This app was mentioned in 4 comments, with an average of 1.00 upvote
Dirt cheap solution: use GPS Share and get in your field. Make sure to mark every spot in a recognizable way: Hill A, Hole 1, Down of the slope 5B, etc. and label the sample you took there with that naming pattern.
So when you will receive your results, with the name you will know where that sample came from to some degree (your smartphone GPS is not that precise, but you will be roughly at the right spot).
I cannot help you with a real software solution, I don’t use any.
A few reasons SMS is a train wreck:
Often SMS just isn't very reliable and MMS is a very fragmented clusterfuck. How many times have you, since the days of feature phones, sent an SMS and wondered whether it got delivered? Or gotten back, "Unable to send message," repeated it 5 times, then been told by the recipient that they actually did get it 5 times?
SMS messages come in out of order. Ever turn airplane mode off and get a weird, confusing jumble of texts? Which you painfully have to figure out the order of?
Delivery confirmation, open confirmation. With WhatsApp (and most apps), you can get confirmation that a message has left your phone, has been received by another phone, and been seen by the user (if they allow that). Did you tell your spouse that dinner was moved to 7? Is their phone dead? You know with WhatsApp, et al.
Location sending. (Full disclosure: I wrote an app with the idea of sending your location via SMS). You often want to tell someone where you are. SMS doesn't do that very well.
MMS isn't well-standardized. Remember in Android 2.x when MMS kept showing up as a slideshow? That's because different OEMs/carriers implemented MMS a bit differently. The resolution of image you can send with MMS is highly limited. You can't send arbitrary attachments. It's hard to send contact data. "Group messaging" is incredibly annoying and a weird bullshit extension Apple forced on the world.
As other users have mentioned, some carriers (especially outside of the US) charge for SMS.
Messaging where you only have wifi (traveling, in airplanes, etc).
Not to disregard tasker, because i do in fact love it, but this app can do what you want i believe https://play.google.com/store/apps/details?id=com.kkinder.sharelocation