Sodium molybdate is the soluble salt that supplies molybdenum as molybdate. The dihydrate form is about 39.7% Mo and 19% Na. Ammonium molybdate is a common alternative with a higher Mo content.
In practice
Molybdenum is needed in the smallest amount of any nutrient, around 0.03-0.05 mg/L (ppm) in the final feedbeing reviewed. At that dose the sodium it brings is negligible. It is always dosed from a concentrated micronutrient stock, since a single gram would supply enough for several thousand litres. It is one of the few micronutrients that becomes more available as pH rises.
Units and formula
1 mg/L gives about 0.4 mg/L (ppm) Mo. To reach 0.05 ppm Mo, add about 0.13 mg/L.
Don't confuse with
- Ammonium molybdate: another Mo salt, with ammonium instead of sodium.
- Molybdenum disulfide: an insoluble lubricant, not a fertiliser.
Molybdenum (Mo) is the micronutrient needed in the smallest amount; plants need it to convert nitrate into usable nitrogen.Ammonium (NH4+) is the positively charged form of nitrogen; a small share stabilises root-zone pH, but too much reduces cannabis yield and quality.Sodium (Na) is not essential for cannabis; it enters through water, softeners and some inputs, and at high levels causes salt stress and crowds out potassium and calcium.A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.A stock solution is a concentrated nutrient mix, often 100x or 200x final strength, diluted into the reservoir; calcium and sulfate/phosphate stocks must stay separate.
