Fill a syringe with an industrial quality, outdoor rated wood glue. Large veterinary syringes, available from farm supply stores, work best. Inject glue into the cracks until the crack is filled.
Wrap two strap webbing clamps around the column, one just below the top of the splitting section and one just above the bottom. Run the strap around the column and back through the cam tightener. Pull the strap tight, and flex the cam lever in and out several times until the strap pulls the cracks closed.
Allow 24 hours for the glue to harden. Remove the strap clamps by pressing the release and pulling the strap from the clamp. Sand the surface of the column to remove any excess glue using 150-grit sandpaper.
Seal the surface with a coat of paint on a painted column, or apply a coat of clear finish if the column is stained. Apply both finishes with a soft bristle brush working in long, straight strokes vertically with the grain. Spread the finish as evenly as possible to prevent runs and drips. Allow the label recommended drying time between coats. Add at least a second coat for adequate protection.
As outlined previously, inject glue into the cracks and clamp the column using strap clamps to pull the splitting section into line as much as possible.
Have a welder cut two 1/8-inch steel plates as wide as your column and 12 inches longer than the splitting section of your column. Drill two rows of holes with a quarter-inch bit, one inch in from each long edge of the steel plates. Make the holes every 6 inches along the plate.
Use one plate as a template to mark the pilot holes on the column. Place it centered over the split section. Drill through the column, keeping the bit straight and level, with a long quarter-inch bit.
Fit the plates on either side of the column, aligning the holes in the plates with the holes in the column. Drive a quarter-inch coarse thread bolt through each hole, and place a washer and nut on the other end.
Use a pair of socket wrenches to hold the head of the bolt and turn the nut tight. Tighten as tight as possible. Allow the plate to set for an hour, then snug the bolts again. Repeat every hour for eight hours. Release the strap clamps after 24 hours. Leave the steel plates in place.