Plumber now? I'm assuming below the tap for the sprinkler is your meter and stop tap so it's not strictly the feed to the house per se but the feed from the meter stop tap to the house. The latter one is definately better.
Unsure of whether there any reliable joints you can buy to fix it. In the UK it would be MDPE (Mains Diameter Polyethylene). I've seen compression joints before but I personally wouldn't be using one on an underground line especially one that feeds drinking water as any contamination might end up with you getting bacteria etc in the supply. I'm guessing the two possibilites would be either some joint I'm unaware of - might be a reliable push fit these days or maybe a plumber can weld the pipe together in some way. Alternatively, I guess it's dig up the pipe from the house connection back to the meter connection and replace.
Edit, looks like there are options if it's MDPE:
I presume these are OK underground as MDPE is usually underground. Still not sure about using compression though as it could work loose over time.
PS if you've never used push fit before, one trick I use with copper pipe, is a piece of plastic pipe (they usually have thepush fit depth marked on them these days) and put it alongside the copper pipe and mark on the copper pipe the depth the fitting has to go to with a sharpie. Then when you push the joints together, you can ensure you have pushed them all the way in. Your MDPE probably won't have marks on it as it probably predates push fit fittings and even now I don't know if they are marked. However, you may be able to get something with the depth marking on or measure it yourself onto a piece of pipe from the outside of the fitting. Also with push fit don't forget you might need pipe inserts depending on the type of pipe to support it before the fitting is fitted. MDPE is tough so I would have thought not, but I can't confess to know the answer.
