He doesn't look like he's having a lot of fun watering, yet he seems to enjoy his little garden nonetheless. The whimsical raised foot in the background makes the shot for me.
there are several things i quite like about this photo
first, the story...a young couple trying to change the world with a bit of planting
second, the leg of the woman - she is showing a pride and love for something - is it the earth, is it the man...we don't care, we are just happy it was captured
a couple of things seems a bit staged perhaps, but i think it works overall