Lettuce is the crop that pays for most commercial NFT systems — and it’s also the crop where new growers lose the most money to preventable mistakes. From seed to harvest takes 30–45 days, which means you get 8–10 cycles a year, which also means every process error repeats 8–10 times before you notice it. This guide covers the full production loop: system setup parameters, the growth calendar, targets for EC/pH, the problems that actually occur, and the economics that decide whether the channel house makes money.
Why Lettuce Dominates NFT Farms
- Fast cycles. 30–45 days seed-to-harvest turns capital over faster than any other commercial crop.
- Perfect root architecture for channels. Shallow, fibrous roots sit happily in a thin film — no anchorage needed.
- High demand, stable pricing. Year-round lettuce supply contracts with distributors and retail chains are the backbone of NFT farm revenue.
- Clean harvest. No media, no washing-heavy soil — product goes from channel to packing line almost directly.
System Setup: The Parameters That Matter
Get these right before germinating a single seed — retrofitting a running system is 3× the work:
| Parameter | Target | Why it matters |
|---|---|---|
| Channel slope | 1–2% | Dead-level channels pool; over-steep channels run dry rivulets |
| Flow per channel | 1–2 L/min | Below 1 L/min the film starves tail-end plants |
| Plant spacing | 18–20 cm | Tighter spacing = smaller heads; don’t chase density past your market’s size spec |
| Solution temperature | 18–24°C | Above ~26°C dissolved oxygen falls and root disease risk climbs |
| Channel length | ≤ 10–12 m | Longer channels arrive at the far end depleted — split into two runs instead |
| Stand height | 80–95 cm working | Harvest ergonomics = your labor cost per head |
One design rule from the field: never let a single channel run exceed ~12 m. On long runs the last plants receive solution the first plants already partially consumed — you’ll see it as a visible size gradient down the row, and no nutrient tweak will fix what is a geometry problem. Split the run and restart the supply.
Growth Calendar: Seed to Harvest
| Stage | Days | What happens | Management focus |
|---|---|---|---|
| Germination | 0–3 | Seed in plug tray, dark & humid | 20–22°C; check moisture daily |
| Seedling | 3–14 | Cotyledons, first true leaves in plugs | Light feed at EC ~0.8–1.0 |
| Transplant | Day 14 | Plug into net pot, into channel | Handle by leaf, never the stem |
| Vegetative growth | 14–35 | Head fills out in channel | Full feed EC 1.2–1.8; monitor daily |
| Harvest window | 35–45 | Head reaches market weight | Harvest cool hours; cold-chain immediately |
Plant weekly, harvest weekly. The commercial trick isn’t growing lettuce — it’s staggering. Seedlings go in every week on a fixed percentage of total channels, so cash also arrives weekly. A farm that plants “when there’s space” has inventory gaps that show up as revenue gaps two cycles later.
EC & pH Targets
- Seedling stage: EC 0.8–1.0 mS/cm, pH 5.8–6.0
- Grow-out: EC 1.2–1.8 mS/cm (summer low end, winter high end), pH 5.8–6.2
- Warm-weather adjustment: lower EC and increase flow slightly — hot plants drink more water than nutrient, and the tank concentrates if you don’t top up
Log EC, pH, water temperature and flow checks daily. Paper, app, whiteboard — format doesn’t matter; the discipline does. The farms that catch problems early are the ones that can show you last Tuesday’s numbers.
Common Problems We Get Called About
Tipburn
Brown leaf edges in the head’s center. Cause is usually calcium transport failure, not calcium shortage — triggered by rapid growth in warm, low-airflow conditions. Fixes: increase airflow across the canopy, avoid peak-heat feeding surges, don’t over-crowd. It’s an environment problem wearing a nutrient costume.
Root browning / root rot
Check solution temperature first — above ~26°C, pathogen pressure rises fast. Then check flow (tail-end channels?) and light leaks at end caps fueling algae. Browning roots plus a warm tank is a pathogen bloom in progress; drop temperature, increase flow, and consider a safe sanitization cycle.
Algae in channels
Every time, it’s light entering the solution. Lid gaps, drilled holes without caps, translucent fittings. Cure is mechanical exclusion of light, not chemicals — seal the leaks once and the problem stays solved.
Size gradient along the channel
Channel too long, flow too low, or slope wrong at one section. Measure actual flow at the far end before touching nutrients. See the setup table above.
Yield & Economics
Working numbers for a 1,000 m² NFT lettuce operation:
- Channels: ~3,500–4,500 m of channel on single level; more with multi-tier stands
- Heads per cycle: ~17,000–22,000 at 20 cm spacing (multi-tier raises this)
- Cycles per year: 8–10 with good climate control
- Labor: harvest + reseeding dominate; NFT keeps both low
For the full investment picture — equipment bands, operating cost and payback — see the commercial hydroponic system cost guide. And for dosing automation that keeps EC/pH on target without a full-time technician, read about nutrient controllers and automation.
FAQ
Can I grow other crops in the same channels?
A: Basil, bok choy and most leafy herbs share the same setup. Fruit crops do not — see dutch bucket vs NFT.
What’s the biggest single risk?
A: Power failure on a hot afternoon. Budget a backup generator before the second production cycle, not after the first incident.
Head weights are inconsistent — why?
A: Work through the gradient checklist in order: flow rate at channel tail, slope, spacing, then nutrition. It’s positional nine times out of ten.
Ready to Spec a Lettuce System?
Send your weekly harvest target and greenhouse dimensions through the quote form — we’ll return a channel layout with counts, pump sizing and a weekly planting plan matched to your market window.