volatilization of ammonia from perennial ryegrass during decomposition, drying and induced senescence

The volatilization of gaseous ammonia was measured from cut herbage (leaf lamina + sheath) of perennial ryegrass (Lolium perenne L.), during a 70 d period of either decomposition or drying, and also from intact plants of perennial ryegrass subjected to induced senescence by shading. Volatilization during decomposition amounted to 20–47% of the herbage nitrogen, but volatilization during drying, and from intact plants during induced senescence, amounted to less than 1% of the herbage nitrogen. During decomposition, volatilization of ammonia was proportionally greater from herbage containing 3.52% nitrogen than from herbage containing 2.32% nitrogen. Volatilization occurred more rapidly at 20 °C than at 10 °C but, with both samples of herbage and at both temperatures, at least 4 d elapsed before appreciable volatilization occurred.