Effect of P and Si amendment on the charge characteristics and management of a Geric soil

Abstract

Improving surface charge characteristics of geric Ferralsols may increase nutrient retention in highly weathered tropical soils of Vietnam. Application of increasing amounts of fused magnesium phosphate (FMP) increased soil pH by one unit and cation exchange capacity (CEC) 10-fold following 7 days incubation near field capacity at 40°C. Similarly, calcium and magnesium silicate amendments at rates designed to apply the same amount of silicon as a high FMP application also increased pH and CEC. In contrast pH₀ remained relatively unchanged except following high silicon application. It is recommended that strategies that increase pH are more likely to increase CEC in geric soils than amendments that aim to lower the pH₀.