Features: 1) Mineral fertilizer with acid solubility 2) Main ingredient: potassium metasilicate 3) Materials: potassium, silicon, magnesium, calcium 4) Distributed in complexation stage, not soluble for water 5) Sustained release fertilizer: nutrient ingredients release speed controlled 6) Nontoxic, odorless and without corrosion 7) Specifications: a) Grain size: 2.5 - 5.0mm b) Moisture content: less than 1.0% c) Hardness: more than 2.0kg/cm2 d) Silicon dioxide solubility in acid: more than 26.0% e) Potassium oxide solubility in acid: more than 21.0% f) W-K2O: less than 3.0% g) C-MgO: more than 7.0% h) Appearance: yellow or grey