I found a coconut door mat for about £5 in wilkinsons (uk cheap hardwear store) recently, very plain, no patterns or colour on it. With a black flexible rubber backing in which the coconut fibbers are inserted in clumps. I had been looking for a mat like this for some time. Having seen some great pictures of wheat fields in Wargames Illustrated.
The top picture shows the backing of the mat, after some experimentation I found that you could pull clumps of fibber out of the backing material. The second picture shows some wheat fields on 3x3 and 3x6 inch art board bases with some metal wheat sheaves bought in the mid 1980's.
I am also producing some small terrain elements on 1p and 2p coins using the fibbers left in the backing with the ground level built up with filler then PVA and sand. I've also used granite chippings, picked up from the road. Click on the pictures for bigger versions.