Nutrient Film Technique (NFT)

Introduction

The Nutrient Film Technique (NFT) is an active hydroponic system in which a thin, continuously flowing film of nutrient-rich water passes over the roots of plants. In an NFT setup, plants are placed in sloped channels or troughs, allowing the nutrient solution to flow down a gentle incline and return to a central reservoir. Because the roots receive a constant supply of oxygen from the exposed undersides and nutrients from the flowing solution, NFT systems can achieve rapid growth rates and efficient resource use. This method is popular for commercial and home growers alike due to its relative simplicity, low media requirements, and ability to support high-density plantings.

Building One Yourself (DIY)

To construct a basic DIY NFT system, you will need:

A sturdy support frame (e.g., PVC or a wooden rack) to hold sloped channels at a slight incline (1-3% grade).
Growing channels or troughs (food-safe PVC pipe, gutter sections, or custom trays) sized to fit your space.
Net pots or plant holders that fit into holes drilled along the top of each channel.
A reservoir (opaque plastic tote or bucket) to store nutrient solution.
A submersible pump capable of delivering 50-150 liters per hour per channel, depending on length and crop type.
PVC or vinyl tubing to connect the pump outlet to the inlet of the highest channel.
An overflow/drain fitting at the lower end of each channel to return excess solution to the reservoir.
Hydroponic nutrient solution formulated for NFT (complete N-P-K and micronutrients).
pH and EC meters to monitor and adjust solution parameters.

Steps for Assembly:

Assemble the Support Frame: Construct a sturdy frame that holds each channel at a slight slope (approximately 1-3 degrees). Channels must be level side-to-side but angled front-to-back to allow solution flow.
Prepare the Channels: Drill evenly spaced holes along the top of each channel, sized to snugly fit your chosen net pots (usually 2-3 inches in diameter for leafy greens).
Install Inlet/Outlet Fittings: At the upstream end of each channel, insert a bulkhead fitting or elbow fitting for the nutrient inlet. At the downstream end, install a drain fitting or simply allow the channel to overflow back into the reservoir.
Connect Tubing and Pump: Place the submersible pump inside the reservoir. Connect pump output tubing to a manifold (if running multiple channels) or directly to the inlet of the first channel. Ensure tubing is secured to prevent leaks.
Fill Reservoir & Prime Pump: Mix fresh nutrient solution in the reservoir, adjusting pH to 5.8-6.2 and EC to the appropriate range (see Growing Parameters below). Turn on the pump, ensuring a gentle but steady flow that creates a thin film at the bottom of each channel.
Place Seedlings or Cuttings: Fill net pots with an inert medium (e.g., rockwool cubes, clay pebbles, or coco coir). Insert healthy seedlings or rooted cuttings into the net pots, then place them into the channel holes so that their roots can grow down into the flowing solution.
Monitor & Adjust: Check flow rate and root coverage daily, ensuring roots neither dry out nor become completely submerged. Maintain nutrient concentration and pH by checking the reservoir every 2-3 days, topping off with fresh solution as needed.

What a Professional Kit or System Might Look Like

Commercial NFT kits streamline many of the DIY steps by providing pre-fabricated components:

Integrated Channels: Molded PVC or food-grade polypropylene channels with built-in net pot holders and endcaps to reduce leaks.
Precision Manifolds: Pump manifolds or PVC manifolds that evenly distribute flow across multiple channels, ensuring uniform nutrient film thickness.
Digital Controllers: Automated pH/EC controllers that dose nutrients and pH adjusters on demand, maintaining optimal parameters without manual intervention.
Prefabricated Frame & Support: Modular racking systems-often made from powder-coated steel or anodized aluminum-designed to hold channels at precisely the correct angle.
Reservoir Covers & Insulation: Reservoir lids to reduce algal growth and thermal insulation jackets to maintain stable water temperature.
High-Efficiency Pumps & Filters: Commercial-grade submersible pumps with inline filters or pre-filters to prevent debris and root hairs from clogging tubing.
LED Grow Light Integration: Many professional NFT systems include integrated LED rails positioned above channels, providing uniform light intensity tailored for each growth stage.

These commercial systems often come with detailed instruction manuals, pre-set nutrient recipes, and options for automatic reservoir top-off and recirculation alarms, making them well-suited for larger growers or those seeking minimal hands-on maintenance.

What Cultivars Do and Don't Work with NFT

Because NFT provides a continuous flow of water, nutrients, and oxygen, it is well-suited for a variety of plants-particularly fast-growing, shallow-rooted crops.

Well-Suited Cultivars:
- Leafy Greens: Lettuce (e.g., Butterhead, Romaine, Leaf), Spinach, Kale, Swiss Chard, and Arugula all thrive under NFT, often ready for first harvest within 4-6 weeks.
- Herbs: Basil (Ocimum basilicum), Mint (Mentha spp.), Cilantro (Coriandrum sativum), and Parsley (Petroselinum crispum) grow vigorously due to consistent nutrient delivery.
- Microgreens & Baby Greens: Fast-maturing microgreens such as Mustard Greens, Swiss Chard Microgreens, and Baby Bok Choy can be harvested early, benefiting from short channel runs.
Less Suitable Cultivars:
- Vining/Fruiting Crops: Tomatoes, Cucumbers, Peppers, and Eggplants develop extensive root systems that can clog channels; they also require higher nutrient volumes and are prone to root diseases if not well-spaced.
- Large Rooted Crops: Carrots, Radishes, and Other Root Vegetables need deeper media for adequate root development, making NFT channels too shallow.
- Large-Leaf Varieties: Crops with heavy foliage (e.g., Large-leaf Lettuce cultivars) can shade out lower plants, and their rapid water uptake can lead to nutrient depletion if channels are overly long.
- Perennial Herbs & Woody Plants: Rosemary, Sage, and Thyme have woodier root structures and slower growth, which don't align well with NFT's fast turnover design.

Nutrient Film Technique (NFT)

Introduction

Building One Yourself (DIY)

What a Professional Kit or System Might Look Like

What Cultivars Do and Don't Work with NFT

Sources