There are many places, from local and stae conservation centers, to many seed companys
from my ecperience, Bio logic's seed company is the cheapest, and fastest
they will e mail, hard mail, you the results, or both too!
just go to there web site, and print out a applacation, and mail it to them
when doing tge soil sample
make sure to get a lot of samples from all over the site, and be careful not to take dirt too close to the metal /next to the shovel
and do not mix in a metal bucket, as it can alter the results
many county Ag offices will do testing for you too, and you can ask your local farmers who does there's