1. National Institute for Agricultural Research (INIA); Remehue Research Station; Casilla 24-O Osorno Chile
2. The University of Reading; Department of Soil Science; Whiteknights, PO Box 233 Reading Berks RG6 6DW UK
3. Institute of Grassland and Environmental Research (IGER); North Wyke Research Station; Okehampton Devon EX20 2SB UK