Dr Sjoerd W. Duiker is Professor of Soil Management and Applied Soil Physics at The Pennsylvania State University, USA. He has made significant contributions to both research and extension in developing more sustainable soil management practices in such areas as no-till systems, the use of cover crops, mulches and more diverse crop rotations. He is a member of the Governing Board of the Northeast Cover Crops Council which brings together universities, farmers, government agencies and others to optimise cover crop use in the north-eastern states of the USA.

Dr Andy Clark recently retired as National Communications Director of the USDA Sustainable Agriculture Research and Education (SARE) Program. The SARE Program operates under cooperative agreements between the University of Maryland, USA and the USDA's National Institute of Food and Agriculture. Dr Clark led the communications arm of the SARE Program that was instrumental in developing and disseminating sustainable crop and livestock management practices in the United States. As Communications Director, Dr Clark oversaw the development of more than 40 publications, including editing the Third Edition of the SARE publication Managing Cover Crops Profitably, widely regarded as the standard reference for farmers, agronomists and others interested in adoption of cover crops on farms in the United States.