How soon can I do a soil test after fertilizing?

The worst time to take a soil sample is right after fertilizing, as it may give a skewed result due to the recent addition of nutrients. We recommend waiting at least 2 weeks after fertilizing before taking a sample.

The things that are most likely to skew the soil test results are getting fertilizer granules in the sample and maybe a little lower pH because of humic acid. When the sample is taken, remove the top 1/8 or so soil and discard to avoid including fertilizer granules. If this is done, it should be fine to sample any time.