Examines cultivated and uncultivated soils of the footslopes of Mt. Hibok-Hibok, down to the nearby coastal areas to assess the effects of cultivation on their chemical characteristics. It determines changes in soil surface charge properties, particularly point of zero charge (pH0) and cation exchange capacity (CEC) after nine months incubation with natural amendments (calcium silicate, ground basaltic pyroclastics and peat). It also investigates the effects of adding the amendment materials on plant growth with maize as test crop in a glasshouse experiment.