May not be exact, but this is how I play it. I'm cribbing from videos I've seen of 
performances by the Brothers Four.

Capo 2nd fret.

For the intro, strum the chords, then arpeggiate -- listen to the song to hear how 
specifically to do it. The strumming pattern for the rest of the song is very 
easy: two down strokes for each chord. There appears to be some palm muting as well.

Intro: Am Dm Am E

Verse:
Am              Dm           Am            E
Once there were green fields kissed by the sun
Am              Dm            Am             E
Once there were valleys where rivers used to run

Chorus:
F               G               C                 A7*
Once there were blue skies with white clouds high above
Dm7            G7         C           E
Once they were part of an everlasting love
Am          Dm         Am   E                 F  Am   Dm  E
We were the lovers who strolled through green fields


Green fields are gone now, parched by the sun
Gone from the valleys where rivers used to run


Gone with the cold wind that swept into my heart
Gone with the lovers who let their dreams depart
Where are the green fields that we used to roam

Bridge:
F                                 C
I'll never know what made you run away
F                                                  C
How can I keep searching when dark clouds hide the day
Am                  Dm
I only know there's nothing here for me
Am              Dm          F              E
Nothing in this wide world, left for me to see

Verse:
Still I'll keep on waiting until you return
I'll keep on waiting until the day you learn

Chorus:
You can't be happy while your heart's on the roam
You can't be happy until you bring it home
Home to the green fields and me once again

Coda: strum, then arpeggiate Am-Dm-Am-E pattern, then end with an Am, barred at 
the 5th fret. Play this:

e|----------------------5--------------------|
B|---------------5------5--------------------|
G|---------5-----5---------------------------|
D|---------7---------------------------------|
A|-------------------------------------------|
E|-5-----------------------------------------|

Odd chords:

A7*: x02223
Dm7: xx0211