Soilless Cultivation

Complete Explanation of Farming Without Field Soil

Soilless cultivation means growing plants without using normal agricultural soil. Plant roots receive water, oxygen and essential nutrients through:

Nutrient-rich water
An inert growing medium
Nutrient mist
Water circulated from a fish-production system

Soilless cultivation does not mean that plants grow only in plain water. Plants still require nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and micronutrients such as iron, zinc, boron, manganese and copper. The grower must supply these nutrients in a controlled form. Closed systems also require regular monitoring because plants continuously change the nutrient composition, pH and water level. (arXiv)

1. Basic Principle

In normal farming, soil performs several functions:

Holds the plant upright.
Stores water.
Supplies nutrients.
Provides air around the roots.
Supports microorganisms.

In soilless cultivation, these functions are performed artificially.

Soil function	Soilless replacement
Plant support	Net pot, cocopeat, rockwool or clay pellets
Water storage	Reservoir or growing medium
Nutrient supply	Prepared nutrient solution
Root oxygen	Air pump, flowing water or root mist
Root environment	Tank, channel, bucket or enclosed chamber

The essential principle is:

Plant roots must receive water, nutrients and oxygen in the correct balance.

Too much water with insufficient oxygen can cause root suffocation. Too little water can make the crop wilt rapidly.

2. Main Categories of Soilless Cultivation

Soilless cultivation can be divided into four major groups:

A. Hydroponics

Plants receive nutrients from water. Roots may be inside water, touched by a thin water film or supported in an inert medium.

Examples: lettuce in PVC channels, basil in floating rafts and tomatoes in cocopeat bags.

B. Aeroponics

Roots hang inside an enclosed chamber and are sprayed with nutrient-rich mist. Aeroponic performance depends strongly on nozzle operation, spray coverage, pressure and droplet delivery to the root zone. (arXiv)

C. Aquaponics

Fish culture and plant cultivation are connected. Fish waste is biologically converted into forms that plants can use. Water then circulates through the plant section and returns to the fish tank. Water quality, aeration, filtration and biological activity must all be controlled. (arXiv)

D. Substrate or media culture

Plants grow in a soil-free material such as:

Cocopeat
Perlite
Vermiculite
Rockwool
Expanded clay pellets
Rice husk
Sand
Gravel

The material normally provides support, moisture retention and root aeration. Nutrients are supplied separately through irrigation.

3. Hydroponic Cultivation

Hydroponics is the most widely recognised soilless method.

A basic hydroponic system contains:

Water reservoir
Nutrient solution
Plant-support system
Water pump, where required
Air pump or another oxygenation method
Pipes or channels
Net pots
pH and EC measuring instruments

Basic circulation

Reservoir → Pump → Plant roots → Return pipe → Reservoir

The same nutrient solution can be recirculated. This is called a closed or recirculating system.

In an open system, nutrient solution passes through the roots only once and is not returned to the reservoir.

4. Types of Hydroponic Systems

4.1 Wick System

The wick system is one of the simplest methods.

How it works

A cotton, nylon or synthetic wick connects the nutrient reservoir to the growing medium. The wick absorbs nutrient solution and carries it upward to the roots through capillary movement.

Main parts

Small reservoir
Plant container
Cocopeat or another light medium
Absorbent wick
Nutrient solution

Suitable crops

Mint
Coriander
Small leafy vegetables
Small ornamental plants
Seedlings

Advantages

No water pump required
Low electricity dependency
Easy for beginners
Low investment

Limitations

Nutrient delivery is slow
Unsuitable for large plants
Wick may become blocked
Root zone may remain too wet
Difficult to meet high water demand

Simple example

Place a basil seedling in a cocopeat-filled pot. Insert two wicks through the pot base and allow their lower ends to remain inside the nutrient reservoir.

4.2 Kratky Method

The Kratky method is a passive hydroponic system without continuous water pumping.

How it works

The plant is held above a nutrient-filled container. Initially, the roots touch the solution. As the plant consumes water, the solution level falls and an air space develops between the plant base and water. Upper roots receive oxygen from this air space, while lower roots absorb water and nutrients.

Suitable crops

Lettuce
Spinach
Basil
Bok choy
Small leafy vegetables

Advantages

No pump
No electricity
Simple construction
Suitable for home use

Limitations

Difficult to correct mistakes after the crop becomes large
Reservoir may overheat
Mosquitoes and algae may develop if the tank is uncovered
Not ideal for long-duration fruiting crops
Water level must not be repeatedly raised over established air roots

Example

One lettuce plant may be grown in a covered bucket with a net pot fitted into the lid.

4.3 Deep Water Culture — DWC

In Deep Water Culture, plant roots remain suspended in oxygenated nutrient solution.

Main parts

Reservoir or bucket
Net pot
Air pump
Air tube
Air stone
Growing medium
Nutrient solution

Working process

The plant is held in a net pot.
Roots grow down into the nutrient solution.
An air pump sends air through an air stone.
Air bubbles increase oxygen availability around the roots.
Roots absorb water and dissolved nutrients.

Suitable crops

Lettuce
Basil
Spinach
Kale
Leafy greens

DWC is commonly used for short-duration leafy crops because these crops can be supported easily and generally have lower structural requirements than large fruiting plants.

Advantages

Simple design
Good nutrient availability
Easy root inspection
Suitable for beginners
Large water volume changes more slowly than a very small reservoir

Limitations

Air pump failure can reduce root oxygen
Warm water can create root-health problems
Large fruiting crops need strong support
A disease entering a common reservoir can affect multiple plants

Simple layout

        Plant
          │
       Net pot
──────────┼────────── Tank lid
          │
        Roots
     Nutrient water
       ○ ○ ○ ○        Air bubbles
          │
       Air stone
          │
       Air pump

4.4 Nutrient Film Technique — NFT

NFT uses a very shallow, continuously moving film of nutrient solution.

How it works

Plants are placed in holes along a slightly sloped channel. A pump sends nutrient solution from the reservoir to the higher end. A thin layer flows past the roots and returns to the reservoir.

NFT systems require reliable control of flow, nutrient concentration and pH. Pump dependency and rapid disease transmission through shared circulating water are important operational risks. (arXiv)

Main parts

Nutrient tank
Submersible pump
PVC or food-grade channels
Net pots
Supply pipe
Return pipe
Supporting frame
Timer or controller, where applicable

Suitable crops

Lettuce
Spinach
Basil
Mint
Coriander
Pak choi
Other lightweight leafy vegetables

Advantages

Efficient use of water and nutrients
Clean harvesting
Many plants can be placed in rows
Easy to expand
Suitable for greenhouse production

Limitations

Pump failure can dry roots quickly
Incorrect channel slope can create stagnation
Large roots can block water movement
Hot nutrient solution can stress roots
A water-borne disease may spread through the entire loop

Simple flow

Reservoir → Pump → Sloped growing channel
                         ↓
                      Plant roots
                         ↓
Return pipe ←────────────┘

Important point

NFT does not mean that the channel should be filled completely. Only a shallow film should pass across the lower root area, leaving part of the root system exposed to air.

4.5 Deep Flow Technique or Floating Raft

In this method, plants are fitted into holes in floating sheets or raft boards placed over a large nutrient-water tank.

How it works

The plant roots hang directly into oxygenated water. Air pumps and air stones maintain root-zone oxygen.

Suitable crops

Lettuce
Basil
Bok choy
Leafy greens

Advantages

Stable water volume
Suitable for large-scale leafy-green production
Water temperature and nutrient concentration usually change more slowly than in very small systems
Floating boards can be moved during production

Limitations

Requires a larger tank
Strong aeration is essential
Raft and tank cleaning require labour
Root diseases can spread through shared water

4.6 Ebb-and-Flow or Flood-and-Drain

The plant tray is periodically flooded with nutrient solution and then drained.

Working process

A pump fills the grow bed.
The growing medium and roots become wet.
The pump stops.
Water drains back into the reservoir.
Fresh air enters the root zone as water drains.

Suitable media

Expanded clay pellets
Gravel
Perlite mixtures
Coco chips

Suitable crops

Leafy vegetables
Herbs
Nursery plants
Ornamentals
Some fruiting vegetables

Advantages

Good alternation between moisture and air
Multiple pots can be irrigated together
Useful for nursery production

Limitations

Timer or drainage failure can flood or dry the crop
Salts may accumulate in the medium
Heavy grow beds require strong structural support

4.7 Drip Hydroponics

Nutrient solution is delivered to each plant through a small drip emitter.

Main components

Reservoir
Pump
Main pipe
Lateral tubes
Drip emitters
Growing bags or buckets
Drainage line

Suitable crops

Tomato
Cucumber
Capsicum
Strawberry
Chilli
Brinjal
Flowers

Common growing media

Cocopeat
Perlite
Rockwool
Cocopeat-perlite mixture

Advantages

Each plant receives controlled irrigation
Suitable for large fruiting crops
Fertigation can be divided into small applications
Easy to use in polyhouses

Limitations

Emitters can block
Unequal pressure can cause uneven irrigation
Drainage must be managed
Media salinity should be monitored
Fruiting crops require trellising and crop training

4.8 Dutch Bucket or Bato Bucket System

Each plant grows in an individual bucket containing an inert medium. Nutrient solution is delivered through a drip emitter and the excess returns through a common drain.

Suitable crops

Tomato
Cucumber
Capsicum
Brinjal
Climbing beans

Advantages

Good for heavy and long-duration crops
Individual plants can be removed
Strong root support
Easy trellis installation

Limitations

More pipes and fittings are needed
Drain lines may become blocked by roots
Every emitter must be checked
Buckets require cleaning between crops

5. Substrate Culture

Substrate cultivation uses a material that is not ordinary soil.

Cocopeat

Produced from coconut husk.

Characteristics:

Holds water well
Provides root support
Lightweight
Commonly used in grow bags and nursery trays

It should be properly washed, buffered and tested because untreated material may contain excessive salts.

Perlite

A lightweight expanded mineral.

Characteristics:

Improves aeration
Has low water-holding capacity compared with cocopeat
Commonly mixed with cocopeat

Vermiculite

A mineral medium with relatively high water and nutrient-holding capacity.

It is often used in seedling and propagation mixtures rather than as the only medium for heavy commercial crops.

Rockwool

A fibrous mineral product used in hydroponic slabs and cubes.

Uses:

Seed germination
Nursery plants
Tomato and cucumber production
Root support in NFT systems

Expanded clay pellets

Hard, porous clay balls.

Uses:

Net pots
Ebb-and-flow systems
Aquaponic grow beds
Plant support around stems

Rice husk

Rice husk or processed rice-husk products may be used as part of a growing-medium mixture. Raw material must be clean, stable and suitable for crop use.

6. Aeroponics

Aeroponics is a more advanced system in which plant roots hang freely inside a dark chamber.

Working process

The plant is held at the top of the chamber.
Roots hang in air.
A pump pressurises nutrient solution.
Nozzles spray the roots at set intervals.
Excess solution drains back into the reservoir.
A timer or controller repeats the cycle.

Aeroponic cultivation depends on uniform mist delivery. Nozzle blockage, pressure loss or poor spray distribution can leave part of the root system dry. (arXiv)

Suitable crops

Lettuce
Herbs
Strawberry
Leafy vegetables
Plant propagation
Seed-potato planting material
Research crops

Advantages

High oxygen availability around roots
Roots can be inspected easily
Efficient nutrient delivery
Suitable for vertical growing structures
No heavy growing medium required

Limitations

High dependence on electricity
Pump or timer failure can damage plants quickly
Mist nozzles can block
Root chamber must remain dark and clean
Higher technical skill is required

Simple diagram

             Plant canopy
                 │
        ┌────────┴────────┐
        │   Root chamber  │
        │   hanging roots │
        │   ↗ mist ↖      │
        │     nozzle      │
        └────────┬────────┘
                 │
             Reservoir
                 │
                Pump

7. Aquaponics

Aquaponics combines:

Aquaculture: raising fish
Hydroponics: growing plants without soil
Biofiltration: using microorganisms to transform fish waste

A practical aquaponic installation generally contains fish, plants and beneficial microorganisms. Fish waste supplies nitrogen-containing material; biological conversion and filtration make the circulating water more suitable for plant uptake and fish survival. (arXiv)

Basic cycle

Fish feed
    ↓
Fish tank
    ↓
Fish waste and ammonia
    ↓
Mechanical filter
    ↓
Biofilter and beneficial bacteria
    ↓
Plant grow bed
    ↓
Cleaner water returns to fish tank

Main parts

Fish tank
Fish
Water pump
Air pump
Mechanical solids filter
Biofilter
Plant bed or NFT channels
Sump tank, where required
Pipes and valves
Water-quality measuring instruments

Suitable plants

Lettuce
Basil
Mint
Spinach
Pak choi
Some tomatoes, cucumbers and peppers in properly designed systems

Advantages

Produces plants and fish
Reuses circulating water
Reduces dependence on prepared mineral fertilizer
Suitable for educational and urban-farming projects

Limitations

More complex than normal hydroponics
Plant, fish and bacterial requirements must be balanced
Fish overfeeding can overload the system
Poor aeration can affect fish, roots and microorganisms
Ammonia, nitrite, dissolved oxygen, pH and temperature require monitoring

Aquaponics research systems commonly use sensors for pH, dissolved oxygen, total dissolved solids, water temperature, air temperature and humidity because deterioration in these conditions can affect both crops and fish. (arXiv)

8. Nutrient Solution

A hydroponic nutrient solution normally supplies:

Macronutrients

Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
Sulphur

Micronutrients

Iron
Manganese
Zinc
Copper
Boron
Molybdenum
Chloride in very small amounts

Do not prepare commercial hydroponic nutrients by randomly mixing normal field fertilizers. Some materials react together and form insoluble deposits. This can remove nutrients from the solution and block pumps, pipes or emitters.

Commercial nutrients are often provided as Part A and Part B concentrates because calcium-containing fertilizer may react with concentrated phosphate or sulphate fertilizer.

Correct mixing sequence

Fill the reservoir with water.
Measure the initial water quality.
Add Part A to the reservoir.
Mix thoroughly.
Add Part B separately.
Mix thoroughly.
Check electrical conductivity.
Check pH.
Make corrections gradually.
Record the final readings.

Never mix concentrated Part A and Part B directly together before dilution.

9. pH, EC and TDS

pH

pH shows whether the nutrient solution is acidic or alkaline.

Incorrect pH can make nutrients unavailable even when those nutrients are present in the reservoir.

Many hydroponic crops are managed in a mildly acidic nutrient solution, but the exact target should be selected according to the crop, growth stage, fertilizer formulation and water quality.

EC — Electrical Conductivity

EC indicates the total concentration of dissolved ions in the nutrient solution.

Low EC may indicate that the solution is too weak.
High EC may indicate excessive fertilizer concentration or salt accumulation.

EC does not identify each individual nutrient. Two solutions can have similar EC values but different nutrient balances. Closed hydroponic systems therefore require periodic solution correction or replacement, not only repeated addition of more concentrate. (arXiv)

TDS

TDS meters estimate dissolved solids from electrical conductivity. Their displayed values can differ depending on the meter’s conversion factor.

For professional hydroponic management, it is generally clearer to record EC directly.

10. Root Oxygen

Roots require oxygen for respiration.

Insufficient root oxygen can result from:

Stagnant water
High solution temperature
Weak aeration
Excessively wet growing media
Blocked drainage
Overcrowded roots
Pump failure

Methods of improving root oxygen include:

Air pump and air stone
Flowing nutrient solution
Drainage intervals
Waterfall return into the reservoir
Ventilated growing media
Aeroponic misting

11. Light Requirements

Plants need sufficient light for photosynthesis.

Sources may include:

Natural sunlight
Greenhouse-filtered sunlight
LED grow lights
A combination of sunlight and artificial light

Insufficient light can cause:

Weak, elongated plants
Pale leaves
Small leaf area
Poor flowering
Low yield

Excess heat or overly intense light can cause:

Leaf scorch
Excessive water loss
Root-zone heating
Poor fruit setting

Indoor farming requires careful calculation of electricity cost. It is not enough to install lights without checking crop value and expected yield.

12. Suitable Crops

Best crops for beginners

Lettuce
Basil
Mint
Spinach
Pak choi
Coriander
Fenugreek leaves

Intermediate crops

Strawberry
Kale
Celery
Swiss chard
Spring onion

Advanced crops

Tomato
Cucumber
Capsicum
Chilli
Brinjal
Melons

Fruiting crops need:

Larger root volume
Stronger nutrient management
Trellising
Pollination management
Crop pruning and training
More light
Longer crop duration

Root and tuber crops are generally more difficult because they need sufficient physical space for the edible underground portion to develop.

13. Beginner Example: 20-Plant Leafy-Green Unit

A simple beginner unit may contain:

One 60–100 litre covered reservoir
Twenty net pots
Air pump and air stones for DWC, or a water pump for NFT
Leafy-green seedlings
Hydroponic nutrient
pH meter
EC meter
Thermometer
Clean water
Shade net or protected growing area

Process

Germinate seeds in clean plugs or cocopeat.
Maintain moisture without waterlogging.
Move seedlings after they develop a stable root system.
Prepare diluted nutrient solution.
Place seedlings into net pots.
Ensure roots can reach moisture.
Start aeration or circulation.
Measure pH and EC daily during initial learning.
Top up with clean water when the level falls.
Inspect roots, leaves, pumps and pipes every day.
Remove dead leaves.
Harvest when the crop reaches marketable size.
Clean and disinfect the system before the next crop.

14. Daily Monitoring Checklist

Every day

Check pump operation.
Check air pump and bubbles.
Check water level.
Observe leaves for wilting or discoloration.
Inspect roots.
Check for leaks.
Check solution temperature.
Remove dead plant material.
Confirm that every channel or emitter receives water.

Regularly

Measure pH.
Measure EC.
Clean filters.
Check nozzle or emitter blockage.
Inspect pipes for algae.
Calibrate meters.
Record water and nutrient additions.
Clean the reservoir when required.

Between crops

Remove old roots.
Wash channels and tanks.
Clean net pots.
Disinfect reusable components appropriately.
Flush drip lines.
Inspect pumps and electrical connections.
Start the next crop only after the system is clean.

15. Common Problems and Solutions

Problem	Possible cause	Corrective action
Leaves wilt suddenly	Pump failure or dry roots	Restore water flow immediately
Roots turn brown	Low oxygen, high temperature or disease	Improve aeration and inspect sanitation
Leaves become pale	Weak nutrition, pH problem or low light	Test pH and EC; inspect lighting
Leaf edges burn	Excess salts or nutrient imbalance	Check EC and water quality
Algae grows in tank	Light entering nutrient solution	Cover tank and channels
Plants grow unevenly	Unequal water flow or light	Check emitters, channel slope and spacing
Drippers block	Sediment or fertilizer precipitation	Improve filtration and flushing
NFT roots dry	Pump or power failure	Restore circulation and provide backup
Aquaponic fish gasp	Insufficient dissolved oxygen	Increase aeration immediately
Bad smell develops	Stagnant anaerobic water	Improve circulation, filtration and cleaning

Brown roots are not always caused by the same problem. Some nutrient products and organic materials can stain roots. Diagnosis should also consider smell, root texture, plant wilting, water temperature and system cleanliness.

16. Advantages

Can be established where agricultural soil is poor or unavailable
Suitable for rooftops, protected structures and urban areas
Precise control of water and nutrients
Fewer soil-borne weeds
Cleaner produce
Easier automation
Vertical arrangement is possible
Root conditions can be monitored
Nutrient solution may be recirculated
Production can be planned more consistently under controlled conditions

17. Limitations

Initial investment may be high
Pumps and controls require electricity
Technical knowledge is necessary
Water-borne disease may spread rapidly in shared systems
pH and nutrient balance require regular measurement
Poor-quality water can create serious problems
Indoor systems may have high lighting and cooling costs
Markets should be identified before commercial investment
Equipment failure can affect crops faster than in soil

Soilless farming is not automatically profitable. Profit depends on crop selection, local climate, energy cost, market price, technical skill, production scale and system reliability.

18. Which System Should You Select?

Requirement	Recommended starting system
Very low-cost home experiment	Wick or Kratky
Beginner leafy-green production	DWC
Multiple lettuce rows	NFT
Commercial tomato or cucumber	Cocopeat drip or Dutch buckets
Nursery and ornamentals	Ebb-and-flow
Vertical high-technology project	Aeroponics
Fish and vegetable integration	Aquaponics
Rooftop leafy vegetables	NFT or DWC
Polyhouse fruiting vegetables	Substrate drip system

Practical recommendation

For a beginner, the safest learning sequence is:

Start with 10–20 lettuce or basil plants.
Use DWC, Kratky or a small NFT unit.
Learn pH, EC, sanitation and water management.
Complete at least two or three crop cycles.
Then move to tomatoes, cucumbers, aeroponics or aquaponics.
Build a commercial unit only after confirming production cost and market demand.

Soilless cultivation replaces the soil, but it does not remove the need for careful farming. The grower becomes responsible for every function that soil normally performs.