Affiliation: | aResearch Institute of Organic Agriculture, CH-5070 Frick, Switzerland;;bInstitute of Agricultural Sciences, Eidgenössische Technische Hochschule Zurich, 8092 Zurich, Switzerland;;cInstitute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 3UU, Scotland; and;dNatural Resources Management and Environment Department, Food and Agriculture Organization of the United Nations, 00153 Rome, Italy |