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CMS (Calcium-Magnesium-Sulphur) Granular Fertilizer

CMS granular fertilisers are FCO-notified secondary-nutrient blends that deliver calcium, magnesium and sulphur in a single granule. The category emerged to address the simultaneous depletion of all three secondary nutrients in intensively cultivated NPK-only soils, and is positioned between primary NPK fertilisers and the single-source secondary inputs such as gypsum and magnesium sulphate.

Composition

A typical CMS analysis carries roughly 20% calcium-equivalent, 5% magnesium and 20% sulphur, although formulations vary by manufacturer. Granules are usually a blend of gypsum, dolomite or kieserite and elemental sulphur, compacted into a free-flowing prill of 2-4 mm. The product is registered under the FCO secondary-nutrient schedule.

Mode of action

Once applied to moist soil, the granule disintegrates and releases the three nutrients over the season. Calcium maintains cell-wall pectin cross-links and supports cell division. Magnesium is the central atom of chlorophyll and a cofactor for many phosphate-transfer enzymes. Sulphur is incorporated into the amino acids cysteine and methionine, into key enzymes, and into oils in oilseed crops.

Target use and dose

CMS is used as a basal or side-dressing amendment at sowing or at flowering/booting in paddy, oilseeds, pulses, cotton, sugarcane, vegetables and fruit crops. It is particularly useful on light-textured or red soils that show simultaneous Ca, Mg and S deficiency, and as a partial replacement for separate applications of gypsum, kieserite and elemental sulphur. Dose follows soil test recommendations and crop nutrient demand.

Safety and regulatory status

Notified under the FCO 1985 secondary-nutrient schedule. A standing compatibility caution applies: calcium nitrate and magnesium sulphate must not be combined in a fertigation stock tank, since they precipitate as calcium sulphate; CMS granules avoid this problem by delivering both as low-solubility salts directly to soil.

See also: Calcium Magnesium Foliar, Input Cms Fertilizer, Sulphur Fertilizer, Gypsum In Groundnut, Multi Nutrient Fertilizer Blends.

References

  1. Fertilizer Compatibility. Purdue Vegetable Crops Hotline.
  2. Why You Should Not Mix Calcium Nitrate and Magnesium Sulphate. Agrisearch India.