toilet habits!

Question
We took in an abandoned dog 2 years ago.  We believe she is about 7 years old.  We live in the countryside in a property with a lot of land including pool, garden, allotment areas etc.  Pip, our dog sleeps outdoors.
In 2 years we haven't been able to  train her to poo in appropriate places away from the house, pool area, garden etc.  She is free to roam on our land and on neighbouring lanes and tracks.  
The problem seems to be getting worse, for instance today she was reprimanded for pooing on the lawn.  Our current response is to take her to the poo and smack her nose and say no. This seems to have no effect whatsoever.  We have young children and my partner and I are becoming increasingly distressed by this situation.  Your thoughts and advice on this situation would be greatly appreciated.  Many thanks for your time and cooperation.


Answer
Dogs have no idea that one part of a yard is not the same as another part until you teach them, and frankly, it is never ok to smack a dog and say no, which doesn't tell her anything about where to go, it just tells her you are unpredictable, and sometimes nasty.  If you have young children, then modeling this kind of behavior toward animals is probably not a good thing - a lot of children get bitten because they copy behavior like this with the wrong dog, so don't let that happen.  Really, the only way to teach a dog where to "go" is to take them there on leash, not giving them freedom in the yard at first - that freedom is what led to your current problem.  To her, grass is grass.  But, if she goes with you to a "spot", and when she eliminates, you praise her and give her a treat once in a while, she will tend to go back to that spot.  If you also use a cue, such as "go potty" as she is doing her biz, eventually she can associate the words and do it pretty much on command.
If you teach her "attention" and "come" you will be able to nicely, with no swatting, divert her when she attempts to use another spot, and take her to the preferred spot.  (To teach those commands, see the free lessons at www.clickerlessons.com).  And, please, read "The Culture Clash" by Jean Donaldson.  She is ever so much more articulate about describing the language barrier between humans and canines that seems to be affecting your relationship with your dog.  And, please, keep your dog safe - wandering off your land could get her hit by a car, or worse.
Even if you don't think that's going to happen, I can tell you from experience that your children may miss her more than you can know if it does...and you just might have a real diamond in the rough if you train her instead of punishing her.