WELCOME BY THE CONVENOR

It is a great pleasure for me to welcome you all here on the occasion of the third international symposium on watersupply and irrigation in the open and under protected cultivation. I am pleased indeed that participants from various countries are present, in particular Prof. Fritz president of the International Society of Horticultural Science (I.S.H.S.) and Prof. Hartmann chairman of the working group on watersupply and irrigation. I am grateful also that Mr. van Soest former director of the department of arable farming and horticulture representing the Ministry of Agricultury and Fisheries is here.

Ladies and gentlemen, when Prof. Hartmann and Dr van Kampen asked me to act as a convenor for this third symposium, I may have underestimated its task and its preparation for the technical and scientific organization but it seemed easy after all due to the extensive assistance from the organizing committee especially its secretaries.

You may have seen from the programme that many participants are not only attending this symposium but are willing to give a lecture as well on a certain topic which I am very grateful. We could, therefore, make a programme which in my opinion is well balanced consisting for instance of lectures on the following topics: various aspects of watersupply, physiological effects in plants, yield-soil moisture relationships, consumptive use of water, practical applications of watersupply and irrigation. Apart from these lectures additional information will be obtained from a poster session.

In order to obtain a general idea of water problems existing in The Netherlands and research on this topic carried out in our country, two days for excursion are reserved in the programme. The first one on tuesday will give an overall idea on water management in The Netherlands e.g. reclamation, polders, distribution of surface water, drainage, etc. In a second excursion a visit to the glasshouse centre of either Naaldwijk or Aalsmeer can be made. Due to the early season, it was not feasable to arrange an excursion on water problems of horticulture in the open. In case time remains available during this week, I would suggest to organize a panel discussion on the subject "which research goals on water supply and irrigation on horticulture in the open and under protected cultivation should be strengthened in the near future".

Ladies and gentlemen, I do hope that together we will have a fruitful and successful symposium and also that our foreign participants feel themselves at home here in The Netherlands.

Thank you.


OPENING ADDRESS ON THE SYMPOSIUM

W. van Soest

Mr Chairman, ladies and gentlemen,

It is a great pleasure for me to have the opportunity to speak a few words at the beginning of this Symposium and to welcome you in our country on behalf of the Ministry of Agriculture and Fisheries in The Hague.

I would like to direct a special word of welcome to Prof Fritz from the Federal Republic of Germany; President of the International Society for Horticultural Science. Prof Fritz, we are very honoured with your attendance to this Symposium. The ISHS is a very active international organization, which is clearly demonstrated by its many international working groups and their activities with regard to Symposia, publications (Acta) and international congresses.

The ISHS has greatly increased and improved international contacts between research workers. Exchange of research results stimulates adjustments to and adaptation of research programmes. It also promotes the application of results into horticultural practice.

Prof Fritz, I must point out that your personal devotion has strongly contributed to ISHS and its activities. Therefore it must give you great satisfaction to know that the next International Horticultural Congress will be held in your country next year in Hamburg.

We wish you all the best with organizing this event and we hope that many research workers all over the world will find the opportunity to attend this congress in West-Germany.

I like to thank the convenor Prof Bierhuizen (Beerhouses) and his staff for the work that has been done and to all who have contributed to this Symposium.


Ladies and Gentlemen,

Welcome in the Netherlands, "low country", Holland. Now I have the opportunity to give you an informal opinion about a birds' eye view on Dutch Horticulture "the salad bowl of West-Europe" / the flower market of the world.

Nowadays the Horticulture in The Netherlands is a rather important economic activity.

The yearly turnover is about 6 mrld florins (5.5 mrld D.mark) (27 mrld U.S. dollars) adjusted by 7 branches of horticulture industry.

Production value 1980 in mln

gld (estimation)

Vegetables under glass	1.420
Vegetables outdoor and mushrooms	678
Fruits	335
Nurseries	325
Flowers and Potplants under glass	2.385
Flower bulbs	575
Seeds	180
Others	16
Total	5.914

5.914 mln = 21% of total agriculture value of 25.527 mln gld.

Of the total horticultural production 60%–70% is exported, mostly to Common Market Countries.

Strong and weak points of Dutch horticulture

There are a great number of natural-, economic-, and social conditions that influence the position of horticulture. Strong points are:

• Skill of the growers and salesman: hard efficient, skilled people, willing to take risks, showing a great flexibility and adaptability, invest know how and capital. Most of them are born with green fingers and a calculator. As to the size of the holdings, middle sized holdings dominate. They are family financed and managed. The strength of Dutch growers seems to me that although their individual holdings are middle sized, they together have managed to grasp as a group the economics of scale. They formed a network of growers owning cooperative organizations instead of being weak as individual growers. For instance: cooperative marketing through auctions, cooperative banking, cooperative research. This "network" brings the grower in a very strong position. In this way they combine the economics of middle sized production with those of large scale enterprise. The horti-cultural holdings in The Netherlands are strongly specialized and mechanized. The same pattern shows the set up of Dutch horticultural research and extension service. Government support in these fields is strong. There is an intensive cooperation and coordination between the four partners growers-research-advisory service-teachings. The flow of information goes quickly and efficiently. A frequent intensive open contact and exchange of ideas is of great benefit to the industry. Last but not least there is much to win in a closer contact between research people in different countries. That is the reason we are here.

Our geographic position is favourable amidst the densely populated areas in West-Europe. That means low transport costs and less quality losses of horticultural produce. Our seaclimate stands for: soft winters, cool summers, regular rainfall so yearround production under glass is possible. Light conditions in winter are less favourable. There are a lot of soil types suitable for horticulture, sandy soils, clay soils, peat soils, etc.

The country is flat with a controlled water-table (polders). Speaking in general, there is no lack of water but actually we have a lack of fresh water of good quality. We thank nature that we have a huge amount of natural gas of good quality. Practically all horticultural holdings use natural gas for heating and CO₂ manuring nowadays.

Dutch horticulture faces the same problems as growers elsewhere. Inflation has cuased rising costs and scarcity of certain basic goods (labour, energy) and a strong currency of 6 florins. As to prices for horticultrual produce we must consider that there is hardly any chance that price levels of horticultural produce will keep up sith cost increases (population West-Europe stable, real incomes of population stable or somewhat lower).

Answer of the grower has been increasing:

• yield per manhour labour - productivity
• energy productivity - energy saving techniques
• Yield per m², growing technique improved considerably
• quality grading and packing and the quality of service to the retailers.

Answer of the growers has been diversifying the production.

Turning to the subject of this Symposium on water supply etc.

An elementary condition for most of thise hoticultrual activities is the availability of water of high quality. In open cultivation we have to take into account a replenishment demand of 150–250 mm each summer in intensive crops. In protected cultivation there is a need for at least a suppletion of 500 mm pro year. Although the coastal area of the Netherlands is famous for its broad canals, lakes and polders, water supply in this region, where 80% of the protected cultivation, 90% of the bulb growing, 25% of the orchards and 50% of the intesive vegetables are situated, is one of the main problems, becasue of the rather high salt content of the "open water".

In summer, the precimpitation deficiency must be supplied by the river Rhine, which is known as the "sewer of Europe". This Rhine water has a rather high salt content (sulphates and chlorides, especially sodium chloride). In periods of low discharges the chloride content even may pass 200 mg/1 at the German/ductch frontier, and chloride contents between 100 and 150 mg/1, corresponding with 500–800 mg total salt, are not exceptionally. To this Rhine water the drainage water out of deep polders is added. Seepage water out of these polders often has a very high salt content, because they are all marine soils (sea deposits).

The picture is completed by the salt intrusion from the Northsea, for instance thorough the harbour of Rotterdam. Though we are proud of having the biggest harbour in the world, it means a deep entrance and a high basin capacity, both enlarging salt intrusion.

Though the susceptibility of salt is not the same for all cops, the quite normal concentrations of 150 mg chloride pro liter means yield reductions of about 5% for tomatoes till 10% or more for pepper and cucumber, if they are grown in soil. Also flower crops and espcially pot plants are highly susceptible of these salt concentrations in irrigation water.

The need for fresh water is growing rapidly because of the development of modern growing techniques like artifical substrates and N.F.T. (nutrient film technique). The interest of practical growers for these advanced techniques is highly stimulated by recent developments in energy prices and the public opinion on the quality of food and environment. The energy prices urge to a better control of temperature in the root zone without high energy losses to the subsoil. The constant growth of one or two crops (monocultures) on the same soil, makes a yearly intensive desinfection of this soil inevitable. Steaming of the soil is very expensive and not always possible, and chemical means are very suspect (methyl bromide).

Using artificial substrates or N.F.T. enables a very sharp conditioned feeding of the plants, and there are indications that in this way for instance the nitrate content of salad growth in winter under low light intensity, can be lowered.

As a result of the demand for better water there is a growing interest for building rainwater basins, in which the roof run-off of the glass-houses can be stored. But they can not be built that large, to ensure enough good quality water. Expecially in June most of these basins are empty. One can mix, for instance when half of the basin is empty, with water out of the canal or with tap-water. But the public water system is not pleased with customers who only buy in dry periods, and moreover the chloride content of this tap-water can easily exceed 100 mg pro liter. Some growers have installed a water cleaning system based on the reversed osmosis system. Nowadays there are filtration modules available with a salt retention of 99%! but this technique requires a lot of energy (cost about ƒ 2,50 till 3,00 pro cubic meter).

In fact, Mr Chairman, the Dutch horticulture is in need of quality water, and welcomes every useful innovation with respect to the improvement of water quality of irrigation efficiency. Therefore a Symposium of so many outstanding experts in the field of irrigation, water management and water quality, is also of great importance to us.

I sincerely hope you will enjoy this symposium. The growing scarcity of funds for research will need a closer cooperation between nations in the field of scientific results.

I hope you will get a good impression of the Dutch Horticulture.

W. van Soest
Formerly Director of Horticulture and Arable Crops
Ministry of Agriculture and Fisheries
The Hague


INTRODUCTION ON THE SYMPOSIUM

H.D. Hartmann

Water is threatening to become a scarce property in the following decades. On the one hand there are still many areas, where water is in great abundance. On the other hand there will be areas where the quantity of the available water is in no proportion to what is needed. These areas may be situated in the highly industrialized Central Europe or in some parts of Africa. In the first case the average water consumption a head of the population has considerably risen today to 350 litres a day. For these quantities industry, agriculture and housholds compete with each other. Thus there are still about 40 percent of the water resources available for agriculture in USA whereas in the Federal Republic of Germany in the aglomeration areas only 20 percent are provided for the farmers. These shares will surely decrease in the future, but the demands to the agrarian production will certainly increase. In order to produce with these water resources sufficient food for the population, water must be used efficiently. Therefore needs arose for a comprehensive research in efficient controlling and irrigation systems.

According to the importance of this problem the Section of Vegetables organized in the late 60th the Working group Water supply and Irrigation. The first Symposium we had in Geisenheim, the second in Israel in Bet Dagan. So we are glad that Prof. Bierhuizen and his staff, especially Mrs Wagenvoort, organized the third symposium "Water supply and Irrigation".

We hope to discuss at this opportunity the different topics like physiological fundamentals on water consumption, water application, water quality as well as on water control.

In my capacity as chairman of the Working Group "Water supply and Irrigation" of the section Vegetables I am very pleased to meet so many scientists from abroad as well as the official representative of the Government, Mr Van Soest. Meetings like the one we are attending are promising signs of international cooperation in the world wide research. We shall meet here more than 50 colleagues from 18 different countries, concerning to different sections and commissions of ISHS. They serve the purpose of better international understanding and friendship, a very important task of the ISHS.

At last I should like to thank very much the organizer and the helpers, for the preparation of this symposium for all that you have done and for the very promising programme as well.

I am sure this symposium will develop very successfully.

H.D. Hartmann,
Chairman of the ISHS working group
Water supply and Vegetable Irrigation.


ADDRESS OF THE PRESIDENT OF THE ISHS

D. Fritz

On behalf of the ISHS I would like to congratulate you - that means the conveners of the symposium, as well as Prof. Hartmann as the chairman of the working group - on the most interesting program of this meeting. You give a good pattern to working croups how to concentrate versatile problems by means of an interdisciplinary symposium. Such an interdisciplinary collaboration fully is in the interest of the ISHS. Not it is the number of established commissions but rather the number of interdisciplinary activities may be initiated by every of the sections, or commissions, or by every of the working groups and are highly welcomed by the Council. In most cases, partners for such collaboration will primarily be found among different technical bodies of our own society, but also should be seeked among other organizations, for example among the 20 international scientific societies that are bound by contract with the ISHS for mutual co-operation.

The ISHS at present is built of 46 member countries, 220 affiliated organizations and 2.000 individual members from 88 different countries. I would be highly pleased if also all of you used the chance of being kept informed on scientific activities in the field of horticulture - ISHS, as well as non-ISHS - that is provided to individual members by means of Chronica Horticulturae and of improving international contacts by means of other ISHS publications. Though fees are relatively low, individual membership provides an advantage of information.

Another opportunity of exchanging experience and information will be given by the 21st International Horticultural Congress, which will take place in Hamburg from 29th August to 4th September 1982. On behalf of the ISHS and the German Society for Horticultural Science I would like to invite you to attend this congress. It will focus on "Horticulture in the Industrial Society". Not only problems arising in industrialized countries with high population density will be emphasized but also all subjects that are of high actuality to horticultural sciences in all countries of the world will be considered. Examples of the wide range of subjects to be dealt with may be seen from the 2nd Announcement, which can be requested from the congress secretariat in Hamburg. The program committee under the chairmanship of Prof. Dr. Bünemann, Hannover is going to arrange eight concurrent sessions with up to 800 papers and 400 posters. The congress language will be English. The congress fee will amount to about 300,- DM.

Local excursions in and around Hamburg will be offered every day considering all branches of horticulute. Hamburg was chosen the place of this congress because of its central location, and the excellent possibilities for excursions to demonstrate growing sites typical of northern Europe.

Pre- and post-congress tours of 5 days' duration will lead to different horticulutral production areas of northern Europe: Arrangements will be offered to travel from the Netherlands, or from Italy, or from Scandinavia to Hamburg, and - following the congress - from Hamburg to Scandinavia, or the Netherlands or to Italy. On all of these excursions, also production sites and holdings typical of the conditions of the Federal Republic of Germany will be visited. Then you will see that consumers' demand for superior quality, and for continual supply with all horticultural products. but also for home gardens and recreational areas are very high in our country. The pre-capita expense spent for flowers in Germany is five times the amount spent in the USA.

I hope that these details may attract many of you to take an interest in the ISHS and in the 21st International Horticultural Congress. Be assured that you are welcome at all of the meetings of the ISHS, and that you are cordially invited to attend the Hamburg Congress.

I wish your symposium to become a success. See you again in Hamburg next year.