Magnesium (Mg) deficiency typically develops in acidic soils, in heavily leached substrates, or where potassium has been over-applied (K antagonises Mg uptake). Magnesium sits at the centre of the chlorophyll molecule and is essential for photosynthesis. The characteristic symptom is interveinal chlorosis on the older leaves — the veins stay green while the lamina between them yellows fairly uniformly. Because Mg is a mobile nutrient, the plant strips it from older leaves first to keep the young growth supplied.
Below are the most widely available and effective options:
1. Epsom salt (magnesium sulphate, MgSO₄)
This is the cheapest and most effective remedy for Mg deficiency.
2. Mag-Phos micronutrient fertiliser (liquid or powder)
A specialist product that produces thick, glossy, dark-green leaves.
3. Combi mid- and micronutrient fertiliser (small sachet)
Suitable when the plant is showing a range of micronutrient deficiencies in addition to Mg.
Note: After treatment, leaves that yellowed severely will not turn green again, but new growth will come in dark green and healthy — that is the sign that treatment is working.
A highly effective nutrient source — white crystalline solid, fully water-soluble, supplying both magnesium and sulphur. Suitable for every growing system (hydroponics, drip irrigation, soil culture, aeroponics, etc.). The cheapest and most effective remedy for Mg deficiency. Mix at the label rate and spray evenly over the foliage in the early morning or late afternoon; combine with a soil drench for severe cases.
The Boron–Calcium–Magnesium–Zinc product is one of Viet Nhat's most popular lines. Visible results in use: - Promotes strong rooting and a robust root system; prevents yellow or rotting shoots; prevents leaf yellowing, root rot, wilting, and daytime droop. - Builds a large, sturdy plant resistant to lodging in adverse weather. - Enhances photosynthesis so new shoots flush vigorously and leaves are deep green, thick, and glossy. - Improves flowering and fruit set, giving large, glossy, heavy fruit. - Reduces acid-sulphate stress and helps detoxify organic residues; the plant recovers quickly after harvest. - Suitable for ornamentals, bonsai, flowering plants, fruit trees, and industrial crops. Dilute 1 kg in 1,000 L of water and either drench the root zone or spray the foliage.
Combi Thailand micronutrient fertiliser, 100 g sachet. A foliar mid- and micronutrient fertiliser containing the full set of essential trace elements (Mg, Fe, Zn, Cu, Mn) in chelate form so they are absorbed quickly and effectively. Helps prevent and correct micronutrient deficiencies and supports balanced overall growth. Mix at the label rate and spray to thoroughly wet the canopy at the recommended interval.
