Third, compost contains a variety of microbes that can store nutrients and make them more readily available to your plants. I'd recommend using a lab familiar with organic recommendations and then asking them if these recommendations take into account the factors discussed above. If you can't find or don't want to spend the extra money on an organic lab, using your local county extension office is fine. Just keep in mind the complications and use fertilizers sparingly. You want your soil to be slightly acidic for most annuals so nutrients are more readily available.
Compost brings most soils close to neutral.
If you want a particular area more basic for the year, you can add lime or ashes to just that area. Then if you use compost at season's end, your pH should be back to slightly acidic for the next season. This makes them more chemically active and easier for plants to pick up. Unfortunately it's not easy to add large amounts of clay or humus to your soil. A better alternative is to make raised beds of compost and topsoil - if you can find quality topsoil.