TLM, can you give any tips of how you approach the fields in the dark? Are you parking a long distance away. Are you using night vision or any special light(red/green).
I use night vision and thermal to drive and spot using no visible light sources at all. Typically the hogs are spotted pretty far of and then I stalk up on foot downwind. There are times when you come right up on them I just drive on by like they were not there. They will usually go back to feeding as they think you can not see them at night. Then I'll circle back around on foot, this also keeps them from being scared of my vehicle. I try not to shoot from my truck if possible Do not want them to relate it with danger.
Of course thes tactics will work in the day or at night with a light, but with night vision and a suppressor they are more effective.