Ball Valve to Sprinkler System

The ball valve lever that shuts off my water supply to my outdoor sprinkler, does not seem to be shutting off the water completely - there is a small drip that is still coming out of the drain hole after shutoff. Is there any adjustment or fix I can do to the valve, without having to replace the copper valve which would mean hiring a plumber?

Thanks

What's the valve orientation?

Are the valve and piping oriented so that you can be sure the drip is caused by the valve leaking, and not water returning from the sprinkler side?

Honestly I dont' know. But I am pretty sure it is not coming from the outside system. The sprinkler system has had all the outside drain valves opened and drained. The drip has been hapenning for about a week now or so. I had turned on the sprinkler system for a while earlier this spring, but have now shut it back off because of the colder weather.