The authors wish to express their appreciation and gratitude to José Benites, AGLL for the advice on preparing this publication. The authors would also like to thank Peter Craufurd of the Department of Agriculture, The University of Reading for information and help on soil water relations and plant physiology, as well as John Gowing for supplying illustrations.
The authors also highly appreciated the valuable comments provided by Amir Kassam, SDRC, P. Koohafkan, AGLL and Bob Steward, West Texas A&M University on draft versions. Special thanks are due to Peter Brinn and Sandrine Vaneph for their comments and the consequent editing they provided. Also valuable were the inputs, final editing and proof reading by Robert Brinkman.
Finally, the authors thank to Antonio Castellanos for his efficient preparation of the text and Lynette Chalk for formatting of this document.
