Nitrogen Fertilizers Impact on CBD and THC Concentrations in Cannabis

Nitrogen Fertilizers Impact on CBD and THC Concentrations in Cannabis
Professor DeBacco

Research Article
Dilena, E., Close, D. C., Hunt, I., & Garland, S. M. (2023). Investigating how nitrogen nutrition and pruning impacts on CBD and THC concentration and plant biomass of Cannabis sativa. Scientific Reports, 13(1), 19533.
https://www.nature.com/articles/s4159...

Total Biomass and Total Cannabinoid Concentrations
Total biomass and total cannabinoid concentrations in % DW (on the y-axis) versus measured N concentrations in % DW (on each x-axis).
Treatment group labels are indicated by different colors.
The shape of the points (circle or triangle) indicates whether or not the plant associated with the data point was on the sun edge.
For each regression n = 20.

Inverse Relationship of [N] to [Cannabinoid]
The increase in biomass as N concentration increased from 3 to 6 was approximately 100%
Note the y-axis scale
However, the corresponding decrease in cannabinoid concentrations was approximately 67%
This entails a net decline in yield in terms of grams as N concentration increases

Three Key Points
1. Biomass was strongly and positively related to N
2. Cannabinoid concentrations were strongly and negatively related to N
3. Plants on the sun-edge tended to have higher biomass levels and cannabinoid concentrations

High Nitrogen Levels
Higher nitrogen nutrition raised the concentration of N in both inflorescence and leaf plant matter.
For very high levels of N nutrition (500 mg/mL), inflorescence cannabinoid concentrations decreased significantly (with little change in biomass) and leaf biomass increased significantly.
With higher N supply stem diameter also increased.
The net effect of increasing nitrogen nutrition on the total yield of cannabinoids was negative because the increase in biomass (which was only significant in leaves) was not enough to offset the consequent decrease in cannabinoid concentrations.

Take Home Message…
Cannabinoid concentration, as well as cannabinoid yield per plant were decreased with the increase in N supply.

Target Nitrogen Levels
Very high concentrations of fertilizer are not advisable because of lower cannabinoid concentration and yield, and that the optimal N nutrition is likely to be between 60 and 210 mg/L.
0.008-0.028 ounces per gallon

Pruning's Impact
Double stem pruning was applied as an additional treatment to investigate efficacy on biomass increase.

Pruning treatment did not increase cannabinoid concentrations or affect biomass when measured at the final harvest.

Study Also Evaluate Sun Edge Plants
Across all treatments, as an artefact of this trial, sun-edge plants that were more directly exposed to sunlight showed a trend towards more biomass and higher cannabinoid concentrations
According to the statistical model developed for this study.
Self-shading of plants can limit the production of cannabinoids, so it is important to consider plant density and light intensity/spectrum.
*However, these results can only be considered preliminary and does warrants further research.

Link to Lecture Slides: https://drive.google.com/file/d/1lgV_...

*Due to the description character limit the full work cited for "Nitrogen Fertilizers Impact on CBD and THC Concentrations in Cannabis" can be viewed at... https://docs.google.com/document/d/1P...