PROCEEDINGS

EIGHTH ANNUAL CONFERENCE

THEME: HYDROPONICS-EFFECTIVE GROWING TECHNIQUES

SAN FRANCISCO AIRPORT MARRIOT HOTEL

APRIL 4, 1987

SPONSORED BY

HYDROPONIC SOCIETY OF AMERICA

Scien\.:e

P.O. BOX 6067 CONCORD, CALIFORNIA 94524

Agr. ;ulture

NOITCE

1he Hydroponic Society of hoorica, or its representatives, makes no warranty, expressed or inplied, or assunes any legal liability or responsibility for the accuracy, conpleteness or usefulness of any infonmtion, apparatus, product or process disclosed, or represents that its use ~uld not infringe privately owned rights. Use of trade names in this publication does not imply endorsen:ent of the products named or criticism of similar ones not Irentioned.

All rights reserved

No part of these Proceedings my be · reproduced in any form without proir written pennission of the Hydroponic Society of hoorica.

FOREWORD

The 1987 Annual Conference is the largest and most comprehensive ever attempted by the Hydroponic Society of America. It reflects our united

. resolve to continue fulfilling our principal goals to promote interest in scientific research and education, and to provide a forum for the reporting of research and the exchange of information about hydroponic growing. This year's theme, Effective Growing Techniques, evolved from the infor-mational questionaires returned by members attending last year's annual conference.

As our Society becomes larger, more mature, and gains greater knowledge of the past and present, we must also look to the future and explore in various directions in order to fulfill our purpose. The greatly expanded space station research being done to devise integrated growing systems should be observed carefully. This work will yield new information on how plants grow and on the technology of environmental control. Most impor-tantly, greater public awareness of the research will provide a much expanded knowledge of and appreciation for hydroponic growing. Therefore, in-cluded in the conference program is a presentation on the art and science of acquaculture to broaden our knowledge of the relationships between plants and animals in an aquatic environment. In addition, in order to provide more comprehensive in~depth information in a timely manner, we are introducing special subject, concurrent mini-sessions organized into a format of lecture, discussion, and demonstration.

Our 1987 conference program would not be possible without the help of a number of people. Included in that group are Scott Karney and his program committee who performed a monumental task in creating and organizing the program. Gene Brisbon, in addition to being our Corresponding Secretary and editor of the newsletter, handled the publicity and performed a thousand other jobs, keeping the Society functioning smoothly all year in preparation for this event. My sincere appreciation to these and to everyone who worked so hard to make it possible for us to continue to learn and share our experiences at this conference.

Q I /) · 1c~ ~O'Brien

President

PROCEEDINGS OF THE EIGTH ANNUAL HYDROPONIC SOCIETY OF AMERICA CONFERENCE

HYDROPONICS: EFFECTIVE GROWING TECHNIQUES

TABLE OF CONTENTS

FOREWORD-PRESIDENT'S ADDRESS

TABLE OF CONTENTS

PRESENTATIONS:

1. Keynote Address-NFT Developments and Hydroponic Update Dr. Allen J. Cooper- Director Nutrient Film Technology Ltd., England 1

2. Aquaculture- Another Hydroponic Technique? Dr. Tom McCormick- McCormick Associates, Berkeley, California 21

3. Hydroponics in Research Mr. Steve Grattan- Plant Water Specialist, U.C Davis Cooperative Extension 41

4. Marketing Hydroponically Grown Products Mr. Robert W. Munyon- Munyon Farms, Lodi, California 50

5. Computerized Environmental Control: The Basics Dr. Strven Schwartzkopf- Plant Physiologist_ U.C Davis 58

6. Trouble Shooting With Tissue Culture Mr. Carl P. Spiva- Consulting Agronomist 64

. 7. Marketing Strategies for Hydroponic Equipment Dr. Joseph E. Howland- Reynolds School of Journalism, University of Nevada, Reno, Nevada 74

8. Computerized Environmental Control: Advanced Dr. Maynard Bates- Campbell Research Institute, Pennsylvania 79

9. Growing Unusual Crops Mr. Brian Mauza- Provincial Greenhouse Specialist_ British Columbia Ministry of Agriculture and Food 92

10. Hydro-Aeroponics Unit for Research Purposes Dr. HilleiSofer- Senior Researcher, Volcani Center, Israel Prepared by Scott Karney 99

11. Nutrient Requirement Changes During Plant Development Dr. Arnold Bloom- Vegetable Crops Department_ UC Davis 104

12. Hydroponics in Infertile Areas- Problems and Techniques Dr. Allen J. Cooper- Director Nutrient Film Technology Ltd., England 113

OFFICERS/BOARD OF TRUSTEES 121

PASTPRESIDENTSUST 122

CONSTITUTION AND BY-LAWS 123

NFT DEVELOPMENTS AND HYDROPONIC UPDATE

BY ALLEN J. COOPER

DR. ALLEN COOPER IS MANAGING DIRECTOR OF NUTRIENT FILM TECHNOLOGY·

LrD •• HooK LANE. ALDINGBOURNE, CHICHESTER. WEST SussEX 02110, ENGLAND. HE IS AN INTERNATIONALLY ACCLAIMED EXPERT ON NUTRIENT FILM

TECHOLOGY• (NFT), AND DEVELOPED THAT SYSTEM AT THE GLASSHOUSE CROPS

RESEARCH INSTITUTE (GCR!) IN LITTLEHAMPTON WHERE HE WAS PLANT PATHOL-

OGIST. DR. COOPER WAS CERTAINLY ONE OF THE FIRST TO RECOGNIZE THE

COMMERCIAL POSSIBILITIES OF NFT, AND HAS SHARED HIS EXPERTISE IN

SEVERAL BOOKS lNCLUDING ROOT TEMPERATURE AND PLANT GROWTH AND THE

;ABC OF NFT.

! WANT TO BEGIN BY CONSIDERING COMMERCIAL HYDROPONIC CROP PRO-

DUCTION IN GREENHOUSES BECAUSE IT IS IN GREENHOUSES THAT THE MAJORITY

OF THE DEVELOPMENT WORK ON HYDROPONICS HAS BEEN DONE. ! ALSO WANT TO

START BY CONSIDERING THE PRESENT SITUATION IN THE ENGLISH GREENHOUSE

INDUSTRY BECAUSE IT IS AN INDUSTRY IN WHICH HAS BEEN A MAJOR

CHANGEOVER TO HYDROPONICS IN RECENT YEARS. THIS MEANS MAINLY

CONSIDERING TOMATO PRODUCTION BECAUSE IT IS FAR AND AWAY THE MAJOR

CROP THAT IS GROWN COMMERCIALLY IN GREENOUSES IN ENGLAND.

FOR MANY YEARS NOW IT HAS BEEN QUITE CLEAR THAT THE

TIME-HONOURED METHOD OF GROWING TOMATO CROPS IN SOIL IS NO LONGER A

VIABLE COMMERCIAL

PROPOSITION FOR TOMATO PRODUCTION IN GREENHOUSES AND THERE ARE

VIRTUALLY NO SOIL GROWERS LEFT. THERE IS NO DEBATE ABOUT THE FACT

THAT SOME FORM OF HYDROPONIC PRODUCTIONHAS TO BE USED. HOWEVER, THERE

IS CONSIDERABLE DEBATE ABOUT WHICH FORM SHOULD BE USED. As IN ALL

DEBATES, THERE ARE CLAIMS AND COUNTER-CLAIMS AND THE GROWER FINDS

HIMSELF IN THE DIFFICULT POSITION OF TRYING TO SORT THE TRUE FROM THE FALSE.

THERE ARE THREE RIVAL HYDROPONIC SYSTEMS CURRENTLY COMPETING FOR

GROWERS' FAVOURS, NAMELY PEAT BAGS, ROCKWOOL SLABS AND NFT. How DOES

A GROWER DECIDE WHICH IS THE BEST SYSTEM?

IT IS OBVIOUSLY NO USE ASKING THE SUPPLIERS OF PEAT BAGs,·

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ROCKWOOL SLABS OR NFT EQUIPMENT. THEIR ANSWER IS A FOREGONE

CONCLUSION. RESULTS FROM COMPARATIVE TRIALS AT AN INDEPENDENT

GOVERN-MENT STATION CAN ALWAYS BE COUNTERED BY THE COMMENT THAT THE SUPER-

VISORY STAFF ARE BETTER AT HANDLING ONE SYSTEM THAN THE OTHER. EVEN

IF A GROWER GOES TO THE EXPENSE OF CARRYING OUT SMALL SCALE COMPARA-

TIVE TRIALS FOR HIMSELF IN HIS OWN GREENHOUSES, HE IS FACED WITH THE

SAME CRITICISM THAT, WITH WITH HIS PRESENT LACK OF EXPERIENCE OF THE

NEW SYSTEMS, HIS PAST KNOWLEDGE HAS CAUSED HIM TO BE INITIALLY MORE

SUCCESSFUL WITH ONE SYSTEM THAN WITH THE OTHERS. ALSO HIS CONFIDENCE

IN HIS RESULTS JS, OR SHOULD BE, UNDERMINED BY THE THOUGHT THAT HE

HAD NO REPLICATION BECAUSE HE WAS JUST ONE INDIVIDUAL ON ONE SITE;

IN SUCH A SITUATION HriW DOES A GROWER DECIDE WHICH SYSTEM TO

USE?

DURING 1986 AN ALMOST CHANCE OCCURANCE HAS ANSWERED THE QUESTION. THERE IS A TRADE MAGAZINE PUBLISHED IN ENGLAND CALLED THE

"GROWER" WHICH IS RATHER SIMILAR TO THE "AMERICAN VEGETABLE GROWER".

THIS MAGAZINE OPERATES EVERY YEAR A RECORDING SCHEME IN WHICH EIGHT

LEADING GREENHOUSE TOMATO GROWERS MAKE THEIR YIELD FIGURES AND THEIR

INCOME AND EXPENDATURE FIGURES AVAILABLE. THESE DATA ARE PUBLISHED

MONTHLY IN THE "GROWER" FOR THE BENEFIT OF THE INDUSTRY AS A WHOLE.

IT IS RATHER LIKE A CHAMPIONSHIP LEAGUE TABLE.

Now, IN 1986 IT SO HAPPENED THAT FOUR OF THESE TOP GROWERS WERE USING ROCKWOOL AND FOUR WERE USING NFT. NONE WERE USING PEAT BAGS.

SLIDE 1 THIS SLIDE SHOWS THE MEAN CUMULATIVE YIELDS MONTH BY MONTH FOR

THE FOUR ROCKWOOL GROWERS AND FOR THE FOUR NFT GROWERS EXPRESSED AS

TONS PER ACRE. IT CAN BE SEEN FROM THE RIGHT-HAND COLUM THAT THE NFT

GROWERS CONSISTENTLY OUTYIELDED THE ROCKWOOL GROWERS.

HOWEVER, THERE IS MORE TO MAKING A PROFIT THAN JUST OBTAINING A

HEAVY YIELD. THE MEAN LABOUR AND FUEL COSTS OF THE ROCKWOOL GROWERS

WERE 37,602 POUNDS PER ACRE WHEREAS THOSE OF THE NFT GROWERS WERE 32,156 POUNDS PER ACREi A DIFFERENCE OF 5446 PoUNDS PER ACRE IN FAVOUR OF NFT.

THE COMBINED EFFECTS OF THE HIGHER YIELDS AND THE LOWER

OPERATING COSTS OF THE NFT GROWERS CAN BE EXPRESSED BY USING THE

MARGIN FIGURES PER TON OF FRUIT, I.E. THE NET RETURN PER TON OF FRUIT

LESS THE LABOUR AND FUEL COSTS. THE MEAN MARGIN OF THE FOUR NFT

GROWERS WAS 360 POUNDS PER TON WHEREAS THE MEAN MARGIN OF THE FOUR NFT GROWERS WAS 427 POUNDS PER TON, AN ADVANTAGE IN THE MARGINS OF 19% IN FAVOUR OF NFT CROPPING.

I HAVE USED THIS EXAMPLE, NOT JUST TO SHOW THAT NFT CROPPING IS

LEADING THE FIELD IN EFFICIENT HYDROPONIC PRODUCTION GREENHOUSE

TOMATO PRODUCTION, BUT ALSO TO SHOW THAT HYDROPONICSINENGLAND IS NO

LONGER MERELY A WAY-OUT IDEA OF ENTHUSIASTS. IT IS COMMERCIAL REALITY

TO SUCH AND EXTENT THAT WITHOUT HYDROPONIC PRODUCTION THE ENGLISH

GR~ENHOUSE TOMATO INDUSTRY WOULD SUFFER FINANCIALLY VERY SEVERELY

BECAUSE THE EVOLUTION OF ITS HIGH OUTPUT STRUCTURE HAS HOMED IN ON

HYDROPONIC CROPPING.

SLIDE 2 THIS IS AN EXAMPLE OF A COMMERCIAL NFT TOMATO NURSERY.

SLIDE 3 THIS IS AN EXAMPLE OF A COMMERCIAL NFT CUCUMBER NURSERY.

SLIDE 4 THIS IS A VERY POOR SLIDE ILLUSTRATING A VERY SUCCESSFUL NFT

LETTUCE OPERATION WHERE THE WHOLE OF THE FLOOR OF TWELVE ACRES OF

GREENHOUSE HAS BEEN COVERED IN CONCRETE IN WHICH CHANNELS HAVE BEEN

FORMED TO CANALISE THE FLOWING SOLUTION PAST THE BARE ROOTS OF THE

LETTUCE. Two OF THE ROWS OF LETTUCE HAVE BEEN REMOVED SO THAT THE

CHANNELS CAN BE SEEN.

THESE SLIDES ARE EXAMPLES OF THE WAY IN WHICH THE ENGLISH

GREENHOUSE INDUSTRY HAS BECOME ALMOST ENTIRELY BASED ON HYDROPONICS

IN ONE FORM OR ANOTHER.

IN THIS PRESENTATION SO FAR I HAVE JUMPED RIGHT INTO THE DEEP

END BECAUSE I WANTED TO SHOW THAT HYDROPONICS IS BEING USEDFOR

SUCCESSFUL COMMERCIAL CROP PRODUCTION ON A VERY LARGE SCALE. IT IS

NOW BIG BUSINES AND HAS TO BE TAKEN SERIOUSLY. IT IS NO LONGER JUST A

HOBBY INTEREST OF AMATEURS TO BE WRITTEN OFF BY THE COMMERCIAL CYNICS.

HAVING, I HOPE, ESTABLISHED THE COMMERCIAL POSITION OF

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HYDROPONIC CROP PRODUCTION IN GENERAL AND THE PRE-EMINENCE OF NFT

CROPPING IN PARTICULAR, I WOULD NOW LIKE TO RETURN TO THE VERY

BEGINNING FOR THE BENEFIT OF THOSE WHO ARE UNFAMILIAR WITH THE

NUTRIENT FILM TECHNIQUE.

NFT CROPPING CAN BE SAID TO HAVE BEGUN IN 1971 WHEN DR.DE STIGTER AT THE PLANT PHYSIOLOGICAL RESEARCH CENTRE IN HoLLAND DEVISED

A LABORATORY TECHNIQUE TO ENABLE HIM TO MAKE AUTORADIOGRAPHS OF THE

UNDISTURBED ROOT SYSTEM OF A MUSK MELON PLANT IN HIS STUDIES ON THE

TRANSLOCATION OF PHOTOSYNTHATES USING A RADIOACTIVE CARBON ISOTOPE.

THE ROOT SYSTEM O.F THE PLANT WAS GROWN IN A RECIRCULATING FILM OF

NUTRIENT SOLUTION.

TEN YEARS LATER THIS PRINCIPLE WAS DEVELOPED AT THE GLASSHOUSE

CROPS RESEARCH INSTITUTE IN ENGLAND INTO THE NUTRIENT FILM TECHNIQUE

OF GLASSHOUSE CROP PRODUCTION. THE ORIGINAL NUTRIENT FILM TECHNIQUE

IS ILLUSTRATED IN THE FOLLOWING SLIDE.

SLIDE 5

A CATCHMENT TRENCH WAS CONSTRUCTED AT THE BOTTOM OF THE SLOPING RECTANGLE OF LAND THAT WAS TO BE CROPPED. THE TRENCH WAS FILLED WITH

NUTRIENT SOLUTION THAT WAS PUMPED UP A PIPE TO THE TOP OF THE SLOPING

LAND. THE NUTRIENT SOLUTION WAS DISCHARGED FROM HOLES IN THE PIPE

INTO THE TOP ENDS OF THE SLOPING CHANNELS IN WHICH THE PLANTS WERE

GROWN. THE SOLUTION THEN FLOWED BY GRAVITY DOWN THE CHANNELS FROM

WHICHIT WAS DISCHARGED BACK INTO THE CATCHMENT TRENCH. THE

CHANNELSWERE FORMED FROM POLYTHENE FILM. THE YOUNG PLANTS WERE RAISED

IN PAPER POTS FILLED WITH COMPOST AND WHEN THE PLANTS WERE PLACED ON

THE LONG, NARROW STRIPS OF POLYTHENE FILM THE EDGES OF THE POLYTHENE

FILM WERE CLIPPED TOGETHER BETWEEN THE PLANTS TO FORM THE CHANNELS.

SLIDE 6

THIS SLIDE PUTS SOME FLESH ON THE PREVIOUS DIAGRAM. IT SHOWS THE

CATCHMENT TRENCH LINED WITH POLYTHENE FILM TO MAKE IT WATER-PROOF,

THE PREPARED SLOPE ON THE GROUND TO BE CROPPED AND THE PLASTIC PIPE

ALONG WHICH THE NUTRIENT SOLUTION WAS PUMPED TO THE TOP OF· THE

SLOPING LAND.

SLIDE 7

THIS SLIDE SHOWS ONE OF THE FIRST CROPS GROWN IN THE ORIGINAL

SYSTEM.

SLIDE 8 THIS SLIDE SHOWS ONE OF THE CHANNELS OPENED UP SO THAT YOU CAN

SEE THE PAPER POTS FILLED WITH COMPOST IN WHICH THE YOUNG PLANTS WERE

RAISED. You CAN ALSO SEE THE ROOT MAT THAT DEVELOPED OUTSIDE THE POTS IN THE RECIRCULATING NUTRIENT SOLUTION IN THE BOTTOM OF THE

CHANNEL.

BECAUSE THIS ROOT MAT WAS ONLY ABOUT ONE CENTIMETER THICK• IT

WAS EASILY SUBMERGED BY THE SOLUTION FLOWING DOWN .THE CHANNEL WHERE-

EVER THERE WAS A SLIGHT DEPRESSION ON THE SLOPING LAND. THIS RESULTED

IN THE ROOTS BEING LITERALLY. DROWNED IN THESE DEPRESSIONS AND EVERY

FARMER KNOWS HOW BADLY PLANTS GROW IF THEIR ROOTS ARE PERMANENTLY

WATERLOGGED. THIS MEANT THAT THE SLOPE OF THE GROUND HAD TO BE

PERFECTLY SMOOTH. THE ACHIEVING OF A PERFECTLY SMOOTH SLOPE ON THE

GROUND IS VERY DIFFICULT AND IT IS EASILY DESTROYED BY SETTLEMENT IF

THE GROUND BECOMES WET. CONSEQUENTLY ONE OF THE FIRST IMPROVEMENTS

MADE TO THE ORIGINAL TECHNIQUE WAS TO PLACE THE POLYTHENE FILM CHAN-

NELS ON SLIGHTLY ELEVATED METAL TRAYS WHOSE HEIGHT COULD BE ADJUSTED

TO GIVE A PERFECTLY SMOOTH SLOPE. THESE TRAYS ACCOUNT FOR ABOUT

40% OF THE EQUIPMENT COST OF CURRENT CONVENTIAL NFT. As THE QUANTITY OF ROOTS WHICH DEVELOPS IN THE CHANNELS

INCREASES WITH PLANT AGE THE MASS OF ROOTS CREATES A PROGRESSIVELY

GREATER DAMMING EFFECT ON THE FLOW OF NUTRIENT SOLUTION EVEN IN THE

PERFECTLY SMOOTH CHANNELS. IT IS THEREFORE NECESSARY TO KEEP A

CAREFUL WATCH ON SOLUTION DEPTH AND TO REDUCE THE FLOW RATE AS THE

QUANTITY OF ROOTS INCREASES SO THAT THE ROOTS ARE NOT SUBMERGED. IT

IS ESSENTIAL TO KEEP THE TOP HALF OF THE ROOT MAT IN THE AIR SO THAT

GASSES CAN DIFFUSE INTO AND OUT OF THE ROOTS BECAUSE THE DIFFUSION

RATE OF GASSES IN AIR IS 10,000 TIMES MORE RAPID IN AIR THAN IT IS IN WATER. IN CONVENTIONAL NFT WITH ONLY ABOUT A ONE CENTIMETRE DEPTH OF

ROOT MAT THERE IS VERY LITTLE TOLERANCE FOR ERROR• AND ONCE THE ROOTS

ARE SUBMERGED THEY RAPIDLY DIE, THE PLANTS WILT AND PYTHIUM AND

PHYTOPHTHERA BEGIN TO INVADE THE ROOT SYSTEM.

IF THIS PRINCIPLE CANNOT BE OBSERVED THEN VERY HIGH FLOW RATES

MUST BE MAINTAINED IN AN ATTEMPT TO CARRY SUFFICIENT DISSOLVED OXYGEN

TO THE SUBMERGED ROOTS.

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ANOTHER CHANGE IN THE ORIGINAL TECHNIQUE THAT IS FOUND IN

CURRENT CONVENTIONAL NFT IS THE ELIMINATION OF THE CATCHMENT TRENCH

IN ORDER TO REDUCE THE WASTE OF VALUABLE GLASSHOUSE SPACE AND ITS

REPLACEMENT BY A CATCHMENT PIPE WHICH DISCHARGES INTO A CATCHMENT

TANK. BECAUSE THE VOLUME OF THE CATCHMENT TANK WAS MUCH LESS THAN THE

VOLUME OF THE ORIGINAL TRENCH THE TOTAL VOLUME OF LIQUID IN THE

SYSTEM WAS LESSo I.E.THE VOLUME OF NUTR.IENT SOLUTION PER PLANT WAS

REDUCED. CONSEQU~NTLYo TO AVOID WIDE FLUCTUATION IN THE NUTRIENT

CONTENT AND THE PH OF THE RELATIVELY SMALL VOLUME OF SOLUTION IN THE

SYSTEM IT BECAME NECESSARY TO DEVELOP MONITORING AND INJECTION

EQUIPMENT TO INJECT ACI~ AND· NUTRIENTS AUTOMATICALLY TO MAINTAIN A

CONSTANT CONCENTRATION OF NUTRIENTS AND A CONSTANT PH IN THE

RECIRCULATING NUTRIENT SOLUTION.

SLIDE 9 THIS SLIDE SHOWS A IN-LINE PH PROBE WHICH SENDS A CONTINUOUS

SIGNAL BACK TO A CONTROL PANEL. THE METHOD USED TO MONITOR THE

NUTRIENT CONCENTRATION OF RECIRCULATING SOLUTION WAS TO MEASURE THE

ELECTRICAL CONDUCTANCE OF THE SOLUTION USING A CONDUCTIVITY PROBE

WHICH ALSO SENT A CONTINUOUS SIGNAL BACK TO THE CONTROL PANEL. THIS

METHOD MERELY MEASURES THE TOTAL SOLUTES IN THE NUTRIENT SOLUTION AND

IGNORES ANY CHANGES IN THE RATIOS OF THE COMPONENT NUTRIENT ELEMENTS.

SLIDE 10 THIS SLIDE SHOWS A TYPICAL CONTROL PANEL. IT COMPRISES A PH

METER AND A CONDUCTIVITY METER AT THE TOP OF THE PANEL WHICH RECEIVE

THE SIGNALS FROM THE MONITORING PROBES AND CONTROL THE AUTOMATIC

OPERATION OF THREE PUMPS AT THE BOTTOM OF THE PANEL WHICH INJECT

DILUTE ACID AND TWO NUTRIENT STOCK SOLUTIONS TO MAINTAIN A CONSTANT

CONDITION IN THE RECIRCULATING NUTRIENT SOLUTION.

THIS SYSTEMo WHICH I WILL CALL "CONVENTIONAL NFT", IS CAPABLE OF PRODUCING A GOOD CROPo AS YOU SAW ON AN EARLIER SLIDE, AND IT HAS

BEEN USED ON A LARGE COMMERCIAL SCALE IN THE UNITED KINGDOM FOR MANY

YEARS NOW FOR THE PRODUCTION OF GLASSHOUSE TOMATOES AND LETTUCE.

SLIDE 11 THIS SLIDE SHOWS ONE OF THE VERY FIRST COMMERCIAL INSTALLATIONS.

SLIDE 12 THIS IS A CLOSE-UP OF THE SAME INSTALLATION AND YOU CAN SEE THAT THE

POLYTHENE CHANNELS ARE RESTING DIRECTLY ON THE GROUND.

SLIDE 13 THIS SLIDE SHOWS A LATER COMMERCIAL INSTALLATION USING SLIGHTLY

ELEVATED, ADJUSTABLE METAL BASES TO PROVIDE THE ESSENTIAL SMOOTH

SLOPE FOR THE CHANNELS TO REST ON •

. SLIDE 14 THIS IS A CLOSE-UP OF THE INLET END OF ONE OF THE ELEVATED

CHANNELS.

SLIDE 15 THIS SHOWS HOW A SMOOTH SLOPE WAS ACHIEVED ON ANOTHER COMMERCIAL

INSTALLATION. THE GROUND WAS COMPLETELY COVERED WITH CONCRETE AND THE

POLYTHENE FILM CHANNELS WERE PLACED DIRECTLY ON THE CONCRETE. THIS

SLIDE HAS AN IMPORTANT IMPLICATION FOR THE THIRD WORLD. I WANT TO

LEAVE DISCUSSION OF THIRD WORLD REQUIREMENTS UNTIL LATER, BUT ONE OF

THE ADVERSE CONDITIONS WHICH EXISTS IN MANY THIRD WORLD COUNTRIES IS

THE LACK OF SUFFICIENT FERTILE LAND. IT IS NOT AN EXAGERATION TO SAY

THAT CONCRETE IS ONE OF THE LEAST FERTILE SOILS IN THE WORLD AND THE

SIGNIFICANCE OF THE LUSH, GREEN GROWTH THAT YOU CAN SEE ON THE SCREEN

IS THAT THE THIRD WORLD LIMITATION OF INFERTILE SOIL CAN BE

ELIMINATED.

LIGHTS

FROM WHAT I HAVE DISCUSSED SO FAR I THINK YOU WILL AGREE THAT

CONVENTIONAL NFT, AS DEVELOPED AT THE GLASSHOUSE CROPS RESEARCH

J INSTITUTE, WAS FOUND TO BE CAPABLE OF PRODUCING GOOD CROPS OF GLAss-~ HOUSE CROPS UNDER LARGE SCALE COMMERCIAL CONDITIONS. THERE THEN

W FOLLOWED SEVERAL YEARS OF FURTHER RESEARCH AIMED AT REFINING THE

EXISTING TECHNIQUE WITHOUT MAKING ANY RADICAL CHANGES IN THE BASIC

FORM OF THE TECHNIQUE.

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ONE OF THE INITIAL FEARS ABOUT NFT TOMATO CROPPING HAD BEEN

RELATED TO THE LACK OF LIGHT IN AN ENGLISH WINTER CHARACTERISED BY

LONG NIGHTS WITH SIXTEEN HOURS OF DARKNESS AND SHORT DAYS IN WHICH

THE LIGHT INTENSITY WAS EXTREMELY LOW DUE TO THICK CLOUDS AND RAIN

BLOTTING OUT THE SUN FOR MOST OF THE TIME. UNDER THESE CONDITIONS

EVERY TOMATO GROWER KNEW THAT THERE WOULD BE RAMPANT VEGETATIVE

GROWTH AND NO FRUIT DEVELOPMENT UNLESS THE VEGETATIVE GROWTH WAS

RESTRICTED BY CAREFULLY RESTRICTING THE WATER AVAILABLE TO THE

PLANTS. IN THE NUTRIENT FILM TECHNIQUE THERE WAS AN ABUNDANT SUPPLY

OF BOTH WATER AND NUTRIENTS AND THIS WAS REGARDED AS A SURE RECIPE

FOR VIGOROUS VEGETATIVE GROWTH AND NO FRUIT PRODUCTION IN POOR LIGHT

CONDITIONS . IT WAS A TRADITIONAL VIEWWHICH I REGARD AS BEING WHOLLY

IRRELEVANT TO NFT CROPPING BECAUSE IT IGNORES THE FACT THAT AN NFT

SYSTEM IS A CLOSED SYSTEM WHEREAS MOST METHODS OF PRODUCTION ARE OPEN

SYSTEMS. To ILLUSTRATE WHAT I MEAN I WOULD DEFINE A PLANT GROWING IN

A POT WITHOUT ANY DRAINAGE HOLES AS GROWING IN A CLOSED SYSTEM

WHEREAS A PLANT GROWING IN THE GROUND WITH FREE DRAINAGE AND

UNLIMITED ROOM FOR ROOT GROWTH AS GROWING IN AN OPEN SYSTEM. THE

TRADITIONAL VIEW OF THE BENEFICIAL EFFECT ON FRUIT DEVELOPMENT OF

RESTRICTING THE WATER SUPPLY UNDER POOR LIGHT CONDITIONS HAD EVOLVED

OVER GENERATIONS OF GROWING TOMATO CROPS IN OPEN SYSTEMS. IT WAS A

WELL FOUNDED AND CORRECT VIEW AND TRADITION DIES HARD IN ENGLAND.

CONSEQUENTLY, WHEN NFT CROPPING INTRODUCED A CHANGE FROM AN OPEN TO

A CLOSED SYSTEM THE TRADITIONAL FEAR OF AN A ABUNDANCE OF WATER

LINGERED ON. As A RESULT OF RESEARCH.EFFORT WAS PUT INTO THE DEVELOPMENT OF METHODS OF INTERRUPTED FLOW IN NFT CROPPING IN WHICH

THE PUMPS RECIRCULATING THE NUTRIENT SOLUTION WERE STOPPED AND THE

SOLUTION WAS ALLOWED TO DRAIN BACK TO THE CATCHMENT TANK SO THAT THE

CHANNELS COULD PROGRESSIVELY DRY OUT UNTIL IT WAS DEEMED TO BE

NECESSARY TO RESTART THE PUMPS.

fORTUNATELY EVERYONE WOULD AGREE THAT THIS PRACTICE IS NOT

REQUIRED IN HIGH LIGHT AREAS AND EVEN IN LOW LIGHT AREA$ THERE WAS

ALWAYS THE RISK THAT AN ERROR OF JUDGEMENT RESULTING IN TOO MUCH

DRYING OUT OF THE ROOTS WOULD HAVE ADVERSE EFFECT. IT IS ALSO

DEBATABLE WHETHER THE BENEFITS CLAIMED FOR THIS PRACTICE ARE

ATTRIBUTABLE TO THE TACITLY ASSUMED CAUSE, NAMELY THE RESTRICTION OF

' !

VEGETATIVE GROWTH. AN EQUALLY LIKELY CAUSE IS AN IMPROVEMENT IN THE

AERATION OF THE ROOT SYSTEM• PARTICULARLY WHERE THERE IS AN

IMPERFECTLY SMOOTH SLOPE. IF THIS IS THE REAL REASONTHEN THERE ARE

SAFER WAYS OF IMPROVING AERATION WHICH I WILL DISCUSS LATER.

A LOT OF VERY INTERESTING WORK ON CROP NUTRITION WAS ALSO

STIMULATED BY THE INTRODUCTION OF NFT CROPPING BECAUSE IN A CLOSED

SYSTEM IT IS VERY EASY TO CALCULATE A NUTRITIONAL BALANCE SHEET.

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IT WAS FOUND THAT THERE WAS A VERY WIDE TOLERANCE TO THE SUPPLY OF

NUTRIENTS. FoR· EXAMPLE• CONCENTRATIONS OF POTASSIUM MAINTAINED

CONSTANT OVER THE RANGE OF 10 PPM TO 400 PPM HAD LITTLE EFFECT ON YIELD. IN TRIALS AT THE GLASSHOUSE CROPS RESEARCH INSTITUTE THE

YIELDS PER PLANT OVER 28 HARVESTS OF TOMATOES WERE 10 KILOGRAMS AT 10, 20, 50, 150 AND 400 PPM OF POTASSIUM. THERE WAS• HOWEVER• AN EFFECT OF POTASSIUM CONCENTRATION ON FRUIT QUALITY. THE PERCENTAGE OF

NON-UNIFORMLY RIPENED DECREASED AS THE POTASSIUM IN THE RECIRCULATING

NUTRIENT SOLUTION WAS INCREASED. WITH 10 PPM OF POTASSIUM 30% OF THE FRUIT SUFFERED FROM UNEVEN RIPENING WHEREAS AT 400 PPM THERE WAS ONLY 8% OF NON-UNIFORMLY RIPENED FRUIT. INCREASING THE CONCENTRATION OF POTASSIUM REDUCED RIPENING DISORDERS AND PROGRESSIVELY INCREASED THE

DRY MATTER CONTENT OF THE FRUIT• THEIR ACID CONTENT• THEIR POTASSIUM

CONTENT AND THE ELECTRICAL CONDUCTIVITY OF THE FRUIT JUICES - ALL OF

WHICH ADDED UP TO AN IMPROVEMENT IN FLAVOUR.

INCREASING THE POTASSIUM CONTENT OF THE SOLUTION, HOWEVER,

ADVERSELY AFFECTED MAGNESIUM UPTAKE AND IT WAS FOUND TO BE NECESSARY

TO MAINTAIN NOT LESS THAN 75 PPM OF MAGNESIUM IN THE SOLUTION, WHILE AT VERY HIGH CONCENTRATIONS OF POTASSIUM IT WAS EVEN NECESSARY TO

RESORT TO FOLIAR SPRAYING WITH A 1% SOLUTION OF MAGNESIUM SULPHATE TO PREVENT THE DEVELOPMENT OF SYMPTOMS OF MAGNESIUM DEFICIENCY.

THE YIELD RESPONSE TO THE CONCENTRATION OF CALCIUM IN THE

SOLUTION WAS ALSO DETERMINED QUITE PRECISELY FOR TOMATOES. AT

CONCENTRATIONS ABOVE 100 PPM OF CALCIUM THERE WAS LITTLE EFFECT ON YIELD BUT AT CONCENTRATIONS BELOW 100 PPM THE YIELD DECREASED WITH A DECREASE IN CALCIUM CONCENTRATION. THIS WAS DUE TO A REDUCTION IN

FRUIT SIZE. AT CONCENTRATIONS OF LESS THAN 50 PPM OF CALCIUM THERE WAS A MARKED INCREASE IN THE OCCURRENCE OF BLOSSOM END ROT AND AT 10 AND 20 PPM THE GROWING POINTS OF THE PLANTS WERE KILLED. THE RESULTS

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SHOWED QUITE CLEARLY THAT THE CALCIUM CONTENT OF THE SOLUTION MUST BE

MAINTAINED AT NOT LESS THAN 100 PPM. WORK ON THE CONCENTRATION OF IRON SHOWED THAT UP TO THE START

OF PICKING TOMATOES,A HIGH CONCENTRATION OF IRON OF ABOUT 15 PPM WAS ASSOCIATED WITH AN INCREASE IN YIELD BUT THAT ONCE PICKING BEGAN,A

LOWER CONCENTRATION OF 5 PPM ~AS BENEFICIAL. SOME WORK WAS ALSO DONE ON THE BORON CONCENTRATION IN THE

RECIRCULATING NUTRIENT SOLUTION AND IT WAS FOUND THAT OVER THE RANGE

OF 0.1 TO 2 PPM OF BORON THERE WAS LITTLE. EFFECT ON TOMATO YIELD BUT HIGHER OR LOWER CONCENTRATIONS REDUCED YIELD.

THE TRADITIONAL B~LIEF THAT IT WAS NECESSARY TO RESTRICT THE

VEGETATIVE GROWTH OF TOMATOES UNDER LOW LIGHT CONDITIONS EVEN SPILLED

OVER INTO THE NUTRITIONAL FIELD AND CONSIDERABLE WORK WAS DONE ON THE

EFFECT OF THE OVERALL CONCENTRATION OF THE SOLUTION, I.E. ITS

SALINITY. IT WAS FOUND THAT SALINITIES ABOVE A cf OF 40 (I.E. 4 MILLIMHOS OR 4000 MICROMHOS OF ELECTRICAL CONDUCTANCE) REDUCED VEGETATIVE GROWTH AND THIS REDUCTION IN VEGETATIVE GROWTH WAS

ASSOCIATED WITH A REDUCTION IN YIELD. HOWEVER• cf VALUES OF UP TO 40 COULD BE MAINTAINED WITHOUT ANY REDUCTION IN YIELD. UP TO THIS LIMIT

AN INCREASE IN SALINITY WAS ASSOCIATED WITH SOME IMPROVEMENT IN FRUIT

QUALITY.

IN DISCUSSING THE NUTRITIONAL WORK THAT HAS BEEN DONE OF NFT

CROPPING , I MAY HAVE GIVEN THE IMPRESSION THAT THE TOLERANCE LEVELS

FOR NUTRIENT SUPPLY ARE SO WIDE THAT THERE IS VERY LITTLE EXPERTISE

REQUIRED IN THE CONTROL OF NUTRITION. IT IS TRUE THAT PLANTS CAN

ADAPT TO A WIDE RANGE OF NUTRIENT FORMULATIONS AND CONCENTRATIONS.

CONSEQUENTLY KEEPING THE PLANTS ALIVE IS EASY, BUT AS I WILL DISCUSS LATER, QUALITY SPECIFICATIONS IN AN INCREASINGLY COMPETITIVE MARKET

ARE BECOMING EVER MORE DEMANDING. I WOULD LIKE TO STRESS THAT THE

ACHIEVEMENT OF THE MAXIMUM YIELD OF HIGH QUALITY PRODUCE DEMANDS THE

MAINTAINING OF TIGHT NUTRITIONAL PROGRAMMES AND, AS THE MARKET

REQUIREMENTS BECOME MORE AND MORE DEMANDING, SO THE REQUIREMENT FOR

NUTRITIONAL EXPERTISE BECOMES INCREASINGLY IMPORTANT.

ALL THE WORK THAT I HAVE DESCRIBED ON NUTRITION WAS DONE WITH CONVENTIONAL NFT SYSTEMS IN WHICH THE AMOUNT OF SOLID ROOTING MEDIUM

,, -· IN THE SYSTEM WAS KEPT TO A MINIMUM, NAMELY THAT WHICH WAS NECESSARY

FOR THE PROPAGATION OF THE PLANTS• USUALLY A FIVE INCH CUBE OF

ROCKWOOL OR A SIMILAR SIZED POT FILLED WITH COMPOST. THERE IS,

HOWEVER• ALMOST AN INSTINCTIVE URGE TO RETURN TO A SOLID ROOTING

MEDIUM AND SEVERAL MODIFICATIONS OF THE NUTRIENT FILM TECHNIQUE WERE

DEVELOPED IN WHICH THIS URGE WAS APPARENT. IN ONE OF THESE

MODIFICATIONS THE CHANNELS WERE MADE OF RIGID PLASTIC AND THEY WERE

FILLED WITH AGGREGATE. THE NUTRIENT SOLUTION WAS RECIRCULATED ALONG

THE BOTTOM OF THE CHANNELS THROUGH THE AGGREGATE. IN ANOTHER VERSION,

THE POLYTHENE FILM CHANNELS WERE RETAINED•, BUT LONG, NARROW SLABS OF

ROCKWOOL WERE PLACED END TO END IN THE BOTTOM OF THE CHANNELS AND THE

NUTRIENT SOLUTION WAS RECIRCULATED ALONG THE BOTTOM OF THE CHANNEL.

THESE MODIFICATIONS IN MY OPINION LEAD DOWN A BLIND ALLEY. IT IS

VERY DIFFICULT TO THINK OF ANY ADVANTAGES IN USING A SOLID ROOTING

MEDIUM THAT ARE NOT OUT WEIGHED BY DISADVANTAGES AND, IN ADDITION,

THE USE OF A SOLID ROOTING MEDIUM LIMITS THE DEVELOPMENT OF THE

POTENTIAL THAT IS LATENT IN THE NUTRIENT FILM TECHNIQUE.

WHILE THESE EXCURSIONS INTO THE INCORPORATION OF SOLID ROOTING

MEDIA WERE GOING ON A MODIFICATION WAS DEVELOPED IN ISRAEL WHICH WENT

TO THE OTHER EXTREME. BARE ROOTED PLANTS WERE SUSPENDED IN THE

CHANNELS AND A NUTRIENT SUPPLY PIPE WITH ~INE HOLES IN IT WAS RUN

ALONG THE TOP OF EACH CHANNEL SO THAT THE RECIRCULATING NUTRIENT

SOLUTION CAME OUT OF THE SUPPLY PIPE AS A SERIES OF FINE JETS WHICH

SPRAYED ON TO THE ROOTS OF THE PLANTS. THE NUTRIENT SOLUTION THEN

DRIPPED OFF THE ROOTS OF THE PLANTS AND FLOWED DOWN THE BASE OF THE

CHANNEL BACK TO THE CATCHMENT TANK. THIS IS THE EIN GEDI SYSTEM

DEVELOPED BY HILLEL SOFFER.

IN MY VIEW, HE WAS MOVING IN THE RIGHT DIRECTION BY USING BARE

ROOTED PLANTS IN A SYSTEM COMPLETELY DEVOID OF ANY SOLID ROOTING

MEDIUM BUT IT WAS AS EXTREME A POSITION AS THE OPPOSITE EXTREME OF

COMPLETELY FILLING THE CHANNELS WITH A SOLID ROOTING MEDIUM. A GOOD COMPROMISE HAS RECENTLY EMERGED WHICH I BELIEVE TO BE TO BE THE MOST

LIKELY WAY AHEAD IN THE FUTURE DEVELOPMENT OF NFT CROPPING. THIS

COMPROMISE WAS TO REDUCE THE AMOUNT OF SOLID ROOTING MEDIUM IN

CONVENTIONAL NFT BY USING SMALL PIECES OF CAPILLARY MATTING FOR PLANT

PROPAGATION INSTEAD OF LARGE ROCKWOOL CUBES OR POTS FILLED WITH

COMPOST.

12

THIS COMPROMISE RESULTED FROM THE FACT THAT IN THE 1970's TWO MAJOR BRITISH PUBLIC COMPANIES BECAME INTERESTED IN EXPLOITING THE

NUTRIENT FILM TECHNIQUE. THESE TWO COMPANIES MADE DIAMETRICALLY

OPPOSED POLICY DECISIONS. ONE OF THEM (DUNLOP PLC) DECIDED TO TAKE

CONVENTIONAL NFT AND MARKET IT WORLD WIDE THROUGH ITS THEN SUBSIDIARY

COMPANY, SOILLESS CULTIVATION SYSTEMS. THE OTHER (ARIEL INDUSTRIES

PLC) DECIDED THAT CONVENTIONAL NFT WAS AND EMBRYONIC TECHNIQUE THAT

HAD LIMITATIONS AND THAT FURTHER RESEARCH AND DEVELOPMENT WAS

REQUIRED PRIOR TO MARKETING IT.

THE LIMITATIONS THAT WERE CONSIDERED TO BE PRESENT WERE AS

FOLLOWS.

1. THE TOLERANCE OF ABOUT ONE CENTIMETRE THAT WAS AVAILABLE TO AVOID DROWNING THE ROOT MAT WAS CONSIDERED TO BE INSUFFICIENT.

2. THE COMPLEXITY OF THE MONITORING AND INJECTION EQUIPMENT WAS CONSIDERED TO BE TOO GREAT. IT NEEDED REGULAR ATTENTION TO MAINTAIN

ACCURACY BECAUSE THE PH PROBES DRIFTED RAPIDLY AND BECAUSE OF ITS

COMPLEXITY• THE EQUIPMENT SOONER OR LATER WOULD BREAK DOWN. THIS

REPRESENTED NO PROBLEM IN A SMALL COUNTRY WITH LONG LINES OF

COMMUNICATION AND A LESS CONCENTRATED TECHNICAL INFRASTRUCTURE, BUT

IN A LARGE COUNTRY WITH LONG LINES OF COMMUNICATION AND A LESS

CONCENTRATED TECHNICAL INFRASTRUCTURE THE TIME THAT ELAPSED BETWEEN

FAILURE AND REPAIR COULD RESULT IN CROP DAMAGE.

3. THE NEED FOR CONTINUOUS RECIRCULATION DEMANDED AN UNINTER-RUPTED SUPPLY OF ELECTRICAL POWER. WITHOUT RECIRCULATION OF THE

NUTRIENT SOLUTION THE CROP WOULD VERY QUICKLY WILT AND DIE. THIS

MEANT THAT AN AUTOMATIC START• STANDBY GENERATOR WAS ESSENTIAL TO

KEEP THE PUMPS OPERATING IN THE EVENT OF A BREAKDOWN IN POWER SUPPLY.

HOWEVER, THE AUTOMATIC START OF A STANDBY GENERATOR DEPENDS ON THE

SUCCESSFUL OPERATION EVERY TIME OF A 12 VOLT BATTERY. THIS IS NOT A GOOD WEAK LINK ON WHICH TO BASE A LARGE FINANCIAL INVESTMENT.

CONSEQUENTLY IT IS ESSENTIAL THAT, IN THE EVENT OF POWER FAILURE,

ALARM CALLS SHOULD BE SENT IMMEDIATELY AND AUTOMATICALLY TO PERSONNEL

SO THAT A CHECK CAN BE MADE THAT THE BATTERY HAS SUCCESSFULLY STARTED

THE GENERATOR. THE SENDING OUT OF SEVERAL AUTOMATIC CALLS• IN CASE

ONE PERSON IS NOT AT HOME, REQUIRES A TELEPHONE SYSTEM OVER WHICH THE

ALARM CALLS CAN BE SENT. IN MANY COUNTRIES IT IS IMPOSSIBLE TO GET A

13

TELEPHONE LINE INSTALLED TO THE SITE WHERE IT IS NEEDED. THIS

REQUIREMENT FOR CONTINUOUS RECIRCULATION OF NUTRIENT SOLUTION

REPRESENTED NO PROBLEM IN A SMALL COUNTRY LIKE ENGLAND WHERE THE

POWER SUPPLY IS VERY RELIABLE AND THERE IS AN UBIQUITOUS TELEPHONE

NETWORK. HOWEVER, IT WAS FELT THAT IN MUCH OF THE WORLD THE NEED FOR

ELECTRICAL POWER REPRESENTED A LIMITATION TO THE USE OF CONVENTIONAL

NFT.

4. THE SUCCESSFUL PRODUCTION OF A CONVENTIONAL NfT CROP REQUIRES SKILLED MANAGEMENT. AGAIN THIS REPRESENTED NO PROBLEM IN ENGLAND

WHERE THE HORTICULTURAL MANAGEMENT IS WELL EDUCATED AND IS SUPPORTED

BY AN ADEQUATE ADVISORY SERVICE, BUT IT WAS FELT THAT IN MANY PARTS

0~ THE WORLD THE NEED FOR SKILLED MANAGEMENT WOULD BE A LIMITATION TO

THE WIDER SUCCESSFUL USE OF CONVENTIONAL NfT.

THESE CONCLUSIONS WERE NOT IN ANY WAY INTENDED TO REPRESENT AN

IMPLIED CRITICISM OF THE DEVELOPMENT OF CONVENTIONAL NfT. IT WAS SUC-

CESSFULLY DEVELOPED FOR A VERY SPECIFIC PURPOSE- TO BE USED BY THE

GLASSAHOUSE INDUSTRY IN THE CLIMATE OF ENGLAND UNDER ENGLISH

CONDITIONS. OUTSIDE THAT CONTEXT PROBLEMS CAN ARISE.

SLIDE 16

THIS SLIDE SHOWS A VERY SIMPLE EXAMPLE OF WHAT CAN HAPPEN WHEN

CONVENTIONAL NfT IS USED OUTSIDE THE CONTEXT FOR WHICH IT WAS

DESIGNED. THIS IS A CONVENTIONAL NfT TOMATO CROP IN SOUTHERN SPAIN.

THE HOT SUN HAS RAISED THE SURFACE TEMPERATURE OF THE POLYTHENE FILM

OF THE CHANNELS WITH THE RESULT THAT THE ROOT TEMPERATURE HAS RISEN

TO LEVELS WHICH THE PLANTS COULD NOT TOLERATE.

THE EXISTENCE OF LIMITATIONS TO THE WI6ER USE OF CONVENTIONAL

NFT, OF WHICH THE SLIDE ON THE SCREEN IS BUT ON EXAMPLE, LED ARIEL

INDUSTRIES TO ERECT FOUR ACRES OF GLASS IN SOUTHERN ENGLAND TO

SERVICE A RESEARCH PROGRAM.

SLIDE 17

THIS SLIDE SHOWS THE BUILDING OF THESE FACILITIES.

SLIDE 18

14

AND THIS SLIDE SHOWS THAT BECAUSE THIS SITE ENJOYS, IF THAT IS

THE RIGHT WORD, THE MILD ENGLISH CLIMATE ARIEL INDUSTRIES ALSO HAD TO

ERECT SIMILAR FACILITIES IN THE HOTTER CLIMATE OF SOUTHERN SPAIN.

SLIDE 19

THIS SLIDE SHOWS THE SITE THAT WAS CHOSEN IN THE DESERT OF

ALMERIA IN SOUTHERN SPAIN WHERE, INCIDENTALLY• NEARLY ALL THE CLASSIC

WESTERNS WERE FILMED. IT WAS FELT THAT THE CONDITIONS WERE

SUFFICIENTLY RUGGED AND THE RADIATION WAS SUFFICIENTLY INTENSE TO

TEST THE DEVELOPMENT WORK UNDER HOSTILE CONDITIONS.

IN ADDITION, ARTIFICIALLY LIT CONTROLLED ENVIRONMENT CHAMBERS

WERE BUILT IN THE UK TO ANSWER THOSE QUESTIONS THAT COULD BE ASKED ONLY IN A CONTROLLED ENVIRONMENT.

THE AIM OF THE WORK THAT IS BEING DONE IN THESE FACILITIES IS

NOT MERELY THEELIMINATION OF THE LIMITATIONS OF CONVENTIONAL NFT THAT

I LISTED EARLIER BUT THE SIMPLIFICATION OF THE SYSTEM WITHOUT

ACCEPTING ANY REDUCTION IN CROP PERFORMANCE. IN FACT, IT WAS ARGUED

THAT SIMPLIFICATION WAS NOT INCOMPATIBLE WITH THE ACHIEVEMENT OF AN

IMPROVEMENT IN CROP PERFORMANCE.

THE WORK BEGAN BY MERELY ENDEAVORING TO IMPROVE AND SIMPLIFY

CONVENTIONAL NFT AND A SYSTEM WAS DEVELOPED WHICH WAS CALLED •sECOND

GENERATION NFT•. IN PRINCIPLE THIS WAS THE SAME AS CONVENTIONAL NFT

BUT DIFFERED CONSIDERABLY IN DETAIL AND IT INCLUDED A NEW NUTRITIONAL

METHOD WHICH WAS GIVEN THE NAME OF •HYPERTONIC FEEDING•.

THE IMPROVEMENTS THAT WERE INCORPORATED DEMANDED A PLANT WITH A ROOT

SYSTEM DIVIDED INTO TWO PARTS AND THIS MEANT THAT THE PROPAGATION

METHOD EMPLOYED FOR CONVENTIONAL NFT COULD NOT BE USE BECAUSE IT

EMPLOYED A SOLID ROOTING MEDIUM IN THE FORM OF A PAPER POT FILLED

WITH COMPOST, OR A ROCKWOOL CUBE. THUS, THE FIRST TASK WAS TO DEVELOP

A SUITABLE PROPAGATION METHOD. THE METHOD THAT WAS ULTIMATELY FOUND

TO BE SUITABLE FOR LARGE SCALE PROPAGATION WAS AS FOLLOWS.

SLIDE 20

THE ROCKWOOL CUBE OR THE PAPER POT FILLED WITH COMPOST WAS REPLACED

BY TWO SMALL PIECES OF CAPILLARY MATTING JOINED TOGETHER AT THE TOP

TO FORM A PROPAGATION POCKET AS SHOWN IN THE SLIDE. THIS CHANGE IN

THE MATERIALS USED REPRESENTS A FINANCIAL SAVING IN THE COST OF

PROPAGATION MATERIALS OF ABOUT 700 POUNDS STERLING PER ACRE PER ANNUM.

A SEED WAS PLACED IN THE TOP OF EACH MOISTENED GERMINATION POCKET AND THE POCKETS WERE PLACED ONE ON TOP OF ANOTHER IN A PLASTIC

TRAY. THIS MEANT THAT A LARGE NUMBER OF POCKETS COULD BE PLACED IM A

VERY SMALL TRAY. THESE TRAYS WERE THEN STACKED ONE ABOVE THE OTHER IN

A WELL INSULATED GERMINATION. BOX THERMOSTATICALLY CONTROLLED AT THE

OPTIMAL TEMPERATURE FOR THE GERMINATION OF THE SPECIES CONCERNED.

BECAUSE A VERY LARGE NUMBER OF POCKETS COULD BE ACCOMMODATED IN A

SMALL WELL INSULATED GERMINATION BOX• THE ENERGY COST OF MAINTAINING

THE REQUIRE TEMPERATURE WAS VERY SMALL.

SLIDE 21

As SOON AS THE FIRST SIGNS OF GROWTH COULD BE SEEN IN THE GERMINATING SEED• THE POCKETS WERE REMOVED FROM THE DARKNESS OF THE

BOX INTO THE LIGHT. IF THE CLIMATE IS SUCH THAT SUBSEQUENT AIR

HEATING IS NOT REQUIRED THEN THE POCKETS CAN BE PLACED IMMEDIATELY IN

THE FINAL GROWING POSITIONS IN THE CHANNELS. IF HEATING FUEL

CONSERVATION IS IMPORTANT THEN THE POCKETS SHOULD BE PLACED AT CLOSE

SPACING ON A PROPAGATION BENCH AS SHOWN ON THE SCREEN. IN THE SLIDE

YOU CAN SEE A TRAY CONTAINING SEVERAL HUNDRED POCKETS AND THE POCKETS

BEING PLACED ASTRIDE RIDGES ON A BENCH WHICH HAS A RIDGE AND FURROW

CONFIGURATION; NUTRIENT SOLUTION IS CONTINUALLY RECIRCULATED DOWN THE

FURROWS OF THE BENCH AND THESE ARE KEPT DARK BY PLACING A LONG,

NARROW STRIP OF POLYTHENE FILM BETWEEN EACH PAIR OF RIDGES. VIRTUALLY

NO FURTHER WORK IS REQUIRED UNTIL THE PLANTS ARE BIG ENOUGH TO BE

PLACED IN THEIR FINAL GROWING POSITIONS IN THE CHANNELS. THUS THE

LABOUR COSTS DURING PROPAGATION ARE VIRTUALLY ELIMINATED AND, EQUALLY

IMPORTANT, NONE OF THE CONVENTIONAL MANAGEMENT DECISIONS HAVE TO BE

MADE ABOUT WHEN TO WATER AND FEED AND HOW MUCH WATER AND FEED SHOULD

BE APPLIED ON EACH OCCASION.

SLIDE 22

THE PLANTS WILL GROW WELL AND UNIFORMLY• AS YOU CAN SEE IN THE

SLIDE, WITH VERY LITTLE ATTENTION OTHER THAN MAINTAINING THE CORRECT

NUTRITION IN THE CATCHMENT TANK.

SLIDE 23

THIS IS A CLOSE-UP SO THAT YOU CAN SEE THE WHITE-ON-BLACK STRIPS OF

POLYTHENE FILM LAID BETWEEN THE PAIRS OF RIDGES OF THE PROPAGATION

BENCH.

SLIDE 24

THIS SHOWS A YOUNG TOMATO PLANT REMOVED FROM THE PROPAGATION

BENCH SO THAT THE DEVELOPING DIVIDED BARE-ROOT SYSTEM CAN BE SEEN.

BECAUSE THERE IS VERY LITTLE SOLID ROOTING MEDIUM, A VERY LARGE

NUMBER OF THESE PLANTS CAN BE LAID ALMOST ONE ON TOP OF EACH OTHER,

IN A PLASTIC CARRYING TRAY FOR TRANSFER FROM THE PROPAGATION BENCH TO

THEIR FINAL GROWING POSITIONS IN THE CHANNELS.THIS ELIMINATION OF THE

WEIGHT AND BULK OF THE SOLID ROOTING MEDIUM REDUCES PLANTING COSTS.

WHAT I HAVE SO FAR DESCRIBED IS THE PROPAGATION METHOD THAT WAS

DEVISED TO ENABLE, AMONG OTHER THINGS, THE TOLERANCE TO DROWNING OF

THE ROOT MAT TO BE INCREASED. THIS TOLERANCE WAS INCREASED BY

CHANGING THE DESIGN OF THE METAL TRAYS ON WHICH THE POLYTHENE FILM

CHANNELS WERE PLACED.

SLIDE 25

THIS SLIDE SHOWS THE DESIGN OF THE METAL TRAY. IT COMPRISES A

CENTRAL RIDGE AND TWO SIDE CHANNELS. BECAUSE THIS CROSS-SECTIONAL

SHAPE IS VERY STRONG IN BENDING• THE TRAYS CAN BE PLACED DIRECTLY ON

THE GROUND OF A ROUGHLY PREPARED SLOPE AND THEY WILL BRIDGE ANY

UNEVENNESS IN THE PREPARATION OF THE SLOPE AND PROVIDE A PERFECTLY

SMOOTH SLOPE.

SLIDE 26

As SHOWN IN THIS SLIDE, THE METAL TRAYS ARE OVERLAPPED LIKE ROOFING TILES STARTING AT THE BOTTOM OF THE SLOPE.

SLIDE 27

THIS SLIDE SHOWS A COMPLETELY LAID ROW OF OVERLAPPING METAL

TRAYS.

SLIDE 28

l7

A SHEET OF WHITE-ON-BLACK POLYTHENE FILM IS THEN LAID ON THE METAL TRAYS AS SHOWN IN THE SLIDE. IN THIS PARTICULAR EXAMPLE, A WIDE

STRIP OF POLYTHENE FILM HAS BEEN USED SO THAT AN AIR FILLED ROLL OF

POOLYTHENE FORMS ABOVE EACH CHANNEL. THESE TWO ROLLS PROVIDE

INSULATION AGAINST SOLAR RADIATION SO THAT THE OVERHEATING OF THE

CHANNELS THAT YOU SAW IN AN EARLIER SLIDE DOES NOT OCCUR.

SLIDE 29

A STRIP OF CAPILLARY MATTING IS THEN LAID ON THE POLYTHENE THAT COVERS THE CENTRAL RIDGE AS YOU CAN SEE IN THIS SLIDE.

SLIDE 30

THE PLANTS IN THEIR PROPAGATION POCKETS WITH DIVIDED ROOT

SYSTEMS ARE THEN PLACED ASTRIDE THE CENTRAL RIDGE AND THE EDGES OF

THE POLLYTHENE FILM ARE CLIPPED TOGETHER BETWEEN THE PLANTS AS SHOWN

IN THE SLIDE.

SLIDE 31

THIS SLIDE SHOWS THE END OF A CHANNEL OPENED UP SO THAT YOU CAN

SEE THE INTERNAL DETAIL. THE NUTRIENT SOLUTION FLOWS DOWN ONE SIDE OF

THE DIVIDED CHANNEL BUT THE DIVIDED ROOT SYSTEM DEVELOPS ON BOTH

SIDES OF THE CENTRAL RIDGE COVERED WITH CAPILLARY MATTING. THIS

18

SEPARATES THE AQUEOUS AND GASEOUS PHASES OF THE ROOT ENVIRONMENT AND

THERE IS NO LIMITATION TO THE FLOW RATE. THE TOLERANCE OF LESS THAN

ONE CENTIMETRE DEPTH OF SOLUTION HAS BEEN INCREASED TO INFINITY AS IT

IS IMPOSSIBLE TO DROWN THE ROOT SYSTEM BECAUSE WHEN THE SOLUTION IS

FLOWING DOWN ONE SIDE OF THE CHANNEL, NUTRIENTS ARE BEING TAKEN UP BY

THE ROOTS ON THAT SIDE OF THE CHANNEL WHILE OXYGEN DIFFUSES INTO THE

ROOTS AND ETHYLENE DIFFUSES OUT OF THE ROOTS ON THE OTHER SIDE OF THE

CHANNEL. THE PLANT ADAPTS TO THIS SITUATION AND EACH HAL,F OF THE ROOT

SYSTEM IS CAPABLE OF SUPPLYING THE NEEDS OF THE WHOLE PLANT. THIS HAS

BEEN DEMONSTRATED BY SUPPLYING RADIOACTIVE PHOSPHOROUS TO ONLY ONE

SIDE OF THE ROOT SYSTEM AND MEASURING THE DISTRIBUTION OF RADIOACTIVE

PHOSPHOROUS WITHIN THE PLANT.

IN SECOND GENERATION NFT, THE COMPLEX MONITORING AND INJECTION

EQUIPMENT FOR THE CONTROL OF ELECTRICAL CONDUCTANCE AND PH HAS ALSO

BEEN ELIMINATED.

SLIDE 32

THIS SLIDE SHOWS THE MOST COMPLICATED PIECE OF EQUIPMENT (OTHER

THAN THE RECIRCULATING PUMP) IN A SECOND GENERATION NFT SYSTEM. IT

CONSISTS OF A PLASTIC BIN WITH A LENGTH OF NARROW BORE PLASTIC TUBING

INSERTED THROUGH THE SIDE WALL NEAR THE BOTTOM OF THE BIN. THERE ARE

THREE OF THESE BiNSo TWO FOR NUTRIENT STOCK SOLUTION AND ONE FOR

DILUTE ACID. THEY ARE SITED ADJACENT TO THE END OF THE CATCHMENT PIPE

FARTHEST AWAY FROM THE CATCHMENT TANKo AND THE NARROW BORE PLASTIC

TUBES ARE INSERTED INTO THE CATCHMENT PIPE. THE QUANTITIES OF

NUTRIENT STOCK SOLUTION AND THE QUANTITY OF ACID REQUIRED BY THE

SYSTEM DURING THE COMING TWENTY FOUR HOURS ARE PLACED IN THE BINS

EACH MORNING AND DRIP SLOWLY INTO THE CATCHMENT PIPE VIA THE NARROW

BORE PLASTIC TUBES.

WHAT I HAVE SO FAR DESCRIBED IS THE BASIC OUTLINE OF SECOND

GENERATION NFT. THERE ISo HOWEVER, ONE VERY IMPORTANT COMPONENT THAT

I HAVE NOT DESCRIBED, AND THIS IS HYPERTONIC FEEDING. IN HYPERTONIC

FEEDING, BECAUSE THE MAJORITY OF THE PLANTS' ROOTS ARE BAREo THEY

COULD HAVE A DILUTE NUTRIENT SOLUTION FLOWING PAST THEM FOR MOST OF

EACH TWENTY FOUR HOURS. THIS WAS CALLED THE "DRINK" SOLUTION. ON

19

SEVEAL OCCASIONS EACH DAY THE DRINK SOLUTION WAS ALLOWED TO DRAIN

BACK TO THEDRINK CATCHMENT TANK. A STRONG NUTRIENT SOLUTION (REFERRED

TO AS THE FEED SOLUTION), IS THEN RECIRCULATED PAST THE PLANTS' ROOTS

FOR A SHORT PERIOD OF TIME, AFTER WHICH, IT IS ALLOWED TO DRAIN BACK

TO THE FEED CATCHMENT TANK AND THE RECIRCULATION OF THE WEAKER DRINK

SOLUTION IS RESUMED. THE INCORPORATION OF HYPERTONIC FEEDING INTO

SECONND GENERATION NFT DOES NOT REQUIRE ANY COMPLEX CONTROL

EQUIPMENT.

SLIDE 33

IT MERELY REQUIRES TWO CIRCULATING PUMPS INSTEAD OF ONE AND THE

CONSTRUCTION OF TWO CATCHMENT TANKS AS SHOWN IN THE SLIDE INSTEAD OF

ONE CATCHMENT TANK. THE CATCHMENT PIPE RETURNS ABOVE THE PARTY WALL

BETWEEN THE TWO TANKS AND DISCHARGES INTO EITHER THE DRINK TANK OR

THE SMALLER FEED TANK ACCORDING TO WHETHER THE FEED SOLUTION OR THE

DRINK SOLUTION IS BEING RECIRCULATED.

IT WAS FOUND THAT WHEN PLANTS WERE FED HYPERTONICALLY, THE

UPTAKE OF NUTRIENTS WAS INCREASED AND THAT THIS WAS ACCOMPANIED BY

THE STOMATA REMAINING OPEN UNTIL LATER IN THE DAY AND BY INCREASES IN

WATER UPTAKE, IN THE CHLOROPHYLL CONTENT OF THE LEAVES, IN THE RATE

OF PLANT GROWTH AND IN YIELD.

THIS FINDING THAT THE STOMATA REMAINED OPEN UNTIL LATER IN THE

DAY AND THAT THE CHLOROPHYLL CONTENT OF THE LEAVES WAS INCREASED BY

HYPERTONIC FEEDING HAS AN INTERESTING IMPLICATION FOR CROP PRODUCTION

IN PLASTIC GREENHOUSES. IT IS SAID THAT THERE IS A REDUCTION IN LIGHT

TRANSMISSION IF PLASTIC FILM IS USED INSTEAD OF GLASS TO CLAD A

GREENHOUSE. THERE WOULD SEEM TO BE NO REASON WHY HYPERTONIC FEEDING

CAN NOT BE USE TO OFFSET THE LIGHT REDUCTION BY KEEPING THE STOMATA

OPEN LONGER AND INCREASING THE CHLOROPHYLL CONTENT OF THE LEAVES.

ANOTHER FACILITY OF HYPERTONIC FEEDING IS THAT IT MAKES IT

POSSIBLE TO STIMULATE ANY DESIRED NUTRIENT INPUT BECAUSE IT IS A TWO

SOLUTION SYSTEM. IN A SINGLE SOLUTION SYSTEM, ION ANTAGONISM CREATES

A LIMITATION TO INCREASING THE CONCENTRATION OF SOME ELEMENTS WHEN

UPTAKE REQUIREMENTS ARE HIGH. THERE ARE VERY FEW TOMATO GROWERS WHO

20

ARE NOT FAMILIAR WITH THE SYMPTOMS OF MAGNESIUM DEFICIENCY OR WHO

HAVE NOT SUFFERED FROM A DECLINE IN FRUIT QUALITY DUE TO AN

INADEQUATE UPTAKE OF POTASSIUM. THE USE OF HYPERTONIC FEEDING WITH

ITS TWO SOLUTIONS MAKES IT POSSIBLE TO AVOID ION ANTAGONISM BY

SEPARATING THE ANTAGONISTIC IONS. IT IS NOT A GOOD PRACTICE TO HAVETO

RESORT TO FOLIAR SPRAYING TO CORRECT INADEQUACIES IN NUTRIENT UPTAKE.

IT IS BETTER TO CORRECT THE UPTAKE PATTERN BEFORE DEFICIENCY SYMPTOMS

OCCUR BY MAKING PREVENTATIVE FORMULATION CHANGES. HYPERTONIC FEEDING

PROVIDES A GREATER FACILITY FOR INTRODUCING FORMULATION CHANGES THAN

IS POSSIBLE WITH A SINGLE SOLUTION SYSTEM.

WHAT I HAVE DESCRIBED SO FAR IS THE DEVELOPMENT OF CONVENTIONAL

NFT INTO SECOND GENERATION NFT. THE OBJECT, HOWEVER, OF DEVELOPING

SECOND GENERATION NFT WAS NOT TO REPLACE FIRST GENERATION NFT, BVT TO

LEAD INTO THE DEVELOPMENT OF A METHOD OF FOOD PRODUCTION APPROPRIATE

FOR THE THIRD WORLD. AND THIS I WILL LEAVE UNTIL MY SECOND TALK. THE

DEVELOPMENT WORK THAT ARIEL INDUSTRIES HAS DONE ON BEHALF OF THE

THIRD WORLD HAS ELIMINATED ANY TECHNICAL PROBLEMS IN SOLVING THEIR

FOOD SUPPLY SITUATION AND IT HAS QUITE CLEARLY SHOWN THAT THE ONLY

PROBLEMS REMAINING ARE POLITICAL. I WILL DEVELOP THIS THEME IN MY

SECOND TALK.

AQUACULTURE: Another Hydroponic Technique?

Thomas B. McCormick McCormick & Associates

1211 Spruce Street Berkeley, CA 94709

2l

On the surface, aquaculture and hydroponics appear to

be to be quite similar since they both deal with aquatic

mediums in which animals and plants are cultivated. I

would like to provide some background on aquaculture and how

it may be relevant to hydroponics.

AQUACULTURE

Aquaculture is the farming and husbandry of

and marine organisms. The practice is not new, but has been

carried out for millennia. The cultivation of fish is well

documented in the the records of ancient Chinese and

Egyptian cultures. Oyster farms once thrived in Rome.

Like agriculture, aquaculture arose as a means of

supplementing wild stocks of aquatic fishes and plants.

While agriculture has long surpassed hunting as a means of

food production, aquaculture has only recently begun to

produce significant quantities of food products on a

worldwide basis. In recent years, capture fishery landings

have leveled off at around 76 million metric tons (~1T).

Over-exploitation of valuable species is parti'ally

responsible for this plateau in the catch. Highly valued

22

species are subjected to greater fishing pressure as the

world demand for fish increases. Production from worldwide

aquaculture has grown 6X each year for the last decade to an

annual total of 10 million MT today. This represents 12X of

the totc

23

The cultivation of trout was begun in Europe more than

200 years ago, when artificial spawning of this fish was

first carried out. Today, trout are grown throughout the

u.s. The most productive area, producing more than 90X of

the fish, or 3,600 MT, is Idaho. Abundant sources of

freshwater close to optimal temperatures (15.7 to 17.2 C,

60.3 to 63 Fl are responsible for Idaho's dominance of the

trout farming industry. These water resburces provide

inexpensive temperature control, o>:ygenation and waste

removal. Typically trout are raised in concrete raceways

through which the water passes only once. A large trout

farming operation may use

minute.

140 1 000 gallons of

In addition to abundant clean water

water per

resources,

manipulation of genetics and diet have contributed to the

success of trout farming. Controlled breeding of

generations of trout has resulted in fish that grow faster

and to a greater dress out weight. Natural feeds have been

replaced with specially formulated rations tailored to every

size of trout. Food conver-siorl efficier1cies have been

increased. Where it cnce took 2 pounds of feed to produce a

pound of trout, it now takes 1.6 pounds of feed. In

addition to the farming phase, the producers also control

the processing, shipping and marketing of the fish. Trout

is now a well established food item in both restaurants and

24

at home.

Catfish is the modern day ugly duckling success story

of the U. S. fish farming industry. In the last ten years,

production of this outwardly unattractive fish has increased

from 8,600 MT to 95,000 MT !total live weithtl in 1986. In

Mississippi, where approximately 75% of the catfish are

raised, 34,300 hectares (hal of ponds were in production by

mid-1986. Like frout, the utilization of an abundant

resource contributed heavily to the success of catfish

farming. In this instance a new industry was born as

farmers switched their skills and resources from cotton and

rice crops to a fish crop.

Today catfish are typically raised in dirt ponds 1.2m

deep. Por1d size may vary, but in flat areas 8 ha ponds are

most economical in terms of construction and management.

Water must be supplied in quantities sufficient to fill

ponds and to replace evaporative losses. A 3,785 gpm well

is adequate to supply a 16 ha fish farm !Lee, 19811. New

ponds are often fertilized to promote the growth of

plankton, which aids in keeping oxygen

reduces light levels at the pond bottom.

in the water and

Generally, 6-inch

fingerlings stocked

marketable size in

in the spring will reach a 0.6kg

18 months. Catfish production has

increased from 300 kg/ha per year in unfed ponds to

4,500kg/ha per year in ponds receiving supplemental feeds.

Feeds are high protein 128 - 39%1 formulations that are

25

primarily composed of soybean meal, fish meal, and

by-products from meat, poultry and grain processing. Feed

conversion ratios from 1.5 to 1.8:1 can be obtained.

Pond-side prices for whole fish range from $1.10 to $1.90

per kilogram. The profit potential from harvests like these

has stimulated researchers and farmers alike to quantify

cultivation practices. #

The environmental requirements of trout, catfish and

other aquatic species are uniquely different. The fish

farmer must be able to understand and accommodate these

differences if successful cultivation is to be accomplished.

Table 1 shows a list of physical

considered when raising catfish.

parameters which must be

Similar lists should be

constructed for other aquatic animals prior to commercial

cultivation. Care must be taken to accommodate the changing

environmental requirements as the organism moves from one

stage of its life cycle to the next .

• POLYCULTURE: A multi-species approach to fish farming.

The creation of a vast irrigation system for the

production of rice in China, 1,000 years before the birth of

Christ, produced two additional side effects which are still

being felt today. One of these effects is the ever present

bureaucracy, which has spread to all nations. The other

side effect, called polyculture, is an system of aquatic

farming where several fish species are raised together,

26

TABLE 1. CHANNEL CATFISH

ENVIRONMENTAL CRITERIA SUMMARY

Item Acceptable Range Optimum

TEMPERATURE

Spawning Zl-Z9°C Z7-Z8°C Hatching zz-zs Z6-Z8 Growth Z0-30 ZB-30

. Survival 0-34 ' ' --OXYGEN CONCENTRATION

Hatching 6-7 mg/1 7 mg/1 Growth 3-7 5-7 mg/1 Survival (Short term) 1.0-Z.O -

TOTAL DISSOLVED GAS PREssuRE

less than Eggs and Fry 101% saturation 100% saturation

less than Adults 106% saturation 100% saturation

lJGHT INTENSITY

Fry 1,000-10,000 lux -WATER QUALITY CONSTITUENTS

Ammonia less than 0.05 mg/1 --Nitrite less than 0.1 mg/1 --Nitrate less than 50 mg/1 --Copper less than 0.01 mg/1 --Zinc less than 0.01 mg/1 --Iron

Eggs and Fry less than 0.1 mg/1 --Adults less than 1.0 mg/1 --

Total Dissolved Solids 100-ZOOO mg/1 --pH 6-9 7.5

27

often with supplemental

terrestrial agriculture.

inputs from aquatic plants and

Today, polyculture is practiced

throughout much of the Asian continent. In China,

production from freshwater polyculture is estimated at 1.5

million t·1T,

pt-oduct ion.

equivalent to 21% of the world aquaculture

Carp cultivation is a typical example of Chinese

polyculture. In this technique dirt ponds are stocked with

three species of fish, 20% of which are grass carp, 30% are

bighead and silver carps and 50% are mud and common carps.

Grass carp feed on aquatic macrophytes and land grass.

Bighead and silve~ carps are plankton feeders. t1ud and

common carps are bottom feeders. Each group of fish

utilizes a different food resource and inhabits a different

portion of the water column. The result is reduced

competition for both food and space, and ma:-: i mi zed

production. The introduction of unwanted wild fish is

controlled by the addition of a few carnivorous fist1, such

as the snakehead.

Nutrient inp(Jts into the pond are grass, pig manure and

grain by-products. Grass is cultivated around the pond and

serves as a food source for the grass carp. The waste from

the grass carp~ in addition to the pig manure, fertilizes

the pond waters, resulting in plankton blooms which feed the

bighead and silver carp. Along with the pig manure, wastes

from the grass carp, bighead and silver carp, settle to the

28

pond bottom where they serve as food for the common and mud

car-ps. Additional grain by-products may be added as a food

supplement.

Nutrients are recycled back from the pond in two ways.

in

canals leading to and from the fish ponds, remove excess

nutrients. These plants are regularly harvested and fed to

the pigs. Second, 'between fish crops, the nutrient-rich

sediments from the pond bottoms are spread on the pond banks

where they act as fertilizer for the grass.

Constant recycling of nutrients within the system

maximizes fish and pig production and reduces the polluting

effects of this intensive farming method on the surrounding

aquatic ecosystems. At 6,000kg per year

nutrients are retained for additional production.

The path of the predominant fish waste, nitrogen,

29

is of

importance to both aquaculture and hydroponics, and will be

reviewed het-e.

Nitrogen is the most toxic metabolic by-product in

aquatic systems, it enters the system from organic sources

that are processed in two ways. First, bacteria may convert

food to amino acids and then to keto acids in the m:id'ative

process of ammonification CStanier et al., 1970). Second,

food ingested and assimilated by aquatic animals is

catabolized for energy, and ammonia is released from the

deamination of amino acids, see Figure 1. (Armstrong, 1979).

Ammonia nitrogen CNH3 -Nl is most toxic to fish.

more than 0~05 mg/1 NH 1 -N are generally

Levels of

considered

hazardous. Fortunately this toxic molecule is utilized as

an energy source by autotrophic, aerobic bacteria (genus

In the process of nitrification, ammonia

30

ORGANIC NITROGEN

-PROTEIN-

(rooo,nAD UlMUS INO PLANTS )

,

31

the fish. Ammonia may e>:ist as NHj or- NH!( ammonium ion.

Nitr-ite might exist as NDz or- HN0 1 , nitr-ous acid. pH

deter-mines the degr-ee to which the nitr-ogen molecules ar-e

ionized. Gener-ally, the un-ionized, non-polar- for-m of

ammonia is most toxic (Ar-mstr-ong, 1979). Tables have been

calculated to help deter-mine NH3 :NH'f pr-opor-tions (Tr-ussel,

Gr-eater-1972; Skar-heim, 1973; and Emer-son et al., 1975).

amounts of ammonia exist as NH 3 when pH r-ises simply because

less H is available.

pr-opor-tion ten fold.

An incr-ease of 1 pH unit r-aises the NH5

Thus a lower- pH would decr-ease NH'

toxicity to fish. As pH dr-ops, the pr-opor-tion of toxic

un-ionized nitr-ite (nitr-ous acid, HND2. increases.

For-tunately, nitr-ite is only one half as toxic as ammonia.

The toxic effects of ammonia and nitr-ite ar-e attributed to

changes in blood pH and inter-fer-ence with oxygen and sodium

tr-anspor-t. Sublethal levels of ammonia, nitr-ite and nitr-ate

will decr-ease fish gr-owth.

As we saw earlier in our example of fish far-ming in

.China, polycultur-e can combine fish cultivation with a for-m

of hydr-oponics to incr-ease pr-oduction, r-ecycle nutr-ients and

r-educe pollution. In the United States ther-e exists nb

integrated fish and plant cultivation.

However-, in the last decade resear-ch has begun on the use of

fish and plants together-

aquatic systems.

in a small car-efully managed

The simplest appr-oach to cultivation fish and plants is

32

shown in Figure 2. This system, described by Zweig (1986)

calls for the cultivation of hydroponic vegetables (lettuce)

on a floating substrate with fish below. An air space above

the water allows the roots access to atmospheric oxygen.

Screening below the plants protects the fish from consuming

the roots. Small lettuce seedlings, started at the center

of the substrate, are moved outward for more room during the

six week growout period. Harvest of 18 heads of

Buttercrunch lettuce (450 gml per week was obtained. The

clear sides of the tank permit solar radiation to enter,

providing heat and energy for the growth of phytoplankton.

Some oxygenation is provided by the algae during the day.

Additional oxygen is provided by submerged air diffusers.

The large volume of water acts as a heat reservoir when the

system is placed in a greenhouse. Blue tilapia

were stocked in the tanks. To

supplement their diet of phytoplankton, the fish were also

fed trout chow and rabbit feed. Feed conversion ratios

averaged 1.75:1. Regular analyses of water chemistry

revealed that the mineralization of NH 3 to NO~ and N0 3

occurred and that these components were well below levels

toxic to the fish. Plants removed 28X of nitrogen from the

system.

Several difficulties are encountered with this type of

system~ Root masses may become so large and clogged with

detritus that they turn anerobic, resulting in root death.

~~~~~r~~~~ ~w~r®~®~~c~ IF U i;3!m Cl\ll U itlYir~ ~W~ttc;!JW

A. Hydr:oponic vegetables on top of pond.

B. Styrofoam flotation and guides forplants.

C. Central core opening for fish feeding.

D. Mesh cage to prevent fish from eating plant roots. E. Fish rearing area in pond.

FIGURE 2. Integrated Hydroponic Fish Culture System ( Z wei g , 1 986) •

33

34

The build-up of sediments on the bottom may lead to

anerobic conditions which adversely affect the fish and

increase maintenance. pH may vary depending upon the growth

of the phytoplankton community. A variation of this design

has been tested

t

l

35

__ JL

\ r I \ J I ' I I

'I II I I

Figure 3. Modified tank cultivation system with rotating biofilter and clarifier .

36

cultivation with a more recognizable hydroponic layout is

shewn in Figures 4 and This system, developed by Lewis

et al.

AGITATOR

FISH TANK

AGITATOR

FISH TANK

. .

1 meier

SCALE

INDOORS~ OUTDOORS I I I

PLAN VIEW 1 I I SETTLING

: TANK

I I

37

r-~~~~--~=-----------~0

IIOFILTER

EQUALIZING RESERVOIR

ELEVATION VIEW

WATER TO FISH TANK

IIOFILTER

I I I

RELIFT PUMP

BYPASS

HYDROPONIC TANKS

SUMP (WALLS PERFORATED)

I 1,------,

----~: ~~==~~~~.

EMERGENCY 1----fl OXYGEN

(SEE DETAIL B)

EQUALIZING RESERVOIR

: SETTLING TANK ~~.-----------~~

AUTOMATIC HYDROPONIC VALVE

TANKS (SEE DET All A)

FigurE 4. A fish production systEm involving biofiltration and plants grown hydroponically. From Lewis et al. (1980).

38 DETAIL A

t

RUBBER BALL

PRESSURE REDUCING

VALVE -........_

OXYGEN SUPPLY TO FISH TANKS

ON-OFF VALVE

~

0 2 CYLINDER

FLEXIBLE CONNECTION

WEIGHT

DETAIL B

TO FISH TANK-----,.---- BYPASS

EQUALIZING RESERVOIR

Figure 5. Details of fish-hydroponic system from Lewis, et al.

39

suggested that this system would also have application in

combination with a single-pass fish culture system, where

it could be used to reduce waste products to levels

permissible for discharge.

The examples g~ven here demonstrate that aquaculture

·and hydroponics can be combined to increase production,

recycle nutrients and reduce pollution. Only a few

combinations of plants and animals have been tried thus

far, and there is great potential for the imaginative

combination of these two cultivation techniques.

REFERENCES

Armstrong, D. A., 1979. Nitrogen toxicity to crustacea and aspects of its dynamics in culture systems. Proc. Second Biennial Crustacean Health Workshop. Texas A & M Sea Grant. TAMU-SG-79-114.

Bardach, J. E., J. H. Ryther and W. 0. McLarney, 1972. 69Y!£YltYC§· Wiley-Interscience. 86Bpp.

Burgoon, P. S. and Baum, 1984. Year round fish and vegetabl~ production in a passive solar greenhouse. Sixth Inti. Congress on Soilless Culture, Lunteren, Proceedings, Intl. Soc. for Soilless Culture, 151-171.

Conrad, J., 1985. Trout Farming in Idaho. Aquaculture Magazine, 11111:32-36.

Emerson, K., R. C Russo, R. Lund and R. V. Thurston., 1975. Aqueous ammonia equilibrium calculations: effects of pH and temperature. J. Fish. Res. Board Can., 32:241-246.

40

Zweig, R. D., 1986. Fish farming wizardry: Tt1e practices cJf t-1r~. Chen Yie Zhao. Aquaculutre Ma9azine. 12(5):25-27.

Lee, J. S. 1981. Commer-cial Cat·fist1 Eelt::!!ltQg. The Inter-state Pr-inter-s & Publisher-s, Inc., 312 pp.

Lewis, W. M. and G. L. Buynak, 1976. Evaluation of a r-evolving plate type biofilter- for- use in r-ecir-culated fish pr-oduction holding units. Tr-ans. Am. Fish. Soc., 105(6):704-708.

Lewis, W. M, J. H. Yopp, H. L. Schr-amM, Jr-. and A. M. Br-andenbur-g, 1978. Use of hydr-oponics to maintain quality of Recir-culated water- in a fish cultur-e system. Trans. Am. Fish. Soc., 107(1):92-99.

Lewis, W. H., J. H .. Yopp, A.M. Br-andenbur-g and K.D. Schnoor-, 1980. On the maintenance of water- quality for- closed fish pr-oduction systems by means of hydr-oponically gr-own vegetable cr-ops. Symp. of New Developments in the Utilization of Heated Effluents and Recir-culation Systems for- Intensive Aquacultur-e, Stavanger- 1 Nor-way 28-30 May 1980.

Rakocy J. M. and R. Allison, 1981. Evaluation of a closed r-ecir-culating system for- the cultur-e of tilapia and aquatic macr-ophytes. Bio-Engineer-ing Symp. for- Fish Cultur-e. Am. Fish. Soc.

Introduction

Hydroponics in Research

S. R. Grattan, Ph.D Plant-Water Relations Specialist University of California, Davis

41

Hydroponics has been perhaps the most important research tool in the study of plant nutrition and physiology. It has provided us with, for example (1) the knowledge of the origin of plant constituents and the elements and amounts essential to plants, (2) a basic understanding of plant-water relations and the transport of water, gases, and nutrients within the plant, and (3) has. provided an ideal growth media for the study of plant response under environmental stresses (drought, salinity, toxics, nutrients, oxygen, temperature, disease, etc.). The creative uses of hydroponics in research depends largely upon the innovative nature of the scie9tist. Although numerous hydroponic studies have been published , much is yet to be learned with regards to factors and interactions among factors that influence plant performance. No doubt hydroponics will remain an important vehicle on the road to a better understanding of · plant physiology in the future.

History of Hydroponics

Centuries before hydroponics was used on a research tool, records indicate that ancient civilizations grew plants in soilless cultures. Particular examples of these ancient hydroponic cultures are the hanging gardens of Babylon or the floating gardens of the Aztecs of Mexico (Resh, 1983). It was not until the 1600's that two classical experiments were conducted that set the stage for the science of hydroponics.

In 1600, Belgian Jan Van Helmont conducted an experiment with a willow tree to obtain an understanding of the origin of plant constituents. He planted a 5-pound willow tree in a container filled with 200 pounds .of soil. Care was exercised so that no soil was added or lost from the container. The tree was watered for 5 years before it was separated from the soil. The tree gained 160 pounds while the soil lost only 2 ounces. He concluded that the tree was made up primarily of constituents from the water and not the soil. He did not account for contributions from atmospheric carbon dioxide.

In 1699, John Woodward grew spearmint in rain water, river water, and conduit water. In one treatment, he added garden

·mold. He found that plant growth was largest in water that contained the most soil. He concluded that plants are made up of constituents in the water derived from soil and not water alone.

See Bibliography of the literature on soilless culture (2nd ed). Compiled by the Department of Soilless Culture of the National Council for Agricultural Research T.N.O. The Netherlands.

42

More than 100 years later, as our understanding of chemistry developed, DeSaussure (1804) suggested that plants are composed of chemical constituents from the air, the soil, and the water. This proposition was confirmed by Jean Boussingault in 1851. In his experiment, chemicals of known composition were added to water to irrigate plants grown in sand, quartz, and charcoal. He concluded that plants are composed of oxygen, hydrogen, and carbon obtained from the soil water and the atmosphere. He also suggested that the plants are made of nitrogen and other minerals.

Prior to the United States Civil War, German plant physiologists, Sachs (1860) and Knop (1861) conducted and documented the first ture hydroponic study i.e. the growth of plants in water that contained nutrient elements in the absence of a solid matrix. They showed that normal plant growth could be achieved by growing plants in a solution that contained nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), and magnesium (Mg). Furthermore, Sachs concluded that the entire life cycle of the plant could be achieved and the plant could produce viable seeds.

The complete assembly of Sachs hydroponic culture i" illustrated in Figure 1. This is a reproduction of Sach~ illustration (1887). The plant is supported by a perforated cor~ (K) and the roots are bathed in the nutrient solution (N). Thi~ simple technique is still used by many scientists today.

Figure 1 • Hydroponic apparatus used by Sachs. a reproduction from Sachs, Lectures Plants, Clarendon Press, 1887.

This figure on Physiology

As time progressed, plant physiologists found, with the use of hydroponics, that plants also required small amounts of other elements such as iron (Fe), chlorine (Cl), manganese (Mn), boron (B), zinc (Zn), copper (Cu), and molybdenun (Mo). By the mid 1950's, all nutrients known today to be essential for plant growth and reproduction were found.

Nutrient solution compositions have been reported in the literature since Sachs in 1860 (Table 1).

Table 1. Composition of nutrient solutions used by early plant physiologists (after Hoagland and Arnon, 1938).

43

Sachs' Solution (1860)

Knop's Solution (1865)

Pfeffer's Solution Crone's Solution (1900) (1902)

nutrient grams/ nutrient _grams/ nutrient grams/ nutrient grams/ salt liter salt liter salt liter salt liter

KN0 3 1.0

Ca 3(P04) 2 0.5

MgS04.7H 2o 0.5

Caso4

NaCl

0.5

0.25

Trace

Ca(N03 ) 2

KN0 3 KH 2Po4

0.8

0.2

0.2

MgS04.1H20 0.2 KH 2P04

FePo4 Trace KCl

Fec1 3

0.8

0.2

0.2

0.2

small amount

Knop (1865) suggested a nutrient solution that was used widely in many plant nutrition studies. Since then other formulas for nutrient solutions have been proposed by Tollens (1882), Schimper (1890), Pfeffer (1900), Crone (1902), Tohinghorn (1914) Shive (1915), Hoagland (1920), Trelease (1933), Arnon (1938), and Robins (1946). Although all these nutrient solutions differ in nutrient concentration, plant physiologists recognized that no one solution was ideal for all plants grown under all environmental conditions. Furthermore, Sachs (1860) indicated that the quantity of various types of salts used in solution culture could vary widely without an apparent change in plant

·performance.

Since early investigators suggested various nutrient solutions, nutrient solution-modification Perhaps the most widely used nutrient solutions physiology studies are those reportedly by Hoagland (1938) or dilutions and slight modifications thereof.

types of continued. in ·plant and Arnon

1.0

0.25

0.25

0.25

Applications of Hydroponics in Research

Hydroponics is best known for its invaluable contribution as a research aide in plant nutrition studies. However, it has been a useful tool in basic physiology studies since it provides a controlled environment where one or more variables can be readily changed. Most frequently studied are vegetable, agronomic, and horticultural plants but hydroponics has been used successfully to study the entire plant kingdom from green algae to large vascular plants such as mature trees. All factors that influence plant growth has been studied, at least for some extent, with the use of hydroponics [e.g. mineral nutrition, pH, aeration, toxics (organic and inorganic), microbes (pathological and symbiotic), nematodes, "-soil" strength, water stress, salinity, hormones and bioregulators, etc.]. I will discuss selected applications to each of these to which I am familiar. The reader should note that these are not all the types of research studies conducted with hydroponics, but should gain an appreciation for the diversity of studies conducted. Since each factor that effects plant growth directly br indirectly effects other factors, ~here are a multitude of potential studies that could be conducted.

Mineral Nutrition

As indicated earlier in this paper, hydroponics is best claimed to fame for its aide in improving our understanding of mineral nutrition in plants. Scientists from earliest studies had determined the essential macronutrients (N, P, K, Ca, Mg, and S as well as the quantities needed for growth. Micronutrients (B, Fe,Cu, Mn, Zn, and Cl) essential for plants were discovered later.

Solution cultures have been extremely valuable for growing plants without an essential element in the substrate to observe nutrient deficiency symptoms. These symptoms were then correlated with the nutrient content in the plant. Since plants can be grown successfully in various soil types, it is not surprising that optimal nutrient concentrations in nutrient solutions have wide ranges. It w.as found that plants differ with respect to nutrient requirements even at the variety level. Furthermore, the nutrient requirement often change with plant age and plant quality and plant phenology can be influenced by varying the nutrient composition without influencing optimal grO\vth.

Hydroponic cultures commonly have nutrient concentrations unlike those found in the soil solutions. This is done so that

·nutrient solutions are not rapidly depleted of an essential nutrient. For example, P and K in the hydroponics is very high with respect to that found in the soil solution. The reason for the difference is that P and K once absorbed by the plant from the hydroponic solution is not replaced by a solid phase, as it is in soils. Also, the movement of these elements in· soils is much slower (movement by diffusion) than in hydroponics (movement

by mass flow). Certain researchers have attempted to grow plants in solutions that are similar in composition and concentration to that in soil solutions. To accomplish this, large volumes of solution were required. Currently, there are scientists (Bloom, Caldwell, for example) that use smaller vo_lumes and closely monitor nutrient uptake and automatically replenish the absorbed nutrient(s) to maintain a particular concentration. These culture systems are quite elaborate but can provide a substantial amount of useful information.

Much work has been done with hydroponics to study root uptake, translocation, and distribution of nutrients. It was found that the rate of nutrient uptake was not linear with the concentr'ation of the nutrient solution. Rather the rate increased rapidly at low concentration and increased progressively slower as concentration increased (Figure 2). These uptake patterns were analogous to Michaelis-Menten enzyme kinetics.

NUTRIENT UPTAKE RATE

------------------------

Nutrient Concentration >

Figure 2. Influence of nutrient concentration on the rate of nutrient uptake.

45

lf6

Since the root media can readily be controlled, interactions of nutrients may be studied. For example, it was found that calcium stimulates potassium uptake at least after two hours (Viets, 1944). Furthermore, calcium is essential for selective nutrient absorption (Epstein, 1961).

Root Growth/Water Use/Water Deficits

Although root morphology in solution cultures is different from that in soils, hydroponics does allow easy root measurements. Plant water use can easily be determined by measuring the volume of water lost in the container by transpiration by the plant. All roots can be removed from the solution, washed, spun in a centrifuge to a constant fresh weight, dried and analyzed for various organic and inorganic constituents. Total weights of plants can be obtained and ratios of shoot to root weights may be calculated. Total root length can be measured with patience or it can be estimated. One scientist at the University of California, Davis constructed a device to measure root elongation of an actively growing root by carefully attaching a thin nylon line to a small weight which was attached to the root tip.

Certain large molecular components such as polyethylene glycol (PEG 8000) has been added to solution cultures to simulate drought. There are numerous controversies over these components in terms of breakdown, toxicities, etc.

Other water stress studies have been conducted in sand cultures since the plant observed water deficits is more realistic. Furthermore, water holding capacity of many sands are low and water stress can be obtained quickly.

Temperature

Hydroponics allows scientists to study the influence of temperature on plant performance. For example, one could examine plant growth (roots, shoots, leaf area, internode length, etc.) by varying root temperatures. Minimal, optimal, and maximal temperatures can be defined for various plants under various conditions. The effects of changing temperature on various plant processes (water uptake, nutrient uptake, respiration, photosynthesis, tolerances to other stresses, etc.) may be and has been studied. Also, the influence of temperature on phenological responses (e.g. flowering) can easily be studied. Under controlled environmental conditions one can change both root and shoot temperature simultaneously and measure various plant processes.

Aeration and pH

The need to provide oxygen to the roots to maintain respiration and adjust the pH (an indication of the acidity or basicity of the solution) in an optimal range in order to optimize plant performance was known for many years. Scientists

have conducted studies under different red-ox potentials by bubbling different gasses [nitrogen (N2), oxygen (02), and air (primarily N2 , o2 , and co2 )J to study plant growth, nutrient and water uptake, respiration, etc. Some plant biochemists believe that roots grown in solution cultures as well as in soils of all textural and structural classes are limited, to some extent, with oxygen. They feel the o2 solubility is insuffient in solution culture and 02 diffusion in soils limits the rate of supply to the roots. Aeroponics has been suggested as a solution culture method to overcome this limitation.

The pH of most solution cultures in research studies are maintained between 5.5 and 6.5. Many studies have e~amined

3pH

and species of the nutrient (e.g. H3Po4, H2Po4-, HP04 -, P04 -) in regards to plant pre~erence i~ uptake. Other species have also been examined (Fe + vs Fe + or NH4+ vs No 3-). Some scientists use a mixture of NH4+ and No 3- (e.g. 10-20# NH4+ and 80-90% No 3-) to ''buffer" the solution from pH change. Often the pH will . increase if anion uptake exceeds cation uptake since solution cultures are poorly buffered.

Salinity/Taxies

Hydroponics has been a valuble tool in salinity and toxic constituent studies. However, the use of hydroponics to predict absolute performance under field conditions has not been extremely helpful since environmental conditions are quite different. Nevertheless, hydroponic studies provide important information with regards to relative performance. For example barley and cotton are more salt tolerant than tomatoes and melons which are more tolerant than beans. Hydroponics also provide us with an understanding of ''how'' salinity effects plants. Growth reduction in most cases are caused primarily by the amounts of salts rather than the type ~f salts. Certain scientists have examined the influence of environmental factors on salt tolerance (e.g. nutrition, temperature, aeration, relative humidity ozone, carbon dioxide (C02 ), etc.). The relative salt tolerance, for example, was found to increase in plants exposed to ozone while the absolute tolerance was found to increase in plants exposed to elevated co 2 levels. Although hypothesize by several scientists, I have not seen any evidence of improved salt tolerance by nutrient addition. Furthermore, nutrient concentrations optimal for plant growth under non-saline conditions may not be optimal under saline conditions. My Ph.D. dissertation addressed a salinity induced phosphorus toxicity in certain soybean varieties. The influence of toxic constituents on plant uptake, distribution and plant performance has been studied extensively

. with the use of hydroponics. Toxic elements such as Lithium, Boron, Aluminum, Arsinic, Chromium, Molybdenum, Lead, Cadmium, and Mercury are examples. Hydroponics has helped scientists learn which factors (e.g. temperature, speciation, salinity, red-ox, etc.) influence toxic availability to the plant. Other scientists label certain pesticides with carbon 14 to obtain an understanding of their fate within the environment. Sand cultures has been useful in these studies.

47

LJS

Bacteria/Fungus

Hydroponics has been a usual research tool in the study of pathological and symbiotic microorganisums in relation to plants. Both sand and solution cultures have been used. Those systems have been valuble to study the mechanism of infection, the factors that influence infection, crop response, etc.

"Soil" Strength and Plant Growth

Surprizingly, hydroponics has been used to study the effect of soil strength on root growth. Figure 3 shows an apparatus by Goss (1977) designed to study this effect. Plants were grown in containers (cells) filled with glass spheres and were irrigat~d with aerated nutrient solution. The walls of the cell containing the glass beads consisted of a flexible impervious polyester material. These cells were submerged into water subjected to various external pressures and root elongation was measured. ·

\

\'

.~0

F

Figure 3. Apparatus used by Goss (1977) to measure the influence of applied soil pressure (simulated soil strength) on root growth. ''I'' and ''0'' are inflow and outflow tubes for nutrient solution. The frame (F) and top (T) hold the membranes (m) in place, (picture from Russell, 1977).

Role of Hydroponics in Future Research

As indicated in the sections above, hydroponics has been used to study the many factors that effect plants, Since there are many factors that influence plant performance, one can envision a multitude of experiments that could be conducted. For example, a study on the influence of a disease infection under saline condition~ at various temperatures or o2 levels could be conducted. The same experimental design could then be repeated with another piant. The combinations appear endless. Therefore innovative scientists will continue to design solution culture, sand culture and aeroponic culture systems to test a multitude of hypotheses that remain untested.

Growing plants in space is an interesting concept not only to scientists but to the general public as well. If scientists were to live for long times in space (either at a space station or long distance travel (e.g. flights to Mars) growing plants as a ·source of food become more attractive than transporting large quantitie~ of food. Hydroponics could play an important role. New doors in hydroponics research can be opened. Unrealistic environment situations now become realist (e.g. high intensity light, elevated co2 levels, extented photoperiods, manipulated temperatures, simulated gravity, etc.). Growing selected plants, valuble from a nutritional and taste perspective, under controlled environmental conditions is currently being addressed (e.g. NASA-Controlled Ecological Life Support Systems), Aeroponics is being used to grow plants in tightly sealed growth chambers. Interest in aeroponics is high since it would require a smaller volume of water than NFT or deep water cultivars (hence less weight). Record harvests will undoubtedly be set with high density planting under these controlled conditions. Although these systems will be open with respect to energy, they will be closed with respect to mass. Although recycling mass is conceptually simple, disease control and the change of elements from available to unavailable forms must first be overcome.

It is clear that hydroponics is not a worn-out rather a tool in which new uses are constantly being No doubt research with hydroponics will continue facinating future.

tool but conceived.

to have a

49

50 Marketing Hydroponically Grown Products

Robert W. Munyon

The topic assigned to me for your meeting may suggest that marketing hydroponically grown products is somehow different from marketing commodities grown in more conventional ways. Conceptionally there isn't too much to differentiate between what the larger commercial grower and the smaller grower must do to get his product from the field or greenhouse into the kitchen.

While the fundamentals may be the same, you can expect to see the successful hydroponic grower involved in many more marketing and sales activities and processes than the typical larger commerical grower. The so called commercial grower typically will sell to only one or two buyers. The hydroponic grower typically will, or should, sell to a larger number of buyers. Generally he won't have as much volume to market; often he may have more items to sell. He probably is not too well mechanized. He's got to be good at selling his products to get the top dollar.

The hydroponic grower and the commercial grower may use the same nuts and bolts in developing marketing and sales plans, but the hydroponic grower will usually have a more diversified marketing activity.

The commercial grower usually sells to a middle-man or broker but seldom reaches the consumer directly. The hydroponic grower may be more likely to reach the consumer with his product(s) and may also sell additionally to retail outlets and/or brokers.

As I use the term "hydroponically grown," I refer to the many faceted cultural practices as usually conducted in environmentally controlled greenhouses. The culture may be in beds of rock or sand, bags, peat, shavings, oasis bags, shredded bark, NFT, rockwool, etc. Soilless culture entrepreneurs will probably come up with even more new growing media as long as it provides a friendly home for the plants' roots.

If you, the grower, can supply your plants with the proper nutrition, maintain them in a friendly climatic environment, free, or nearly free, of insects and diseases, you should be a successful grower. The plants don't really care too much which kind of media you employ as lo