Like blattsalat said, there's a ton of ways to make something like that. But...my question is, do you want the texture to look like that, or the map to look like that?

You can make the texture in photoshop using a couple layers and the blur and smudge tools.

If you want your terrain to look like that, you can set up a blend material (I'm talking MAX here) with the grass texture and sand texture and make a blend map for it (w/ photoshop).