Silicon (Si) is the second most abundant element in the earth's crust (after oxygen) with most of the silicon existing in various forms of silicon dioxides (silica) or silicates such as quartz. In soils these minerals undergo chemical and physical weathering, which results in the release of Si in solution, which then either combines with other elements and forms clay minerals or is absorbed by plants.
Whilst Si is no yet classed as an essential nutrient it exists in all plants and the lack of it is widely recognised as a critical limiting factor for crop production, particularly in soils that are deficient in Plant Available Silicon (PAS). It is also widely assumed that Si is not a limiting element in soils. However under modern agricultural systems the removal of Si from many cultivated soils exceeds the amount of dissolved Si entering the soil each year. This is the reason we observe plants responding to additions of Si.
Most of the widely produced crops in the world are Si accumulators, therefore understanding the role of Si in crop production is now subject to an enormous amount of research.
Source : Benefits of plant silicon for crops F Guntzer et al 2011.
Trials on Strawberries with the application of Agrisilica (left) and without (right).