[1] Rothamsted Res, Okehampton, Devon EX20 2SB, England
[2] Tech Univ, Chem & Agr Anal, Madrid, Spain
[3] Univ Plymouth, Sch Geog Earth & Environm Sci, Davy Bldg,Drake Circus, Plymouth PL4 8AA, Devon, England
[4] Agri Food & Biosci Inst, Newforge Lane, Belfast BT9 5PX, Antrim, North Ireland
[5] Thunen Inst Agrarklimaschutz, Bundesallee 50, D-38116 Braunschweig, Germany