For generating plants such as the Barley in the Pasture biome you are using The vanilla TallGrass Worldgen. However, when that worldgen checks whether a plant block can stay ( canBlockStay() ), it only checks for the block ID, but NOT for the metadata.
Since you're using the same block ID for plants that need sand and plants that need grass blocks to grow, it thinks that the Barley can stay on Sand blocks.

I tried some ways to fix this problem but still without success :/