So I took a look and I noticed a couple things.

The grass was reflective but because the diffuse texture was missing on the ground plane, it turned it into a kind of black hole. Your grass is set to have very rough, blurry reflections, this coupled with the black hole made the grass appear like it wasn't reflecting anything.

Also, the raytrace reflection trace render settings were low so the reflections stopped being calculated too soon for the grass to look good.