Be more interesting than whatever she's sniffing. Smooch, whistle, clap your hands, etc. Try not to use your recall cue because you will dilute its meaning if she isn't advanced enough to obey it when she wants to sniff something.
Work in a less distracting environment, for instance in the house, on teaching her a cue to come back in your direction and continue walking. Walk through the house(on her leash) and if she gets interested in something(she may look for something because walking in the house is boring!), become really interesting and say your cue("Let's Go!" for instance). Be really exciting, not scolding or cooing. Exciting and fun! Sniffing this bush was pretty interesting, but Mom sure sounds fun right now! Reward her when she does come to you--whether it's treats or praise or toys or whatever, just reward her.
Most of my walks are also in the country, but off-leash. My newest dog is just starting leash training, one of my others is working on being trustworthy off-leash, and the other is completely trustworthy off-leash. Regardless they have all learned a release word. They have to walk in heel position for a while, and then they get their release word. For Mud, the most advanced, "GO!" means she can run off and sniff or whatever she wants to an extent. She can only go so far, basically within earshot so I can call her back, so she has a pretty good amount of "free rein" to do as she pleases. But, she has learned the distance where I will probably call her back, and when she gets there she will stop and look back, waiting for me to either call her back and not say anything so she can still run. After a little while, she gets called back and has to come back to heel position and walk nicely for a while.
So basically, for my dogs they are expected to have structured walks, but this is rewarded with free time--the release word. But, they still have to come back and walk nicely again, so recall is very important. Coming back is rewarding though, because they get praised for coming back and they know that coming back and walking nice gets them more free time. If they were to not come back the rest of the walk would be leashed with no free time. (This is SUPER BORING for my dogs, all working breeds and very bored with just a plain old walk.)
In a 1 hour walk, they may get the release word 5-10 times depending on their behavior, with up to 3-5 minutes of free time each time. Of course, this depends on the dog. The amount of times they get "released" depends on how well they are doing, so as they get better they get more and more free time. For the less advanced two, the free time is very short because they can't have too much free time. It's harder to get them back and focused on walking nicely. They work their way up and earn more and more free time. If I wanted to, I could really give Mud her release word right from the get go and at the end of the one hour walk call her back, and she'd come right back, but I don't. We also incorporate a lot of tricks in our walk. Sure you can sniff stuff when you're "released," but when you come back you get to play a whole bunch and do tricks with Mom! Mud looooves trick-training, so when we do tons of tricks during our walk she just loves it. Being with me is more rewarding than running off and sniffing stuff.
For my newest, this will be a bit harder to train, as she loooooooooves using her nose. But her recall is excellent already, and I do everything I can with all the dogs to make time with me more rewarding than anything else in the world. Walks for my dogs are very active, we're not just walking. The entire walk is basically a training exercise. Random tricks throughout the walk, work on recall, work on stays, work on releasing, work on walking nicely, etc. The whole thing is extremely mentally stimulating along with the physical part of it.
Freedom is perfectly fine, and it's great to want to give your dog that, but remember it has to be trained.
That being said, if they are sniffing because they are about to relieve themselves, there is a very good probability that you won't be able to call them away. When you gotta go, you gotta go!
Hope this helps.
Good luck!
My dog is free most of the time and walk time is generally training, playing, running around but always in control.
