At least three Juncus species look like this. Most likely species, given height, is Juncus fockei or a short J. prismatocarpus. However, J. fockei is usually tufted, and a bright apple green (and often grazed being palatable to fauna), and is septate (hollow, with septa going across like a membrane: see second photo Sighting 4631365, Sighting 4557200).