Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02...

45
1

Transcript of Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02...

Page 1: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

1

Page 2: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

2

Contents

Page No:

01 Why Hydroponics/Soil-less culture?

02 Hydroponics/Soil less culture - What is it?

02 History of hydroponics

03 Basic Requirements of Hydroponics

03 Classification of Hydroponics/Soil-less culture

04 Liquid or Solution Culture

04 Circulating Methods

04 Nutrient Film Technique (NFT)

05 Deep Flow Technique (DFT)-Pipe System

06 Non-Circulating Methods

07 Root Dipping Technique

10 Floating Technique

10 Capillary Action Technique

11 Solid Media Culture or Aggregate System

11 Hanging bag Technique (Open System)

12 Grow Bag Technique

13 Trench or Trough technique

15 Pot Technique

15 Aeroponic Technique

16 Nursery Techniques for hydroponics

17 Seed Germination

17 Planting material Production

17 Nutrient Supply

18 Nursery Period

18 Sponge Nursery Technique

Page 3: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

3

...Contents

Page No:

19 Nutrient Solution for Soil-less culture

22 Electrical Conductivity (Ec)

22 Preparation of Nutrient Solution

23 Fertilizer Mixtures for Hydroponics

24 Fertigation

26 Training and Pruning

28 Management Requirements of Hydroponics/Soil-less culture

29 Soil-less culture and Controlled Environment agriculture

30 Some Problems and Solutions in Hydroponics

32 Insect Pest and Disease Damage in Hydroponics

32 Nutritional Disorders

36 Advantages of Hydroponics/Soil-less culture

36 Limitations of Hydroponics/soil less culture

37 Crops to grow with Hydroponics/Soil-less Culture

37 Harvesting, Grading, Storage and Marketing

38 Equipments for Hydroponics

42 Acknowledgements

Page 4: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

4

HYDROPONICS/SOIL-LESS CULTURE

Soil is usually the most availablegrowing medium and plants normally grow init. It provides anchorage, nutrients, air, water,etc. for successful plant growth. Modificationof a soil an alternate growing medium tendsto be expensive. However, soils do poseserious limitations for plant growth, at times.Presence of disease causing organisms andnematodes, unsuitable soil reaction,unfavourable soil compaction, poor drainage,degradation due to erosion, etc. are some ofthem.

Further, continuous cultivation of cropshas resulted in poor soil fertility, which in turnhas reduced the opportunities for natural soilfertility build up by microbes. This situationhas lead to poor yield and quality.

In addition, conventional crop growingin soil (Open Field Agriculture) is difficult as itinvolves large space, lot of labour and largevolume of water. And in some places likemetropolitan areas, soil is not available for cropgrowing. Another serious problem experiencedsince of late is the dif ficulty to hire labour forconventional open field agriculture.

Why Hydroponics/Soil-less Culture?

Hydroponics or soil-less culture is asystem of growing plants which helps reducesome of the above mentioned problemsexperienced in conventional crop cultivation.

Figure 2: Hydroponics lettuce plant

Figure 1: A plant grown in soil

Air

Water

Nutrients

An

c h o r ag

e

Page 5: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

5

Figure 3: Examples for hydroponics/ soil-less culture

Hydroponics offers opportunities toprovide optimal conditions for plant growth andtherefore, higher yields can be obtainedcompared to open field agriculture.

Hydroponics or soil less culture offersa means of control over soil-borne diseasesand pests, which is especially desirable in thetropics where the life cycles of these organismscontinues uninterrupted and so does the threatof infestation. Thus the costly and time-consuming tasks of soil sterilization, soilamelioration, etc. can be avoided withhydroponics system of cultivation. It offers aclean working environment and thus hiringlabour is easy.

Hydroponics/Soil-less Culture–What is it?

Hydroponics or soil-less culture is atechnology for growing plants in nutrientsolutions that supply all nutrient elementsneeded for optimum plant growth with orwithout the use of an inert medium such asgravel, vermiculite, rockwool, peat moss, sawdust, coir dust, coconut fibre, etc. to providemechanical support.

History of HydroponicsHydroponics was practiced many

centuries ago in Amazon, Babylon, Egypt, chinaand India where ancient men used dissolvedmanure to grow cucumber, watermelons andother vegetables in sandy riverbeds. The“hanging harden of Babylon” and the Aztec’sfloating farms were actually prototypes ofhydroponic systems. Later, when plantphysiologists started to grow plants with specificnutrients for experimental purposes, they gavethe name “nutriculture.”

Interest in practical application of“nutriculture” developed in 1925 when thegreen house industry expressed interest in itsuse. Green house soils had to be replacedfrequently to overcome problems of soilstructure, fertility and pests. As a result,researchers became interested in the potentialuse of nutriculture to replace conventional soilculture.

In 1929, Dr. William F. Gericke of theUniversity of California succeeded in growingtomato vines of 7.5 m height in nutrientsolutions. He named this new productionsystem “hydroponics” a word derived fromGreek to reflect the importance of ‘Hydros’(water) and ‘Ponos’ (working). Thus,hydroponics broke the laboratory bounds andentered the world of practical horticulture. Theterm hydroponics originally meant nutrientsolution culture. However, crop growing in inertsolid media using nutrient solution is alsoincluded in hydroponics in broad sense.

During 1960s and 70s, commercialhydroponics farms were developed in AbuDhabi, Arizona, Belgium, California, Denmark,German, Holland, Iran, Italy, Japan, RussianFederation and other countries. During 1980s,many automated and computerizedhydroponics farms were established around theworld. Home hydroponics kits became popularduring 1990s.

Page 6: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

6

In Sri Lanka, the hydroponics systemof cultivation is in its infancy. Many use inertsolid medium such as coconut fibre or coir-dustwith fertigation and some use balanced nutrientsolution alone employing both circulating andnon-circulating methods in small and mediumscales.

This requirement must be artificially maintainedin hydroponics. In any hydroponics systemthe following basic requirements must bemaintained at optimum levels.

v Buffer action of water or the inertmedium used.

v The nutrient solution or the fertilizermixture used must contain all micro andmacro elements necessary for plantgrowth and development.

v Buffer action of the nutrient solutionmust be in the suitable range so thatplant root system or the inert medium isnot affected.

v The temperature and aeration of theinert medium or the nutrient solution issuitable for plant root system.

Classification ofHydroponics/Soil-less Culture

The term hydroponics originally meantnutrient solution culture with no supportingmedium. However, plant growing in solid mediafor anchorage using nutrient solution is alsoincluded in hydroponics. This technique iscalled aggregate system. Hydroponicssystems are further categorized as open (i.e.,once the nutrient solution is delivered to theplant roots, it is not reused) or closed (i.e.,surplus solution is recovered, replenished andrecycled). Current hydroponics systems ofcultivation can be classified according to thetechniques employed. A hydroponic techniquerefers to the method of applying nutrientsolution to the plant roots.

Large numbers of hydroponictechniques are available. However, considerfollowing factors in selecting a technique.

Basic Requirements ofHydroponics

Soils naturally maintain the temperatureand aeration needed for root growth. When thesoil is poor, plant growth and yield decline alsodue to unsuitable aeration and temperature.Plant cultivation is impossible under ill drainedcondition due to these conditions. Soil adjustsitself to provide suitable conditions for plantgrowth. It is called the buffer action of the soils.Plants also absorb nutrients released throughnatural mineralization.

In a solution or inert medium,maintenance of acidity or alkalinity (pH) andelectrical conductivity (Ec) in suitable rangesfor plant root system is called buffer action.

Figure 4: Hydroponics strawbery plants in a net house

Page 7: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

7

Submersible pump

Nutrient solution

Solution container

Sieve

PVC pipeTap valve

Wooden plank

Channel made offlexible sheet

TimerFigure 5: Main features of a NFT system

l Space and other resources available

l Expected productivity

l Availability of suitable growing medium

l Expected quality of the produce – colour,appearance, free from pesticides, etc.

1. Solution culture or Liquid hydroponics

-Circulating methods (closed system)

Nutrient film technique (NFT)

Deep flow technique (DFT)

-Non-circulating method (open systems)

Root dipping technique

Floating technique

Capillary action technique

2. Solid media culture (Aggregate systems) –These can be open systems or closed

systems.

-Hanging bag technique

-Grow bag technique

-Trench or trough technique

-Pot technique

3. Aeroponics

-Root mist technique

-Fog feed technique

Liquid or SolutionCulture

CIRCULATING METHODS

The nutrient solution is pumpedthrough the plant root system and excesssolution is collected, replenished and reusedin these methods.

Nutrient Film Technique(NFT)

NFT is a true hydroponics systemwhere the plant roots are directly exposed tonutrient solution. A thin film (0.5 mm) of nutrientsolution flows through channels. The mainfeatures of a NFT system are shown in figure5.

The channel is made of flexible sheet.The seedlings with little growing medium areplaced at the centre of the sheet and bothedges are drawn to the base of the seedlingsand clipped together (Figure 6) to preventevaporation and to exclude light. The crosssection of the channel is shown in figure 7.The growing medium absorbs nutrient solutionfor young plants and when the plants grow theroots form a mat in the channels.

Page 8: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

8

Drainage pipe tosend recycledsolution to the tank

Underground nutrientsolution stock tankPump

Delivery tube

Figure 8: An illustration of a single plane pipe system DFT

100mm PVC pipepainted white

The maximum length of the channel is5-10 m and is placed at a slope drop of 1 in 50to 1 in 75. The nutrient solution is pumped tothe higher end of each channel and flows bygravity to the lower end wetting the root mat.

At lower end of the channels nutrientsolution gets collected and flows to the nutrientsolution tank. The solution is monitored forsalt concentration before recycling. Somegrowers replace the nutrient solution everyweek with fresh solution.

Adjust the flow rate of the nutrientsolution to 2-3 litres per minute depending onthe length of the channel. Provide enoughsupport for tall growing plants in this technique.

In practice, it is very difficult to maintaina very thin film of nutrient solution and therefore,this technique has undergone severalmodifications.

Deep Flow Technique (DFT)– Pipe System

As the name implies, 2-3 cm deepnutrient solution flows through 10 cm diameterPVC pipes to which plastic net pots with plantsare fitted. The plastic pots contain plantingmaterials and their bottoms touch the nutrientsolution that flows in the pipes. The PVC pipesmay be arranged in one plane or in zig zagshape depending on the types of crops grown.The figure 8 and 10 below shows the mainfeatures of a DFT – pipe system.

Figure 7: Cross Section of a NFT channelFigure 6: Basic structures of a NFT channel

→ Clip

Page 9: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

9

The zig zag system utilizes the spaceefficiently but suitable for low growing crops.The single plane system is suitable for both talland short crops.

Figure 9: A Single plane pipe system DFT

Figure 11: A zig zag pipe system DFT

Figure 10: An illustration of a zig zag pipe system DFT

Undergroundnutrient solutionstock tank

PVC pipepainted

white

Dranage pipe tosend recycledsolution to the tank

Delivery tube

Pump

Page 10: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

10

Plants are established in plastic net potsand fixed to the holes made in the PVC pipes.Old coir dust or carbonised rice husk or mixtureof both may be used as planting material to fillthe net pots. Place a small piece of net as a

lining in the net pots to prevent the plantingmaterial falling into the nutrient solution. Smallplastic cups with holes on the sides and bottommay be used instead of net pots.

When the recycled solution falls into thesolution in the stock tank, the nutrient solutiongets aerated. The PVC pipes must have aslope of drop of 1 in 30-40 to facilitate the flowof nutrient solution. Painting the PVC pipeswhite will help reduce the heating up of nutrientsolution. This system can be established inthe open space or in protected structures aspart of CEA.

NON-CIRCULATINGMETHODS

The nutrient solution is not circulatedbut used only once. When its nutrientconcentration decreases or pH or Ec changes,it is replaced.

Root Dipping Technique

In this technique, plants are grown insmall pots filled with little growing medium. Thepots are placed in such a way that lower 2 - 3cm of the pots is submerged in the nutrientsolution (figure 14). Some roots are dipped inthe solution while others hang in the air abovethe solution for nutrient and air absorption,respectively.

This technique is easy and can bedeveloped using easily available materials.This ‘low tech’ growing method is inexpensiveto construct and needs little maintenance.Importantly, this technique does not requireexpensive items such as electricity, waterpump, channels, etc. For root crops (beet,raddish, etc.) however, an inert medium has tobe used.

Net pot with establishedplant

Net pot plastic pot

Figure12

Plastic pot withestablished plant

Figure 13: Cross section of a PVC pipe system DFT

PVC pipe

Nutrientsolution

Air spaceAir absorbingroots

Page 11: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

11

Figure 15: Container with black polythene lining

1. Root dipping technique fornon-root tuber crops

First, select a container for nutrientsolution. The container can be almost anykind and shape except metal containers.Styrofoam or wooden boxes, plastic bucketsor even cement troughs can be used.Styrofoam boxes are good as they can maintainthe temperature of the nutrient solution. Placea black plastic sheet of at least 0.15 mmthickness as lining inside the boxes to avoidleakage and to reduce the light (figure 15).The depth of the box must be about 25 – 30cm to provide enough solution as well asenough space above the solution for oxygenabsorbing roots.

A board is required to place on thecontainer to prevent light penetration. Theplanting pots are also fixed to this board (figure16). The number of holes in the board to fixthe pots depends on the crops to be grown.An additional hole is necessary for aircirculation and refilling.

Seedlings are transplanted in plasticpots filled with sterilized old coir-dust orcarbonised rice husk or the mixture of the two.Plastic net pots or plastic cups can be used.

Make some holes at the bottom and onsides of the plastic cups for roots to emergeand for the nutrient solution to seep into the

Figure 16: Boards with holes to cover the box andto which pots are fixed

Planting medium

Planting pot Hole for air passageand refilling

Nutrient solution

Container

Air absorbing roots

Nutrient absorbing roots

A board to covercontainer and to fixplanting pots

Figure 14: Diagrammatic view of a non-circulating hydroponics non-root tuber plant

Page 12: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

12

potting material (figure 17). Place a smallpiece of net inside the pots or cups to preventpotting materials falling into the solution. Seedscould also be planted directly in the pots toraise the crop.

Fill 2/3rd of the container with nutrientsolution. The pots with the plants are fitted onto the board as shown in figure 18 and will beplaced on top of the box. Only the bottom 2cm of the pots will be submerged in nutrientsolution.

The above steps complete the formationof non-circulating hydroponics system. Theseboxes can be placed in net houses or in openspace or under rain shelters or in-door. Tallgrowing plants will require some support toprevent from falling.

Figure 18: Potted plants fixed to the board tocover the container

Maintain adequate air space above thenutrient solution in the container. Success ofthe non-circulating hydroponics systemdepends on the rapid growth and quantity ofroots that are exposed to the air. These rootsabsorb oxygen for the plants. Ideally, top two

thirds of the young root system must be in theair and the rest must be floating/dipping in thenutrient solution.

During crop growth, when the solutionlevel in the container goes down, the ionconcentration may increase. Such increase isdetrimental to plant growth. If this condition isobserved, siphon out the remaining solutionand refill with fresh solution.

2. Root dipping technique forroot tuber crops

A 20 – 30 cm deep container can beused. It is lined with black polythene sheetand filled 1/3rd with nutrient solution. Leavinga space of about 7.5 cm above the solutionlevel, fix a wire mesh in the box and fill with aninert medium (Figure 20). The seedlings/seedsare planted in the medium.

Figure 19: Non-circulating hydroponic plantsgrowing in a Styrofoam box

Figure 17: planting pots

Page 13: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

13

At the early stage, nutrient solution willreach the planting medium through theperforated PVC pipe filled with the growingmedium by capillary action. Later, plant rootswill grow into the nutrient solution through wiremesh. At this stage, the perforated tube willbe removed. The resulting hole will facilitateaeration and refilling.

Floating Technique

This is similar to box method butshallow containers (10 cm deep) can be used.Plants established in small pots are fixed to a

Styrofoam sheet or any other light plate andallowed to float on the nutrient solution filled inthe container (Figure 21) and solution isartificially aerated.

Capillary Action Technique

Planting pots of different sizes andshapes with holes at the bottom are used. Fillthese pots with an inert medium and plantseedlings/seeds in that inert medium. Thesepots are placed in shallow containers filled withthe nutrient solution. Nutrient solution reachesinert medium by capillary action (Figure 22).

Aeration is very important in thistechnique. Therefore, old coir dust mixed withsand or gravel can be used. This technique issuitable for ornamental, flower and indoor

Figure 20: Diagrammatic view of the root dipping technique for root tuber crops

Perforated tube fillwith gowing mediumwhich will be removedletter

Inert growingmedium

Air space

Nutrian Solution

Wire mesh

Styrofoam boardfloating innutrientsolution

Figure 21: Diagrammatic view of floating technique

Artificialaeratiobn

Planting pots fixedto styrofoam board

NutrientsolutionContainer

Page 14: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

14

plants.

Solid Media Culture orAggregate System

The following techniques involvinginert solid media can be practiced using locallyavailable materials. The media materialselected must be flexible, friable, with waterand air holding capacity and can be drainedeasily. In addition, it must be free of toxicsubstances, pests, disease causingmicroorganisms, nematodes, etc. The mediumused must be thoroughly sterilized before use.

• Inorganic natural media (gravelculture)

• Organic natural media (smoked ricehusk, saw dust, coconut fibre, coir dustpeat moss)

• Inorganic artificial media (rockwool,perlite, vermiculite)

• Organic artificial media (polyurethane,polyphenol, polyether, polyvinyl)

Tanins and acids present in the newlyextracted coir-dust affect plants. Therefore,use at least 06 months old coir-dust. Dry, cleancompressed coir-dust blocks are available forsale in the market.

Different techniques described below,according to the method of holding the plantingmedium, can be practiced.

Hanging Bag Technique(Open system)

About 1 m long cylinder shaped, white(interior black) UV treated, thick polythenebags, filled with sterilized coconut fibre areused. These bags are sealed at the bottomend and tied to small PVC pipe at the top.

These bags are suspended verticallyfrom an overhead support above a nutrientsolution-collecting channel. Therefore, thistechnique is also knows as ‘verti-grow’technique. Seedlings or other planting materialsestablished in net pots are squeezed into holeson the sides of the hanging bags. The nutrientsolution is pumped to top of each hanging bagthrough a micro sprinkler attached inside thehanging bags at the top. This micro sprinklerevenly distributes the nutrient solution insidethe hanging bag. Nutrient solution drips downwetting the coconut fibre and plant roots.Excess solution gets collected in the channelbelow through holes made at the bottom of thehanging bags and flows back to the nutrientsolution stock tank (Figure 23).

This system can be established in theopen space or in protected structures. Inprotected structures, the hanging bags in therows and amongst the rows must be spacedin such a way that adequate sunlight falls onthe bags in the inner rows.

Highly porousgrowing medium

Nutrient solution

Figure 22: Capillary action technique

Container with holes at bottom

Page 15: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

15

The bags are not heavy as they are filledwith coconut fibre and can be used for about02 years. The number of plants per bag variesdepending on the plants. About 20 lettuceplants can be established per bag. This systemis suitable for leafy vegetables, strawberry, andsmall flower plants. Black colour tubes will haveto be used for nutrient solution delivery toprevent mould growth inside.

Grow Bag Technique

In this technique 1 – 1.5 m long white(inside black), UV resistant, polythene bagsfilled with old, sterilized coir-dust are used.These bags are about 6 cm in height and 18cm wide. These bags are placed end to endhorizontally in rows on the floor with walkingspace in between (Figure 25). The bags maybe placed in paired rows depending on thecrop to grow.

Make small holes on the upper surfaceof the bags and squeeze seedlings or otherplanting materials established in net pots into

Nutrientsolution

delivery pipe Hanging bagsfilled with coirfiber

Pump

Recyclednutrient solution

Figure 23: Diagrammatic view of hanging bag technique

Underground nutrient solution stock tank

Figure 24: Strawbery plants growing inhanging bags

Page 16: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

16

the coir-dust. 2-3 plants can be establishedper bag. Make 02 small slits low on eachside of the bags for drainage or leaching.

Fertigation with black capillary tubeleading from main supply line to each plant ispracticed. The nutrient solution and water mayalso be added manually to these bags.Depending on the stage of crop growth andthe prevailing weather conditions, vary the

amount of water applied. Make sure that thegrowing media is not completely saturated withwater or nutrient solution, as it prevents theoxygen supply to plant roots.

Cover the entire floor with white UVresistant polythene before placing the bags.This white polythene reflects the sunlight tothe plants. It also reduces the relative humidityin between plants and incidence of fungaldiseases. When tall growing plants areestablished supporting structures will benecessary.

Trench or Trough Technique

In this open system, plants are grownin narrow trenches in the ground (Figure 27) orabove ground troughs (figure 28) constructedwith bricks or concrete blocks.

Both trenches and troughs are linedwith waterproof material (thick UV resistantpolythene sheets in two layers) to separatethe growing media from rest of the ground.The width of the trench or trough can bedecided depending on the ease of operation.Wider trenches or troughs will permit two rowsof plants. The depth varies depending on theplants to grow and a minimum of 30 cm maybe necessary.Figure 26: Tomato plants growing in grow bags

Grow bags filedwith coir-dust

Nutrient solutiondelivery tube

Nutrien solutionsupply line

Figure 25: Diagrammatic view of plants in grow bags

Page 17: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

17

Old coir dust, sand or gravel, peat,vermiculite, perlite, old sawdust or mixture ofthese materials can be used as the media forthis culture. The nutrient solution and waterare supplied through a drip irrigation systemor manual application is also possible subjectto labour availability. A well-perforated pipe of

Figure 27: Cross section of hydroponic trenches

Trench filed with growingmedium

Drainage pipe

Nutrient solution supplyline

Nutrient solution deliverypipe

Polythene film

Drainage pipe

Nutrient solutionsupply line

Nutrient solutiondelivery pipe

Polythene film

Trough filed withgrowing medium

Figure 28: Cross section of above ground troughs

2.5 cm diameter may be placed at the bottomof the trough or trench to drain out excessnutrient solution.

Tall growing vine plants (cucumber,tomato, etc.) need additional support towithstand the weight of the fruits.

Page 18: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

18

Pot Technique

Pot technique is similar to trench ortrough culture but growing media is filled inclay or plastic pots (Figure 29). Volume of thecontainer and growing media depend on thecrop growth requirements. The volume rangesgenerally from 01 to 10 litres.

Growing media, nutrient solutionsupply, providing support to plants, etc. issimilar to that of trough or trench culture.

Aeroponic Technique

Aeroponic is a method of growingplants where they are anchored in holes inStyrofoam panels and their roots aresuspended in air beneath the panel. Thepanels compose a sealed box to prevent lightpenetration to encourage root growth andprevent algae growth. The nutrient solution issprayed in fine mist form to the roots. Mistingis done for a few seconds every 2 – 3 minutes.This is sufficient to keep roots moist and nutrientsolution aerated. The plants obtain nutrientsand water from the solution film that adheresto the roots.

Pot filed withgrowing medium

Nutrient solutiondelivery pipe

Nutrient solutionsupply line

Figure 29: Hydroponics plants in pot technique

The aeroponic culture is usuallypracticed in protected structures and is suitablefor low leafy vegetables like lettuce, spinach,etc.

The principal advantage of thistechnique is the maximum utilization of space.In this technique twice as many plants may beaccommodated per unit floor area as in othersystems. Another potential application of thistechnique is in the production of plants free ofsoil particles from cuttings for exports.

Nutrient solution mist

Styrofoam pannel

Plastic lining

Figure 30: Aeroponic A-frame unit, developed by Jensen and Collins in 1985 at the University of Arizona

Page 19: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

19

Nursery Techniques forHydroponics

As in open fielda g r i c u l t u r e ,production of

v i g o r o u sseedlings orp l a n t i n gmaterial of

high yieldingvarieties is an essential

step of hydroponics/soil-less culture, to obtaineconomic yields.

Nursery Medium

The growing medium must providesatisfactory conditions for seed germinationand to raise pest and disease free seedlings.A material that is friable, moderately fertile, welldrained yet have sufficient water holdingcapacity and good aeration and free of pestsand disease causing organisms must beselected as medium for seed germination orrooting the planting materials.

The following materials can be usedas medium to raise seedlings or to root plantingmaterials.

- Old coir-dust

- Carbonised rice husk

- Fine sand or fine sand and old coir dust mixture

- Rockwool, Peat, perlite or vermiculite, etc.

Sterilize the medium before use. Forcoir-dust, add hydrated lime to bring its pH toneutral. For a 05 kg coir-dust block, about 100– 250 g hydrated lime is needed.

Nursery Containers/ Trays

Use a container that provides thesuitable condition for seed germination and alsoaccording to crop and cultivation method.

Individual containers / Growing blocks:paper pots, plastic pots, clay pots,Styrofoam pots, coconut fibre pots, rockwoolblocks, sponge blocks

Figure 31: Some individual containers

Trays:Styrofoam trays, speedling/cell plug trays

Trays made up of different materialsare available for sale in market. Depending onthe requirements, trays may be selected.

Figure 32: Trays

Page 20: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

20

Gotukola- Plantlets or runners separatedfrom mother plants.

Strawberry- Plantlets or runners separatedfrom mother plants

Gerbera- Plantlets separated frommother plants

Mukunuwenna- 10 – 12 cm long semi-hardwood or hardwoodstem cuttings.

Kang Kong- 20 cm long semi-hardwoodcuttings with 3-4 nodes.

Mint- 10 – 12 cm long semi-hardwood stem cuttings

Sarana- Semi-hardwood stem cuttings.

Seed Germination

Thorough cleaning of the pots followedby washing with 10% Calcium or Sodiumhypochloride will ensure disease free condition.Place one seed per block filled with growingmedium at the correct depth in the pots or trays.

Such necessary conditions for seedgermination as moisture, temperature, humiditymust be provided. Germination trays can becovered with wet papers or cloth to provideadequate temperature for germination until theseeds sprout. Remove these papers at thetime of seedling emergence.

Maintain the moisture level of themedium at correct level for uniform germinationand application of water in the mornings ispreferred.

Planting Material Production

Vegetative parts separated frommother plants can also be rooted and used asplanting materials. Individual containers ortrays filled with growing medium are used forrooting these vegetative parts. Selectvegetative parts that are free from pests,disease causing organisms and nematodes forpropagation. For example, following materialscan be used for propagation.

Nutrient Supply

Nutrient supply is not necessary until theemergence of first two true leaves. Until suchtime apply only clean water. However, whenthey unfold, nutrient supply must begingradually as the growing medium contains verylittle plant nutrients. The fertilizer mixture meanthydroponics plants could also be used fornursery plants. Diluted nutrient solution canbe applied every day or nutrient solutionprepared by dissolving 10 g of Albert’s mixturein 10 litre of water can applied every other day.

Figure 33: Selected Kang Kong stem cutting

Figure 34: Rooted Kang Kong stem cutting readyfor planting

Page 21: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

21

At the early stage, place the trays or potsin shallow containers that is filled with nutrientsolution in such a way that the tray’s or pots’lower portion is submerged in the solution. Thenutrient solution will reach the media throughthe holes at the bottom of the pots or nurserytrays by capillary action. Vegetative parts forpropagation planted in individual containers ortrays are also placed in shallow nutrient solutioncontainers as seedling trays.

Once the seedlings or plantingmaterials reach the correct size for planting,they can be planted with the medium.Vegetative parts can sometimes be directlyestablished in the hydroponics system.

Nursery Period

The nutrient solution can also be applieddirectly to nursery pots after seed germinationor sprouting of planting materials. Whenapplying nutrient solution directly to nurserypots,

• place the pots or trays on a flat planeand pour solution so that it does not comeinto direct contact with the small plant;

• at the early stage apply 5-10 ml solutiononce a day; and

• when plants grow, 10-25 ml a day once ortwice till establishment.

Tomato 3 - 4 weeks (2-3 true leaves stage)

Cabbage 4 - 5 weeks (3-4 true leaves stage)

Salad cucumber 3 weeks (3-4 true leaves stage)

Lettuce 2 - 3 weeks

Bell Pepper 4 - 5 weeks

Select vigorous seedlings with thecharacteristics for the variety concerned forestablishment in hydroponics. Also tissue-cultured plants can be established inhydroponics.

Sponge Nursery Technique

Sponge pieces can be used as nurserymedium instead of the above mentioned mediamaterials. 2.5 cm cube sponge blocks can beused for this purpose. Place the seeds at thecentre in a cut made on the topside of thesponge block.

Sponge nursery is maintained as othernurseries. Nutrient supply must begin whenthe first true leaf begin to unfold. Dependingon the cultivation method, the seedlings canbe planted in hydroponics system with thesponge block intact. The sponge block maybe removed with minimum damage to rootswhen plants begin to grow .

Figure 35: Nursery pots placed in shallow nutrientsolution containers

The nursery period varies with the crops.

Page 22: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

22

Nutrient Solution forHydroponics

Plants require 17 essential elementsfor their growth and development. Withoutthese nutrients plants cannot complete theirlife cycles and their roles in plant growth cannotbe replaced by any other elements. These 17essential elements are divided into macro-elements (required in relatively large quantities)and micro or trace elements (required inconsiderably small quantities).

The macro elements are carbon (C),hydrogen (H), Oxygen (O), nitrogen (N),phosphorous (P), potassium (K), calcium (Ca),magnesium (Mg) and sulphur (S). The microelements are iron (Fe), chlorine (Cl), boron (B),manganese (Mn), copper (Cu), zinc (Zn),molybdenum (Mo) and nickel (Ni).

All essential nutrients are supplied tohydroponics plants in the form of nutrientsolution, which consists of fertilizers saltsdissolved in water. The hydroponic grower musthave a good knowledge of the plant nutrients,

Figure 36: Sponge block for seed germination

Figure 37: Seedling in a sponge block ready fortransplanting

NCl

PB

KMn

Ca

Cu

Mg

S

Fe

Zn

Mo

Ni

Figure 38: Plant nutrients in nutrient solution

Page 23: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

23

as management of plant nutrition throughmanagement of nutrient solution is the key tosuccess in hydroponic gardening.

The hydroponic methods enablegrowers to control the availability of essentialelements by adjusting or changing the nutrientsolution to suit the plant growth stage and toprovide them in balanced amounts. As thenutrients are present in ionic forms in thenutrient solution and also, not needing to searchor compete for available nutrients as they doin soil, hydroponic plants reach maturity muchsooner. Optimization of plant nutrition is easilyachieved in hydroponics than in soil.

Nutrient SolutionManagement

While optimum nutrition is easy toachieve in hydroponics, incorrect managementof the nutrient solution can damage the plantsand lead to complete failure. The success orfailure of a hydroponic garden therefore,depends primarily on the strict nutrientmanagement programme. Carefullymanipulating the nutrient solution pH level,temperature and electrical conductivity andreplacing the solution whenever necessary, willlead to a successful hydroponic garden.

pH Level

In simple terms, pH is a measure ofacidity or alkalinity on a scale of 1 to 14. In anutrient solution, pH determines the availabilityof essential plant elements. A solution isconsidered to be neutral at pH 7.0, alkaline ifabove and acidic if below.

For pH values above 7.5, iron,manganese, copper, zinc and boron becomesless available to plants. Should the pH of anutrient solution fall below 6.0, then the

solubility of phosphoric acid, calcium andmanganese drops sharply. The optimum pHrange for hydroponic nutrient solution isbetween 5.8 and 6.5.

The further the pH of a nutrient solutionfrom recommended pH range, the greater theodds against the success.

The figure 40 indicates the nutrientelement availability at different pH levels of thesolution. Nutrient deficiencies will becomeapparent or toxicity symptoms will develop ifthe pH is higher or lower than therecommended range for individual crops. Forexample, if pH is consistently 7.5, one canexpect intra-veinal chlorosis to occur, anindication of iron deficiency.

Figure 39: Measuring nutrient solution pH using aportable digital pH meter

Page 24: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

24

Figure 40: Chart showing the availability of nutrient elements at different pH levels.

strongly acid acidslightly

acid

veryslightly

acid

veryslightlyalkaline alkaline

slightlyalkaline strongly alkaline

Nitrogen

Manganese

Boron

Iron

Magnesium

Calcium

Sulpher

Potassium

Phosphorus

Copper & zinc

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10

6.25

The chart shows a pH range of 4.0 to10.0. The width of the coloured section for eachnutrient represents the availability of thatnutrient. The widest place denotes themaximum availability. The narrowest placedenotes the least availability. The red line atpH 6.25 indicates the maximum number ofelements at their highest availability.

When plants absorb nutrients and waterfrom solution, pH of the solution changes.Therefore, it must be monitored daily, andadjusted to be between the recommendedranges. Chemical buffers can adjust the pH ofa nutrient solution, when it strays outside theideal. It can be lowered by adding diluteconcentrations of phosphoric or nitric acids and

Page 25: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

25

raised by adding a dilute concentration ofpotassium hydroxide. Although it is importantto stay within recommended range, it is farmore important to prevent large fluctuations.

Electrical Conductivity (Ec)

The electrical conductivity indicates thestrength of nutrient solution, as measured byan Ec meter. The unit for measuring Ec is dS/m. A limitation of Ec is that it indicates only thetotal concentration of the solution and not theindividual nutrient components.

The ideal Ec range for hydroponicsis between 1.5 and 2.5 dS/m. Higher Ec willprevent nutrient absorption due to osmoticpressure and lower Ec severely affect planthealth and yield.

When plants take up nutrients and waterfrom the solution, the total salt concentration,i.e., the Ec of the solution changes. If the Ecis higher than the recommended range, freshwater must be added to reduce it. If it is lower,add nutrients to raise it.

Preparation of NutrientSolution

Though hydroponic growers canformulate their own fertilizer mixtures to preparenutrient solutions using completely water-soluble nutrients salts, a number offormulations are available in the market tochoose.

It is important to avoid any formulationsthat contain impurities like sand, clay or silt.Such impurities do not supply any nutrientsbut they are harmful as they can block thedelivery tubes.

Also avoid any formulation that hasinsoluble or less soluble salts. In hydroponics,the nutrients must be available in solution inionic form for plant absorption. If they are foundas salts, plants will suffer from nutrientdeficiency symptoms.

Although urea is completely soluble inwater, it cannot be used in hydroponics, as itdoes not break into ionic form in the solutionas it does in soils.

Some fertilizer salts react with eachother to produce insoluble precipitations. Forexample, ammonium sulphate and potassiumchloride form less soluble potassium sulphatein the tank. Phosphate fertilizers actproblematic in the presence of high calciumand magnesium concentrations, causingprecipitation of low soluble phosphates.Therefore, select fertilizers that are compatiblewith each other. The table 1 indicatescompatibility of some saltsFertilizer Mixturesfor Hydroponics

Figure 41: Measuring nutrient solution Ec using aportable digital Ec meter

Page 26: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

26

Table 2: Chemicals needed to prepare 1000 litresof nutrient solution proposed by Dr. Alan Cooper.

Nutrient chemicals Weight in grams

Potassium dihydrogen phosphate 263.00

Potassium nitrate 583.00

Calcium nitrate 1003.00

Magnesium sulphate 513.00

EDTA iron 79.00

Manganese sulphate 6.10

Boric acid 1.70

Copper sulphate 0.39

Ammonium molybdate 0.37

Zinc sulphate 0.44

Table 1: Compatibility chart for some soluble fertilizers

Soluble fertilizers AN AS CAN MAP SOP MOP

Ammonium nitrare (AN) - C C C C C

Ammonium sulphate (AS) C - L C C C

Calcium nitrate (CAN) C L - X C C

Mono ammonium phosphate (MAP) C C X - C C

Potassium sulphate (SOP) C C L C - C

Potassium chloride (MOP) C C X C C -

Gypsum (G) X X X X C C

Kieserite (KS) C C C X C C

Potassium nitrate (PN) C L C C - C

C: compatible, can be mixed in the solutionL: Limited compatibility, mix at the time of use or some precautions must be takenX: Incompatible, do not mix

Fertilizer Mixtures forHydroponics

The tables 2 and 3 give nutrient saltcontents of two hydroponics formulations.

These fertilizer mixtures are not suitableas foliar spray as the EDTA iron (iron chelate)does not disintegrate easily on plant surfaceand therefore, can be harmful to consumers.

Page 27: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

27

Fertigation

Fertigation combines the two mainfactors of supplying water and plant nutrientsthat are essential for plant growth. The rightcombination of the two is the key to obtainhigh yields and quality produce.

Advantages of Fertigation

• Accurate and uniform application offertilizers

• Ability to meet plant nutrient demand undergiven climatic conditions and during differentcrop growth stages

• Improving fertilizer use efficiency andreducing leaching below root zone thusminimizing pollution

• Saving on labour

• Increasing both yield and quality of produce

Factors to be Considered inFertigation

1. Growing media

2. Fertilizers used

3. Irrigation water quality

As the first two factors were discussedearlier, only irrigation water quality is discussedhere.

Figure 42: Fertilizer mixing tank

Table 3: Chemicals needed to prepare 1000litres of nutrient solution (Albert’s mixture,locally available in the market).

Nutrient chemicals Weight in grams

Multi-K (Potassium nitrate) 38.00

Refined grade calcium nitrate 952.00

Magnesium sulphate 308.00

EDTA iron 8.00

Zinc sulphate 0.15

Boric acid 0.20

Manganese sulphate 1.15

Copper sulphate 0.10

Mono potassium phosphate 269.00

Potassium sulphate 423.00

Ammonium molybdate 0.03

Page 28: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

28

Irrigation Water Quality

Use good quality water with its pH andEc suitable for plant growth. Based on pH, Ecand soluble salt content, water quality can bedivided into 03 classes (Table 4).

Non-hazardous and medium class watercan be used for fertigation. However, whenlatter is used for fertigation, thoroughly leachthe growing medium at least once a year.

Methods of Fertigation

Mix the fertilizers required for a particularcrop with daily water requirement of that cropand apply manually or through fertigationsystem.

The amounts of fertilizers mixed withirrigation water will vary depending on the

crops, crop growth stage and the hydroponicstechnique used. The example below explainsthis situation.

However, at all stages of crop growth, the pHof the nutrient solution must be maintainedbetween 5.8 - 6.5 and Ec between 1.5 - 2.5dS/m.

For circulating techniques (DFT andNFT), supply the nutrient solution for apredetermined time period.

For aggregate systems (solid mediaculture), fertigation can be done manually orthrough drip irrigation system. Supply thefertilizers with irrigation water for apredetermined time period so that the watercontent of the growing media does not increasebeyond field capacity. When fertigation is notdone, the crop must be irrigated with water tomaintain the medium at field capacity.

Quality Factors Unit Water Quality classes

Non-hazardous Slight to Moderate Severe

pH --- Normal Range 6.5 - 8.4 ---

Salinity Ecw

dS/m 0.00 – 0.8 0.8 – 3.0 >3

Sodium me/lit <3 >3 -

Chloride me/lit <3 >3 -

Boron mg/lit <0.7 0.7-3 >3

Bicarbonates me/lit <1.5 1.5-8.5 >8.5

(Courtesy: Guidelines for interpretation of water quality for irrigation. Western fertilizer handbook.Page 38).

Table 4: Irrigation water quality classes

Page 29: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

29

Training and PruningIn hydroponics, the growing medium

does not provide enough anchorage as soils.This is more so in liquid cultures as no plantingmedium is used. Therefore, growers mustprovide artificial supporting structures and trainplants along those structures. Support isespecially important, when tall growingindeterminate type crop varieties (tomatoes,cucumber, etc.) or crops bearing relativelyheavy fruits (bell pepper, egg plant, etc.) areused in hydroponics.

A polythene string can be tied at thebase of each plant using a plastic plant clip orby a loose non-slip knot as shown in figure 43and the string is tied vertically to the overheadhorizontal support to hold the plants. Whenplants grow, wind the main stems looselyaround the string for support. In the case oftall growing indeterminate tomato varieties,placing additional plant clips every 3rd to 4thnodes will be necessary to prevent the plantsfrom slipping down.

For salad cucumbers, the verticalstring is attached to each plant with plastic plantclips or by a loose non-slip knot at the base.As the plants grow, wind the main stem looselyaround the string for support. Additional plantclips are attached to prevent plants fromslipping.

Tall growing indeterminate typetomatoes are trained to a single stem. All lateralbranches are removed when they are about 5cm long (Figure 44). Prune the lateral branchesevery 3 – 4 days, and it is best done early inthe day.

Indeterminate type tomato plants thatproduce long term crops are lowered to aworking height as they grow, keepingproduction limited to fruit grown on the 2 – 2.5m of the main stem. When plants grow taller,remove about 04 leaves at the bottom and untie

the string from the overhead horizontal supportand lower the plants about 60 cm and tie thestring shifting to a side (figure 45). This mustbe done every 2 weeks, and the strings mustbe long enough to permit lowering during theentire cropping period.

Figure 43: Training plants on vertical support.

Figure 44: Removal of side branches in tomatoplants

Page 30: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

30

Tomatoes produce large number of fruitsat each cluster. To get large, quality fruits, fruitthing will be necessary. Depending on the sizerequired, 3 to 5 fruits may be left in a cluster.

For salad cucumbers, umbrella systemof pruning can be adopted. It involves pruningall lateral branches until the plant reaches theoverhead horizontal support (figure 46). There,the terminal bud is removed and two sidebranches are allowed to grow downwards.Vigorous plants will continue to produce fruits

Bell pepper plants are trained to twostems. Vertical strings tied to overheadhorizontal support, support them. Guide theseside stems to the vertical strings. Flowers occurin axils of each branch. Side shoots arisingfrom the stems must be pruned after 2 – 3leaves so that fruiting takes place only on thetwo main branches. Periodic fruit thinning maybe required to obtain large, good quality fruits.

on the downward growing lateral branches,although the rate of fruit production tends toslow down.

Salad cucumber may produce more than onefruit per node; these can be thinned out to onefruit per node or allowed to develop if they arenot curved or otherwise distorted in shape.Heavy fruiting at lower part of the vine willreduce production higher up.

Figure 46: The umbrella training system forcucumber

Figure 45: Tomato plant at left will be lowered theposition at right by retying the support string to the

overhead horizontal support several cm to theright

Page 31: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

31

ManagementRequirements ofHydroponics/Soil-less Culture

Meet the following requirements todevelop and maintain a successfulhydroponics/soil-less cultivation of crops. Ifany of these conditions are not fulfilled, onecannot obtain economical yields.

• Maintain the nutrient solution pH in therange of 5.8 to 6.5, and electricalconductivity (Ec) in the range of 1.5 to 2.5dS/m, as these ranges are suitable for plantgrowth. Any pH or Ec outside these rangeswill reduce availability and uptake ofnutrients and will also damage plant roots.

Plants are the best indicators of the nutrientavailability. Look for nutritional disordersymptoms in plants and adjust nutrientsolution accordingly (Figure 47).

• Maintain adequate solution temperature. Asthe temperature goes up, plant respirationincreases causing a higher demand foroxygen. At the same time, the solubility ofoxygen decreases. This requirement ismore critical in green houses and nethouses where the temperature is bound toincrease during mid afternoons. Steps mustbe taken to counter such increase.

• Always ensure that there is plenty ofdissolved oxygen in the nutrient solution asthe plant roots absorb oxygen. Lack ofoxygen will reduces up take of nutrients andthereby the yield and also causes root rot.In closed systems, if the recollected solutionis allowed to fall into the solution tank froma height, natural aeration will take place.

• In root dipping techniques, maintainadequate air space above the nutrientsolution in the container as successdepends on the rapid growth and quantityof roots that are exposed to the air. Theseroots absorb oxygen for the plants. Ideally,top two thirds of the young root system mustbe in the air and the rest must be floatingin the nutrient solution.

• Avoid any sudden changes in nutrientsolution concentration as it can result inunsuitable pH and Ec.

Figure 47: Iron deficiency symptom in strawberry

Figure 48: Luxuriant growth of water and airabsorbing roots takes place when there is

adequate air space above solution

Page 32: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

32

• In root dipping techniques, during cropgrowth, when the solution level in thecontainer goes down, the ion concentrationmay increase. Such increase is detrimentalto plant growth. If this condition is observed,siphon out the remaining solution and refillwith fresh solution.

• Ensure adequate light for the hydroponics/soil-less culture plants. Light and all otherrequirements are the same as though grownin open fields.

• Always use pest and disease free seedlingsand planting materials for establishment ofhydroponics crops. Remove and destroyany infected plants as soon as they arefound.

• If nematode problem is observed in solidmedia culture, discard the plants andsterilize the growing medium. If in doubt,discard and replace the medium. Alsoensure that he water supply is also freefrom nematodes.

• Algae can build up in the system and blockthe small tubes used for the delivery ofnutrient solution. Use black colour tubes toavoid such problems. Between crops,thoroughly clean the system using a mildsolution of chlorine. After cleaning,thoroughly flush the system with fresh waterbefore replanting.

• Adequate spacing is necessary for plantgrowth and when vine crops are grown,supports must be provided.

• In open aggregate techniques, there is apossibility for nutrients to leach when wateris applied. Therefore nutrient solution maybe applied continuously instead of water tosupply both water and nutrients.

Soil-less Culture andControlled EnvironmentAgriculture

Hydroponics culture is probably themost intensive method of crop production intoday’s agricultural industry. In combination withgreen houses and protective covers (controlledenvironment agriculture), it is high technologyand capital intensive. With the possibility ofadjusting air and root temperature, light, water,plant nutrition, and adverse climate, thiscombination can be made highly productive,conservative of water and land and protectiveof the environment.

Figure 49: Protected structure

Advantages

High-density maximum crop yield, cropproduction where no suitable land exists, cropcultivation regardless of seasonality, moreefficient use of water and fertilizers and minimaluse of land area are the principal advantagesof soil-less culture in combination withcontrolled environment agriculture. Another

Page 33: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

33

major benefit is the possibility of obtainingpesticide free products, which fetch higherprices at the increasingly ready markets, atpresent.

Precautions

High temperature

One serious concern in Sri Lanka andother tropical countries is the rise of solutiontemperature during mid afternoons in green/net houses and under protective covers.Adoption of closed system of hydroponicswhere the solution is recycled helps reducesuch rise in temperature to some extend.Further, misting of water to crops whentemperature rises, use of exhaust fans, use ofwhite colour containers to hold solutions,painting gullies/pipes with white colour, etc. willhelp reduce the build up of heat from sunlight.

Sunlight

In protected structures, it wasobserved that growth and yield of plants ofinner rows of hanging bag and grow bagtechniques were poor due to low sunlightavailability. Therefore, ensure that enoughsunlight reaches the inner rows of thesetechniques.

Pollination

As protected structures effectivelyprevent insects reaching crops, pollination byinsects does not take place in the protectedstructures. Also lack of natural airflow alsoreduces the chances of natural pollination.High temperatures normally experienced insideprotected structures also interfere withpollination as it reduces pollen viability.Therefore, artificial pollination must be done

by the use of mechanical vibrators. Blowerscan be used to improve the airflow inside thestructures.

Hormones may also be used toincrease the chances of pollination insideprotected structures. For example, 0.15% 4-CPA (Para chlorophenoxy acetic acid - a kindof auxin) is widely used to induce fruiting oftomato in Japan. Hormone application iseffective for tomato 3 days before and 3 daysafter blooming. Application more than once,higher concentration or too early applicationcan result in malformed fruits.

Some Problems andSolutions inHydroponics

As experienced in normal crophusbandry, pests diseases and too affecthydroponics plants and they also showphysiological as well as nutritional disordersunder unfavourable conditions.

Physiological Disorders

Sudden changes in environmentalfactors, incorrect nutrition supply or irrigationcan bring about physiological disordersymptoms in plants. Some crop varieties aremore prone to these conditions than others.

Blossom end rot of tomato

At the bottom end of tomato fruits, brown,sunken leathery spots appear (Figure 50).Calcium deficiency, dry growing medium andsudden supply of water, salt accumulation inroot zone are some causal factors. Avoidingthese conditions will prevent blossom end rot.

Page 34: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

34

Concentric fruit cracking of tomato

Concentric cracks appear around thefruit stalk (Figure 51) or cracks extending fromfruit stalk (Figure 52) appear. High daytemperatures, large differences between dayand night temperature and sudden change ingrowing media moisture content are the causesof this condition.

Shrink cracks of bell pepper

Shrink cracks appear commonly aroundthe fruit shoulders. Rapid evaporation ofcondensed moisture on fruit surface causesshrink cracks. Gradual change from day tonight temperatures and night ventilation canprevent this condition.

Figure 50: Blossom end rot of tomato

Figure 51: Concentric fruit cracking of tomato

Figure 52: Cracks extending from stalk

Figure 53: Shrink cracks of bell pepper

Page 35: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

35

Fruit crooking of cucumber

Fruit crooking is a serious physiologicaldisorder in cucumber (Figure 54). Thecurvature of known as fruit crooking begins atearly stages of fruit development and may becaused by adverse temperature, excessivemoisture in growing medium, poor nutrition,excessive fruit load or insect damage. Affectedfruits must be removed as soon as noticed.

Insect Pest andDisease Damage inHydroponics

In hydroponics, soil borne diseases arevirtually eliminated. Certain common pests anddiseases however, can affect these plants.Vigilance and early identification are importantin controlling such problems. Keep theenvironment of the hydroponics plants cleanand adopt correct cultural practices such assupply of well-balanced nutrients to maintainthe plants healthy. Pests and diseases lessaffect healthy plants. Always start thecultivation with healthy seedlings/plantingmaterials.

Adopt Integrated Pest Management(IPM) strategies recommended for vegetables.If necessary apply recommended chemicalsto control insect pests or diseases and alwaysstrictly adhere to recommended pre-harvestintervals.

Nutritional DisordersIn hydroponics all the essential

nutrients are supplied through the nutrientsolution. If the solution is deficient or excess(toxic) in any of these nutrients or the pH orthe Ec of the solution is beyond the suitablerange, the plants will show nutritional disordersymptoms.

These symptoms include changes ingrowth rate, size of plants, leaf shape andcolour, leaf thickness, stem colour, inter nodedistance, nature of root system, etc. In addition,fruiting characteristics may change. Althoughthese external symptoms vary according tocrops and varieties, some common symptomsare described in table 5 and figures 55 to 62.

Figure 54: Fruit crooking of cucumber

Page 36: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

36

Table 5: Some common nutritional disorder visual symptoms exhibited by plants

Plants usually dark green incolour abundant foliage butusually with a restricted rootsystem.Flowering and seedproduction can be retarded.

Phosphorus Plants are stunted and often a dark greencolour. Anthocyanin pigments may acumulate.Dificiency sympems occur first in matureleaves. Plant maturit is often delayed.

No primary symptems yetnoted. Sometimes copper andZinc dificiency occurs in thepresence of excessPhosphorus.

Pottassium Symptoms first visible on orlder leaves. Indicots, these leaves are initially chloroticbut soon scattered dark necrotic lesions(dead areas) develop. In many monocots,the tips and margins of the leaves die first.

Usually not exesively absorbedby plants. Exess potassiummay lead to magnesiumdificiency and possiblemanganese, zinc or irondificiency.

Sulfur It not often encountered. Generally yellowingof leaves, usually first visible in younger leaves.

Nitrogen

Nutrient Element Deficiency Symptom Excessive/Toxicity symptoms

Growth is restricted and plants are generallyyellow (chlorotic) from lack of chlorophyll,especially older leaves. Younger leaves remaingreen longer. Stems, petioles and lower leafsurfaces of tomato can turn purple.

Reduction in growth and leafsize. Leaf symptoms oftenabsent or poorly defineed.Sometimes intervienal yellowingor leaf burning.

Magnesium Intervienal chlorosis which first develops onthe older leaves. The chlorosis may start atleaf margins or tip and progress inwardintervienally.

Very little information available onvisual symptoms.

Bud development is inhibited and root tips oftendie.Young leaves are affected before old leavesand become distorted and small with irregularmargins and spotted or necrotic areas.

Calcium No consistent visiblesymptoms.Usually associatedwith excess carbonate.

Page 37: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

37

Iron

Nutrient Element Deficiency Symptom Excessive/Toxicity symptoms

Table 5: Continued

Pronounce intervienal chlorosissimilar to that caused bymagnesium deficiency but on theyounger leaves.

not often evident in naturalconditions. Has been observedafter the application of spryswhere it appears as necrotic spots.

Chlorine Wilted leaves which then becomechlorotic and necrotic,eventuallyattaining a bronze colour. Rootsbecome stunted and thikened neartips.

Burning or firing of leaf tip ormargins. Bronzing, yellowing andleaf abscission and sometimeschlorosis. Reduced leaf size andlower growth rate.

Manganese Initial symptoms are often intervienalchlorosis on younger or older leavesdepending on species. Necroticlesions and leaf sheding can developlater.

Some times chlorosis, unevenchlorophyll distribution. Reductionin growth.

Boron Yellowing of leaf tip followed byprogressive necrosis of the leafbeginning at tip or margins andproceeding toward midrib.

Symptoms vary with species. Stem androot apical meristems often die. Roottips often become swollen anddiscoloured. Internal tisues sometimesdisintegrate (or discolour) (e.g.”heartrot” of beets). leaves show varioussymptoms including thikening,brittleness,curling, wilting, and chloroticspotting.

Zinc Reduction in internode length and leafsize. Leaf margins are often distortedor puckered. Sometimes intervienalchlorosis.

Exess zinc commonly produces ironchlorosis in plants.

Copper Natural deficiency is rare. Young leavesoften become dark green and twistedor misshapen, often with necrotic spots.

Reduced growth followed bysymptoms of iron chlorosis,stunting, reduced branching,thickening and abnormal darkeningof rootlets.

Molybdenum Often intervienal chlorosis developingfirst on older or midstem leaves, thenprogressing to the youngest (similar tonitrogen deficiency). sometimesmarginal scoching or cupping of leaves.

Rarely observed. Tomato leaves turngolden yellow.

Page 38: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

38

Pictures curtsey: Compendium of strawberry diseases and compendium of tomato diseasesby American Pathological Society.

Figure 55: Calcium deficiency in strowberry

Figure 56: Iron deficiency in strowberry

Figure 57: Manganese deficiency in tomato

Figure 58: Iron defRiciency in tomato

Figure 59: Nitrogen deficiency in tomato

Figure 60: Zinc deficiency in strowberry

Figure 61: Magnesium deficiency in tomato

Figure 62: Sulphur deficiency in strowberry

Page 39: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

39

Advantages ofHydroponics/Soil-less Culture• Land is not necessary. It can be practiced

even in upstairs, open spaces and inprotected structures.

• Clean working environment. The grower willnot have any direct contact with soil.

• Low drudgery. No need of making beds,weeding, watering, etc.

• Continuous cultivation is possible.

• No soil borne diseases or nematodedamage.

• Off-season production is possible.

• Vegetable cultivation can be done withleisure sense.

• Many plants were found to give yield earlyin hydroponics system.

• Higher yields possible with correctmanagement practices.

• Easy to hire labour as hydroponics systemis more attractive and easier than cultivationin soil.

• No need of electricity, pumps, etc. for thenon-circulating systems of solution culture.

• Possibility of growing a wide variety ofvegetable and flower crops includingAnthurium, marigolds, etc.

• Water wastage is reduced to minimum.

• Possible to grow plants and rooted cuttingsfree from soil particles for export.

Limitations ofHydroponics/Soil-less Culture• Higher initial capital expenditure. This will

be further high if the soil-less culture iscombined with controlled environmentagriculture.

• High degree of management skills isnecessary for solution preparation,maintenance of pH and Ec, nutrientdeficiency judgment and correction,ensuring aeration, maintenance offavourable condition inside protectedstructures, etc.

• Considering the significantly high cost, thesoil-less culture is limited to high value cropsof the area of cultivation.

• A large-scale cultivator may have topurchase instruments to measure pH andEc of the nutrient solution.

• Energy inputs are necessary to run thesystem.

• Yields were found to decrease whentemperature of the solution rises duringwarm periods.

Page 40: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

40

Crops to Grow withHydroponics/Soil-less Culture

A variety of crops can be grown usinghydroponics/soil-less culture. However, prioritymust be given to high-value crops dependingon the market situation.

Leafy vegetables - Lettuce, Head lettuce, Kang kong, Gotukola

Vegetables - Tomato, Egg Plant, Green bean,Beet, Winged bean, Capsicum,Bell pepper, Cabbage,Cauliflower,

cucumbers, melons, raddish

Fodder crops - Sorghum, Alphalfa, Barley,Bermuda grass, Carpetgrass

Cereals - Rice, Maize

Condiments - Parsley, Mint, Oregano,Sweet basil

Fruit crops - Strawberry,

Flower/ornamental crops - Anthurium,Merrygold, Coleus, roses,carnations, orchids,chrysanthemums,

Medicinal crops - Alovera

Harvesting, Grading,Storage and Marketing

Harvesting

Harvesting at correct maturity will reducepost harvest loses. One must know the age ofthe fruits or plants to correctly identify maturity.Reports on crops may be maintained for thispurpose. Harvest fruits by cutting with a sharpknife with minimum damage to fruits and plantstem.

Figure 63: Some crops that can be hydroponically grown

Page 41: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

41

Harvest bell pepper after they developtheir standard colour. For salads, harvestsbefore the fruits reach full red ripen stage; whenthey are at yellow-red stage. It is better towear a pair of gloves while harvesting and usedisinfected knife or scissors.

At least some colour should beshowing in tomato fruit before harvest. If thestems are attached care should be taken duringhandling to avoid any cuts or bruises.

Cucumbers must be harvested with noattached stem when they reach a uniformdiameter throughout the fruit length, but beforeany yellowing appears at the blossom end.Harvest strawberry fruits when they begin toturn red.

Leafy vegetables must be harvestedbefore they reach their full maturity. Select thecorrect stage of maturity for ornamental plantsand fruits depending on the marketrequirements.

Grading

When the harvest is in fruit form,discard odd shaped, damaged, or spotted fruitsand grade according to their sizes into large,medium and small size groups. It may besuitably labelled to indicate its quality (forexample, free of pesticides).

Storage

After grading, most vegetables mustbe stored in cool dry place. Storing in largeplastic containers with large holes for aerationis advisable.

Marketing

Depending on the market requirement,produce can be sold in small packing. Theycan be suitably labelled. The packing musthave aeration holes.

Figure 64: Packing of tomato for marketing

Page 42: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

42

Equipment forHydroponics

Submersible or ordinary water pumps,Ec meter, pH meter are the essential equipmentnecessary to operate a circulating hydroponics.PVC pipes can be used as channels in thesesystems.

Water Pumps

The water pump must be made up ofmaterials that are non-reactive with nutrientsalt solution. Stainless steel shaft,polycarbonate or stainless steel impeller, pump-house and water seal must be there in thepump to be used in hydroponics.

One does not require a pump with veryhigh head for circulating the nutrient solutionin hydroponics systems. Therefore, a domesticwater pump with 0.5 HP will suffice. A safetydevice is a must with the water pump as thenutrient solution more effectively conductselectricity compared to water. Therefore, a verysensitive trip switch must be used to disconnectelectricity supply whenever the need arises.

Figure 65: A domestic water pump

Figure 66: A submersible water pump

Page 43: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

43

Timer and OxygenDetection Sensor

When the plants are small, theiroxygen requirement is low. Therefore, thenutrient solution circulating time period can belimited. Limiting the circulating time periodscan also reduce the electricity consumption.For this purpose a timer may be used to setthe circulating time manually or an oxygenconcentration detection sensor may beincluded in the system, so the sensor canactivate the pump whenever the oxygenconcentration of the nutrient solution level goesdown.

Figure 67: PVC pipe system for hydroponics

PVC Pipes

Type 400 or class 4 100 mm PVC pipeshave to be used in circulating hydroponics asthe channels. PVC pipes with thinner wallswill sag and thereby reduce the flow rate ofnutrient solution. The result will be lack ofoxygen supply for the plant roots. UV resistantpipelines are preferable. Painting these pipeswhite will prevent the increase of nutrientsolution temperature. The flow rate requiredin hydroponics is very small ranging from 1 to3 litres per minute. Therefore, an over-flowpipe will have to be fitted to adjust the flowrate.

Page 44: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

44

pH and Ec Meters

Simple and portable Ec and pH metersmust be used to monitor and maintain the Ecand pH at correct levels.

Blowers

These devices help send airflowthrough the plants so that plants shake andpollens are distributed to facilitate pollinationinside protected structures.

Figure 69: A simple blower

Figure 68: Simple digital pH and Ec meters

Page 45: Contents · PDF file2 Contents Page No: 01 Why Hydroponics/Soil-less culture? 02 Hydroponics/Soil less culture - What is it? 02 History of hydroponics 03 Basic Requirements of Hydroponics

45

Pollinators

These simple electrical device vibratethe individual plants when touch them so thatpollination is facilitated inside the protectedstructures.

Nurtimeter

In addition to the Ec, this meter helpsmeasure the nutrient contents of the solution.

Figure 70: A nutri-meter