Magnesium fertilizers are priced at $200–$450 per ton in spring 2026, depending on source. K-Mag (0-0-22-11Mg-11S, sulfate of potash-magnesia) is $320–$420/ton. Magnesium sulfate (Epsom salt, 9.9% Mg) runs $200–$280/ton. Dolomitic lime is the most economical magnesium source on acidic soils ($40–$85/ton with 10–12% Mg equivalent). Magnesium deficiency is most common on sandy, high-rainfall soils and soils with high potassium-to-magnesium ratios.
Current Signal: HOLD
Year-over-year change: +5–10%
| Market / Region | Price Range |
|---|---|
| K-Mag (0-0-22-11Mg-11S) | $320 – $420/ton |
| Magnesium sulfate (Epsom) | $200 – $280/ton |
| Dolomitic lime (pH adjustment) | $40 – $85/ton |
| 50 lbs K-Mag/acre cost | $8 – $10.50/acre |
On acidic soils (pH < 6.5), dolomitic lime (calcium-magnesium carbonate) is the most economical magnesium source — it corrects pH and supplies magnesium simultaneously. High-calcium lime does not supply magnesium and can worsen K:Mg ratio imbalances.
K-Mag (also called sulfate of potash-magnesia or langbeinite) is used when magnesium is needed without raising pH. It supplies potassium, magnesium, and sulfur simultaneously and is especially useful in specialty crop and vegetable production.
High potassium application (from fertilizer or manure) can suppress magnesium uptake even on soils with adequate magnesium levels. K:Mg ratios above 5:1 are associated with induced deficiency in forages and occasionally in corn and soybeans.
Magnesium chloride (bittern, MgCl2) is a cheaper magnesium source but adds chloride that can be detrimental to chloride-sensitive crops. Magnesium sulfate is preferred for crop production.
Dolomitic lime is the most economical magnesium source on acidic soils. For neutral-pH soils needing magnesium without pH change, magnesium sulfate is the most cost-effective option. K-Mag is preferred when potassium and sulfur are also needed.
Forages (alfalfa, grass hay) are the most magnesium-demanding crops. Corn and soybeans show deficiency primarily on sandy, high-rainfall soils or where K:Mg ratios exceed 5:1. Grass tetany in cattle is linked to low forage magnesium.
K-Mag (sulfate of potash-magnesia, 0-0-22-11Mg-11S) is $320–$420/ton in spring 2026.
Soil testing for exchangeable magnesium (base saturation method) is the most reliable indicator. Target magnesium base saturation of 10–15% is typical for most grain crops. DTPA magnesium below 80 ppm in CEC-adjusted soils suggests potential deficiency.
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