Better than a regular sub-soiler you need a fancy one to do the job right!
Go to the hardware store and buy a small piece of plastic pipe with a right angle bend, 2 large hose clamps and a new drill bit (about 5/8"). Drill 2 holes in the trailing edge of the subsoiler, one near the bottom, one about 10" up from the other hole.
String your 2 hose clamps through the newly drilled holes, and use them to clamp the pipe to the trailing edge of the subsoiler.
Now mount the subsoiler to your tractor, run some wire down through the pipe on the back and stake it off at the beginning of your wire run. Drive forward with subsoiler down and it will automatically bury your cable while digging the trench. Be sure to slowly feed the wire while you drive.
Modification costs =
$2.00 for the plastic pipe (muffler pipe works well too)
$0.99 for a 2 pack of hose clamps
$1.50 for a new drill bit (cheapo)
Cost of not having to manually bury cable
and telling your wife it was your idea so she thinks you are brilliant /forums/images/graemlins/wink.gif = Priceless!