Hydroponics / Soilless Culture

Lesson No. 04

Introduction

• Def. & explanation: Growing crops in a liquid based growth medi um.

• Growing crops in a complete nutrient solution with or without solid phase.

• Also called "water culture" or "nutr ient culture" or "soilless culture".

• However, sometimes top soil or components of soi l such as sand or gravel are used as the sol id phase.

•Need to: Control the - dosage (EC) and

-volume of supply-Adjust pH

• Advantages: Providing all the nutrients in -- Right amount

- Right time

2. Fertigation / Hydroponics

Other advantages: Adequate Aeration,

Sterility (Disease free)

Lack of soil contaminations

Reasons for practicing hydroponics

• A. To overcome poor soil conditions • i.e. Rocky soils, • sandy or gravel soils, • clay soils, • undesirable pH (salinity, acidity etc.), toxicity, • deficiencies, • Low temperature, • contamination (P & D).

• Soil is a complicated system. The factors, which influence plant growth are very hard to monitor and manipulate.

• By using a nutrient solution with or without a solid growth medium for physical support, closer control of these factors can be done.

• B. To provide optimum resources for the growing plants and the best root environment for the root system for its growth and functioning.

• - And thereby, to achieve the maximum possible yield and the highest yield

Significance within the world agriculture and in Sri Lanka

• Area under hydroponics:• Productivity (in comparison with the

conventional soil culture):• In Sri Lanka: Almost all the CEA growers

in Sri Lanka practice hydroponics.• Problems?

Common hydroponics methods

• Trough culture• Nutrient solution is kept in a container. • Usually square in shape. • Size is variable. Usually 2-4 ft2. • May be practiced with or without having a

growth medium (solid phase).

• Main components: • Container, • Lid (crop support ) • nutrient solution, • aeration. • Can be practiced for any crop.

Aeration is relatively poor. • So far good results have been

received for leafy vegetables, tomato, bell pepper and some root vegetables too.

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Commercial scale

2 Coir bag or grow bag culture(coco-peat culture)

• Plants are grown in horizontally or vertically oriented coir dust filled polythene bags.

• A single bag is 100 x 20 cm in size (fit for 3-5 plants in horiz. orientation).

• Bags are avai lable in the market wi th compressed coi r dust lined with silver/black polythene and sometimes sterilized coir blocks (Fig. ).

Grow bag culture i.e. Greenhouse Vegetables in Sri Lanka

• Flush with water before use. • Provide nutrients through a fertigation

system (i.e. drip tubes or tapes). • Hence it is in flowing phase. • Mostly the run off is not collected and re-

circulated. Ideal for tomato, bel l pepper and even for sal ad cucumbers.

• In vertical orientation, strawberries, lettuce and some fol iage ornamentals are grown (saving greenhouse space)(Fig. ).

Media based cultures/derivations

• Rock wool culture- Use compressed rock wool blocks.

• Glass wool culture- Replace with glass wool in the system.

• Vermiculite culture- Replace with vermiculite in the system 4. 4. Peat bag culture- Few compressed peat blocks are inserted

• Sand or gravel culture- In large soil trenches (gullies) with (pumice) adequate depth to accomodate the root system, gravel or sand are filled and the nutrient solution is provided mostly as a soil drench (through drip methods).

Block cultures

1. Rockwool block culture

2. Drip-fertigated sub-soil cultire

Nutrient film technique (NFT)

• Nutrient solution flown in a shallow gully at a very low pace (very slight slope).

• Gullys are made using 4" diameter PVC pipes in Sri Lanka.

• In other countries, a flexible PVC or fibreglass films, fold in triangular shape (Fig.

•

• Flow is collected at the col lection tank at the distal end.

• It is then brings back to the i nitial solution with the help of a pressure pump and circulated again.

• Occasionally the solution is adjusted and renewed.

Hydroponics: Nutrient Film Technique (NFT)

NFT

Other popular methods

• Deep flow technique (DFT) - Use a deep channel instead of the shal low gully in

• Good for plants with relatively deep root system.

Aeroponics• - Plants are hanged to the roof. • Nutrients are sprayed on to the fol iage and

root system.

Flood and drain system

• In any aggregate-type hydroponics culture nutrient solution is provided by flodding the medium at frequent intervals and allowing to drain out (instead of drip fertigation).

• The aggregates shoul d have a better water holding capacity and nutrient retention capacity.

Floating culture

• – The plants mounted to a fl oating board and is floated on a pool of nutrients (in a solution). Commonly used for lettuce, onions and other leafy vegetables.

Fertigation / Hydroponics:Manual

Mechanical

AutomatedAutomated Fertigation unit

For vegetable crops: Alberts fert.Growth stage (WAP)Dosage (g/pl) EC (mS/cm) Volume (ml)Early veg. 0.2 0.8 400

Late veg. 0.4 1.0 600

Flowering 0.6 1.2 800

Fruit set 0.8 1.6 1200

Fruit growth 1 2 1500

Fruit ripening 0.6-0.8 1.6 1200

1. Dosage: solute conc entration, measured by EC

ud;%dj

Factors considered in selecting a growing system

• i.e. Crop factors; • Climate of the area and weather

conditions; • Affordability (cost of implementing and

maintenance); • Availability of materials; • Labour requirement; • Availability of infrastructure (electricity,

clean water etc.); Market demand.

Classification of hydroponics• 1. Based on the method of nutri ent supply • Continuous liquid phase• Maintenance of fi eld capacity (drip fertigation)• 2. Movement of the nutri ent solution• Sationary liquid phase• Flowing (circulation)• 3. Status of recovery of used nutrients • Open (Non-recirculation) - Run off is not collected and

reused by adjusting of the nutrient composition.• Closed -(Recirculation) - Run off is collected and reused by adj usting

of the nutrient composition.• 4. Use of aggregates• Aggregate (media) hydroponics• Non-aggregate hydroponi cs or water culture• 5. Type of aggregates• According to the origin: Natural/artificial• According to the nature : Organi c/inorganic• According to the nature of the particals: granules/ • fibre/others

Status in Sri Lanka

• Problems – Mixing soil, lack of drainage, roots penetrate into soil, manual irrigation, No –fertigation, experimenting fertilizers, no EC and pH Control

• Need to address?

Advantages of hydroponics

• 1. Continuous cultivation in the same land• 2. Low cost and ti me for land preparation and soil

sterilization• 3. Low possibilit y for residues of fumigants and other

pesticides • 4. Low costs of irrigatio n and fertigation• 5. Low labour requirement • 6. All-weather working conditions• 7. Maintenance of clean products• 8. Minimum environmental pollution (under proper

handling of waste materials)• 9. Low soil and water borne pest and diseases

Disadvantages

• 1. High initial cost (hydroponics st ructures and equipments)

• 2. High running cost (power requirement)• 3. Requirement of technical know how for the

farmer.• 4. Requirement of quality water (low Na and Cl

ions, less contamination)• 5. Less forgiving for mistakes• 6. Need of thourogh understanding or

knowledge on the agronomy and a substantial knowledge on the crop physiology.