Exposed wiring outside
Pound a 2' - 3' pressure treated 2x4 into the ground, so that about 12" to 18" is above ground (cutting an angle in the end going into the ground, will help it go in better). 
Mount a weatherproof 1-gang electrical box on the 2x4. 
Pull the wiring into the box, using the appropriate clamp/bushing.
Secure the wiring to the 2x4 below the box, using an appropriate means.
Cap the wires off using weatherproof twist-on wire connectors.
Cover the box with a weatherproof blank cover.