SOP Potash (Sulphate of Potash) 0-0-50

Chloride-free potassium sulphate, 50% K₂O + 18% S

Sulphate of potash is the premium potash: potassium sulphate at 50% K₂O minimum, carrying about 17–18% sulphur as a second nutrient, with chloride held below 1.5% and often below 1%. That chloride limit is the whole reason to buy it, and it is the number to certify. Three grades serve three uses. Granular SOP, about 2–4 mm, for direct application and blends. Standard or powder grade, fine, for compound manufacturers and for markets that broadcast it. Water-soluble SOP, a finer, purer crystalline grade with insolubles below 0.1% and solubility at around 110 g/l, for fertigation and foliar programmes, sold in 25 kg bags at a further premium. SOP is made either by the Mannheim process (potassium chloride and sulphuric acid, the source of most Chinese and European product) or from natural brines and minerals, and the two routes give different trace profiles, so ask which you are getting.

Buy SOP for crops that dislike chloride or where the market pays for quality: tobacco, potatoes, citrus, grapes, tree fruit, vegetables, tea and flowers; for saline, sodic and irrigated soils where chloride accumulates; and where the sulphur is wanted as well. Buy MOP for everything else, because SOP costs roughly twice as much per unit of potassium. The trade moves from China, Belgium and Germany, Chile and Egypt into horticultural markets on every continent, mostly in containers and bagged, with some bulk into the larger buyers. CBIL brokers granular, standard and water-soluble SOP against independent certification of K₂O, sulphur, chloride, moisture and, for the soluble grade, insolubles at load, in bulk, 50 kg and 25 kg bags and jumbo bags, on FOB, CFR and CIF terms.