Hello Jason,

A sampling of University studies advise to wait weeks to months after fertilizing, before taking a soil sample for testing.

If the starter fertilizer was a slow release product, it may take a long time for it to fully dissolve and travel through your soil. If you wait for two to three months, you are looking at September or October before you can take your samples. You can take your soil sample late fall (November) or in the spring next year.

Here is an article that says to wait several months after applying a fertilizer, before doing a soil test: https://extension.wvu.edu/natural-resources/soil-water/soil-testing

Here is a link to the information on MSU soil tests: https://homesoiltest.msu.edu/