1. Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, SY23 3EB, U.K. (M.S.D., S.J.L.); and NIR-Systems, Perstorp Analytical Ltd., Highfield House, Foundation Park, Roxborough Way, Maidenhead, Berkshire, SL6 3UD, U.K. (R.J.B.)