Crude potassium salts
There are no potassium deficiencies in the heavy soils of central Europe. These soils arose from the weathering of feldspars, miki i hornblendy, therefore they contain a lot of this element, which can be made available to plants by appropriate cultivation treatments. On the example of feldspar, which contains 17% K2O, 18% Al2O3 i 64—65% SiO2, can be seen, what are its reserves. Despite this, in horticultural crops, plants very often suffer from potassium deficiency, especially there, where manure is rarely fertilized and almost no liquid manure is used (1 m3 of cattle manure contains approx 15 kg of potassium). In the garden, this deficiency can be easily corrected by using potassium-rich wood ash, which is added to the compost or spread over the soil surface.
In commercial horticulture, chlorine-free calimagnesia is used, which includes 28% potassium and 9% magnezu w formie siarczanowej. Kalimagnezja nie jest obecnie produkowana w Polsce, and a fertilizer with a similar effect is potassium sulphate containing approx 50% K2O. The most economical way to use this fertilizer is to add it to the compost heap, in which it turns into a form that is easily digestible for plants. You should not add more than 10 kg in 1 m3 kompostu. Larger doses may disturb the processes of decomposition of organic matter.