I've checked all the other threads on this question and there are ones similar but not quite explaining the effect I'm looking for.

Essentially in cycles, I want to fade a sand unit into a clay unit gradually transitioning from one to the other. The image shown has a harsh, unrealistic change that makes my already amateur equipment look appalling!!

I've set it up with two planes (1 Sand (below) and a similar Clay 1. Intuition says I should probably be using only one plane to get the gradient I want but this is what I have so far..

Thanks for any help