Plastic Mesh
A fine plastic mesh can be placed around the garden. Plants can grow through the mesh, preventing the eyesore of its appearance, but pigs will not like to walk on something that their feet will get tangled in. Keep it suspended several inches off the ground. Make sure at least one corner of the mesh can be lifted so you can still retain access to the garden yourself.
Motion Detected Sprinkler
Pigs will try to get at your garden and lawn when you are not there to discourage them. To ensure there is still a deterrent in your absence, set up a sprinkler system that is activated by motion detection. The motion detector will emit a beam of light that, when broken, will discharge a stream of water that will scare the pigs. Although this is one of the more expensive ways to repel pigs, it can also be very effective.
Fence
A panel fence can be installed that physically prevents the pigs from entering areas where they are forbidden. The fence must be extremely secure to hold up against rooting snouts, as well as have panels that are too small for the pigs to fit through. An electric strand of wire can be run along the perimeter as well, but this tends to be less effective on pigs than it is for larger animals.
Predator Mimicry
Various types of predator mimicry can be used to repel pigs from the back lot. Audio tapes that play noises of their natural predators can be looped to run through the night. The urine of predators, such as coyotes or wolves, can be sprinkled around the garden every couple of days. This is less effective with domestic pigs, however, or in areas where feral pigs have few natural enemies.