Take her out to potty and play on a long leash - also consider fencing off a smaller area for her to have as her own 'back yard', just off your back door, rather than opening the door to give her free access to all two acres.
The leash is the best method though to teach her NOT to bark - use it, pop it on before you open the door - the second you hear a noise, reward her, so that you change her associations with sound from 'means I must bark' to 'means I get a reward'. If you miss that chance, and she barks, say nothing, march straight back inside with her (easy as you already have her on a leash) - count five and go back out again. This latter part IS important, if you just go inside, she miiiiiight eventually learn that it is her barkign that makes this happen, but it will take ages. If you use inside as a 5 second time out, she will learn much much faster.
Whenever you use a time out though, you must make sure she IS getting the physical and mental exercise and the attention she needs - if shes found that barking at sounds/neighbours is a fun, rewarding thing to do and she ISN'T getting what she needs, it will be filling a hole.. as long as that hole remains she will find some way to fill it, even if you stopped the barking (for example, some dogs might dig holes instead, or learn to spin round and round chasing their tails).
You won't get anywhere even in a small yard, by letting her out alone, or even going with her and then chasing her around to get her on a leash and back in, you will just make the game more interesting, and you are absolutely right, shock collars will not fix the problem even if they did remove the symptom!