R&D Trial | In-Canopy LED Supplementation | 47-Day Controlled Study
Winter is the production constraint for most commercial hydroponic operations in the UK. Supplemental lighting is the standard response — but overhead systems deliver light from above a dense canopy, where a significant proportion of emitted photons never reach the leaf surfaces they need to reach. Saturn's research team tested a different approach: LED placement at multiple heights directly within the canopy, delivering light precisely to where the crop needs it.
47-day controlled trial. Three crops. Two spectrum combinations. Basil yield improvement with Blue and Green spectrum: +404%.
The Problem
For UK commercial hydroponic operations, winter creates a predictable production constraint. Natural light falls below the threshold required for commercial output rates, and the gap has to be closed with supplemental lighting. The conventional approach is to increase overhead LED provision — adding more output from above the canopy.
The problem with overhead supplementation in dense vertical growing systems is photon distribution. A standard overhead array delivers maximum photon intensity at the top of the canopy. By the time light penetrates through multiple leaf layers to reach the lower tiers of a dense vertical system, intensity has dropped substantially. The lower sections of the crop — which may represent 50% or more of total growing area in a column system — are receiving a fraction of the light the upper sections receive.
Increasing overhead LED output addresses this by brute force: raise total output until even the attenuated lower-tier light is sufficient. This works, but it means the upper canopy is receiving far more light than it needs, wasting energy and cost on photons that never contribute to yield.
Saturn's research team's hypothesis was that positioning LEDs at multiple heights directly within the canopy — rather than only above it — would deliver comparable or superior yield improvements at materially lower energy cost per unit of output.
Trial Design
The trial was conducted at Saturn's UK research facility over a 47-day period, with lighting running at 16 hours per day consistently throughout. Three crops were selected to represent different leaf structures and light response characteristics: basil, lettuce, and coriander. Two spectrum combinations were tested simultaneously against a non-supplemented control baseline.
Targeting photomorphogenesis and biomass accumulation pathways. Red light drives photosynthesis directly; Far Red extends the photoperiod response and influences plant architecture through phytochrome activation.
Focusing on photosystem efficiency and leaf development. Blue light drives stomatal opening and compact growth; Green light penetrates deeper into the canopy than other wavelengths, reaching lower leaf surfaces overhead light cannot reach efficiently.
Results
All results are yield improvements versus the non-supplemented control baseline grown under identical conditions. The trial confirmed that spectrum response is strongly crop-specific — the optimal spectrum combination varies by crop, and selection should be calibrated accordingly.
The basil result deserves specific attention. A sevenfold difference in yield response between the two spectrum combinations on the same crop — +59% vs +404% — demonstrates that spectrum selection is not a minor optimisation. It is the primary determinant of outcome for spectrum-sensitive crops. Applying the wrong spectrum to basil is not just suboptimal; it leaves the majority of achievable yield improvement unrealised.
Commercial Economics
At the UK commercial electricity rate of £0.14/kWh, the total LED supplementation cost in this trial was £0.578 per square metre per crop cycle. Against yield improvements of 129–404%, this cost is recovered within the crop cycle in which it is deployed.
The economics are most direct for space-constrained operations. A facility with fixed growing area that cannot expand its footprint can multiply output per square metre by two to five times — depending on crop and spectrum — for an additional variable cost of under £0.58/m² per cycle. The capital cost of the LED arrays is a one-time investment; the energy cost is the recurring operational figure, and at £0.578/m², it is low relative to the yield value it generates.
For operations currently experiencing winter production drops, the comparison is not between supplemented and non-supplemented cost. It is between the revenue lost to a winter yield reduction and the cost of preventing it. At these economics, in-canopy LED supplementation is difficult to argue against on cost grounds for any operation where winter yield matters commercially.
Key Finding
The most commercially significant finding from this trial is not the scale of the yield improvements — it is the variation in spectrum response between crops. Basil responded to Blue and Green spectrum at nearly seven times the rate it responded to Red and Far Red. Lettuce showed strong improvement with both spectrums, with only modest differentiation between them. Coriander was similarly consistent across both.
The practical implication is that LED supplementation specified generically — "add supplemental light for winter production" — will systematically underperform for crops with strong spectrum specificity. A basil operation running Red and Far Red supplementation, unaware of the Blue and Green response data, is achieving +59% yield improvement when +404% is available for the same energy input and capital cost.
Saturn's research team holds complete 47-day trial datasets across all three crops and both spectrum combinations. For facilities running crops tested in this trial, the spectrum recommendation is based on measured data rather than general principles. For other crops, the trial methodology and placement approach are transferable — with spectrum calibration determined by the specific crop requirements.
Lighting as Part of an Integrated Growing System
Lighting strategy in isolation delivers a fraction of what it delivers when coordinated with environmental management and root-zone nutrition. Saturn's approach treats light as one input within an integrated system — where spectrum, intensity, and photoperiod are specified alongside VPD targets, CO₂ strategy, and nutrition. The conversation starts with your facility and what you are trying to achieve.
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Full Portfolio
Selected highlights from Saturn's completed project portfolio across 15 years.
Saturn Bioponics
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