Just so you know, razor wire or evena single strand across one of the runs can end you up in jail and getting sued. I highly recommend sitting at where they are entering the field in the evening and intercepting them. If they are in a truck, take down the license plate number. A nice talk about trespassing and respecting someone else's property. End the conversation with further incidents will involve law enforcement. If it happens again, find a secretive spot and call law enforcement as soon as they show up. Get photos & when law enforcement shows up, ask for a copy of the police report to follow up with civil action afterwards.