ACKNOWLEDGEMENTS

First, we gratefully acknowledge financial help from RABO Bank The Netherlands at Utrecht, DSM Agro Specialties at Sittard, Plant Publicity Holland at Boskoop, and the Export Promotion Department of the Ministry of Agriculture and Fisheries at The Hague.

We thank Mr. H.W. Floressen at Dronten and Mr. W. Roelofs at Zeewolde for hospitality at their fruit orchards and fruit tree nurseries.

We are indebted to the staff of the Institute of Agricultural Engineering (IMAG) at Wageningen, especially Mr. P. van Lookeren Campagne and Mr. H. Wiedenhoff of the National Extension Service on Farm Equipment for organising the excursion at the IMAG research garden at Wageningen and for showing their harvesting machinery. We also thank members of the "Federatie Het Landbouwwerktuig" who kindly showed various machines for orchard management.

We are grateful to many workers of the Research Station at Wilhelminadorp for their valuable assistance. The staff of the Research Station for Fruit Growing at Wilhelminadorp is thanked for the receipt of all the participants at the Station. Special thanks are due to Mrs. A.M.T. Mateijsen for her extending secretarial work and for her care of the accompanying persons. Mr. M.L. Josse was a great treasurer and Mr. A.J.P. van der Waart did a good job in technical assistance. Mr. C. Kortleve (National Extension Service on Fruit Growing) capably organised both the horticultural and the tourist excursions. Mr. J. Goedegebure (Agricultural Economic Institute) was, besides other qualities, a valuable member of the organization committee.

We owe thanks to John Jackson and John Palmer for the correction of all papers and the editing of this volume of Acta Horticulturae, and to Mrs. Linda Barwick who has retyped a number of the papers.


Patricia S. Wagenmakers and S.J. Wertheim
(Conveners)


WELCOMING ADDRESS

It is a pleasure for me to extend to you on behalf of the ISHS Fruit Section our sincere welcome and best wishes at the fourth HDP Symposium here at the Flevohof.

The Netherlands not only hosts the ISHS at its prestigious agricultural research centre in Wageningen, but it is also the country which more than any other has fostered the idea, in apple growing, that orchard planting density could be increased by introducing dwarfing rootstocks, spindle training systems, and management techniques that the Dutch themselves helped to establish, adapt and promote.

The original idea was to increase tree density and the name High Density Planting comes from the working group founded by Dr. Jackson, who with the collaboration of Dr. Wertheim organised the first HDP Symposium in England and the Netherlands in 1976. Then, following the symposium at Lana d'Adige in 1980 and Montpellier in 1984, the name of the group was changed to "Research and development in orchard and plantation systems". This more correctly reflected the fact the HDP is a relative concept that cannot be pushed ad libitum, not to mention the risk of having to redesignate the group at a later date as that of "Lowering planting density". It also underscores the need for in depth research of the physiological effects on trees, fruiting and fruit quality, and on the economics of orchard management for all species as induced by different design layouts. This explains too why the group not only investigates factors involved in production, pruning and training systems but why it avails itself of the expertise of specialists in such fields as physiology, microclimate, light and photosynthesis, growth regulators, genetics, micropropagation, mechanization and economics.

This cooperation has resulted in integrated research studies of international validity, as exemplified in the joint project involving six European countries of which Dr. Palmer will comment at length. It is in the finest spirit of international cooperation that this project has been undertaken, displaying itself to be a viable problem-solving and collaborative effort.

Let me conclude my remarks by mentioning with pride that the activities of the Fruit Section, which now numbers 15 working groups, includes an average of 10 symposia and meetings annually. It is to be hoped that the group will be even stronger following this Symposium, and that new ISHS members will decide to join it. For it is by contributing to the development of research in these fields that all future renewal and success in the fruit growing industry will be determined.

Silviero Sansavini
Chairman ISHS Fruit Section