CHEMICAL-PROPERTIES OF ASH DERIVED FROM EUCALYPTUS LITTER AND ITS EFFECTS ON FOREST SOILS

The concentration of elements in ash from eucalyptus litter varied sev eral-fold depending upon the type of fuel and combustion conditions. I n vegetation fires, and where ash is used as a soil amendment, signifi cant amounts of nutrients and heavy metals will be added to soils. Thr ee patterns of dissolution of ash constituents in water were observed: (1) high (> 70% of element content of ash quickly soluble), but with a residual component which was not solubilized by further dilution (el ements K, S, and B); (2) relatively insoluble, but where the amount di ssolved is related to dilution (Ca, Mg, Si and Fe), and (3) highly ins oluble (such as P). The capacity of ash to neutralize acid was well co rrelated with the total amount of basic cations (K + Ca + Mg) in the a sh. Addition of 4-20 t ash ha(-1) to a range of forest soils increased pH (KCl) by one to three units depending on soil C content, decreased exchangeable Al and H content, increased exchange sites (variable neg ative charges) and increased basic-cation levels. Ash addition increas ed respiration rates in all soils, especially in those with higher org anic matter content. Addition of ash increased N mineralization rate a nd nitrification in most of the soils, although the magnitude of respo nse was not clearly related to assessed soil properties. This study su ggests that account must be taken of soil and ash properties when asse ssing the utility of plant ash for soil amelioration.