Michigan State University Extension
Soils & Soil Management - Fertilizer - 05209702
07/10/97
Secondary and Micronutrients for Vegetables and Field Crops Extension Bulletin E-486, Revised August 1994
By M.L. Vitosh, D.D. Warncke and R.E. Lucas Department of Crop and Soil Sciences Michigan State University Extension
Calcium, an essential part of plant cell wall structure, provides for normal transport and retention of other elements and strength in the plant. It is thought to counteract the effect of alkali salts and organic acids within the plant. Calcium is absorbed as the Ca++ ion and exists in a delicate balance with magnesium and potassium in the plant. Too much of any one of these three elements may cause insufficiencies of the other two.
Calcium Deficiency Symptoms
Calcium deficiency is usually observed as a failure of terminal buds and apical root tips to develop. In corn, new leaves fail to emerge from the whorl because of a sticky, gelatinous material on the edges of the leaves. The tips of these leaves are also very chlorotic (yellowish). The young leaves of new plants are the first to be affected. They are often distorted and small, the leaf margins are often irregular, and the leaves may show spotted or necrotic areas.
Disorders such as blossom end rot in peppers and tomatoes, blackheart in celery, internal tip burn in cabbage and cavity spot in carrots are attributed to calcium deficiency. These disorders are usually related to the inability of the plant to translocate adequate calcium to the affected plant part rather than to insufficient soil calcium levels.
In Michigan, calcium deficiency occurs only on very acid soil (< pH 5.0) or where excessive quantities of potassium or magnesium have been used. Soils that are adequately limed are high in calcium. Even soils that are moderately acid(between pH 5.0 and 6.0) generally contain sufficient calcium for plants. Poor plant growth on these soils is usually due to excess soluble aluminum, manganese and/or iron rather than inadequate calcium. In Michigan, calcium deficiency symptoms sometimes occur when the root system has been so damaged by nematodes, insects or diseases that the plant cannot take up adequate calcium.
Correcting Calcium Deficiency
Calcium in plants is a relatively immobile element. Where deficiencies exist and foliar sprays are used to correct the deficiency, it is very important to cover the young terminal growth with calcium. Applications on older leaves will not benefit the plant. The suggested rate for foliar application of calcium is 1 to 2 pounds of calcium in 30 gallons of water, using either calcium chloride or calcium nitrate. Agricultural lime should be used to correct calcium deficiency on acid soils. Calcitic lime is suggested when the Ca/Mg equivalent ratio is less than 1.
Calcium Toxicity
Excessive levels of calcium are rarely detrimental to plant growth, though excessive calcium carbonate in the soil may result in other nutritional problems associated with high pH. Band applications of acid-forming fertilizer may lower pH in the band and increase availability of other nutrients. Spreading or spraying calcium oxide over the top of plants may burn the foliage.
Excessive amounts of soluble calcium, such as calcium chloride or calcium sulfate, have been known to cause problems in certain instances, but the problem is generally associated with the anions Cl- or S04= rather than calcium per se.