Bromus rigidus

Soils were collected from underneath bracken stands following the first rain of the season. The wetted upper 2 to 3-cm layer was screened and placed in storage dishes. Grassland soils similarly collected served as controls. Seeds were planted in these soils, watered with distilled water, and the dishes sealed with parafilm and stored. All species tested, except for Bromus rigidus, were inhibited in radicle growth. 

It was shown that soil colloids could adsorb volatile terpenes from the atmosphere (Muller del Moral 1966). Fresh soil exposed to volatile terpenes and also soil that had been stored several months were both toxic when bioassayed with a grass, Bromus rigidus. Other work showed that cineole and camphor could be recovered from soil in bare zones next to Salvia, but not in adjacent grassland (C.H. Muller 1965). Growth of the grass in surface soils of the bare zone was reduced compared to controls from nearly artificial bare areas. By 4-6 weeks into the growing season, terpenes were no longer detectable in the soil (Muller Chou 1972). 

---