live with the fact, say, that after you handed it over to Animal Control it was possibly euthanized, then you don’t have a problem after all, and you can get on with your gardening.
Myself, I wouldn’t advocate going out there and plugging it yourself, or even getting your landlord to do it. I’d trap it, hand it over to Animal Control, and walk away. Because, yanno, even supposedly unadoptable animals do get adopted, so I could live with that. YMMV. 