Effect of calcium silicate and superphosphate application on surface charge properties of volcanic soils from West Sumatra, Indonesia

Abstract

Silicate and phosphate are known to change soil's charge properties. A study was conducted to determine the effects of their application on charge of volcanic soils of Sumatra, Indonesia. This study showed in the beginning that calcium (Ca)-silicate application increased soil pH and zero point of charge (pH0). The cation exchange capacity (CEC) increased from 3 to 15 cmolc kg−1 in direct relationship to the rate of silicate application and from 3 to 8 cmolc kg−1 after applying superphosphate. The inverse relations obtained between pH0 and the CEC as well as with the sum of basic cations verify the beneficial effect of applying silicate and superphosphate in increasing cation retention of volcanic ash soils. The AEC values were unchanged as the soil pH values were well above the pH where amphoteric surfaces can generate positive charge. For silicate application, it is believed that nine months incubation period is sufficient to make a major improvement in cation retention and significantly increase soil pH and negative ΔpH values.