The fertilizer made of plant ash has the character of a mineral potassium-lime fertilizer. It is gained from the ash under the gridiron left from biomass incineration and from fly ash collected during biomass incineration. By plant biomass incineration up to 98% of organic substances are lost and plant nutrients remain in the plant ash especially calcium, potassium, phosphorus and magnesium. That is why it is recommended to use the plant ash as a fertilizer that makes the return of plant nutrients back to the soil possible. The fertilizer made of plant ash is used after the harvest of the plant preceding the main crop plant before stubble-tillage. It is good to plough the recommended amount of 0.5 – 1t/ha in the soil or to use a cultivator. With respect to strict conditions concerning the initial material especially the requirements as to the fuel without any chemical ingredients, the ash is thanks to its high rate of calcium and potassium certified as a biological fertilizer. The production of this fertilizer reaches 1,500 t a year. It is a mineral potassium-lime fertilizer that contains apart from potassium (at least 20%) and calcium (at least 3%) also a small percentage of magnesium, phosphorus and nitrogen. The fertilizer is supplied in the form of loose hygroscopic powder having a distinctive colour. The fertilizer manufactured on the basis of plant ash is used for the treatment of an unwanted acid soil reaction and for the improvement of physical and chemical properties of soil.