text: Acidic, sandy, or coarse soils often contain less calcium. Uneven soil moisture and overuse of fertilizers can also cause calcium deficiency. At times, even with sufficient calcium in the soil, it can be in an insoluble form and is then unusable by the plant or it could be attributed to a "transport protein". Soils containing high phosphorus are particularly susceptible to creating insoluble forms of calcium.
  Calcium and magnesium are opposed within the plant cells, and have antagonistic interactions. As a result, a homeostatic balance between Ca and Mg within the plant is necessary for optimal growth and proper development.