Try putting the hair effector on a floor, so its infinite.
If you don't want it so flat try messing around with the terrain shape.
You can make it very large, with very low bumps.

My C4D R13 doesn't even have the hair effector, for some reason?
I spent a few hours today trying to make some scenery, and I couldn't make the grass look good without it. Plus my computer "didn't have enough memory" to continue...

Anyway, good stuff. I like it.
It could use some work, obviously.

@injustice thanks for the responce on both pieces. Thanks for the advice as in my next piece I will use these to get better.I think I'm going to do low poly stuff for a bit as it seems interesting. Thanks for the help. As for the grass, I'm going to hopefully practise today. Thanks again.

no problem, anytime you have a question feel free to ask