Stopping trespassers

Pop down with a gun over your shoulder if you hold a licence and tell them next time you'll be firing it.

Good way of getting the guards interested in your case, for all the wrong reasons.

Maybe have the gun taken off you too.

Any chance of putting some farm animals in there temporarily or is the ground too unsuitable in it's current state?

Mountain bikers definitely won't want to cycle around a field covered in cow shite. Even if you just had a few animals for a bit to turn them off they might just move on somewhere else and then forget about your field.

The only thing those sort of veiled threats will achieve is the Gardai on your doorstep and forfeiture of your gun and licence.

There really is limited list of things you can do.

1. Fence off the land with palisade fencing, with you and that chap having the keys.
2. reclaim the land and plant it with forestry, with a more modest fence

At the end of the day the field is now seen as a borderline public amenity with people going in and out willy nilly. The only thing that will stop them is to fundamentally change the perception of the place.

No they don't, unless that trespasser is a dog. Guards take a very dim view of using guns to threaten a person, even in in jest.

Make sure you have public liability insurance anyway. Stick away up signs if you want but they have feckall legal defense afaik. Best prob to put up a decent fence and reclaim the field for some form of use of your own.

Finally, the voice of reason and sense. Take good heed of that post above OP.

And ignore the juvenile nonsense of swaggering around with a shotgun under your arm 'Murica style. If you did that, a few lads making ramps for mountain bikes would be the least of your worried while you are up in front of a judge for using your gun to intimidate someone.

I somehow think this is am unused field at the edge of a large urban area. It's has been used as a dumping ground historically for builders rubble. This type of neglected land always attracts near do wells. A couple of the rough boys with horses are your best bet.

PS there is one other options, 10 -12 JE or JEx 2year old bulls. Nobody will go into a field with them

Again, an electric fence and gate during like that will have you up in front of a judge when the wrong person gets a rap off it and sees that it was deliberately wired up to hurt someone. That's assault you could be up for. And if you're very very unlucky someone with a weak heart or pacemaker could die from a shock like that that would be nothing to you or I.

Op ignore ludicrously bad and dangerous advice like this. It'll only get you into trouble. Potentially very serious trouble.