Changing the resolution of landscape layers

Hi, I have a problem with painting on my landscape. I tryed all brush settings but it always looks blocky :

http://img4.hostingpics.net/pics/659276landscape.jpg

I know about the LandscapeCoords node in landscape material but I don’t use textures as I want a flat shading style so my material only contain colors and color nodes don’t have UV input. How can I change the resolution of the landscape layers please?