There's a technique called HDR Photography that might have been used for the image in question. HDR stands for High Dynamic Range. Both responders above are exactly right about their comments which is why it's unlikely that the image was taken by a single shot.
HDR utilizes the optimum setting for exposure for image areas of interest which in this case include the sky and the foreground, two primary areas of interest. Read about this technique and you'll understand the basis for what I'm referring to. It's a much better article than I could summarize in a few sentences but it might give you some ideas on the technique used.
http://www.idigitalphoto.com/high-dy...phy-explained/
One other technique I've seen used with what they call 'the magic hour' where the sun set causes a really nice deep and brilliant blue that isn't as dark as the sky shown. The photographer utilizes a relatively long shutter speed, say 20 seconds or so with exposure set to 'bulb' - manually timed basically. The person taking the image uses a flashlight and 'paints' the foreground - grass, objects in the foreground that are relatively dark since it's getting dark outside and the overall image ends up with the proper exposure for the foreground while the background colors become saturated due to the long exposure time. It's another really neat technique that I saw someone use on a photography forum with a tractor in the foreground sitting in the midst of some tall grasses and a brilliant blue sky at sunset. If I can find the photo I'm referring to, I'll come back and place a link.