cobshopgrow
Well-Known Member
It looks like there are new studies made on cannabis i have missed so far.
Am curious to hear your opinions, especially for K.
A little compilation.
Scientifically-Based Optimal NPK Levels for Cannabis
Sources: Caplan et al. (2017–2018, Univ. of Guelph), Bernstein et al. (2020–2021, Israel), Zamlout et al. (2022, Front. Plant Sci.), Saloner & Bernstein (2021, MDPI Agronomy)
Growth (Vegetative Phase):
Flowering Phase:
Notes:
pH & EC Targets:
• Caplan et al. (2017) – Optimal nitrogen levels in vegetative phase
HortScience 52(11)
https://doi.org/10.21273/HORTSCI12310-17
• Caplan et al. (201
– Drought stress increases cannabinoids
HortScience 53(5)
https://doi.org/10.21273/HORTSCI12847-18
• Bernstein et al. (2019) – Mineral nutrition vs. secondary metabolite profile
Frontiers in Plant Science
doi.org
• Bernstein et al. (2020) – Excess potassium reduces cannabinoids & terpenes
Industrial Crops and Products 145
Redirecting
• Saloner & Bernstein (2021) – Nitrogen effects under long-day conditions
Plants 10(3): 559
https://doi.org/10.3390/plants10030559
• Zamlout et al. (2022) – Phosphorus above 60 ppm gives no benefit
Frontiers in Plant Science 13
https://doi.org/10.3389/fpls.2022.834435
Summary:
These peer-reviewed studies show that cannabis:
Am curious to hear your opinions, especially for K.
A little compilation.
Scientifically-Based Optimal NPK Levels for Cannabis
Sources: Caplan et al. (2017–2018, Univ. of Guelph), Bernstein et al. (2020–2021, Israel), Zamlout et al. (2022, Front. Plant Sci.), Saloner & Bernstein (2021, MDPI Agronomy)
Growth (Vegetative Phase):
- Nitrogen (N): 100–160 ppm
- Phosphorus (P): 20–40 ppm
- Potassium (K): 60–100 ppm
Flowering Phase:
Stage | N (ppm) | P (ppm) | K (ppm) |
---|---|---|---|
Early Bloom | 80–100 | 30–50 | 80–120 |
Late Bloom | 30–50 | 20–40 | 60–100 |
Notes:
Excess N (>160 ppm) can reduce biomass (Caplan et al.)
Excess K (>120 ppm) may reduce cannabinoids and terpenes (Bernstein et al.)
P above 60 ppm shows no benefit (Zamlout et al.)
pH & EC Targets:
- Soil: pH 6.0–6.5 | EC 1.2–1.8 mS/cm
- Coco: pH 5.8–6.2 | EC 1.6–2.2 mS/cm
• Caplan et al. (2017) – Optimal nitrogen levels in vegetative phase
HortScience 52(11)
https://doi.org/10.21273/HORTSCI12310-17
• Caplan et al. (201

HortScience 53(5)
https://doi.org/10.21273/HORTSCI12847-18
• Bernstein et al. (2019) – Mineral nutrition vs. secondary metabolite profile
Frontiers in Plant Science

Frontiers | Impact of N, P, K, and Humic Acid Supplementation on the Chemical Profile of Medical Cannabis (Cannabis sativa L)
Mineral nutrition is a major factor affecting plant growth and function. Increasing evidence supports the involvement of macro and micronutrients in secondar...
• Bernstein et al. (2020) – Excess potassium reduces cannabinoids & terpenes
Industrial Crops and Products 145
Redirecting
• Saloner & Bernstein (2021) – Nitrogen effects under long-day conditions
Plants 10(3): 559
https://doi.org/10.3390/plants10030559
• Zamlout et al. (2022) – Phosphorus above 60 ppm gives no benefit
Frontiers in Plant Science 13
https://doi.org/10.3389/fpls.2022.834435
Summary:
These peer-reviewed studies show that cannabis:
- Grows best with moderate N (100–160 ppm)
- Does not benefit from excess P (>60 ppm)
- Loses quality with excess K (>120 ppm)
- Requires balanced micronutrients, especially Ca, Mg, Fe