While not an essential plant nutrient, supplemental silicon (Si) has been shown to improve plant yields and quality under certain conditions. For example, Si-accumulators, like rice and sugarcane, can yield more when supplemental silicates are provided (e.g. as liming materials). Additionally, powdery mildew of cucurbits, like pumpkin, can be reduced by added Si. For non-accumulators, like Cannabis, sufficient Si is provided in most water supplies, natural soils, enriched potting mixes, and some organic fertilizers. Still, supplemental Si is recommended if you are using RO water and/or growing hydroponically or aeroponically (i.e. without natural soil components).