Thanks for links Lou. Its not a accumulator but will passively uptake with mass flow, is what I got out of them. At least the hemp varities tested were uptaking it, each hemp variety at different rates. Looks like 300 to 600kg per hectare, which is a lot but since its passive uptake it will take large amount in the solution to get much into the plant. for example rice is a accumulator, at Si concentration of 162mg Si Liter in the nutrient solution rice had 124grams SiO2 per kg. Soy at the same Si concentration had 4grams per Kg. Cannabis would be closer to soys uptake. Probably why I never could tell any difference with or without, I was giving way too low concentration.