Work out potash requirement instantly with clear inputs, formula shown and shareable results.
Potash sources differ in grade: muriate of potash is 60% K2O, sulphate of potash 50% and potassium nitrate 44%. Divide the K2O requirement by the grade to get the product weight, then multiply by area. Chloride-sensitive crops such as tobacco, potato for crisping and many fruits should use SOP despite its higher cost.
Product from K2O
Product (kg/ha) = K2O required / grade fraction (MOP 0.60, SOP 0.50, KNO3 0.44)
On chloride-sensitive crops, saline soils where added chloride is a problem, and where the crop also needs sulphur. Otherwise MOP is the cheaper source of K2O.
Usually not on medium and heavy soils, where potassium is held on the exchange complex. On sandy soils and for long-duration crops such as sugarcane and banana, split it to reduce leaching.