Go to a local Ag agent and get the sample bags. It will give you details on how many cores to pull. That mainly will be dependent on your field size and goals.
I do mine at Whitetail Institute. A kit costs $12/$15 and you'll get your results by email in less than a week after you mail the sample . The form asks you what you're planting and makes recommendations accordingly. It will tell you how much lime, if any, and how much and what kind of fertilizer to use. It's geared to food plots, not hay or cattle graze.
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