Methods for Investigations of the Biologically Active Forms of Si in Soil, Plants, and Agrochemicals

A set of methods for determining the active forms of silicon—monomers and polymers of silicic acid—in the soil–plant system is described to assess the silicon state of soils and the level of plant availability of silicon as well as to assess the potential effectiveness of solid silicon-containing compounds as a source of bioavailable silicon. The parameter “active silicon” proposed to characterize the availability of bioavailable silicon in soils includes actual silicon, i.e., the content of monosilicon acid present in the soil solution now, and “potential silicon”—monosilicon acid—which can pass into the soil solution from the solid phase. Based on the active silicon parameter, a classification of soils has been developed depending on the level of bioactive silicon deficiency.