Optimizing Magnesium Fertilizer Rates for Cannabis

Optimizing Magnesium Fertilizer Rates for Cannabis
Professor DeBacco

Research Article
Morad, D., & Bernstein, N. (2023). Response of medical cannabis to magnesium (Mg) supply at the vegetative growth phase. Plants, 12(14), 2676.
https://www.mdpi.com/2223-7747/12/14/...

Importance of Magnesium
Magnesium is an essential macronutrient for plant growth and metabolism which may be disrupted under Mg deficiency or toxicity conditions.
It involves in photosynthesis by activation of ribulose-1,5-bisphosphate carboxylase-oxygenase enzyme and as a central component of the chlorophyll molecule.

Magnesium Deficiency Symptoms
Interveinal yellowing of the leaves
Typically first seen on the lower (older) leaves.
30 Days After Initiation of Mg Treatments
Visual appearance of the plant parts under 2, 20, 35, 70, and 140 mg L-1 Mg supply…

Effect of Mg Supply
Effect of Mg supply on macro- and micronutrient concentrations in leaves, stems, and roots of medical cannabis plants.
Total
N (A)
P (B)
K (C)
Mg (D)
Ca (E)
Mn (F)
Zn (G)
Fe (H)

Mg Interactions with Ca and K
Increased Mg supply impaired uptake of Ca and K and their root-to-shoot translocation, demonstrating competitive cation inhibition
Possible Effects Mg +2 cations on Soil Aggregation
Excessive fertilizer applications may have more impact than just nutrient levels.
Possible effects of Ca +2 and Mg +2 cations on soil aggregation. 

Min-Max Levels
Mg-deficiency symptoms developed first in old leaves (at 2 mg L-1 Mg) and progressed towards young-mature leaves, demonstrating ability for Mg in plant storage and remobilization.
Mg toxicity symptoms appeared in old leaves from the bottom of the plants, under 140 mg L-1 Mg.

Target Range
The findings suggest 35–70 mg L-1 Mg as the optimal concentration range for cannabis plant development and function at the vegetative growth phase.

This can also be converted to…
35-70ppm Mg
0.0045oz.-0.0093oz per gallon of Mg
Magnesium Based Fertilizers
Dolomitic Lime (9.5% Mg)
Epsom Salts (9.87% Mg)
Cal-Mag (1.2% Mg)


Link to Lecture Slides: https://docs.google.com/document/d/1y...

*Due to the description character limit the full work cited for "Upper Limbs" can be viewed at... https://drive.google.com/open?id=1SnJ...