The Secondary Nutrients & Plant Growth - Calcium's Role

The fifth most abundant element in the earth's crust and an important component of most plants and animals, Calcium (Ca) is a constituent of cell walls and is involved in production of new growing points and root tips.

Calcium provides elasticity and expansion of cell walls, which keeps growing points from becoming rigid and brittle. It is immobile within plants and remains in the older tissue throughout the growing season. It acts as a base for neutralizing organic acids generated during the growing process and aids in carbohydrate translocation and nitrogen absorption. Indeed, calcium might be considered as the bricks in plant assembly, without which cell manufacture and development would never occur!

Calcium deficiency symptoms appear in the meristem regions (new growth) of leaves, stems, buds and roots. Younger leaves are affected first and are usually deformed. In extreme cases, the growing tips die. The leaves of some plants hook downward and exhibit marginal necrosis. Roots on calcium-deficient plants are short and stubby. In tomatoes and peppers, a black leathery appearance develops on the blossom end of the fruit (a disorder called blossom-end rot). In such cases, the fruit ceases to develop and eventually falls off. In peanuts, low calcium causes "pops", a condition that prevents nuts from developing.

Plants must obtain calcium from the soil. Soil reserves are replenished and maintained with frequent applications of lime. Calcium can also be supplied by applying fertilizers such as calcium nitrate (19.4% Ca), calcium sulfate (22.5% Ca) and normal superphosphate (20.4% Ca).

Calcium deficiency is generally an indication of the need for lime. Soils that are properly limed will provide adequate calcium for several years. For crops like peanuts that require a high calcium concentration near the soil surface at pegging, a banded or broadcast application of gypsum (CaSO4, 22.5% Ca) will supply adequate calcium for normal crop production. For certain specialty crops, a foliar application of calcium nitrate is effective in correcting a deficiency.