Calcium (Ca) is found all around us, and the very existence of plants and animals depends on it. Plants take up Ca as the Ca2+ cation. Once inside the plant, Ca functions in several essential ways.
The secondary nutrients, calcium (Ca), magnesium (Mg) and sulfur (S), are as important to plant nutrition as the primary nutrients. Deficiency in secondary nutrients, including Ca, can depress plant growth as much as primary nutrient deficiencies do.
Calcium replaces hydrogen (H) ions from the surface of soil particles when limestone is added to reduce soil acidity. This changeover is essential for microorganisms because they turn crop residues into organic matter, release nutrients, and improve soil aggregation and water-holding capacity. Calcium helps enable nitrogen (N)-fixing bacteria that form nodules on the roots of leguminous plants to capture atmospheric N gas and convert it into a form that plants can use.
When Ca translocates within the plant, it improves plant roots’ ability to absorb other nutrients. It activates a number of plant growth-regulating enzyme systems, helps convert nitrate N into forms needed for protein formation, allows cell wall formation and normal cell division to occur, and contributes to improved disease resistance. Further, Ca, along with Mg and potassium (K), helps neutralize organic acids that form during plant-cell metabolism.
Calcium deficiency isn’t likely for most crops if producers properly lime soils to adjust pH to optimum levels for crop production. As soils become more acidic, crop growth is often restricted by toxic soil concentrations of aluminum, manganese, or both – not a Ca shortage. Soil testing and a good liming program are the best management practices to prevent these problems.
Abnormal development of growing points (in the form of terminal buds) and poor root growth are common symptoms of a Ca deficiency. Young leaves and other new tissue develop symptoms first because Ca does not translocate within the plant. New tissue needs Ca pectate for cell wall formation, so a Ca deficiency can cause gelatinous leaf tips and growing points. In severe cases, the growing point dies and the roots turn black and rot. Calcium deficiency can also cause foliage to take on an abnormal dark green color. Deficient plants might shed blossoms and buds prematurely.
Symptoms of deficiency can vary across crop species, but similarities exist for how nutrient insufficiency impacts plant tissue color and appearance. Nutrient deficiencies are commonly associated with the physical location on the plant
(i.e., whether the symptoms are primarily observed on older versus newly formed plant tissue), but these symptoms can spread as the severity of the deficiency progresses.