Deep flow technique /Flood and drain

• It uses a flooded tray to hold the plants, and a water reservoir underneath.
• Plants are supported by net cups or other growing vessels that are filled with a growing medium such as clay pellets, rockwool, or coco coir, etc.
• The water is tray is constantly oxygenated by an air pump, and the water level is maintained at a consistent depth to submerge the base of the plants but not their leaves.
• The water is constantly recirculated, and the nutrient solution is added to the water in the reservoir and then pumped up to the tray, and gravity pulls it through the growing medium and back into the reservoir.
• The water flow is designed to be just enough to keep the roots submerged without flooding them.

Advantages

a. Good root aeration

• Roots are exposed to oxygen during the drain phase, preventing suffocation.
• Reduces risk of anaerobic conditions.

b. Efficient nutrient and water use

• Recirculation minimizes wastage.
• Nutrients are evenly distributed during flooding.

c. Flexibility in crop choice

• Supports a wide range of crops including leafy greens, herbs, strawberries, and even fruiting crops (tomato, pepper) with suitable medium.

d. Buffer against power interruptions

• Unlike NFT, roots are surrounded by moist medium that retains water and nutrients for a while, reducing risk of sudden crop loss during short power failures.

e. Scalability and simplicity

• Easy to set up at both small and commercial scale.
• Less technical precision needed compared to NFT or aeroponics.

f. Better root support

• Growing medium provides anchorage and stability for plants.

Disadvantages

a. High water volume required

• System requires a large amount of nutrient solution to flood beds.
• Heavy structures need strong support.

b. Risk of disease spread

• Pathogens like Pythium can spread rapidly through the shared nutrient solution.
• Standing water in flood trays may encourage algae and fungal growth.

c. Maintenance and cleaning

• Growing medium and trays require regular cleaning to avoid salt buildup, clogs, or biofilm formation.
• Pump and plumbing need frequent checks.

d. Energy consumption

• Pumps must work regularly to flood and drain the system.
• Energy costs can be significant for large setups.

e. Not suitable for all crops

• Some sensitive crops may suffer from root stress due to alternating wet and dry cycles.

f. System management required

• pH and EC must be monitored regularly.
• Flooding intervals must be carefully managed to avoid waterlogging or root drying.