The problems: Sports surfaces if left un-protected will inevitably attract youths and other miscreants who want to have a kick about, on your shiny new 3G pitch. This can lead to damage, which is expensive to repair.
Metal security fencing of at least 10 feet high is the optimal protection around the perimeter of your pitch or club.
In some situations, it's not practical to protect the entire club grounds, due to the expanse, but certainly it shoudl be possible to at least protect the pitch itself , allowing enough spectator space around it. Gates can then be locked when not in use.
CCTV cameras shoudl be considered, as both a deterrent and an aid to catch tresspassers. You may well find that your insurance requires it anyway, in order to prevent astronomical premiums.
Any clubhouse and outbuildings that contain expensive maintenance machinery should be protected by an intruder alarm system. This should preferably linked to a monitoring service, so that the Police can be notified in the event it is triggered.
If this is not possible, or cost prohibitive, you can get systems that call or text preset numbers, such as club offices.
(Alarm system image courtesy of www.brightonburglaralarms.co.uk )
Most burglar alarm systems are wireless, which means running cables
and making good, are not a real issue. Do make sure that any systems
are installed by NSI approved installers.