Calcium in agriculture and crop production.

Calcium (Ca2+) is an essential mineral for plants, functioning both as a nano- to micromolar signaling ion in gene regulation and, at millimolar levels, in nutrition-supporting structural integrity and enzyme activation. These functions depend on adequate fertilization. However, Ca2+ problems stem mainly from hydraulic access and local availability within specific tissues and compartments rather than bulk supply; thus, deficiency can occur even in Ca2+-rich soils due to soil immobilization and physiological constraints. Because Ca2+ is poorly phloem-mobile and moves mainly via transpiration-driven xylem flow, its distribution is uneven. By binding to cell walls, calcium also enhances plant stability and fruit firmness. Here we review deficiency symptoms, management strategies, developmental roles, soil interactions, detoxification, and recent fertilizer approaches.