The Role of Silicon in Surface Charge Characteristics, Phosphorus Sorption Capacity and Aluminium Toxicity of Variable Charge Soils

Abstract

Silicon (Si) is the second most abundant element in the Earth's crust, and it has been widely demonstrated that it is a beneficial nutrient for stimulating the growth and development of many higher plants. The potential effects are associated with the ameliorating/mitigating effects of Si on both abiotic and biotic stresses, which occur through the interactions between plants and external media, such as climate and soil conditions. However, Si solubility (monosilicic acid) in soils, which is an important factor determining these effects, is often low due to leaching or desilication during soil development under tropical climate conditions, and this is particularly the case with variable charge soils (VCS). Variable charge soils are often acidic, and typically have soil fertility constraints of aluminium toxicity, high phosphorus fixation and low cation retention. Silicon repletion by the application of Si amendments is one management option for improving the fertility of these soils. The overall objectives of this study were: a) to investigate the role of Si in ameliorating/amending major constraints of VCS from north Queensland and New South Wales (NSW), and b) to apply the results to other relevant VCS, particularly in the uplands of Vietnam where VCS have similar characteristics to those investigated in this study and where Si amendments are available, yet their use is not widespread because of a lack of awareness of their potential benefits.