Potash Requirement Calculator

Work out potash requirement instantly with clear inputs, formula shown and shareable results.

About Potash Requirement Calculator

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.

Formula

Product from K2O

Product (kg/ha) = K2O required / grade fraction (MOP 0.60, SOP 0.50, KNO3 0.44)

Worked example

With the default values below, Potash Requirement Calculator returns Potash Fertiliser Required of 133.33. Change any input above and every figure here is recalculated in your browser.

Inputs used

Potash Requiredminimum 0 kg K2O: 40 kg K2O
Potash Sourceone of Muriate of potash (60% K2O), Sulphate of potash (50% K2O), Potassium nitrate (44% K2O): Muriate of potash (60% K2O)
Areaminimum 0.01 ha: 2 ha
Bag Sizeminimum 1 kg: 50 kg

Results

Potash Fertiliser Required: 133.33
Product Per Hectare: 66.67
Bags Required: 2.67
Total K2O Applied: 80.00

Step by step

1Values used
2Product from K2O
3Potash Fertiliser Required= 133.33
4Product Per Hectare= 66.67
5Bags Required= 2.67
6Total K2O Applied= 80.00

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

When is sulphate of potash worth the extra cost?

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.

Does potash need splitting like nitrogen?

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.