Oceania Lithosphere Data - Page 5

Reserve potassium (Kc) is a measure how much potassium is available to plants. There are three potassium pools: dissolved, extractable, and reserve potassium. Potassium (K) is continuously drawn from the extractable to the dissolved pool when it is used by plants, and likewise from the reserve pool to the extractable pool. The reserve potassium is held in minerals in the soil such as mica. An example of the utility of this information is for organic farmers, who are not allowed to add potassium chloride to their soils (they can add potassium sulphate, but this is much more expensive). Class 3 for Kc will indicate where organic farming is practical. If you zoom in on the map and click on a soil area it will show the Kc class (pot class). The classes are:

0 No data
1 Low (0-0.3 cmolK/kg)
2 Medium (0.3-0.6 cmolK/kg
3 High (>0.6 cmolK/kg)
4 Lakes
5 Alpine
6 Urban