That's pretty good work Boni. I don't think you need to use the bump channel though. Using the displacement channel should be enough. Bump only simulates texture and depth so using both to do your grass seems overkill. Using the displacement channel is a good way to do it though. I use a noise node myself, but I like the way the node you used varies the color.

It's all fun and games...
Until the flying monkeys attack!!!