Why is nitrogen demand so high during veg?
During vegetative growth the plant synthesizes chlorophyll, enzymes, and structural proteins at a rapid pace. Nitrogen is the central atom in all of those compounds — without available N the plant cannibalizes what's already in the older leaves (yellowing that climbs from the bottom up) and growth stalls.
Saloner & Bernstein (2019) measured the effect of different N levels on vegetative biomass in cannabis and found that the optimal range sits around 150–250 ppm of total N in solution, depending on where in veg you are and the size of the plant. Below that range growth rate drops off; above it toxicity starts to show up (burnt leaf tips, abnormally dark green coloring).
What EC and feeding ramp should I use?
EC (electrical conductivity) is the fastest proxy for total salt concentration in your solution. In veg it pays to increase EC gradually so you don't stress young roots or stall growth:
- Seedling / freshly rooted clone: EC ~0.8–1.0 mS/cm — tender roots, keep the solution light.
- Early veg (weeks 1–2): EC ~1.0–1.4 mS/cm — the plant starts building structure.
- Late veg (week 3+ or before flip): EC ~1.4–1.8 mS/cm — peak demand, the plant can handle a heavier feed.
These ranges apply to hydro and coco. In soil, soluble nutrients interact with the substrate's CEC, so the irrigation water EC is usually kept a bit lower (0.8–1.4 mS/cm) and you let the medium contribute the rest.
What pH keeps nutrients available in each substrate?
The medium's pH determines what chemical form nutrients exist in and whether the roots can actually take them up. Bevan et al. (2021) and Veazie et al. (2025) describe optimal pH ranges for cannabis by substrate:
- Hydroponics (NFT, DWC, rockwool): pH 5.5–6.0. The solution controls everything; outside that window Fe, Mn, and Zn precipitate fast.
- Coco coir: pH 5.8–6.2. Coco has its own CEC that buffers somewhat, but it's still an inert substrate and your feed water pH is what matters.
- Soil / perlite mix: pH 6.0–6.5. Humus and clay particles buffer pH; in this range phosphorus and micronutrients stay accessible.
If pH drifts out of range, the plant can show deficiencies even when EC is on point and the solution is well-formulated. That's nutrient lockout: the elements are present, but the chemical form they exist in at that pH can't be absorbed by the root.
What role do Ca and Mg play in veg?
Calcium and magnesium are the two secondary nutrients most overlooked in veg and most complained about in flower. In veg, calcium holds cell walls together and keeps new growth healthy (deficiency = brown spots on tips, deformed new leaves), while magnesium is the central atom in chlorophyll (deficiency = interveinal chlorosis on older leaves, then spreading to new ones).
In hydro and coco, RO or soft water contributes no Ca or Mg, so you have to include them in your base solution. In soil a quality mix with compost usually has Ca and Mg built in, but with frequent watering they deplete faster than you'd expect.
What signs tell me my veg nutrition is off?
- Chlorosis climbing from old leaves to new growth, overall pale green → N deficiency.
- Deformed new leaves, brown tips, hollow stems → Ca deficiency (check pH and whether you're on soft or RO water).
- Interveinal chlorosis starting on older leaves → Mg deficiency.
- Burnt tips, abnormally dark glossy green, slow growth → N excess or EC too high.
- Multiple deficiencies with correct EC → nutrient lockout from pH being out of range.
How do I go from these ranges to actual milliliters of nutrient?
The N, EC, and pH ranges are the targets; the mL per nutrient depend on the product's concentration, your local water profile, and whether you're combining base nutrients, additives, and pH adjusters. Every formulation has its own nutrient density.
