Plant Available Silicon

Plants can only absorb Silicon (Si) in the form of soluble monosilicic acid or Plant Available Silicon (PAS). Different Si sources have different dissolution rates of PAS, for example quartz (sand) maybe 80% Silica but it is locked up in a crystalline structure and it has a very low PAS compared to the more easily soluble amorphous silica which Agripower's products are made of. Many fertilisers express Si as the total elemental content, however this approach does not advise what is Plant Available Si, i.e. what the plant can actually take up.


Given that many soils are Si deficient it is important to understand the extent of the deficiency before recommending a treatment program. Soil testing is the best way to measure the amount of PAS in the soil. Agripower recommends the calcium chloride 0.01M extraction method be used to analyse soils.


With the recognition that Si is an important nutrient for optimum growth of plants, many methodologies have been used to determine the Plant Available Si of the Si source. Many such methodologies used to estimate PAS of the Si source  do not correlate well with the uptake of Si once applied to the soil. It is widely accepted that the calcium chloride 0.01M extraction method (extracted at a ratio of 1:100) provides an accurate correlation between PAS, plant uptake and crop yield responses.


Soils that have low PAS concentrations are commonly amended with silica fertilisers to increase yield and quality of produce. Agrisilica has been proven to have a very high level of PAS and is ideal for using as a Silica fertiliser without the contaminants that may be found in other Si fertilisers. Agrisilica also has the added benefits of a high cation exchange capacity (CEC) enabling better retention and uptake of other nutrients. Agripower's products also absorb and hold water and slow release moisture in the root zone.