Here we would recommend a PH soil test first. But you really can't go wrong adding compost. I really like worm castings the best! What type of soil do you have up there in Nebraska?
I agree with Four Season. Get a soil test, and they will tell you exactly what you need. I actually found out last year that I had more than enough organic matter, so I slowed down on the worm compost a little bit. I usually recommend cooperative extension offices for most states, but it looks like University of Nebraska doesn't offer that (silly Huskers). There is a private alternative here:
Good luck with those veggies.
Not that this will help you this season, Deb, but, if you have large vegetable garden, you may want to consider planting a cover crop in the fall that you can till into the soil in the spring. Here are some of the basics from the University of Illinois's Extension Service:
Deb, there are some good tips on cover crops for home vegetable gardens in this article from the Cornell University Department of Horticulture: