Use the chart below to decide how much you need, and how much potassium, magnesium and calcium your polyhalite application will provide.
| Crops | Risk of deficiency | Advised rate (kg/ha) | Other nutrients applied (kg/ha) | Notes* | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SO3 | S | Polysulphate | K2O | K | MgO | Mg | CaO | Ca | |||
| Cereals | higher | 50 | 20 | 100 | 14 | 11.7 | 6 | 3.6 | 17 | 12.2 | Apply in early spring before the start of stem extension. |
| lower | 25 | 10 | 50 | 7.5 | 6.2 | 3 | 1.8 | 8.5 | 6.1 | ||
| Oilseed rape | higher | 75 | 30 | 150 | 21 | 17.4 | 9 | 5.4 | 25.5 | 18.4 | Apply in early spring. Spring crops may be less susceptible to deficiency. |
| lower | 50 | 20 | 100 | 14 | 11.6 | 6 | 3.6 | 17 | 12.2 | ||
| Peas (for dried, vining and fresh markets) | 25 | 10 | 50 | 7.5 | 6.2 | 3 | 1.8 | 8.5 | 6.1 | Apply where soil is sandy, shallow or medium textured and contains little organic matter. | |
| Brussels sprouts, cabbage, cauliflowers, calabrese | 50 | 20 | 100 | 14 | 11.6 | 6 | 3.6 | 17 | 12.2 | Apply where sulphur content of soils is low, e.g. light soils following wet winters where there is no history of organic manures application. | |
| Grassland | 40 | 16 | 80 | 11.2 | 9.3 | 4.8 | 2.9 | 13.6 | 9.8 | Apply at the start of growth before each cut. May not be required before first cut on medium/heavy soils. | |
* Generally applications should be made where a deficiency has been recognised or is expected. This can be assessed through tissue analysis, crop observation or whether in a high-risk area. Refer to official recommendations for further details.