钙镁肥 (Cal-Mag) 是一种液态水培补充剂，结合了钙 (Ca) 和镁 (Mg)，这两种次要常量营养素在软水、椰糠或某些基础营养配方中生长时经常缺乏。钙能强化细胞壁，防止顶端腐烂；镁是叶绿素中的核心元素，对光合作用至关重要。钙镁肥除了标准的基础营养素外，还会添加到营养液中。
关键事实
- Soft water and RO (reverse osmosis) water lack baseline Ca and Mg — Cal-Mag compensates
- Coco coir actively binds calcium ions, making additional supplementation essential
- Calcium deficiency: brown leaf edges, tip burn, blossom end rot in fruiting crops
- Magnesium deficiency: interveinal chlorosis (yellowing between veins) on older leaves
- Typical dose: 2–5 mL per litre depending on water hardness and base nutrient formula
- Add Cal-Mag to water before base nutrients to prevent precipitation