Organic and Mineral Nutrition: Finding Your Efficiency Point

Nutrient Efficiency Over Maximum Output

What You Need to Know

Most growers feed to the ceiling. The bottle says 300 ppm nitrogen in flower, so they run 300. Or higher. The assumption: maximum input produces maximum yield. It doesn’t. Massuela’s team at the University of Hohenheim tested this directly. They grew CBD-dominant cannabis under three nitrogen levels — 80, 160, and 240 mg/L — with both organic and mineral fertilisers. The plant at 160 mg/L produced 95% of the yield of the plant at 240 mg/L. Ninety-five percent. For a third less fertiliser.

But there’s a secondary finding that’s just as important: the plant at 160 mg/L converted nutrients into cannabinoids more efficiently than the plant at 240 mg/L. This means you’re not just saving money on nutrients — you’re running a cleaner system with better nutrient use efficiency. This module shows the data and what it means for how you build your flower nutrition.

The Science

The trial used a CBD-dominant cultivar (‘Cannatonic’-type, high CBD, low THC) grown in pots under controlled greenhouse conditions. The design crossed two fertiliser types (organic liquid vs. mineral salt) with three nitrogen application rates (80, 160, and 240 mg N/L). This gave six treatments, each replicated, with measurements taken on biomass, cannabinoid concentration, and nutrient use efficiency.

Yield response to nitrogen: Increasing nitrogen from 80 to 160 mg/L substantially increased dry flower weight. But increasing from 160 to 240 mg/L produced only a marginal additional gain — around 5%. The plant had essentially reached its ceiling at 160 mg/L. Above that, additional nitrogen contributed almost nothing to yield while increasing runoff pollution and fertiliser cost. If you’re running 240 mg/L N in flower, you’re paying for nutrients that mostly come out the bottom of the pot.

Organic vs. mineral: Here’s where it gets interesting. Organic-fed plants produced 12% higher CBD concentration than mineral-fed plants at the same nitrogen rate. The total CBD yield per plant was comparable, but the cannabinoid density in the flower was higher with organic nutrition. This isn’t a massive gap — it won’t turn bad genetics into good genetics — but it’s a measurable, reproducible advantage.

Nutrient use efficiency (NUE): This is the number that should change how you feed. NUE measures how much usable product you get per unit of nutrient applied. At the reduced rate (160 mg/L), nutrient use efficiency increased by 34% for organic and 72% for mineral compared to the high rate (240 mg/L). In plain language: the plant converted a much higher proportion of the nutrient into bud when it wasn’t being drowned in excess. Overfeeding doesn’t just waste nutrients — it makes the plant less efficient at using the nutrients it does absorb.

Plant morphology: The 240 mg/L plants were not significantly taller or heavier than the 160 mg/L plants. They didn’t produce more branches or larger root systems. The excess nitrogen didn’t translate into more plant — it translated into more waste. The 80 mg/L plants were visibly stunted, confirming that there IS a floor below which yield suffers. The sweet spot was the middle: enough to grow vigorously, not so much that the plant’s internal processing gets overwhelmed.

How To Apply This

The research points to a specific strategy: dial in for efficiency, not maximum output.

• If you’re running 200+ mg/L nitrogen in flower, try dialling back to 160 mg/L and see what happens. Massuela’s data (and Bevan’s from Module 2.2a, which found an optimal N of 194 mg/L in a different cultivar) both point to the same conclusion: the plant doesn’t need as much nitrogen as most feed charts suggest. The convergence between two independent trials in different countries with different cultivars is significant. Start at 160, run a full cycle, compare to your baseline. You’ll likely find yield is nearly identical and your plant is noticeably cleaner.

• If you’re in organic, the 12% CBD concentration advantage is worth knowing but not worth obsessing over. If you’re growing in coco or hydro and you’re dialled in on mineral nutrition, switching to organic won’t transform your harvest. If you’re already in organic soil, this data confirms you’re not leaving cannabinoid concentration on the table. The advantage is there, but it’s modest.

• Pay attention to nutrient use efficiency, not just yield. A 72% improvement in NUE at a reduced feed rate means less salt buildup in your medium, less runoff waste, less flushing needed, and lower nutrient cost. For a home grower running ten cycles a year, the cumulative saving is real. For a commercial operation, it’s substantial. Lower EC throughout the cycle also means less risk of nutrient burn and more stable growing conditions.

• Understand diminishing returns. The maximum yield in this trial came at 240 mg/L, but the 160 mg/L treatment got 95% of the way there. That last 5% of yield cost 50% more fertiliser. In engineering, they call that the point of diminishing returns. In growing, they call it the feed chart.

• Apply the principle across your nutrient mix, not just nitrogen. Massuela tested nitrogen rates. Bevan tested nitrogen, phosphorus, and potassium. The pattern is consistent: the plant’s response curve flattens before the maximum input the industry recommends. This suggests a broader principle: most commercial nutrient lines are calibrated for safety (feed enough that deficiency is nearly impossible) rather than for efficiency (feed the amount that optimizes yield per nutrient dollar). You’re paying for a buffer you don’t need.

Seb’s Corner (Level 2+)

The Hohenheim trial adds to a growing body of evidence that optimal nitrogen for cannabis is substantially below industry-recommended rates. Bevan et al. (2021) found a yield optimum of 194 mg/L N in hydroponic cannabis (Module 2.2a); Massuela et al. find diminishing returns above 160 mg/L in pot culture. The slight difference may reflect substrate effects — in pot culture with organic amendments, nitrogen is released gradually through mineralisation, creating a more sustained supply than the immediate availability of hydroponic mineral nutrition. The organic advantage in CBD concentration is mechanistically plausible: organic nitrogen sources release ammonium that is then converted to nitrate by soil microbes, and this slower nitrogen cycling may favour secondary metabolite production by mildly limiting the nitrogen available for vegetative growth relative to the total applied. This aligns with the broader agronomic principle that mild nutrient stress during reproductive phases can redirect carbon flux toward secondary metabolism. However, the effect was modest (12%), and the trial used a single CBD-dominant cultivar — whether THC-dominant cultivars show the same pattern remains untested. The 72% NUE improvement at 160 mg/L mineral N is particularly striking and has environmental implications for commercial operations, where fertiliser runoff is an increasingly regulated concern.

Watch Out For

• Assuming higher feed = higher yield at all concentrations. The response curve flattens. Beyond 160 mg/L N, yield improvement is marginal. You hit a point where you’re feeding excess, not fueling growth.

• Missing the NUE advantage of lower feeding. A 72% improvement in nutrient use efficiency is huge. It means less waste, less pollution, less flushing, lower cost. And it happens while you’re producing 95% of the maximum yield. This is the real story — not that you get less, but that you get nearly as much while running cleaner.

• Assuming all cultivars respond the same. This trial used CBD-dominant. THC-dominant cultivars might show different cannabinoid response to nitrogen rate. The yield response (diminishing returns above 160 mg/L) is likely to be consistent across cultivars, but the cannabinoid profile effects may not be.

• Organic vs. mineral becoming a philosophical argument instead of a practical choice. The 12% CBD concentration advantage for organic is measurable but modest. Choose based on your growing system, your skill level, and your budget — not on ideology. Both systems work.

• Ignoring the veg/flower split. This trial measured flower, but nitrogen demand during vegetative growth is higher (the plant is building structure). You can run higher N in veg (180–220 mg/L) and dial back for flower (140–180 mg/L). The mistake is running high N in both phases.

Quiz

1. In Massuela’s trial, what was the yield of plants fed at 160 mg/L nitrogen compared to plants fed at 240 mg/L nitrogen? a) 75% as much b) 85% as much c) 95% as much * d) 99% as much

2. True or False: Plants fed at 240 mg/L nitrogen were significantly taller and produced larger root systems than plants fed at 160 mg/L nitrogen. False *

3. What was the improvement in nutrient use efficiency (NUE) when mineral-fed plants were reduced from 240 mg/L to 160 mg/L nitrogen? a) 34% b) 50% c) 72% * d) 95%

4. Scenario: A grower is running two identical setups, one in organic soil and one in coco with mineral nutrients. Both are at 160 mg/L nitrogen in flower. Based on Massuela’s findings, what is the expected difference in CBD concentration between the two systems? The organic system will produce approximately 12% higher CBD concentration than the mineral system. However, total yield and plant size will be roughly similar. *

5. According to the module, what is the “point of diminishing returns” in this trial? The point where yield increase slows dramatically relative to nutrient input — approximately 160 mg/L nitrogen, where the 240 mg/L treatment produced only 5% more yield for 50% more fertiliser input. *

FAQ

Does this mean organic is better than mineral? For CBD concentration in this trial, yes — by about 12%. For yield, they were roughly equal at the same nitrogen rate. “Better” depends on what you’re optimising for. If you want maximum control and fast response times, mineral is easier to manage. If you want slightly higher cannabinoid density and you’re comfortable with slower nutrient cycling, organic has a marginal edge. Neither is dramatically superior.

My feed chart says 300+ ppm nitrogen in flower. Should I really cut that? Two independent research groups (Bevan and Massuela) both found that cannabis doesn’t need more than 160–200 mg/L nitrogen for near-maximum yield. If your chart says 300, you’re almost certainly overfeeding. Start at 160, watch the plant, and adjust from there. The worst thing that happens is you save money on nutrients and your runoff stops looking like a chemistry experiment.

Will reducing nutrients lower my THC? This trial used a CBD-dominant cultivar, so we can’t directly extrapolate to THC. But Bevan’s 2021 trial (Module 2.2a) tested a THC-dominant cultivar and found no NPK effect on cannabinoid concentration. The pattern across multiple studies is consistent: cannabinoid potency is set by genetics, not by how much fertiliser you pour in.

What about adding more nitrogen in veg and cutting back in flower? That’s actually reasonable. Nitrogen demand is highest during vegetative growth when the plant is building leaves and stems. In flower, the plant shifts resources toward reproductive tissues and needs proportionally less N. Most research supports higher N in veg (180–220 mg/L) and moderate N in flower (140–180 mg/L). The problem isn’t the concept — it’s that most feed charts push both numbers too high.

Source

Massuela DC, Hartung J, Öz L, Goergen A, Grille T and Hemmer P (2023). “Cannabis Hunger Games — Nutrient Stress Induction in Pot Culture of Cannabis sativa L.” Agronomy 13:2294. doi: 10.3390/agronomy13092294. CC-BY 4.0.